from __future__ import annotations

from io import BytesIO

from openpyxl import Workbook
from openpyxl.styles import Alignment, Font, PatternFill, Border, Side


def build_export(result: dict) -> bytes:
    wb = Workbook()
    thin = Border(
        left=Side(style="thin", color="D9D1C3"),
        right=Side(style="thin", color="D9D1C3"),
        top=Side(style="thin", color="D9D1C3"),
        bottom=Side(style="thin", color="D9D1C3"),
    )
    head = PatternFill("solid", fgColor="12233D")
    head_font = Font(color="F4EFE6", bold=True)
    wrap = Alignment(wrap_text=True, vertical="center")

    first = True
    for g in result["groups"]:
        for t in g["targets"]:
            title = f"{g['group']}-{t['name']}"[:31]
            ws = wb.active if first else wb.create_sheet(title)
            if first:
                ws.title = title
                first = False
            ws.append(
                ["班级", "测算人数", "最近一次在线", "滤波期望", "下达指标", "保底下界", "冲刺上界", "相对最近一次"]
            )
            for cell in ws[1]:
                cell.fill = head
                cell.font = head_font
            for row in t["classes"]:
                ws.append(
                    [
                        row["class_name"],
                        row["n"],
                        row["current"],
                        row["expected"],
                        row["assigned"],
                        row["floor"],
                        row["stretch"],
                        row["delta"],
                    ]
                )
            ws.append([])
            ws.append(["说明：下达指标为预估中位水平，班级应努力超越该人数。保底/冲刺来自模拟分布的约20%/80%分位。"])

    ws = wb.create_sheet("学生明细")
    exams = result["exams"]
    headers = ["学号", "姓名", "班级", "方向", "学籍", "选科"]
    headers += [f"{e}-排名" for e in exams]
    # collect target names
    tcols = []
    for g in result["groups"]:
        for t in g["targets"]:
            tcols.append((g["group"], t["id"], f"{g['group']}-{t['name']}概率"))
    headers += [c[2] for c in tcols]
    headers += ["滤波水平", "预测方差"]
    ws.append(headers)
    for cell in ws[1]:
        cell.fill = head
        cell.font = head_font
        cell.alignment = wrap
    for s in result["students"]:
        row = [s["sid"], s["name"], s["class_name"], s["group"], s.get("status") or "", s.get("subjects") or ""]
        ranks = s.get("ranks") or []
        for i, _e in enumerate(exams):
            row.append(ranks[i] if i < len(ranks) else None)
        for gname, tid, _ in tcols:
            if s["group"] == gname:
                row.append((s.get("probs") or {}).get(tid))
            else:
                row.append(None)
        row.append(s.get("pred_mean"))
        row.append(s.get("pred_var"))
        ws.append(row)

    bio = BytesIO()
    wb.save(bio)
    return bio.getvalue()