rewrited logic structure

2026-09-09 16:43:57 +08:00
parent 1947a27514
commit ac6d2cf3b4
20 changed files with 1717 additions and 1496 deletions
--- a/README.md
+++ b/README.md
@@ -74,6 +74,21 @@ TEACHER_USER=yourname TEACHER_PASSWORD=your-strong-password python3 app.py
 - `selfgroup.db`：学生、密码、分组、班级状态和登录会话。
 - `2025mt.xlsx`：首次启动导入的原始名单。

+## 代码结构
+
+服务端按职责拆分在 `group_system/` 包中：
+
+```text
+app.py                       启动入口，保留 python3 app.py 的用法
+group_system/config.py       路径、端口、账号和业务默认值
+group_system/security.py     PBKDF2 密码散列与校验
+group_system/storage/        SQLite 连接、名单导入、账号、分组、管理、导出
+group_system/http/           API 适配、静态文件路由和 HTTP 服务器
+group_system/xlsx_io.py      无第三方依赖的 XLSX 读取/生成
+```
+
+前端仍在 `static/` 目录中，接口协议保持不变。
+
 ## 建议部署方式

 1. 在教师电脑上运行 `python3 app.py`。
--- a/app.py
+++ b/app.py
--- a/group_system/init.py
+++ b/group_system/init.py
@@ -0,0 +1 @@
+"""学生自助分组系统应用包。"""
--- a/group_system/config.py
+++ b/group_system/config.py
@@ -0,0 +1,17 @@
+"""运行配置和环境变量。"""
+
+from __future__ import annotations
+
+import os
+from pathlib import Path
+
+BASE_DIR = Path(__file__).resolve().parent.parent
+DB_PATH = Path(os.environ.get("GROUP_DB", BASE_DIR / "selfgroup.db"))
+XLSX_PATH = Path(os.environ.get("GROUP_XLSX", BASE_DIR / "2025mt.xlsx"))
+STATIC_DIR = BASE_DIR / "static"
+TEACHER_USER = os.environ.get("TEACHER_USER", "teacher")
+TEACHER_PASSWORD = os.environ.get("TEACHER_PASSWORD", "teacher!@#")
+GROUP_LIMIT = 6
+SESSION_DAYS = 7
+MAX_JSON_BYTES = 1024 * 1024
+MAX_UPLOAD_BYTES = 10 * 1024 * 1024
--- a/group_system/http/init.py
+++ b/group_system/http/init.py
@@ -0,0 +1 @@
+"""HTTP 路由和响应工具。"""
--- a/group_system/http/api.py
+++ b/group_system/http/api.py
@@ -0,0 +1,358 @@
+"""学生和教师 API 适配层。"""
+
+from __future__ import annotations
+
+import json
+import logging
+import sqlite3
+import urllib.parse
+from http import HTTPStatus
+from typing import Any
+
+from group_system.config import BASE_DIR, MAX_JSON_BYTES, MAX_UPLOAD_BYTES
+from group_system.http.responses import (
+    clear_session_cookie,
+    json_response,
+    make_session_cookie,
+)
+from group_system.storage.store import GroupStore
+
+LOG = logging.getLogger("group-system")
+
+
+class GroupRequestHandler:
+    """把 HTTP 请求转换成 GroupStore 调用，不直接访问数据库。"""
+
+    server_version = "StudentGroupSystem/1.0"
+
+    def __init__(self, handler, store: GroupStore):
+        self.handler = handler
+        self.store = store
+
+    def cookies(self) -> dict[str, str]:
+        header = self.handler.headers.get("Cookie", "")
+        result = {}
+        for part in header.split(";"):
+            if "=" in part:
+                key, value = part.strip().split("=", 1)
+                result[key] = urllib.parse.unquote(value)
+        return result
+
+    def token(self) -> str | None:
+        return self.cookies().get("GROUP_SESSION")
+
+    def session(self) -> dict[str, Any] | None:
+        result = self.store.get_session(self.token())
+        if result:
+            result["_token"] = self.token()
+        return result
+
+    def read_json(self) -> dict[str, Any]:
+        length = int(self.handler.headers.get("Content-Length", "0") or 0)
+        if length <= 0:
+            return {}
+        if length > MAX_JSON_BYTES:
+            raise ValueError("请求体过大")
+        raw = self.handler.rfile.read(length)
+        return json.loads(raw.decode("utf-8"))
+
+    def require_teacher(self):
+        session = self.session()
+        if not session or session["role"] != "teacher":
+            return None, json_response(HTTPStatus.UNAUTHORIZED, {"ok": False, "message": "请先登录教师后台"})
+        return session, None
+
+    def require_student(self):
+        session = self.session()
+        if not session or session["role"] != "student" or not session["student_id"]:
+            return None, json_response(HTTPStatus.UNAUTHORIZED, {"ok": False, "message": "请先登录"})
+        return session, None
+
+    def handle_api(self, action: str, method: str):
+        try:
+            return self.dispatch_api(action, method)
+        except (ValueError, sqlite3.IntegrityError, sqlite3.OperationalError) as exc:
+            LOG.warning("API error %s %s: %s", method, action, exc)
+            return json_response(HTTPStatus.BAD_REQUEST, {"ok": False, "message": str(exc)})
+        except Exception:
+            LOG.exception("Unexpected API error")
+            return json_response(HTTPStatus.INTERNAL_SERVER_ERROR, {"ok": False, "message": "服务器内部错误"})
+
+    def dispatch_api(self, action: str, method: str):
+        if action == "login" and method == "POST":
+            data = self.read_json()
+            result, message = self.store.login_student(data.get("username", ""), data.get("password", ""))
+            if not result:
+                return json_response(HTTPStatus.UNAUTHORIZED, {"ok": False, "message": message})
+            return json_response(
+                HTTPStatus.OK,
+                {"ok": True, "message": message, "user": result["student"]},
+                [{"value": make_session_cookie(result["token"])}],
+            )
+
+        if action == "teacher-login" and method == "POST":
+            data = self.read_json()
+            result, message = self.store.login_teacher(data.get("username", ""), data.get("password", ""))
+            if not result:
+                return json_response(HTTPStatus.UNAUTHORIZED, {"ok": False, "message": message})
+            return json_response(
+                HTTPStatus.OK,
+                {"ok": True, "message": message, "user": result["teacher"]},
+                [{"value": make_session_cookie(result["token"])}],
+            )
+
+        if action == "logout" and method == "POST":
+            self.store.destroy_session(self.token())
+            return json_response(HTTPStatus.OK, {"ok": True, "message": "已退出"}, [{"value": clear_session_cookie()}])
+
+        if action == "state" and method == "GET":
+            session = self.session()
+            if not session:
+                return json_response(HTTPStatus.OK, {"ok": True, "authenticated": False})
+            active = self.store.active_class()
+            common = {
+                "ok": True,
+                "authenticated": True,
+                "role": session["role"],
+                "active_class": active,
+                "classes": self.store.class_list() if session["role"] == "teacher" else [],
+            }
+            if session["role"] == "teacher":
+                selected = self.handler.path.split("class=", 1)[1].split("&", 1)[0] if "class=" in self.handler.path else active
+                selected = urllib.parse.unquote(selected)
+                if selected and selected != active:
+                    # Teacher can preview any class, but active_class remains explicit.
