import SwiftUI
import EventKit

struct ContentView: View {
    @StateObject private var calendarService = CalendarService()
    @State private var scrollToToday = false
    @State private var showingSettings = false

    var body: some View {
        VStack(spacing: 0) {
            if calendarService.hasAccess {
                ScrollViewReader { proxy in
                    List {
                        ForEach(groupedEventsByDay(), id: \.date) { dayGroup in
                            Section(header: dayHeader(for: dayGroup.date)) {
                                ForEach(dayGroup.events, id: \.eventIdentifier) { event in
                                    EventRow(event: event)
                                }
                            }
                            .id(dayGroup.date)
                        }
                    }
                    .listStyle(.plain)
                    .onAppear {
                        if !scrollToToday {
                            let today = Calendar.current.startOfDay(for: Date())
                            proxy.scrollTo(today, anchor: .top)
                            scrollToToday = true
                        }
                    }
                    .onChange(of: scrollToToday) { _, newValue in
                        if newValue {
                            let today = Calendar.current.startOfDay(for: Date())
                            withAnimation {
                                proxy.scrollTo(today, anchor: .top)
                            }
                            scrollToToday = false
                        }
                    }
                }
            } else {
                VStack {
                    Text("カレンダーへのアクセス権限が必要です")
                        .font(.headline)
                    Text("システム設定からアクセスを許可してください")
                        .font(.subheadline)
                        .foregroundColor(.secondary)
                }
                .padding()
            }
        }
        .sheet(isPresented: $showingSettings) {
            SettingsView(calendarService: calendarService)
        }
        .toolbar {
            ToolbarItem(placement: .primaryAction) {
                Button(action: {
                    showingSettings = true
                }) {
                    Label("設定", systemImage: "gearshape")
                }
            }
            ToolbarItem(placement: .primaryAction) {
                Button(action: {
                    scrollToToday = true
                }) {
                    Label("今日", systemImage: "calendar")
                }
            }
        }
    }

    private func groupedEventsByDay() -> [DayGroup] {
        let calendar = Calendar.current
        let grouped = Dictionary(grouping: calendarService.events) { event in
            calendar.startOfDay(for: event.startDate)
        }

        let today = calendar.startOfDay(for: Date())
        guard let startDate = calendar.date(byAdding: .day, value: -14, to: today),
              let endDate = calendar.date(byAdding: .day, value: 14, to: today) else {
            return []
        }

        var allDates: [Date] = []
        var currentDate = startDate
        while currentDate <= endDate {
            allDates.append(currentDate)
            guard let nextDate = calendar.date(byAdding: .day, value: 1, to: currentDate) else { break }
            currentDate = nextDate
        }

        return allDates.map { date in
            DayGroup(date: date, events: grouped[date] ?? [])
        }.sorted { $0.date < $1.date }
    }

    private func dayHeader(for date: Date) -> some View {
        let calendar = Calendar.current
        let isToday = calendar.isDateInToday(date)
        let formatter = DateFormatter()
        formatter.dateFormat = "M月d日(E)"
        formatter.locale = Locale(identifier: "ja_JP")

        return HStack {
            Text(formatter.string(from: date))
                .font(.headline)
                .foregroundColor(isToday ? .blue : .primary)
            if isToday {
                Text("今日")
                    .font(.caption)
                    .padding(.horizontal, 6)
                    .padding(.vertical, 2)
                    .background(Color.blue)
                    .foregroundColor(.white)
                    .cornerRadius(4)
            }
        }
    }
}

struct DayGroup {
    let date: Date
    let events: [EKEvent]
}

struct EventRow: View {
    let event: EKEvent
    @State private var showingDetail = false

    var body: some View {
        Button(action: {
            showingDetail = true
        }) {
            VStack(alignment: .leading, spacing: 4) {
                HStack {
                    if event.isAllDay {
                        Text("終日")
                            .font(.caption)
                            .foregroundColor(.secondary)
                    } else {
                        Text(timeString(from: event.startDate, to: event.endDate))
                            .font(.caption)
                            .foregroundColor(.secondary)
                    }
                    if let calendar = event.calendar {
                        Circle()
                            .fill(Color(calendar.color))
                            .frame(width: 8, height: 8)
                    }
                }
                Text(event.title ?? "無題のイベント")
                    .font(.body)
                if let location = event.location, !location.isEmpty {
                    Text(location)
                        .font(.caption)
                        .foregroundColor(.secondary)
                }
            }
            .padding(.vertical, 4)
            .frame(maxWidth: .infinity, alignment: .leading)
            .contentShape(Rectangle())
        }
        .buttonStyle(.plain)
        .popover(isPresented: $showingDetail) {
            EventDetailView(event: event)
        }
    }

    private func timeString(from start: Date, to end: Date) -> String {
        let formatter = DateFormatter()
        formatter.dateFormat = "HH:mm"
        return "\(formatter.string(from: start)) - \(formatter.string(from: end))"
    }
}

struct EventDetailView: View {
    let event: EKEvent

    var body: some View {
        VStack(alignment: .leading, spacing: 12) {
            HStack {
                if let calendar = event.calendar {
                    Circle()
                        .fill(Color(calendar.color))
                        .frame(width: 12, height: 12)
                    Text(calendar.title)
                        .font(.caption)
                        .foregroundColor(.secondary)
                }
            }

            Text(event.title ?? "無題のイベント")
                .font(.headline)

            Divider()

            VStack(alignment: .leading, spacing: 8) {
                if event.isAllDay {
                    HStack {
                        Image(systemName: "clock")
                            .foregroundColor(.secondary)
                            .frame(width: 20)
                        Text("終日")
                    }
                } else {
                    HStack(alignment: .top) {
                        Image(systemName: "clock")
                            .foregroundColor(.secondary)
                            .frame(width: 20)
                        VStack(alignment: .leading, spacing: 2) {
                            Text(formatDateTime(event.startDate))
                            Text("〜")
                                .foregroundColor(.secondary)
                                .font(.caption)
                            Text(formatDateTime(event.endDate))
                        }
                    }
                }

                if let location = event.location, !location.isEmpty {
                    HStack(alignment: .top) {
                        Image(systemName: "location")
                            .foregroundColor(.secondary)
                            .frame(width: 20)
                        Text(location)
                    }
                }

                if let notes = event.notes, !notes.isEmpty {
                    HStack(alignment: .top) {
                        Image(systemName: "note.text")
                            .foregroundColor(.secondary)
                            .frame(width: 20)
                        Text(notes)
                            .textSelection(.enabled)
                    }
                }

                if let url = event.url {
                    HStack(alignment: .top) {
                        Image(systemName: "link")
                            .foregroundColor(.secondary)
                            .frame(width: 20)
                        Link(url.absoluteString, destination: url)
                    }
                }
            }
        }
        .padding()
        .frame(minWidth: 300, maxWidth: 400)
    }

    private func formatDateTime(_ date: Date) -> String {
        let formatter = DateFormatter()
        formatter.dateFormat = "M月d日(E) HH:mm"
        formatter.locale = Locale(identifier: "ja_JP")
        return formatter.string(from: date)
    }
}