//
//  CourseManagerView.swift
//  TeachMate
//
//  Created by Hongli on 2025/3/17.
//

import SwiftUI
import SwiftData

struct CourseManagerView: View {
    @Environment(\.modelContext) private var modelContext
    @Query(sort: \CourseModel.name) private var courses: [CourseModel]
    @Query(sort: \Semester.title) private var semesters: [Semester]
    
    @State private var selectedCourse: CourseModel?
    @State private var showingCourseForm = false
    @State private var courseToEdit: CourseModel?
    
    var filteredCourses: [CourseModel] {
        var result = courses
        
        // 按当前学期筛选
        if let currentSemester = semesters.first(where: { $0.isCurrent }) {
            result = result.filter { $0.semester?.id == currentSemester.id }
        }
        return result
    }
    
    var body: some View {
        NavigationSplitView {
            VStack(spacing: 0) {

                // 课程列表
                List(selection: $selectedCourse) {
                    ForEach(filteredCourses) { course in
                        CourseRow(course: course)
                            .tag(course)
                    }
                    .onDelete(perform: deleteCourses)
                }
                .listStyle(.plain)
                .overlay {
                    if filteredCourses.isEmpty {
                        ContentUnavailableView {
                            Label("没有课程", systemImage: "book.closed")
                        } description: {
                            Text("点击右上角的 + 按钮添加课程")
                        }
                    }
                }
            }
            .navigationTitle("课程管理")
            .toolbar {
                ToolbarItem(placement: .automatic) {
                    Button(action: {
                        courseToEdit = nil
                        showingCourseForm = true
                    }) {
                        Image(systemName: "plus")
                    }
                }
                
                ToolbarItem(placement: .automatic) {
                    Button(action: {
                        if let course = selectedCourse {
                            courseToEdit = course
                            showingCourseForm = true
                        }
                    }) {
                        Image(systemName: "pencil")
                    }
                    .disabled(selectedCourse == nil)
                }
            }
        } detail: {
            if let course = selectedCourse {
                CourseDetailView(course: course)
            } else {
                Text("请选择一门课程查看详情")
                    .foregroundColor(.secondary)
            }
        }
        .sheet(isPresented: $showingCourseForm) {
            if let course = courseToEdit {
                CourseFormView(
                    mode: .edit(course),
                    onSave: { _ in }
                )
                .frame(idealWidth: 600, idealHeight: 400)
            } else {
                CourseFormView(
                    mode: .add,
                    onSave: { newCourse in
                        modelContext.insert(newCourse)
                        selectedCourse = newCourse
                    }
                )
                .frame(idealWidth: 600, idealHeight: 400)
            }
        }
        .onAppear {
            // 如果没有选中的课程且有可用课程，自动选择第一个课程（对预览特别有用）
            if selectedCourse == nil && !filteredCourses.isEmpty {
                selectedCourse = filteredCourses.first
            }
        }
    }
    
    private func deleteCourses(at offsets: IndexSet) {
        for index in offsets {
            let course = filteredCourses[index]
            modelContext.delete(course)
        }
    }
}

// 课程行视图
struct CourseRow: View {
    let course: CourseModel
    
    var body: some View {
        HStack {
            // 颜色标记
            RoundedRectangle(cornerRadius: 4)
                .fill(course.backgroundColor)
                .frame(width: 4, height: 40)
            
            VStack(alignment: .leading, spacing: 4) {
                HStack {
                    Text(course.name)
                        .font(.headline)
                }
                
                Text("周 \(course.sessions.count) 节")
                    .font(.caption)
                    .foregroundColor(.secondary)
            }
            .padding(.leading, 8)
            
            Spacer()
        }
        .padding(.vertical, 4)
    }
}

// 课程详情视图
struct CourseDetailView: View {
    @Environment(\.modelContext) private var modelContext
    let course: CourseModel
    
    @State private var showingSessionForm = false
    @State private var sessionToEdit: ClassSession?
    