+                    return json_response(
+                        HTTPStatus.OK,
+                        {
+                            **common,
+                            "view_class": selected,
+                            "snapshot": self.store.class_snapshot(selected),
+                        },
+                    )
+                return json_response(
+                    HTTPStatus.OK,
+                    {
+                        **common,
+                        "view_class": active,
+                        "teacher": {"username": session["username"]},
+                        "snapshot": self.store.class_snapshot(active),
+                    },
+                )
+
+            student = self.store.get_student(session["student_id"])
+            if student is None:
+                return json_response(HTTPStatus.OK, {"ok": True, "authenticated": False})
+            membership = self.store.student_membership(student["id"])
+            snapshot = self.store.class_snapshot(student["class_name"])
+            return json_response(
+                HTTPStatus.OK,
+                {
+                    **common,
+                    "user": {
+                        "id": student["id"],
+                        "name": student["name"],
+                        "student_no": student["student_no"],
+                        "class_name": student["class_name"],
+                        "must_change_password": bool(student["must_change_password"]),
+                    },
+                    "membership": membership,
+                    "snapshot": snapshot,
+                },
+            )
+
+        if action == "change-password" and method == "POST":
+            session, error = self.require_student()
+            if error:
+                return error
+            data = self.read_json()
+            ok, message = self.store.change_student_password(
+                session, data.get("old_password", ""), data.get("new_password", "")
+            )
+            status = HTTPStatus.OK if ok else HTTPStatus.BAD_REQUEST
+            return json_response(status, {"ok": ok, "message": message})
+
+        if action == "teacher/change-password" and method == "POST":
+            session, error = self.require_teacher()
+            if error:
+                return error
+            data = self.read_json()
+            ok, message = self.store.change_teacher_password(
+                session, data.get("old_password", ""), data.get("new_password", "")
+            )
+            status = HTTPStatus.OK if ok else HTTPStatus.BAD_REQUEST
+            return json_response(status, {"ok": ok, "message": message})
+
+        if action == "teacher/group-limit" and method == "POST":
+            _, error = self.require_teacher()
+            if error:
+                return error
+            data = self.read_json()
+            ok, message = self.store.set_group_limit(int(data.get("limit", 0)))
+            return json_response(HTTPStatus.OK if ok else HTTPStatus.BAD_REQUEST, {
+                "ok": ok, "message": message, "group_limit": self.store.group_limit()
+            })
+
+        if action == "groups" and method == "POST":
+            session, error = self.require_student()
+            if error:
+                return error
+            student = self.store.get_student(session["student_id"])
+            if student and student["must_change_password"]:
+                return json_response(HTTPStatus.FORBIDDEN, {"ok": False, "message": "首次登录必须先修改密码"})
+            data = self.read_json()
+            ok, message, _ = self.store.create_group(session["student_id"], data.get("name", ""))
+            return json_response(
+                HTTPStatus.OK if ok else HTTPStatus.BAD_REQUEST,
+                {"ok": ok, "message": message},
+            )
+
+        if action == "join" and method == "POST":
+            session, error = self.require_student()
+            if error:
+                return error
+            data = self.read_json()
+            ok, message = self.store.join_group(
+                session["student_id"], int(data.get("group_id", 0)), bool(data.get("confirmed"))
+            )
+            return json_response(
+                HTTPStatus.OK if ok else HTTPStatus.BAD_REQUEST,
+                {"ok": ok, "message": message, "require_confirm": (not ok and "确认后才会执行" in message)},
+            )
+
+        if action == "leave" and method == "POST":
+            session, error = self.require_student()
+            if error:
+                return error
+            data = self.read_json()
+            ok, message = self.store.leave_group(session["student_id"], bool(data.get("confirmed")))
+            return json_response(
+                HTTPStatus.OK if ok else HTTPStatus.BAD_REQUEST,
+                {"ok": ok, "message": message, "require_confirm": (not ok and "确认后才会执行" in message)},
+            )
+
+        if action == "groups/remove-member" and method == "POST":
+            session, error = self.require_student()
+            if error:
+                return error
+            data = self.read_json()
+            ok, message = self.store.leader_remove_member(
+                session["student_id"], int(data.get("student_id", 0))
+            )
+            return json_response(
+                HTTPStatus.OK if ok else HTTPStatus.BAD_REQUEST,
+                {"ok": ok, "message": message},
+            )
+
+        if action == "teacher/class" and method == "POST":
+            _, error = self.require_teacher()
+            if error:
+                return error
+            data = self.read_json()
+            ok, message = self.store.switch_class(str(data.get("class_name", "")))
+            return json_response(HTTPStatus.OK if ok else HTTPStatus.BAD_REQUEST, {"ok": ok, "message": message})
+
+        if action == "teacher/lock" and method == "POST":
+            _, error = self.require_teacher()
+            if error:
+                return error
+            data = self.read_json()
+            class_name = str(data.get("class_name", self.store.active_class()))
+            ok, message = self.store.set_locked(class_name, bool(data.get("locked")))
+            return json_response(HTTPStatus.OK if ok else HTTPStatus.BAD_REQUEST, {"ok": ok, "message": message})
+
+        if action == "teacher/create-group" and method == "POST":
+            _, error = self.require_teacher()
+            if error:
+                return error
+            data = self.read_json()
+            ok, message = self.store.teacher_create_group(
+                str(data.get("class_name", self.store.active_class())), data.get("name", "")
+            )
+            return json_response(HTTPStatus.OK if ok else HTTPStatus.BAD_REQUEST, {"ok": ok, "message": message})
+
+        if action == "teacher/rename-group" and method == "POST":
+            _, error = self.require_teacher()
+            if error:
+                return error
+            data = self.read_json()
+            ok, message = self.store.teacher_rename_group(int(data.get("group_id", 0)), data.get("name", ""))
+            return json_response(HTTPStatus.OK if ok else HTTPStatus.BAD_REQUEST, {"ok": ok, "message": message})
+
+        if action == "teacher/set-leader" and method == "POST":
+            _, error = self.require_teacher()
+            if error:
+                return error
+            data = self.read_json()
+            student_id = data.get("student_id")
+            ok, message = self.store.teacher_set_leader(
+                int(data.get("group_id", 0)), int(student_id) if student_id else None
+            )
+            return json_response(HTTPStatus.OK if ok else HTTPStatus.BAD_REQUEST, {"ok": ok, "message": message})
+
+        if action == "teacher/add-member" and method == "POST":
+            _, error = self.require_teacher()
+            if error:
+                return error
+            data = self.read_json()
+            ok, message = self.store.teacher_add_member(int(data.get("group_id", 0)), int(data.get("student_id", 0)))
+            return json_response(HTTPStatus.OK if ok else HTTPStatus.BAD_REQUEST, {"ok": ok, "message": message})
+
+        if action == "teacher/remove-member" and method == "POST":
+            _, error = self.require_teacher()
+            if error:
+                return error
+            data = self.read_json()
+            ok, message = self.store.teacher_remove_member(int(data.get("student_id", 0)))
+            return json_response(HTTPStatus.OK if ok else HTTPStatus.BAD_REQUEST, {"ok": ok, "message": message})
+
+        if action == "teacher/disband" and method == "POST":
+            _, error = self.require_teacher()
+            if error:
+                return error
+            data = self.read_json()
+            ok, message = self.store.teacher_disband_group(int(data.get("group_id", 0)))
+            return json_response(HTTPStatus.OK if ok else HTTPStatus.BAD_REQUEST, {"ok": ok, "message": message})
+
+        if action == "teacher/import" and method == "POST":
+            _, error = self.require_teacher()
+            if error:
+                return error
+            length = int(self.handler.headers.get("Content-Length", "0") or 0)
+            if length <= 0 or length > MAX_UPLOAD_BYTES:
+                return json_response(HTTPStatus.BAD_REQUEST, {"ok": False, "message": "Excel 文件大小无效"})
+            raw = self.handler.rfile.read(length)
+            temp_path = BASE_DIR / ".upload-roster.xlsx"
+            temp_path.write_bytes(raw)
+            try:
+                student_count, class_count = self.store.import_roster(temp_path)
+            finally:
+                temp_path.unlink(missing_ok=True)
+            return json_response(
+                HTTPStatus.OK,
+                {"ok": True, "message": f"导入成功：{student_count} 名学生，{class_count} 个班。所有原分组已重置。"},
+            )
+
+        if action == "teacher/export" and method == "GET":
+            _, error = self.require_teacher()
+            if error:
+                return error
+            query = urllib.parse.parse_qs(urllib.parse.urlparse(self.handler.path).query)
+            class_name = query.get("class", [None])[0]
+            if class_name:
+                class_name = urllib.parse.unquote(class_name)
+            content, filename = self.store.export_groups(class_name)
+
+            def send(handler):
+                handler.send_response(HTTPStatus.OK)
+                handler.send_header("Content-Type", "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet")
+                quoted = urllib.parse.quote(filename)
+                handler.send_header("Content-Disposition", f"attachment; filename*=UTF-8''{quoted}")
+                handler.send_header("Content-Length", str(len(content)))
+                handler.send_header("Cache-Control", "no-store")
+                handler.end_headers()
+                handler.wfile.write(content)
+
+            return send
+
+        return json_response(HTTPStatus.NOT_FOUND, {"ok": False, "message": "接口不存在"})
--- a/group_system/http/responses.py
+++ b/group_system/http/responses.py
@@ -0,0 +1,41 @@
+"""HTTP 响应和 Cookie 工具。"""
+
+from __future__ import annotations
+
+import json
+from http import HTTPStatus
+from http.server import BaseHTTPRequestHandler
+from typing import Any
+
+from group_system.config import SESSION_DAYS
+
+
+def json_response(
+    status: int | HTTPStatus,
+    payload: Any,
+    cookies: list[dict[str, Any]] | None = None,
+):
+    """Return a callable that serializes and sends a JSON response."""
+    def send(handler: BaseHTTPRequestHandler):
+        body = json.dumps(payload, ensure_ascii=False).encode("utf-8")
+        handler.send_response(int(status))
+        handler.send_header("Content-Type", "application/json; charset=utf-8")
+        handler.send_header("Cache-Control", "no-store")
+        handler.send_header("Content-Length", str(len(body)))
+        for cookie in cookies or []:
+            handler.send_header("Set-Cookie", cookie["value"])
+        handler.end_headers()
+        handler.wfile.write(body)
+
+    return send
+
+
+def make_session_cookie(token: str) -> str:
+    return (
+        f"GROUP_SESSION={token}; Path=/; HttpOnly; SameSite=Lax; "
+        f"Max-Age={SESSION_DAYS * 86400}"
+    )
+
+
+def clear_session_cookie() -> str:
+    return "GROUP_SESSION=; Path=/; HttpOnly; SameSite=Lax; Max-Age=0"
--- a/group_system/http/server.py
+++ b/group_system/http/server.py
@@ -0,0 +1,138 @@
+"""HTTP 服务器、静态路由和应用启动流程。"""
+
+from __future__ import annotations
+
+import http.server
+import logging
+import os
+import socket
+import urllib.parse
+from http import HTTPStatus
+from pathlib import Path
+
+from group_system.config import STATIC_DIR, XLSX_PATH
+from group_system.http.api import GroupRequestHandler
+from group_system.http.static_files import send_text, serve_file
+from group_system.storage.store import GroupStore
+
+LOG = logging.getLogger("group-system")
+
+
+class GroupHTTPServer(http.server.ThreadingHTTPServer):
+    """Carry the application store on the standard threading HTTP server."""
+
+    def __init__(self, address: tuple[str, int], store: GroupStore):
+        super().__init__(address, RequestHandler)
+        self.store = store
+
+
+class RequestHandler(http.server.BaseHTTPRequestHandler):
+    @property
+    def store(self) -> GroupStore:
+        return self.server.store  # type: ignore[attr-defined]
+
+    def do_GET(self) -> None:
+        route(self)
+
+    def do_POST(self) -> None:
+        route(self)
+
+    def do_HEAD(self) -> None:
+        route(self)
+
+    def log_message(self, format_string: str, *args) -> None:
+        LOG.info("%s - %s", self.address_string(), format_string % args)
+
+
+def route(handler: RequestHandler) -> None:
+    path = urllib.parse.urlparse(handler.path).path
+    if path.startswith("/api/"):
+        request = GroupRequestHandler(handler, handler.store)
+        result = request.handle_api(path[len("/api/"):], handler.command)
+        if callable(result):
+            result(handler)
+        return
+
+    if path in ("/", "/index.html", "/student"):
+        serve_file(handler, STATIC_DIR / "index.html")
+        return
+    if path in ("/teacher", "/admin"):
+        serve_file(handler, STATIC_DIR / "teacher.html")
+        return
+
+    static_root = STATIC_DIR.resolve()
+    safe_path = (static_root / urllib.parse.unquote(path).lstrip("/")).resolve()
+    try:
+        safe_path.relative_to(static_root)
+    except ValueError:
+        send_text(handler, HTTPStatus.NOT_FOUND, "Not Found")
+        return
+    serve_file(handler, safe_path)
+
+
+def local_ipv4_addresses() -> list[str]:
+    addresses: set[str] = set()
+    try:
+        host_name = socket.gethostname()
+        for item in socket.getaddrinfo(host_name, None, socket.AF_INET):
+            address = item[4][0]
+            if address != "127.0.0.1":
+                addresses.add(address)
+    except socket.gaierror:
+        pass
+
+    # A UDP connection does not send packets here, but reveals the default-route address.
