import SwiftUI
import UIKit
import UniformTypeIdentifiers

struct RootView: View {
    @StateObject private var auth = AuthManager()
    @StateObject private var controller = PlayerController()
    @StateObject private var catalogVM = CatalogViewModel()
    @State private var activeModule: Module = .course
    @State private var continuousPlayback = false
    @State private var showImporter = false
    @State private var showFullscreenPlayer = false
    @State private var courses: [Course] = []
    @State private var currentCourse: Course?
    @State private var courseStatusText = "正在同步"
    @State private var showCourseGuardToast = false

    enum Module {
        case course
        case train
        case test
        case mine
    }

    var body: some View {
        if auth.isLoggedIn {
            mainContent
        } else {
            AuthView(auth: auth) {
                Task { await loadCourses() }
            }
        }
    }

    private var mainContent: some View {
        ZStack {
            Theme.background.ignoresSafeArea()
            VStack(spacing: 0) {
                header
                moduleTabs
                switch activeModule {
                case .course:
                    coursePage
                case .train:
                    TrainingView(
                        controller: controller,
                        catalogVM: catalogVM,
                        continuousPlayback: $continuousPlayback,
                        onFullscreen: enterFullscreen
                    )
                case .test:
                    TestView(controller: controller, onFullscreen: enterFullscreen)
                case .mine:
                    minePage
                }
            }

            if showCourseGuardToast {
                VStack {
                    Spacer()
                    Text("请先选择课程")
                        .font(.system(size: 14))
                        .foregroundColor(.white)
                        .padding(.horizontal, 20)
                        .padding(.vertical, 12)
                        .background(Theme.overlay)
                        .clipShape(RoundedRectangle(cornerRadius: 8))
                    Spacer().frame(height: 80)
                }
            }
        }
        .preferredColorScheme(.dark)
        .onAppear {
            if auth.isLoggedIn && courses.isEmpty {
                Task { await loadCourses() }
            }
        }
        .onChange(of: activeModule) { module in
            if module == .train {
                controller.setContinuousPlayback(continuousPlayback)
            } else {
                controller.setContinuousPlayback(true)
            }
        }
        .fileImporter(
            isPresented: $showImporter,
            allowedContentTypes: [.movie],
            allowsMultipleSelection: false
        ) { result in
            if case .success(let urls) = result, let url = urls.first {
                Task {
                    await catalogVM.importVideo(at: url)
                }
            }
        }
        .fullScreenCover(isPresented: $showFullscreenPlayer) {
            FullscreenPlayerView(controller: controller) {
                exitFullscreen()
            }
            .onAppear(perform: enterFullscreen)
        }
    }

    private var header: some View {
        HStack(spacing: 0) {
            VStack(alignment: .leading, spacing: 2) {
                Text("八哥口语")
                    .font(.system(size: 32, weight: .bold))
                    .foregroundColor(.white)
                Text(auth.nickname.isEmpty ? "外语跟读训练神器" : "你好，\(auth.nickname)")
                    .font(.system(size: 15))
                    .foregroundColor(Theme.textMuted)
            }
            Spacer()
            if activeModule == .train {
                headerButton("导入") {
                    showImporter = true
                }
            }
            headerButton("刷新") {
                Task { await loadCourses() }
            }
            headerButton("退出") {
                auth.logout()
                currentCourse = nil
                courses = []
                activeModule = .course
            }
        }
        .padding(.horizontal, 18)
        .padding(.top, 8)
        .padding(.bottom, 10)
    }

    private func headerButton(_ label: String, action: @escaping () -> Void) -> some View {
        Button(action: action) {
            Text(label)
                .font(.system(size: 14, weight: .bold))
                .foregroundColor(.white)
                .padding(.horizontal, 14)
                .frame(height: 40)
                .background(Theme.buttonBlue)
                .clipShape(RoundedRectangle(cornerRadius: 8))
        }
        .buttonStyle(.plain)
        .padding(.leading, 8)
    }

    private var moduleTabs: some View {
        HStack(spacing: 0) {
            moduleTab("课程", module: .course)
            moduleTab("训练", module: .train)
            moduleTab("测试", module: .test)
            moduleTab("我的", module: .mine)
        }
        .padding(.horizontal, 16)
        .padding(.bottom, 8)
    }

    private func moduleTab(_ label: String, module: Module) -> some View {
        Button {
            if module != .course && currentCourse == nil {
                showCourseGuardToast = true
                DispatchQueue.main.asyncAfter(deadline: .now() + 2) {
                    showCourseGuardToast = false
                }
            } else {
                activeModule = module
            }
        } label: {
            Text(label)
                .font(.system(size: 15, weight: .bold))
                .foregroundColor(activeModule == module ? .white : Theme.textMuted)
                .frame(maxWidth: .infinity)
                .frame(height: 38)
                .background(activeModule == module ? Theme.buttonBlue : Theme.surface)
                .clipShape(RoundedRectangle(cornerRadius: 8))
        }
        .buttonStyle(.plain)
    }