    // 星期标题
    private let weekdays = ["一", "二", "三", "四", "五", "六", "日"]
    
    var body: some View {
        VStack(alignment: .leading, spacing: 16) {
            // 课程基本信息
            HStack(alignment: .center) {
                VStack(alignment: .leading, spacing: 4) {
                    HStack {
                        Text(course.name)
                            .font(.title)
                            .fontWeight(.bold)
                    }
                    
                    if let semester = course.semester {
                        Text("学期: \(semester.title)")
                            .foregroundColor(.secondary)
                    }
                }
                
                Spacer()
                
                // 颜色标记
                Circle()
                    .fill(course.backgroundColor)
                    .frame(width: 24, height: 24)
            }
            .padding(.horizontal)
            
            Divider()
            
            // 课时列表
            VStack(alignment: .leading, spacing: 8) {
                HStack {
                    Text("课时列表")
                        .font(.headline)
                    
                    Spacer()
                    
                    Button(action: {
                        sessionToEdit = nil
                        showingSessionForm = true
                    }) {
                        Label("添加课时", systemImage: "plus.circle")
                    }
                    .buttonStyle(.borderless)
                }
                .padding(.horizontal)
                
                if course.sessions.isEmpty {
                    Text("没有课时信息")
                        .foregroundColor(.secondary)
                        .frame(maxWidth: .infinity, alignment: .center)
                        .padding()
                } else {
                    List {
                        ForEach(course.sessions, id: \.self) { session in
                            SessionRow(session: session, weekdays: weekdays)
                                .contextMenu {
                                    Button(action: {
                                        sessionToEdit = session
                                        showingSessionForm = true
                                    }) {
                                        Label("编辑", systemImage: "pencil")
                                    }
                                    
                                    Button(role: .destructive, action: {
                                        deleteSession(session)
                                    }) {
                                        Label("删除", systemImage: "trash")
                                    }
                                }
                        }
                    }
                    .listStyle(.plain)
                }
            }
        }
        .padding(.vertical)
        .sheet(isPresented: $showingSessionForm) {
            if let session = sessionToEdit {
                SessionFormView(mode: .edit(session), course: course)
            } else {
                SessionFormView(mode: .add, course: course)
            }
        }
    }
    
    private func deleteSession(_ session: ClassSession) {
        modelContext.delete(session)
    }
}

// 课时行视图
struct SessionRow: View {
    let session: ClassSession
    let weekdays: [String]
    
    var body: some View {
        VStack(alignment: .leading, spacing: 8) {
            HStack {
                Text("周\(weekdays[session.weekday - 1])")
                    .font(.headline)
                
                Text("第\(session.timeSlot)节")
                    .foregroundColor(.secondary)
                
                Spacer()
                
                Text(timeSlotString(for: session.timeSlot))
                    .font(.caption)
                    .foregroundColor(.secondary)
            }
            
            HStack {
                Image(systemName: "mappin.and.ellipse")
                    .foregroundColor(.secondary)
                    .font(.caption)
                
                Text(session.location)
                    .font(.subheadline)
                
                Spacer()
                
                if !session.schoolCalss.isEmpty {
                    Text(session.schoolCalss)
                        .font(.caption)
                        .padding(.horizontal, 6)
                        .padding(.vertical, 2)
                        .background(Color.gray.opacity(0.2))
                        .cornerRadius(4)
                }
            }
        }
        .padding(.vertical, 4)
    }
    
    private func timeSlotString(for slot: Int) -> String {
        let slots = TimeSlot.defaultSlots
        if slot >= 1 && slot <= slots.count {
            return slots[slot - 1].timeRange
        }
        return ""
    }
}

#Preview("课程管理") {
    CourseManagerView()
        .modelContainer(PreviewData.createContainer())
        .onAppear {
            // 预览时给一些时间让数据加载
            DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {
                // 这个空的闭包会触发视图刷新，有助于在预览中显示数据
            }
        }
}