+    try:
+        probe = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+        try:
+            probe.connect(("192.0.2.1", 9))
+            address = probe.getsockname()[0]
+            if address != "127.0.0.1":
+                addresses.add(address)
+        finally:
+            probe.close()
+    except OSError:
+        pass
+    return sorted(addresses)
+
+
+def bootstrap_store(store: GroupStore, xlsx_path: Path) -> None:
+    """Import the initial roster only when the database is still empty."""
+    if any(store.class_list()):
+        return
+    if not xlsx_path.exists():
+        LOG.warning("未找到 %s，请先通过教师后台上传学生名单", xlsx_path)
+        return
+    student_count, class_count = store.import_roster(xlsx_path)
+    LOG.info("已导入 %s： %d 名学生 / %d 个班", xlsx_path, student_count, class_count)
+
+
+def run(
+    store: GroupStore,
+    xlsx_path: Path = XLSX_PATH,
+    host: str | None = None,
+    port: int | None = None,
+) -> None:
+    bootstrap_store(store, xlsx_path)
+    host = host or os.environ.get("HOST", "0.0.0.0")
+    port = port if port is not None else int(os.environ.get("PORT", "8000"))
+    server = GroupHTTPServer((host, port), store)
+    LOG.info("学生分组系统已启动：http://0.0.0.0:%d", port)
+    addresses = local_ipv4_addresses()
+    if addresses:
+        for address in addresses:
+            LOG.info(
+                "学生入口：http://%s:%d/    教师入口：http://%s:%d/teacher",
+                address,
+                port,
+                address,
+                port,
+            )
+    else:
+        LOG.warning("未能自动获取局域网 IP，请在教师机上查看网络设置；端口：%d", port)
+    try:
+        server.serve_forever()
+    except KeyboardInterrupt:
+        LOG.info("服务停止")
+    finally:
+        server.server_close()
--- a/group_system/http/static_files.py
+++ b/group_system/http/static_files.py
@@ -0,0 +1,43 @@
+"""静态页面与资源文件服务。"""
+
+from __future__ import annotations
+
+from http import HTTPStatus
+from http.server import BaseHTTPRequestHandler
+from pathlib import Path
+
+from group_system.config import STATIC_DIR
+
+CONTENT_TYPES = {
+    ".html": "text/html; charset=utf-8",
+    ".htm": "text/html; charset=utf-8",
+    ".css": "text/css; charset=utf-8",
+    ".js": "text/javascript; charset=utf-8",
+    ".mjs": "text/javascript; charset=utf-8",
+    ".svg": "image/svg+xml",
+    ".png": "image/png",
+}
+
+
+def send_text(handler: BaseHTTPRequestHandler, status: int, text: str) -> None:
+    body = text.encode("utf-8")
+    handler.send_response(status)
+    handler.send_header("Content-Type", "text/plain; charset=utf-8")
+    handler.send_header("Content-Length", str(len(body)))
+    handler.end_headers()
+    handler.wfile.write(body)
+
+
+def serve_file(handler: BaseHTTPRequestHandler, path: Path) -> None:
+    path = path if path.is_absolute() else STATIC_DIR / path
+    if not path.is_file():
+        send_text(handler, HTTPStatus.NOT_FOUND, "Not Found")
+        return
+    content_type = CONTENT_TYPES.get(path.suffix.lower(), "application/octet-stream")
+    content = path.read_bytes()
+    handler.send_response(HTTPStatus.OK)
+    handler.send_header("Content-Type", content_type)
+    handler.send_header("Content-Length", str(len(content)))
+    handler.send_header("Cache-Control", "no-cache")
+    handler.end_headers()
+    handler.wfile.write(content)
--- a/group_system/security.py
+++ b/group_system/security.py
@@ -0,0 +1,26 @@
+"""密码散列与校验。"""
+
+from __future__ import annotations
+
+import hashlib
+import hmac
+import secrets
+
+
+def hash_password(password: str, salt: bytes | None = None) -> str:
+    salt = salt or secrets.token_bytes(16)
+    digest = hashlib.pbkdf2_hmac("sha256", password.encode("utf-8"), salt, 180_000)
+    return salt.hex() + "$" + digest.hex()
+
+
+def verify_password(password: str, stored: str | None) -> bool:
+    if not stored or "$" not in stored:
+        return False
+    try:
+        salt_hex, digest_hex = stored.split("$", 1)
+        salt = bytes.fromhex(salt_hex)
+        expected = bytes.fromhex(digest_hex)
+    except ValueError:
+        return False
+    actual = hashlib.pbkdf2_hmac("sha256", password.encode("utf-8"), salt, 180_000)
+    return hmac.compare_digest(actual, expected)
--- a/group_system/storage/init.py
+++ b/group_system/storage/init.py
@@ -0,0 +1 @@
+"""SQLite 存储层。"""
--- a/group_system/storage/accounts.py
+++ b/group_system/storage/accounts.py
@@ -0,0 +1,152 @@
+"""账号登录、会话和密码管理。"""
+
+from __future__ import annotations
+
+import hashlib
+import secrets
+import time
+from typing import Any
+
+from group_system.config import SESSION_DAYS, TEACHER_USER
+from group_system.security import hash_password, verify_password
+
+
+class AccountStoreMixin:
+
+    def create_session(self, role: str, username: str, student_id: int | None = None) -> str:
+        token = secrets.token_urlsafe(32)
+        token_hash = hashlib.sha256(token.encode()).hexdigest()
+        now = int(time.time())
+        with self.lock, self.connection:
+            self.connection.execute(
+                "INSERT INTO sessions(token_hash,role,username,student_id,created_at,expires_at) VALUES(?,?,?,?,?,?)",
+                (token_hash, role, username, student_id, now, now + SESSION_DAYS * 86400),
+            )
+            self.connection.execute(
+                "DELETE FROM sessions WHERE expires_at < ?", (now,)
+            )
+        return token
+
+    def get_session(self, token: str | None) -> dict[str, Any] | None:
+        if not token:
+            return None
+        token_hash = hashlib.sha256(token.encode()).hexdigest()
+        now = int(time.time())
+        with self.lock:
+            row = self.connection.execute(
+                """SELECT s.token_hash,s.role,s.username,s.student_id,s.expires_at,
+                          st.class_name,st.student_no,st.name,st.must_change_password
+                FROM sessions s LEFT JOIN students st ON st.id=s.student_id
+                WHERE s.token_hash=? AND s.expires_at>?""",
+                (token_hash, now),
+            ).fetchone()
+        if row is None:
+            return None
+        return dict(row)
+
+    def destroy_session(self, token: str | None) -> None:
+        if not token:
+            return
+        token_hash = hashlib.sha256(token.encode()).hexdigest()
+        with self.lock, self.connection:
+            self.connection.execute("DELETE FROM sessions WHERE token_hash=?", (token_hash,))
+
+    def login_student(self, student_no: str, password: str) -> tuple[dict[str, Any] | None, str]:
+        student_no = student_no.strip()
+        active = self.active_class()
+        with self.lock:
+            student = self.connection.execute(
+                "SELECT * FROM students WHERE student_no=?", (student_no,)
+            ).fetchone()
+        if student is None or not verify_password(password, student["password_hash"]):
+            return None, "学号或密码不正确"
+        if student["class_name"] != active:
+            return None, f"当前仅开放 {active} 班登录，{student['class_name']} 班暂不能登录"
+        token = self.create_session("student", student["student_no"], student["id"])
+        return {
+            "token": token,
+            "student": {
+                "id": student["id"],
+                "name": student["name"],
+                "student_no": student["student_no"],
+                "class_name": student["class_name"],
+                "must_change_password": bool(student["must_change_password"]),
+            },
+        }, "登录成功"
+
+    def login_teacher(self, username: str, password: str) -> tuple[dict[str, Any] | None, str]:
+        with self.lock:
+            expected_user = self.get_setting("teacher_username") or TEACHER_USER
+            expected_password = self.get_setting("teacher_password")
+        if username.strip() != expected_user or not verify_password(password, expected_password):
+            return None, "教师账号或密码不正确"
+        token = self.create_session("teacher", expected_user, None)
+        return {"token": token, "teacher": {"username": expected_user}}, "登录成功"
+
+    def change_teacher_password(
+        self, session: dict[str, Any], old_password: str, new_password: str
+    ) -> tuple[bool, str]:
+        if session.get("role") != "teacher":
+            return False, "教师会话无效"
+        old_password = old_password or ""
+        new_password = new_password or ""
+        if len(new_password) < 8:
+            return False, "新密码至少 8 位"
+        if new_password == old_password:
+            return False, "新密码不能与原密码相同"
+        with self.lock:
+            expected_user = self.get_setting("teacher_username") or TEACHER_USER
+            if session.get("username") != expected_user:
+                return False, "教师账号已变更，请重新登录"
+            stored_password = self.get_setting("teacher_password")
+            if not verify_password(old_password, stored_password):
+                return False, "原密码不正确"
+            self.set_setting("teacher_password", hash_password(new_password))
+        return True, "教师密码修改成功"
+
+    def change_student_password(
+        self, session: dict[str, Any], old_password: str, new_password: str
+    ) -> tuple[bool, str]:
+        student_id = session.get("student_id")
+        if not student_id:
+            return False, "学生会话无效"
+        old_password = old_password or ""
+        new_password = new_password or ""
+        if len(new_password) < 8:
+            return False, "新密码至少 8 位"
+        if new_password == old_password:
+            return False, "新密码不能与原密码相同"
+        with self.lock:
+            student = self.connection.execute(
+                "SELECT * FROM students WHERE id=?", (student_id,)
+            ).fetchone()
+            if student is None or not verify_password(old_password, student["password_hash"]):
+                return False, "原密码不正确"
+            if new_password == student["student_no"]:
+                return False, "新密码不能设置为学号"
+            with self.connection:
+                self.connection.execute(
+                    "UPDATE students SET password_hash=?, must_change_password=0 WHERE id=?",
+                    (hash_password(new_password), student_id),
+                )
+                token_hash = hashlib.sha256(session["_token"].encode()).hexdigest()
+                self.connection.execute(
+                    "DELETE FROM sessions WHERE student_id=? AND token_hash<>?",
+                    (student_id, token_hash),
+                )
+        return True, "密码修改成功"
+
+    def get_student(self, student_id: int) -> dict[str, Any] | None:
+        with self.lock:
+            row = self.connection.execute("SELECT * FROM students WHERE id=?", (student_id,)).fetchone()
+        return dict(row) if row else None
+
+    def student_membership(self, student_id: int) -> dict[str, Any] | None:
+        with self.lock:
+            row = self.connection.execute(
+                """SELECT m.group_id,g.name,g.class_name,g.leader_student_id
+                FROM group_members m JOIN groups g ON g.id=m.group_id
+                WHERE m.student_id=?""",
+                (student_id,),
+            ).fetchone()
+        return dict(row) if row else None
--- a/group_system/storage/admin.py
+++ b/group_system/storage/admin.py
@@ -0,0 +1,136 @@
+"""教师端班级和分组管理。"""
+
+from __future__ import annotations
+
+import sqlite3
+
+
+class TeacherGroupAdminMixin:
+
+    def switch_class(self, class_name: str) -> tuple[bool, str]:
+        with self.lock:
+            row = self.connection.execute(
+                "SELECT COUNT(*) AS n FROM students WHERE class_name=?", (class_name,)
+            ).fetchone()
+        if row["n"] == 0:
+            return False, "班级不存在"
+        self.set_setting("active_class", class_name)
+        return True, f"已切换到 {class_name} 班，仅该班学生可登录"
+
+    def set_locked(self, class_name: str, locked: bool) -> tuple[bool, str]:
+        with self.lock:
+            exists = self.connection.execute(
+                "SELECT 1 FROM students WHERE class_name=? LIMIT 1", (class_name,)
+            ).fetchone()
+        if not exists:
+            return False, "班级不存在"
+        with self.lock, self.connection:
+            self.connection.execute(
+                """INSERT INTO class_controls(class_name,locked) VALUES(?,?)