    // MARK: - Course Page

    private var coursePage: some View {
        ScrollView {
            VStack(alignment: .leading, spacing: 0) {
                Text("课程首页")
                    .font(.system(size: 26, weight: .bold))
                    .foregroundColor(.white)
                    .padding(.horizontal, 16)
                Text("选择一门课程开始训练")
                    .font(.system(size: 13))
                    .foregroundColor(Theme.textMuted)
                    .padding(.horizontal, 16)
                    .padding(.top, 4)
                Text(courseStatusText)
                    .font(.system(size: 13))
                    .foregroundColor(Theme.textMuted)
                    .padding(.horizontal, 16)
                    .padding(.top, 8)

                if courses.isEmpty {
                    Text("暂无课程")
                        .font(.system(size: 14))
                        .foregroundColor(Theme.textMuted)
                        .padding(.horizontal, 16)
                        .padding(.top, 20)
                } else {
                    LazyVStack(spacing: 10) {
                        ForEach(courses) { course in
                            courseCard(course)
                        }
                    }
                    .padding(.horizontal, 16)
                    .padding(.top, 8)
                }
            }
            .padding(.top, 12)
        }
    }

    private func courseCard(_ course: Course) -> some View {
        let isSelected = currentCourse?.videoHash == course.videoHash
        return Button {
            selectCourse(course)
        } label: {
            VStack(alignment: .leading, spacing: 6) {
                Text(course.title)
                    .font(.system(size: 16, weight: .bold))
                    .foregroundColor(isSelected ? Theme.textDark : .white)
                    .lineLimit(2)
                Text("\(course.enrolled ? "已选修" : "未选修") · \(course.sentenceCount) 句\(isSelected ? " · 当前课程" : "")")
                    .font(.system(size: 13))
                    .foregroundColor(isSelected ? Theme.accentDeep : Theme.textMuted)
            }
            .frame(maxWidth: .infinity, alignment: .leading)
            .padding(14)
            .background(isSelected ? Theme.selected : Theme.surface)
            .overlay(
                RoundedRectangle(cornerRadius: 10)
                    .stroke(isSelected ? Theme.accent : Theme.border, lineWidth: 1)
            )
            .clipShape(RoundedRectangle(cornerRadius: 10))
        }
        .buttonStyle(.plain)
    }

    private func selectCourse(_ course: Course) {
        currentCourse = course
        let video = course.toVideoSummary()
        catalogVM.select(video)
        activeModule = .train
    }

    // MARK: - Mine Page

    private var minePage: some View {
        ScrollView {
            VStack(alignment: .leading, spacing: 12) {
                Text(auth.nickname.isEmpty ? "我的学习" : auth.nickname)
                    .font(.system(size: 26, weight: .bold))
                    .foregroundColor(.white)
                    .padding(.horizontal, 16)
                    .padding(.top, 12)

                if let course = currentCourse {
                    Text("当前课程：\(course.title)")
                        .font(.system(size: 14, weight: .bold))
                        .foregroundColor(.white)
                        .padding(.horizontal, 16)
                }

                Text("此页面显示当前课程的测试记录和配音分享")
                    .font(.system(size: 13))
                    .foregroundColor(Theme.textMuted)
                    .padding(.horizontal, 16)
            }
        }
    }

    // MARK: - Load Courses

    private func loadCourses() async {
        courseStatusText = "正在同步"
        do {
            courses = try await AuthAPI.courses(token: auth.token)
            courseStatusText = "\(courses.count) 个课程"
        } catch {
            courseStatusText = "课程加载失败：\(error.localizedDescription)"
        }
    }

    // MARK: - Fullscreen

    private func enterFullscreen() {
        AppDelegate.orientationLock = UIDevice.current.userInterfaceIdiom == .pad ? .all : .landscape
        updateSupportedInterfaceOrientations()
        showFullscreenPlayer = true
    }

    private func exitFullscreen() {
        AppDelegate.orientationLock = UIDevice.current.userInterfaceIdiom == .pad ? .all : .portrait
        updateSupportedInterfaceOrientations()
        showFullscreenPlayer = false
    }

    private func updateSupportedInterfaceOrientations() {
        let scenes = UIApplication.shared.connectedScenes.compactMap { $0 as? UIWindowScene }
        let controllers = scenes.flatMap { $0.windows }.compactMap(\.rootViewController)
        for controller in controllers {
            if #available(iOS 16.0, *) {
                controller.setNeedsUpdateOfSupportedInterfaceOrientations()
            } else {
                UIViewController.attemptRotationToDeviceOrientation()
            }
        }
    }
}