import SwiftUI

struct TrainingPlanDetailView: View {
    let plan: TrainingPlan
    @State private var expandedWeek: Int? = 1

    var body: some View {
        ScrollView {
            VStack(alignment: .leading, spacing: 16) {
                planHeader
                progressSection
                planDescription
                weeklyWorkoutsSection
            }
            .padding(.horizontal)
            .padding(.bottom, 32)
        }
        .navigationTitle(plan.title)
        .navigationBarTitleDisplayMode(.inline)
    }

    private var planHeader: some View {
        VStack(spacing: 8) {
            HStack {
                Image(systemName: plan.planType.icon)
                    .font(.system(size: 36))
                    .foregroundColor(plan.difficulty.color)
                VStack(alignment: .leading, spacing: 4) {
                    Text(plan.planType.displayName)
                        .font(.title2)
                        .fontWeight(.bold)
                    Text(plan.difficulty.displayName)
                        .font(.subheadline)
                        .foregroundColor(plan.difficulty.color)
                }
                Spacer()
                Toggle("", isOn: Binding(
                    get: { plan.isFollowing },
                    set: { _ in }
                ))
            }

            Divider()

            HStack(spacing: 24) {
                statLabel(value: "\(plan.durationWeeks)", label: "Weeks")
                statLabel(value: "\(plan.progress.totalSessions)", label: "Sessions")
                statLabel(value: "\(Int(plan.progress.percentage))%", label: "Progress")
            }
        }
        .padding()
        .background(Color.secondary.opacity(0.1))
        .cornerRadius(12)
    }

    private func statLabel(value: String, label: String) -> some View {
        VStack(spacing: 4) {
            Text(value)
                .font(.title3)
                .fontWeight(.bold)
            Text(label)
                .font(.caption)
                .foregroundColor(.secondary)
        }
    }

    private var progressSection: some View {
        VStack(alignment: .leading, spacing: 8) {
            Text("Overall Progress")
                .font(.headline)
            ProgressView(value: plan.progress.percentage)
                .tint(.blue)
            HStack {
                Text("\(plan.progress.completedWeeks)/\(plan.progress.totalWeeks) weeks")
                Spacer()
                Text("\(plan.progress.completedSessions)/\(plan.progress.totalSessions) sessions")
            }
            .font(.caption)
            .foregroundColor(.secondary)
        }
    }

    private var planDescription: some View {
        VStack(alignment: .leading, spacing: 4) {
            Text("About This Plan")
                .font(.headline)
            Text(plan.description)
                .font(.subheadline)
                .foregroundColor(.secondary)
        }
    }

    private var weeklyWorkoutsSection: some View {
        VStack(alignment: .leading, spacing: 12) {
            Text("Weekly Schedule")
                .font(.headline)

            ForEach(plan.weeklyWorkouts, id: \.id) { week in
                WeekCard(week: week, isExpanded: expandedWeek == week.weekNumber) {
                    expandedWeek = expandedWeek == week.weekNumber ? nil : week.weekNumber
                }
            }
        }
    }
}

struct WeekCard: View {
    let week: WeeklyWorkout
    let isExpanded: Bool
    let toggleAction: () -> Void

    var body: some View {
        VStack(alignment: .leading, spacing: 8) {
            HStack {
                Text("Week \(week.weekNumber)")
                    .font(.headline)
                Spacer()
                Text("\(week.completedSessions)/\(week.totalSessions)")
                    .font(.caption)
                    .foregroundColor(.secondary)
                Image(systemName: isExpanded ? "chevron.up" : "chevron.down")
                    .font(.caption)
            }
            .padding(.vertical, 8)
            .padding(.horizontal)
            .background(Color.secondary.opacity(0.1))
            .cornerRadius(8)
            .onTapGesture { toggleAction() }

            if isExpanded {
                ForEach(week.dailySessions) { session in
                    DailySessionRow(session: session)
                }
            }
        }
    }
}

struct DailySessionRow: View {
    let session: DailySession

    var body: some View {
        HStack(spacing: 12) {
            Image(systemName: session.workoutType.icon)
                .font(.system(size: 20))
                .foregroundColor(session.workoutType.color)
                .frame(width: 32)

            VStack(alignment: .leading, spacing: 2) {
                Text("\(session.dayOfWeek.displayName): \(session.workoutType.displayName)")
                    .font(.subheadline)
                    .fontWeight(.medium)
                if session.status == .completed {
                    Text("Completed")
                        .font(.caption)
                        .foregroundColor(.green)
                } else if let distance = session.targetDistanceKm {
                    Text("\(distance) km")
                        .font(.caption)
                        .foregroundColor(.secondary)
                }
            }

            Spacer()

            switch session.status {
            case .completed:
                Image(systemName: "checkmark.circle.fill")
                    .foregroundColor(.green)
            case .inProgress:
                Image(systemName: "pause.circle.fill")
                    .foregroundColor(.orange)
            case .skipped:
                Image(systemName: "xmark.circle.fill")
                    .foregroundColor(.red)
            case .pending:
                Image(systemName: "circle")
                    .foregroundColor(.secondary)
            }
        }
        .padding(.vertical, 4)
    }
}

#Preview {
    NavigationView {
        TrainingPlanDetailView(plan: samplePlan)
    }
}

private var samplePlan: TrainingPlan {
    TrainingPlan(
        id: "1",
        title: "5K Beginner Plan",
        description: "A 8-week plan designed to help beginners complete their first 5K race.",
        planType: .fiveK,
        durationWeeks: 8,
        difficulty: .beginner,
        startDate: Date(),
        endDate: Date().addingTimeInterval(8 * 7 * 24 * 3600),
        weeklyWorkouts: [
            WeeklyWorkout(id: "w1", weekNumber: 1, dailySessions: [
                DailySession(id: "s1", dayOfWeek: .monday, workoutType: .easyRun, title: "Easy Run", description: "Start with a comfortable pace", targetDistanceKm: 2.0, targetDurationMinutes: 20, targetPaceMinPerKm: 10, intensity: .easy, status: .completed),
                DailySession(id: "s2", dayOfWeek: .wednesday, workoutType: .rest, title: "Rest Day", description: "Recovery", targetDistanceKm: nil, targetDurationMinutes: nil, targetPaceMinPerKm: nil, intensity: .veryEasy, status: .completed),
                DailySession(id: "s3", dayOfWeek: .friday, workoutType: .easyRun, title: "Easy Run", description: "Build endurance", targetDistanceKm: 2.5, targetDurationMinutes: 25, targetPaceMinPerKm: 10, intensity: .easy, status: .pending),
                DailySession(id: "s4", dayOfWeek: .saturday, workoutType: .longRun, title: "Long Run", description: "Gradually increase distance", targetDistanceKm: 3.0, targetDurationMinutes: 30, targetPaceMinPerKm: 10, intensity: .moderate, status: .pending)
            ])
        ],
        progress: PlanProgress(completedWeeks: 0, totalWeeks: 8, completedSessions: 2, totalSessions: 32, currentWeekNumber: 1),
        isFollowing: true,
        createdAt: Date()
    )
}