+                ON CONFLICT(class_name) DO UPDATE SET locked=excluded.locked""",
+                (class_name, int(locked)),
+            )
+        return True, ("已停止学生操作" if locked else "已恢复学生操作")
+
+    def _require_teacher_group(self, class_name: str) -> tuple[bool, str, sqlite3.Row | None]:
+        if not any(item["class_name"] == class_name for item in self.class_list()):
+            return False, "班级不存在", None
+        return True, "", None
+
+    def teacher_create_group(self, class_name: str, name: str) -> tuple[bool, str]:
+        if not self._require_teacher_group(class_name)[0]:
+            return False, "班级不存在"
+        name = name.strip() or "未命名小组"
+        with self.lock, self.connection:
+            self.connection.execute(
+                "INSERT INTO groups(class_name,name,leader_student_id) VALUES(?,?,NULL)",
+                (class_name, name),
+            )
+        return True, f"小组“{name}”已创建"
+
+    def teacher_rename_group(self, group_id: int, name: str) -> tuple[bool, str]:
+        name = name.strip()
+        if not name:
+            return False, "组名不能为空"
+        with self.lock, self.connection:
+            cursor = self.connection.execute("UPDATE groups SET name=? WHERE id=?", (name, group_id))
+            if cursor.rowcount == 0:
+                return False, "小组不存在"
+        return True, "组名已保存"
+
+    def teacher_set_leader(self, group_id: int, student_id: int | None) -> tuple[bool, str]:
+        with self.lock, self.connection:
+            group = self.connection.execute("SELECT * FROM groups WHERE id=?", (group_id,)).fetchone()
+            if group is None:
+                return False, "小组不存在"
+            if student_id is None:
+                self.connection.execute(
+                    "UPDATE groups SET leader_student_id=NULL WHERE id=?", (group_id,)
+                )
+                return True, "已取消组长"
+            member = self.connection.execute(
+                "SELECT 1 FROM group_members WHERE group_id=? AND student_id=?",
+                (group_id, student_id),
+            ).fetchone()
+            if not member:
+                return False, "组长必须是该组成员"
+            self.connection.execute(
+                "UPDATE groups SET leader_student_id=? WHERE id=?", (student_id, group_id)
+            )
+        return True, "组长已设置"
+
+    def teacher_add_member(self, group_id: int, student_id: int) -> tuple[bool, str]:
+        with self.lock, self.connection:
+            group = self.connection.execute("SELECT * FROM groups WHERE id=?", (group_id,)).fetchone()
+            student = self.connection.execute("SELECT * FROM students WHERE id=?", (student_id,)).fetchone()
+            if group is None or student is None:
+                return False, "小组或学生不存在"
+            if group["class_name"] != student["class_name"]:
+                return False, "不能跨班调整"
+            current_group = self.connection.execute(
+                "SELECT group_id FROM group_members WHERE student_id=?", (student_id,)
+            ).fetchone()
+            if current_group and current_group["group_id"] == group_id:
+                return False, "学生已在该组"
+            count = self.connection.execute(
+                "SELECT COUNT(*) AS n FROM group_members WHERE group_id=?", (group_id,)
+            ).fetchone()["n"]
+            group_limit = self.group_limit()
+            if count >= group_limit:
+                return False, f"该组已有 {group_limit} 人；请先移出一人"
+            if current_group:
+                self.connection.execute(
+                    "DELETE FROM group_members WHERE student_id=?", (student_id,)
+                )
+                self.connection.execute(
+                    "UPDATE groups SET leader_student_id=NULL WHERE id=? AND leader_student_id=?",
+                    (current_group["group_id"], student_id),
+                )
+            self.connection.execute(
+                "INSERT INTO group_members(group_id,student_id) VALUES(?,?)",
+                (group_id, student_id),
+            )
+        return True, "已加入小组"
+
+    def teacher_remove_member(self, student_id: int) -> tuple[bool, str]:
+        with self.lock, self.connection:
+            membership = self.connection.execute(
+                "SELECT * FROM group_members WHERE student_id=?", (student_id,)
+            ).fetchone()
+            if not membership:
+                return False, "学生当前未分组"
+            self.connection.execute(
+                "DELETE FROM group_members WHERE student_id=?", (student_id,)
+            )
+            self.connection.execute(
+                """UPDATE groups SET leader_student_id=NULL
+                WHERE leader_student_id=?""", (student_id,)
+            )
+        return True, "已移出小组"
+
+    def teacher_disband_group(self, group_id: int) -> tuple[bool, str]:
+        with self.lock, self.connection:
+            cursor = self.connection.execute("DELETE FROM groups WHERE id=?", (group_id,))
+            if cursor.rowcount == 0:
+                return False, "小组不存在"
+        return True, "小组已解散"
--- a/group_system/storage/database.py
+++ b/group_system/storage/database.py
@@ -0,0 +1,142 @@
+"""数据库连接、Schema 和系统级设置。"""
+
+from __future__ import annotations
+
+import sqlite3
+import threading
+from pathlib import Path
+from typing import Any
+
+from group_system.config import GROUP_LIMIT, TEACHER_PASSWORD, TEACHER_USER
+from group_system.security import hash_password
+
+
+class DatabaseCore:
+
+    def __init__(self, path: Path):
+        self.path = path
+        self.lock = threading.RLock()
+        self.connection = sqlite3.connect(str(path), check_same_thread=False)
+        self.connection.row_factory = sqlite3.Row
+        self.connection.execute("PRAGMA foreign_keys = ON")
+        self.init_database()
+
+    def init_database(self) -> None:
+        with self.lock, self.connection:
+            self.connection.executescript(
+                """
+                CREATE TABLE IF NOT EXISTS students (
+                    id INTEGER PRIMARY KEY AUTOINCREMENT,
+                    class_name TEXT NOT NULL,
+                    student_no TEXT NOT NULL UNIQUE,
+                    name TEXT NOT NULL,
+                    gender TEXT DEFAULT '',
+                    admission_no TEXT DEFAULT '',
+                    remark TEXT DEFAULT '',
+                    password_hash TEXT NOT NULL,
+                    must_change_password INTEGER NOT NULL DEFAULT 1
+                );
+                CREATE TABLE IF NOT EXISTS groups (
+                    id INTEGER PRIMARY KEY AUTOINCREMENT,
+                    class_name TEXT NOT NULL,
+                    name TEXT NOT NULL,
+                    leader_student_id INTEGER REFERENCES students(id) ON DELETE SET NULL,
+                    created_at TEXT NOT NULL DEFAULT CURRENT_TIMESTAMP
+                );
+                CREATE TABLE IF NOT EXISTS group_members (
+                    group_id INTEGER NOT NULL REFERENCES groups(id) ON DELETE CASCADE,
+                    student_id INTEGER NOT NULL UNIQUE REFERENCES students(id) ON DELETE CASCADE,
+                    joined_at TEXT NOT NULL DEFAULT CURRENT_TIMESTAMP
+                );
+                CREATE TABLE IF NOT EXISTS class_controls (
+                    class_name TEXT PRIMARY KEY,
+                    locked INTEGER NOT NULL DEFAULT 0
+                );
+                CREATE TABLE IF NOT EXISTS settings (
+                    key TEXT PRIMARY KEY,
+                    value TEXT NOT NULL
+                );
+                CREATE TABLE IF NOT EXISTS sessions (
+                    token_hash TEXT PRIMARY KEY,
+                    role TEXT NOT NULL,
+                    username TEXT NOT NULL,
+                    student_id INTEGER REFERENCES students(id) ON DELETE CASCADE,
+                    created_at INTEGER NOT NULL,
+                    expires_at INTEGER NOT NULL
+                );
+                """
+            )
+            self.connection.execute(
+                "INSERT OR IGNORE INTO settings(key,value) VALUES('active_class','1')"
+            )
+            self.connection.execute(
+                "INSERT OR IGNORE INTO settings(key,value) VALUES('teacher_username',?)",
+                (TEACHER_USER,),
+            )
+            self.connection.execute(
+                "INSERT OR IGNORE INTO settings(key,value) VALUES('teacher_password',?)",
+                (hash_password(TEACHER_PASSWORD),),
+            )
+            self.connection.execute(
+                "INSERT OR IGNORE INTO settings(key,value) VALUES('group_limit',?)",
+                (str(GROUP_LIMIT),),
+            )
+
+    def get_setting(self, key: str, conn: sqlite3.Connection | None = None) -> str | None:
+        conn = conn or self.connection
+        row = conn.execute("SELECT value FROM settings WHERE key=?", (key,)).fetchone()
+        return None if row is None else row["value"]
+
+    def set_setting(self, key: str, value: str) -> None:
+        with self.lock, self.connection:
+            self.connection.execute(
+                "INSERT INTO settings(key,value) VALUES(?,?) "
+                "ON CONFLICT(key) DO UPDATE SET value=excluded.value",
+                (key, value),
+            )
+
+    def class_list(self) -> list[dict[str, Any]]:
+        with self.lock:
+            rows = self.connection.execute(
+                """SELECT class_name, COUNT(*) AS student_count
+                FROM students GROUP BY class_name
+                ORDER BY CAST(class_name AS REAL), class_name"""
+            ).fetchall()
+            active = self.get_setting("active_class")
+            locked = {
+                row["class_name"]: bool(row["locked"])
+                for row in self.connection.execute("SELECT class_name,locked FROM class_controls")
+            }
+        return [
+            {
+                "class_name": row["class_name"],
+                "student_count": row["student_count"],
+                "locked": bool(locked.get(row["class_name"], False)),
+                "active": row["class_name"] == active,
+            }
+            for row in rows
+        ]
+
+    def active_class(self) -> str:
+        return self.get_setting("active_class") or ""
+
+    def group_limit(self) -> int:
+        value = self.get_setting("group_limit")
+        try:
+            limit = int(value or GROUP_LIMIT)
+        except ValueError:
+            limit = GROUP_LIMIT
+        return max(2, limit)
+
+    def set_group_limit(self, limit: int) -> tuple[bool, str]:
+        if limit < 2 or limit > 100:
+            return False, "分组上限必须在 2 到 100 人之间"
+        self.set_setting("group_limit", str(limit))
+        return True, f"分组上限已调整为 {limit} 人"
+
+    def is_locked(self, class_name: str) -> bool:
+        with self.lock:
+            row = self.connection.execute(
+                "SELECT locked FROM class_controls WHERE class_name=?", (class_name,)
+            ).fetchone()
+        return bool(row and row["locked"])
--- a/group_system/storage/export.py
+++ b/group_system/storage/export.py
@@ -0,0 +1,92 @@
+"""分组数据导出。"""
+
+from __future__ import annotations
+
+from group_system.xlsx_io import export_filename, write_xlsx
+
+
+class ExportStoreMixin:
+
+    def export_groups(self, class_name: str | None = None) -> tuple[bytes, str]:
+        with self.lock:
+            if class_name:
+                class_filter = "WHERE g.class_name=?"
+                params: tuple[Any, ...] = (class_name,)
+            else:
+                class_filter = ""
+                params = ()
+                class_name = None
+            group_rows = self.connection.execute(
+                f"""SELECT g.id,g.class_name,g.name,s1.student_no leader_no,s1.name leader_name
+                FROM groups g LEFT JOIN students s1 ON s1.id=g.leader_student_id
+                {class_filter} ORDER BY g.class_name,g.id""",
+                params,
+            ).fetchall()
+            member_rows = self.connection.execute(
+                f"""SELECT m.group_id,s.student_no,s.name,s.gender,s.class_name
+                FROM group_members m JOIN groups g ON g.id=m.group_id
+                JOIN students s ON s.id=m.student_id
+                {class_filter}
+                ORDER BY g.class_name,g.id,CASE WHEN s.id=g.leader_student_id THEN 0 ELSE 1 END,s.student_no""",
+                params,
+            ).fetchall()
+            ungrouped_rows = self.connection.execute(
+                f"""SELECT s.class_name,s.student_no,s.name,s.gender
+                FROM students s WHERE s.id NOT IN (SELECT student_id FROM group_members)
+                {'AND s.class_name=?' if class_name else ''}
+                ORDER BY s.class_name,s.student_no""",
+                ((class_name,) if class_name else ()),
+            ).fetchall()
+
+        by_group: dict[int, list[sqlite3.Row]] = {}
+        for row in member_rows:
+            by_group.setdefault(row["group_id"], []).append(row)
+        summary_headers = ["序号", "班级", "组名", "组内序号", "学号", "姓名", "性别", "是否组长"]
+        summary_records = []
+        row_number = 0
+        for group in group_rows:
+            for member_number, member in enumerate(by_group.get(group["id"], []), 1):
+                row_number += 1
+                summary_records.append(
+                    {
+                        "序号": row_number,
+                        "班级": member["class_name"],
+                        "组名": group["name"],
+                        "组内序号": member_number,
+                        "学号": member["student_no"],
+                        "姓名": member["name"],
+                        "性别": member["gender"],
+                        "是否组长": "是" if member["student_no"] == group["leader_no"] else "否",
+                    }
+                )
+        if not summary_records:
+            summary_records.append({
+                "序号": "", "班级": "", "组名": "暂无分组", "组内序号": "",
+                "学号": "", "姓名": "", "性别": "", "是否组长": "",
+            })
+
+        ungrouped_headers = ["序号", "班级", "学号", "姓名", "性别", "说明"]
+        ungrouped_records = [
+            {
+                "序号": index,
+                "班级": row["class_name"],
+                "学号": row["student_no"],
+                "姓名": row["name"],
+                "性别": row["gender"],
+                "说明": "未分组",
+            }
+            for index, row in enumerate(ungrouped_rows, 1)
+        ]
+        if not ungrouped_records:
+            ungrouped_records.append({
+                "序号": "", "班级": "", "学号": "", "姓名": "", "性别": "", "说明": "全部学生均已分组"
+            })
+
+        title = f"{class_name}班" if class_name else "全部班级"
+        xlsx = write_xlsx(
+            [
+                (f"{title}分组", summary_headers, summary_records),
+                ("未分组学生", ungrouped_headers, ungrouped_records),
+            ]
+        )
+        return xlsx, export_filename("学生分组", class_name)
--- a/group_system/storage/groups.py
+++ b/group_system/storage/groups.py
@@ -0,0 +1,195 @@
+"""学生端分组用例和班级快照查询。"""
+
+from __future__ import annotations
+
+from typing import Any
+
+
+class GroupOperationsMixin:
+
+    def class_snapshot(self, class_name: str) -> dict[str, Any]:
+        with self.lock:
+            groups = self.connection.execute(
+                """SELECT g.id,g.name,g.leader_student_id,g.created_at,
+                          s.student_no AS leader_student_no,s.name AS leader_name
+                FROM groups g LEFT JOIN students s ON s.id=g.leader_student_id
+                WHERE g.class_name=? ORDER BY g.id""",
+                (class_name,),
+            ).fetchall()
+            group_ids = [row["id"] for row in groups]
+            members: dict[int, list[dict[str, Any]]] = {row["id"]: [] for row in groups}
+            if group_ids:
+                placeholders = ",".join("?" for _ in group_ids)
+                member_rows = self.connection.execute(
+                    f"""SELECT m.group_id,st.id,st.student_no,st.name,st.gender,g.leader_student_id
+                    FROM group_members m JOIN students st ON st.id=m.student_id
+                    JOIN groups g ON g.id=m.group_id
+                    WHERE m.group_id IN ({placeholders})
+                    ORDER BY CASE WHEN st.id=g.leader_student_id THEN 0 ELSE 1 END,m.joined_at,st.student_no""",
+                    group_ids,
+                ).fetchall()
+                pending = [dict(row) for row in member_rows]
+                for member in pending:
+                    member["is_leader"] = member["id"] == member["leader_student_id"]
+                    member.pop("leader_student_id", None)
+                    members[member["group_id"]].append(member)
+
+            ungrouped_rows = self.connection.execute(
+                """SELECT id,student_no,name,gender FROM students
+                WHERE class_name=? AND id NOT IN (SELECT student_id FROM group_members)
+                ORDER BY student_no""",
+                (class_name,),
+            ).fetchall()
+            total = self.connection.execute(
+                "SELECT COUNT(*) AS n FROM students WHERE class_name=?", (class_name,)
+            ).fetchone()["n"]
+            grouped = self.connection.execute(
+                """SELECT COUNT(*) AS n FROM group_members m
+                JOIN students s ON s.id=m.student_id WHERE s.class_name=?""",
+                (class_name,),
+            ).fetchone()["n"]
+
+        group_data = []
+        for row in groups:
+            group_data.append(
+                {
+                    **dict(row),
+                    "locked": self.is_locked(class_name),
+                    "member_count": len(members[row["id"]]),
+                    "full": len(members[row["id"]]) >= self.group_limit(),
+                    "members": members[row["id"]],
+                }
+            )
+        return {
+            "class_name": class_name,
+            "locked": self.is_locked(class_name),
+            "group_limit": self.group_limit(),
+            "groups": group_data,
+            "ungrouped": [dict(row) for row in ungrouped_rows],
+            "statistics": {"total_students": total, "grouped_students": grouped, "group_count": len(group_data)},
+        }
+
+    def create_group(self, student_id: int, group_name: str) -> tuple[bool, str, int | None]:
+        student = self.get_student(student_id)
+        if student is None:
+            return False, "学生不存在", None
+        if self.is_locked(student["class_name"]):
+            return False, "老师已停止分组操作，当前只能查看", None
+        current = self.student_membership(student_id)
+        if current is not None:
+            return False, "你已加入其他组，不能创建组；请先退出当前组", None
+        if student["must_change_password"]:
+            return False, "首次登录必须先修改密码", None
+        group_name = group_name.strip() or student["name"]
+        with self.lock, self.connection:
+            count = self.connection.execute(
+                "SELECT COUNT(*) AS n FROM groups WHERE class_name=?", (student["class_name"],)
+            ).fetchone()["n"]
+            cursor = self.connection.execute(
+                "INSERT INTO groups(class_name,name,leader_student_id) VALUES(?,?,?)",
+                (student["class_name"], group_name, student_id),
+            )
+            group_id = int(cursor.lastrowid)
+            self.connection.execute(
+                "INSERT INTO group_members(group_id,student_id) VALUES(?,?)",
+                (group_id, student_id),
+            )
+        return True, f"“{group_name}”创建成功，你是组长", group_id
+
+    def join_group(self, student_id: int, group_id: int, confirmed: bool) -> tuple[bool, str]:
+        student = self.get_student(student_id)
+        if student is None:
+            return False, "学生不存在"
+        if student["must_change_password"]:
+            return False, "首次登录必须先修改密码"
+        if self.is_locked(student["class_name"]):
+            return False, "老师已停止分组操作，当前只能查看"
+        with self.lock:
+            group = self.connection.execute(
+                "SELECT * FROM groups WHERE id=?", (group_id,)
+            ).fetchone()
+            current = self.connection.execute(
+                """SELECT m.group_id,g.name,g.leader_student_id
+                FROM group_members m JOIN groups g ON g.id=m.group_id WHERE m.student_id=?""",
+                (student_id,),
+            ).fetchone()
+            if group is None:
+                return False, "目标小组不存在"
+            if group["class_name"] != student["class_name"]:
+                return False, "不能加入其他班级的小组"
+            if current and current["group_id"] == group_id:
+                return False, "你已经在这个组里"
+            member_count = self.connection.execute(
+                "SELECT COUNT(*) AS n FROM group_members WHERE group_id=?", (group_id,)
+            ).fetchone()["n"]
+            group_limit = self.group_limit()
+            if member_count >= group_limit:
+                return False, f"该组已有 {group_limit} 人，不能再加入新成员"
+            if current and not confirmed:
+                role = "组长，原组会被解散" if current["leader_student_id"] == student_id else "成员"
+                return False, f"你当前是“{current['name']}”的{role}。加入新组前必须退出原组；确认后才会执行。"
+
+        with self.lock, self.connection:
+            if current:
+                if current["leader_student_id"] == student_id:
+                    self.connection.execute("DELETE FROM groups WHERE id=?", (current["group_id"],))
+                else:
+                    self.connection.execute(
+                        "DELETE FROM group_members WHERE student_id=?", (student_id,)
+                    )
+            self.connection.execute(
+                "INSERT INTO group_members(group_id,student_id) VALUES(?,?)",
+                (group_id, student_id),
+            )
+        return True, "加入成功"
+
+    def leave_group(self, student_id: int, confirmed: bool) -> tuple[bool, str]:
+        if self.get_student(student_id) is None:
+            return False, "学生不存在"
+        current = self.student_membership(student_id)
+        if current is None:
+            return False, "你当前没有加入任何小组"
+        if self.is_locked(current["class_name"]):
+            return False, "老师已停止分组操作，当前只能查看"
+        is_leader = current["leader_student_id"] == student_id
+        if not confirmed:
+            if is_leader:
+                return False, "你是组长。退出时你创建的组将被解散，所有成员都会变为未分组；确认后才会执行。"
+            return False, "退出后可以再加入其他组；确认后才会执行。"
+        with self.lock, self.connection:
+            if is_leader:
+                self.connection.execute("DELETE FROM groups WHERE id=?", (current["group_id"],))
+            else:
+                self.connection.execute(
+                    "DELETE FROM group_members WHERE group_id=? AND student_id=?",
+                    (current["group_id"], student_id),
+                )
+        return True, "组长已解散小组" if is_leader else "已退出小组"
+
+    def leader_remove_member(self, leader_student_id: int, member_student_id: int) -> tuple[bool, str]:
+        with self.lock, self.connection:
+            leader_group = self.connection.execute(
+                """SELECT m.group_id,g.name,g.class_name,g.leader_student_id
+                FROM group_members m JOIN groups g ON g.id=m.group_id
+                WHERE m.student_id=?""",
+                (leader_student_id,),
+            ).fetchone()
+            if leader_group is None or leader_group["leader_student_id"] != leader_student_id:
+                return False, "只有组长可以移出组员"
+            if leader_student_id == member_student_id:
+                return False, "组长不能移出自己；如需退出请解散小组"
+            if self.is_locked(leader_group["class_name"]):
+                return False, "老师已停止分组操作，当前只能查看"
+            member = self.connection.execute(
+                """SELECT st.name
+                FROM group_members m JOIN students st ON st.id=m.student_id
+                WHERE m.student_id=? AND m.group_id=?""",
+                (member_student_id, leader_group["group_id"]),
+            ).fetchone()
+            if member is None:
+                return False, "该学生不在你的小组中"
+            self.connection.execute(
+                "DELETE FROM group_members WHERE student_id=? AND group_id=?",
+                (member_student_id, leader_group["group_id"]),
+            )
+        return True, f"已将 {member['name']} 移出小组"
--- a/group_system/storage/roster.py
+++ b/group_system/storage/roster.py
@@ -0,0 +1,69 @@
+"""学生名单导入。"""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+from group_system.security import hash_password
+from group_system.xlsx_io import read_xlsx_rows
+
+
+class RosterStoreMixin:
+
+    def import_roster(self, path: Path) -> tuple[int, int]:
+        rows = read_xlsx_rows(path)
+        students = []
+        errors = []
+        seen = set()
+        for index, row in enumerate(rows, 2):
+            student_no = str(row.get("学号", "")).strip()
+            name = str(row.get("姓名", "")).strip()
+            class_name = str(
+                row.get("班级", row.get("班别", row.get("行政班", "")))
+            ).strip()
+            gender = str(row.get("性别", "")).strip()
+            admission_no = str(row.get("录取编号", "")).strip()
+            remark = str(row.get("备注", "")).strip()
+            if not student_no or not name or not class_name:
+                errors.append(f"第 {index} 行：学号、姓名、班级均不能为空")
+                continue
+            if student_no in seen:
+                errors.append(f"第 {index} 行：学号 {student_no} 重复")
+                continue
+            seen.add(student_no)
+            students.append(
+                (class_name, student_no, name, gender, admission_no, remark)
+            )
+        if errors:
+            raise ValueError("；".join(errors[:8]))
+        if not students:
+            raise ValueError("Excel 中没有可导入的学生")
+
+        with self.lock, self.connection:
+            self.connection.executescript(
+                "DELETE FROM sessions; DELETE FROM group_members; DELETE FROM groups; DELETE FROM students;"
+            )
+            self.connection.executemany(
+                """INSERT INTO students
+                (class_name,student_no,name,gender,admission_no,remark,password_hash,must_change_password)
+                VALUES(?,?,?,?,?,?,?,1)""",
+                [
+                    (
+                        item[0],
+                        item[1],
+                        item[2],
+                        item[3],
+                        item[4],
+                        item[5],
+                        hash_password(item[1]),
+                    )
+                    for item in students
+                ],
+            )
+            active = self.get_setting("active_class", conn=self.connection) or students[0][0]
+            if not any(item[0] == active for item in students):
+                active = students[0][0]
+                self.connection.execute(
+                    "UPDATE settings SET value=? WHERE key='active_class'", (active,)
+                )
+        return len(students), len({item[0] for item in students})
--- a/group_system/storage/store.py
+++ b/group_system/storage/store.py
@@ -0,0 +1,23 @@
+"""GroupStore 组合各个存储模块，作为兼容旧代码的门面。"""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+from group_system.storage.accounts import AccountStoreMixin
+from group_system.storage.admin import TeacherGroupAdminMixin
+from group_system.storage.database import DatabaseCore
+from group_system.storage.export import ExportStoreMixin
+from group_system.storage.groups import GroupOperationsMixin
+from group_system.storage.roster import RosterStoreMixin
+
+
+class GroupStore(
+    DatabaseCore,
+    RosterStoreMixin,
+    AccountStoreMixin,
+    GroupOperationsMixin,
+    TeacherGroupAdminMixin,
+    ExportStoreMixin,
+):
+    """封装所有 SQLite 持久化操作。HTTP 层只依赖这个门面。"""
--- a/group_system/xlsx_io.py
+++ b/group_system/xlsx_io.py
@@ -0,0 +1,242 @@
+#!/usr/bin/env python3
+"""Minimal XLSX reader/writer using only the Python standard library."""
+
+from __future__ import annotations
+
+import re
+from datetime import datetime
+from pathlib import Path
+from xml.etree import ElementTree as ET
+from zipfile import ZIP_DEFLATED, ZipFile
+
+
+MAIN_NS = "http://schemas.openxmlformats.org/spreadsheetml/2006/main"
+REL_NS = "http://schemas.openxmlformats.org/officeDocument/2006/relationships"
+PKG_REL_NS = "http://schemas.openxmlformats.org/package/2006/relationships"
+NS = {"m": MAIN_NS, "r": REL_NS, "p": PKG_REL_NS}
+
+
+def _column_number(cell_ref: str) -> int:
+    letters = re.match(r"([A-Z]+)", cell_ref.upper())
+    if not letters:
+        return 0
+    value = 0
+    for letter in letters.group(1):
+        value = value * 26 + ord(letter) - 64
+    return value
+
+
+def _column_letter(number: int) -> str:
+    result = ""
+    while number:
+        number, remainder = divmod(number - 1, 26)
+        result = chr(65 + remainder) + result
+    return result
+
+
+def _shared_strings(archive: ZipFile) -> list[str]:
+    if "xl/sharedStrings.xml" not in archive.namelist():
+        return []
+    root = ET.fromstring(archive.read("xl/sharedStrings.xml"))
+    values = []
+    for item in root.findall("m:si", NS):
+        values.append("".join(node.text or "" for node in item.iter(f"{{{MAIN_NS}}}t")))
+    return values
+
+
+def _relationships(archive: ZipFile) -> dict[str, str]:
+    root = ET.fromstring(archive.read("xl/_rels/workbook.xml.rels"))
+    return {item.attrib["Id"]: item.attrib["Target"] for item in root}
+
+
+def _cell_value(cell, shared: list[str]) -> str:
+    cell_type = cell.attrib.get("t")
+    inline = cell.find("m:is", NS)
+    if cell_type == "inlineStr" and inline is not None:
+        return "".join(node.text or "" for node in inline.iter(f"{{{MAIN_NS}}}t")).strip()
+    value_node = cell.find("m:v", NS)
+    raw = "" if value_node is None else (value_node.text or "")
+    if cell_type == "s" and raw:
+        return shared[int(raw)].strip()
+    return raw.strip()
+
+
+def read_xlsx_rows(path: str | Path) -> list[dict[str, str]]:
+    """Read the first worksheet as dictionaries keyed by header text."""
+    path = Path(path)
+    with ZipFile(path, "r") as archive:
+        shared = _shared_strings(archive)
+        relationships = _relationships(archive)
+        workbook = ET.fromstring(archive.read("xl/workbook.xml"))
+        sheets = workbook.findall("m:sheets/m:sheet", NS)
+        if not sheets:
+            raise ValueError("Excel 文件中没有工作表")
+        relationship_id = sheets[0].attrib[f"{{{REL_NS}}}id"]
+        target = relationships[relationship_id].lstrip("/")
+        if not target.startswith("xl/"):
+            target = "xl/" + target
+        worksheet = ET.fromstring(archive.read(target))
+
+    rows: list[dict[int, str]] = []
+    for row in worksheet.findall("m:sheetData/m:row", NS):
+        values: dict[int, str] = {}
+        for cell in row.findall("m:c", NS):
+            number = _column_number(cell.attrib.get("r", "A1"))
+            value = _cell_value(cell, shared)
+            if value != "":
+                values[number] = value
+        rows.append(values)
+
+    header_row_index = -1
+    for index, values in enumerate(rows[:20]):
+        texts = set(values.values())
+        if "学号" in texts and "姓名" in texts:
+            header_row_index = index
+            break
+    if header_row_index < 0:
+        raise ValueError("Excel 中必须包含“学号”和“姓名”表头")
+
+    headers = rows[header_row_index]
+    result: list[dict[str, str]] = []
+    for values in rows[header_row_index + 1:]:
+        row = {headers.get(number, f"列{number}"): value for number, value in values.items()}
+        if any(str(value).strip() for value in row.values()):
+            result.append(row)
+    return result
+
+
+def _xml_escape(value: object) -> str:
+    return (
+        str(value)
+        .replace("&", "&amp;")
+        .replace("<", "&lt;")
+        .replace(">", "&gt;")
+        .replace('"', "&quot;")
+    )
+
+
+def _sheet_xml(headers: list[str], records: list[dict[str, object]]) -> str:
+    all_headers = list(headers)
+    all_records = list(records)
+    row_xml: list[str] = []
+    header_cells = []
+    for column_number, header in enumerate(all_headers, 1):
+        reference = f"{_column_letter(column_number)}1"
+        header_cells.append(
+            f'<c r="{reference}" t="inlineStr"><is><t>{_xml_escape(header)}</t></is></c>'
+        )
+    row_xml.append(f'<row r="1">{"".join(header_cells)}</row>')
+
+    for row_number, record in enumerate(all_records, 2):
+        cells = []
+        for column_number, header in enumerate(all_headers, 1):
+            value = record.get(header, "")
+            reference = f"{_column_letter(column_number)}{row_number}"
+            if isinstance(value, bool):
+                cells.append(f'<c r="{reference}" t="inlineStr"><is><t>{_xml_escape("是" if value else "否")}</t></is></c>')
+            elif isinstance(value, (int, float)) and not isinstance(value, bool):
+                cells.append(f'<c r="{reference}"><v>{value}</v></c>')
+            else:
+                text = "" if value is None else str(value)
+                preserve = ' xml:space="preserve"' if text != text.strip() else ""
+                cells.append(
+                    f'<c r="{reference}" t="inlineStr"><is><t{preserve}>{_xml_escape(text)}</t></is></c>'
+                )
+        row_xml.append(f'<row r="{row_number}">{"".join(cells)}</row>')
+
+    column_xml = []
+    for number in range(1, len(all_headers) + 1):
+        column_xml.append(f'<col min="{number}" max="{number}" width="18" customWidth="1"/>')
+
+    return f'''<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<worksheet xmlns="{MAIN_NS}">
+<sheetViews><sheetView workbookViewId="0"/></sheetViews>
+<cols>{"".join(column_xml)}</cols>
+<sheetData>{"".join(row_xml)}</sheetData>
+</worksheet>'''
+
+
+def write_xlsx(sheets: list[tuple[str, list[str], list[dict[str, object]]]]) -> bytes:
+    """Create a valid XLSX in memory. Each item is (sheet name, headers, records)."""
+    import posixpath
+
+    used_names = set()
+    safe_names = []
+    for index, (name, _, _) in enumerate(sheets, 1):
+        clean = re.sub(r"[\\/?*\\[\\]:]", "-", name).strip() or f"Sheet{index}"
+        clean = clean[:31]
+        candidate = clean
+        suffix = 2
+        while candidate.lower() in used_names:
+            tail = f"-{suffix}"
+            candidate = clean[: 31 - len(tail)] + tail
+            suffix += 1
+        used_names.add(candidate.lower())
+        safe_names.append(candidate)
+
+    sheet_entries = []
+    workbook_entries = []
+    worksheet_files = []
+    for index, name in enumerate(safe_names, 1):
+        filename = f"xl/worksheets/sheet{index}.xml"
+        worksheet_files.append((filename, _sheet_xml(sheets[index - 1][1], sheets[index - 1][2])))
+        sheet_entries.append(
+            f'<sheet name="{_xml_escape(name)}" sheetId="{index}" '
+            f'r:id="rId{index}"/>'
+        )
+        workbook_entries.append(
+            f'<Relationship Id="rId{index}" '
+            f'Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/worksheet" '
+            f'Target="worksheets/sheet{index}.xml"/>'
+        )
+    style_relationship_id = len(sheets) + 1
+
+    content_overrides = "".join(
+        f'<Override PartName="/xl/worksheets/sheet{index}.xml" '
+        'ContentType="application/vnd.openxmlformats-officedocument.spreadsheetml.worksheet+xml"/>'
+        for index in range(1, len(sheets) + 1)
+    )
+
+    files = {
+        "[Content_Types].xml": f'''<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<Types xmlns="http://schemas.openxmlformats.org/package/2006/content-types">
+<Default Extension="rels" ContentType="application/vnd.openxmlformats-package.relationships+xml"/>
+<Default Extension="xml" ContentType="application/xml"/>
+<Override PartName="/xl/workbook.xml" ContentType="application/vnd.openxmlformats-officedocument.spreadsheetml.sheet.main+xml"/>
+<Override PartName="/xl/styles.xml" ContentType="application/vnd.openxmlformats-officedocument.spreadsheetml.styles+xml"/>{content_overrides}
+</Types>''',
+        "_rels/.rels": '''<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships">
+<Relationship Id="rId1" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/officeDocument" Target="xl/workbook.xml"/>
+</Relationships>''',
+        "xl/workbook.xml": f'''<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<workbook xmlns="{MAIN_NS}" xmlns:r="{REL_NS}">
+<sheets>{"".join(sheet_entries)}</sheets>
+</workbook>''',
+        "xl/_rels/workbook.xml.rels": f'''<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships">{"".join(workbook_entries)}
+<Relationship Id="rId{style_relationship_id}" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/styles" Target="styles.xml"/>
+</Relationships>''',
+        "xl/styles.xml": '''<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<styleSheet xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main">
+<fonts count="2"><font><sz val="11"/><name val="Calibri"/></font><font><b/><sz val="11"/><name val="Calibri"/></font></fonts>
+<fills count="2"><fill><patternFill patternType="none"/></fill><fill><patternFill patternType="gray125"/></fill></fills>
+<borders count="1"><border/></borders>
+<cellStyleXfs count="1"><xf numFmtId="0" fontId="0" fillId="0" borderId="0"/></cellStyleXfs>
+<cellXfs count="2"><xf numFmtId="0" fontId="0" fillId="0" borderId="0" xfId="0"/><xf numFmtId="0" fontId="1" fillId="0" borderId="0" xfId="0" applyFont="1"/></cellXfs>
+</styleSheet>''',
+    }
+    files.update(worksheet_files)
+
+    import io
+    output = io.BytesIO()
+    with ZipFile(output, "w", ZIP_DEFLATED) as archive:
+        for filename, content in files.items():
+            archive.writestr(filename, content.encode("utf-8"))
+    return output.getvalue()
+
+
+def export_filename(prefix: str, class_name: str | None = None) -> str:
+    timestamp = datetime.now().strftime("%Y%m%d-%H%M%S")
+    suffix = f"-{class_name}班" if class_name else ""
+    return f"{prefix}{suffix}-{timestamp}.xlsx"
--- a/xlsxio.py
+++ b/xlsxio.py
@@ -1,242 +1,5 @@
-#!/usr/bin/env python3
-"""Minimal XLSX reader/writer using only the Python standard library."""
+"""Compatibility import facade for the original xlsxio module."""

-from __future__ import annotations
+from group_system.xlsx_io import export_filename, read_xlsx_rows, write_xlsx

-import re
-from datetime import datetime
-from pathlib import Path
-from xml.etree import ElementTree as ET
-from zipfile import ZIP_DEFLATED, ZipFile
-
-
-MAIN_NS = "http://schemas.openxmlformats.org/spreadsheetml/2006/main"
-REL_NS = "http://schemas.openxmlformats.org/officeDocument/2006/relationships"
-PKG_REL_NS = "http://schemas.openxmlformats.org/package/2006/relationships"
-NS = {"m": MAIN_NS, "r": REL_NS, "p": PKG_REL_NS}
-
-
-def _column_number(cell_ref: str) -> int:
-    letters = re.match(r"([A-Z]+)", cell_ref.upper())
-    if not letters:
-        return 0
-    value = 0
-    for letter in letters.group(1):
-        value = value * 26 + ord(letter) - 64
-    return value
-
-
-def _column_letter(number: int) -> str:
-    result = ""
-    while number:
-        number, remainder = divmod(number - 1, 26)
-        result = chr(65 + remainder) + result
-    return result
-
-
-def _shared_strings(archive: ZipFile) -> list[str]:
-    if "xl/sharedStrings.xml" not in archive.namelist():
-        return []
-    root = ET.fromstring(archive.read("xl/sharedStrings.xml"))
-    values = []
-    for item in root.findall("m:si", NS):
-        values.append("".join(node.text or "" for node in item.iter(f"{{{MAIN_NS}}}t")))
-    return values
-
-
-def _relationships(archive: ZipFile) -> dict[str, str]:
-    root = ET.fromstring(archive.read("xl/_rels/workbook.xml.rels"))
-    return {item.attrib["Id"]: item.attrib["Target"] for item in root}
-
-
-def _cell_value(cell, shared: list[str]) -> str:
-    cell_type = cell.attrib.get("t")
-    inline = cell.find("m:is", NS)
-    if cell_type == "inlineStr" and inline is not None:
-        return "".join(node.text or "" for node in inline.iter(f"{{{MAIN_NS}}}t")).strip()
-    value_node = cell.find("m:v", NS)
-    raw = "" if value_node is None else (value_node.text or "")
-    if cell_type == "s" and raw:
-        return shared[int(raw)].strip()
-    return raw.strip()
-
-
-def read_xlsx_rows(path: str | Path) -> list[dict[str, str]]:
-    """Read the first worksheet as dictionaries keyed by header text."""
-    path = Path(path)
-    with ZipFile(path, "r") as archive:
-        shared = _shared_strings(archive)
-        relationships = _relationships(archive)
-        workbook = ET.fromstring(archive.read("xl/workbook.xml"))
-        sheets = workbook.findall("m:sheets/m:sheet", NS)
-        if not sheets:
-            raise ValueError("Excel 文件中没有工作表")
-        relationship_id = sheets[0].attrib[f"{{{REL_NS}}}id"]
-        target = relationships[relationship_id].lstrip("/")
-        if not target.startswith("xl/"):
-            target = "xl/" + target
-        worksheet = ET.fromstring(archive.read(target))
-
-    rows: list[dict[int, str]] = []
-    for row in worksheet.findall("m:sheetData/m:row", NS):
-        values: dict[int, str] = {}
-        for cell in row.findall("m:c", NS):
-            number = _column_number(cell.attrib.get("r", "A1"))
-            value = _cell_value(cell, shared)
-            if value != "":
-                values[number] = value
-        rows.append(values)
-
-    header_row_index = -1
-    for index, values in enumerate(rows[:20]):
-        texts = set(values.values())
-        if "学号" in texts and "姓名" in texts:
-            header_row_index = index
-            break
-    if header_row_index < 0:
-        raise ValueError("Excel 中必须包含“学号”和“姓名”表头")
-
-    headers = rows[header_row_index]
-    result: list[dict[str, str]] = []
-    for values in rows[header_row_index + 1:]:
-        row = {headers.get(number, f"列{number}"): value for number, value in values.items()}
-        if any(str(value).strip() for value in row.values()):
-            result.append(row)
-    return result
-
-
-def _xml_escape(value: object) -> str:
-    return (
-        str(value)
-        .replace("&", "&amp;")
-        .replace("<", "&lt;")
-        .replace(">", "&gt;")
-        .replace('"', "&quot;")
-    )
-
-
-def _sheet_xml(headers: list[str], records: list[dict[str, object]]) -> str:
-    all_headers = list(headers)
-    all_records = list(records)
-    row_xml: list[str] = []
-    header_cells = []
-    for column_number, header in enumerate(all_headers, 1):
-        reference = f"{_column_letter(column_number)}1"
-        header_cells.append(
-            f'<c r="{reference}" t="inlineStr"><is><t>{_xml_escape(header)}</t></is></c>'
-        )
-    row_xml.append(f'<row r="1">{"".join(header_cells)}</row>')
-
-    for row_number, record in enumerate(all_records, 2):
-        cells = []
-        for column_number, header in enumerate(all_headers, 1):
-            value = record.get(header, "")
-            reference = f"{_column_letter(column_number)}{row_number}"
-            if isinstance(value, bool):
-                cells.append(f'<c r="{reference}" t="inlineStr"><is><t>{_xml_escape("是" if value else "否")}</t></is></c>')
-            elif isinstance(value, (int, float)) and not isinstance(value, bool):
-                cells.append(f'<c r="{reference}"><v>{value}</v></c>')
-            else:
-                text = "" if value is None else str(value)
-                preserve = ' xml:space="preserve"' if text != text.strip() else ""
-                cells.append(
-                    f'<c r="{reference}" t="inlineStr"><is><t{preserve}>{_xml_escape(text)}</t></is></c>'
-                )
-        row_xml.append(f'<row r="{row_number}">{"".join(cells)}</row>')
-
-    column_xml = []
-    for number in range(1, len(all_headers) + 1):
-        column_xml.append(f'<col min="{number}" max="{number}" width="18" customWidth="1"/>')
-
-    return f'''<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
-<worksheet xmlns="{MAIN_NS}">
-<sheetViews><sheetView workbookViewId="0"/></sheetViews>
-<cols>{"".join(column_xml)}</cols>
-<sheetData>{"".join(row_xml)}</sheetData>
-</worksheet>'''
-
-
-def write_xlsx(sheets: list[tuple[str, list[str], list[dict[str, object]]]]) -> bytes:
-    """Create a valid XLSX in memory. Each item is (sheet name, headers, records)."""
-    import posixpath
-
-    used_names = set()
-    safe_names = []
-    for index, (name, _, _) in enumerate(sheets, 1):
-        clean = re.sub(r"[\\/?*\\[\\]:]", "-", name).strip() or f"Sheet{index}"
-        clean = clean[:31]
-        candidate = clean
-        suffix = 2
-        while candidate.lower() in used_names:
-            tail = f"-{suffix}"
-            candidate = clean[: 31 - len(tail)] + tail
-            suffix += 1
-        used_names.add(candidate.lower())
-        safe_names.append(candidate)
-
-    sheet_entries = []
-    workbook_entries = []
-    worksheet_files = []
-    for index, name in enumerate(safe_names, 1):
-        filename = f"xl/worksheets/sheet{index}.xml"
-        worksheet_files.append((filename, _sheet_xml(sheets[index - 1][1], sheets[index - 1][2])))
-        sheet_entries.append(
-            f'<sheet name="{_xml_escape(name)}" sheetId="{index}" '
-            f'r:id="rId{index}"/>'
-        )
-        workbook_entries.append(
-            f'<Relationship Id="rId{index}" '
-            f'Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/worksheet" '
-            f'Target="worksheets/sheet{index}.xml"/>'
-        )
-    style_relationship_id = len(sheets) + 1
-
-    content_overrides = "".join(
-        f'<Override PartName="/xl/worksheets/sheet{index}.xml" '
-        'ContentType="application/vnd.openxmlformats-officedocument.spreadsheetml.worksheet+xml"/>'
-        for index in range(1, len(sheets) + 1)
-    )
-
-    files = {
-        "[Content_Types].xml": f'''<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
-<Types xmlns="http://schemas.openxmlformats.org/package/2006/content-types">
-<Default Extension="rels" ContentType="application/vnd.openxmlformats-package.relationships+xml"/>
-<Default Extension="xml" ContentType="application/xml"/>
-<Override PartName="/xl/workbook.xml" ContentType="application/vnd.openxmlformats-officedocument.spreadsheetml.sheet.main+xml"/>
-<Override PartName="/xl/styles.xml" ContentType="application/vnd.openxmlformats-officedocument.spreadsheetml.styles+xml"/>{content_overrides}
-</Types>''',
-        "_rels/.rels": '''<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
-<Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships">
-<Relationship Id="rId1" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/officeDocument" Target="xl/workbook.xml"/>
-</Relationships>''',
-        "xl/workbook.xml": f'''<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
-<workbook xmlns="{MAIN_NS}" xmlns:r="{REL_NS}">
-<sheets>{"".join(sheet_entries)}</sheets>
-</workbook>''',
-        "xl/_rels/workbook.xml.rels": f'''<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
-<Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships">{"".join(workbook_entries)}
-<Relationship Id="rId{style_relationship_id}" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/styles" Target="styles.xml"/>
-</Relationships>''',
-        "xl/styles.xml": '''<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
-<styleSheet xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main">
-<fonts count="2"><font><sz val="11"/><name val="Calibri"/></font><font><b/><sz val="11"/><name val="Calibri"/></font></fonts>
-<fills count="2"><fill><patternFill patternType="none"/></fill><fill><patternFill patternType="gray125"/></fill></fills>
-<borders count="1"><border/></borders>
-<cellStyleXfs count="1"><xf numFmtId="0" fontId="0" fillId="0" borderId="0"/></cellStyleXfs>
-<cellXfs count="2"><xf numFmtId="0" fontId="0" fillId="0" borderId="0" xfId="0"/><xf numFmtId="0" fontId="1" fillId="0" borderId="0" xfId="0" applyFont="1"/></cellXfs>
-</styleSheet>''',
-    }
-    files.update(worksheet_files)
-
-    import io
-    output = io.BytesIO()
-    with ZipFile(output, "w", ZIP_DEFLATED) as archive:
-        for filename, content in files.items():
-            archive.writestr(filename, content.encode("utf-8"))
-    return output.getvalue()
-
-
-def export_filename(prefix: str, class_name: str | None = None) -> str:
-    timestamp = datetime.now().strftime("%Y%m%d-%H%M%S")
-    suffix = f"-{class_name}班" if class_name else ""
-    return f"{prefix}{suffix}-{timestamp}.xlsx"
+__all__ = ["export_filename", "read_xlsx_rows", "write_xlsx"]