import SwiftUI

struct WorkoutSessionView: View {
    let session: DailySession
    @StateObject private var viewModel = TrainingPlanViewModel()
    @State private var isRunning: Bool = false
    @State private var elapsedSeconds: Int = 0

    var body: some View {
        ScrollView {
            VStack(spacing: 20) {
                sessionHeader
                metricsSection
                workoutInstructions
                actionButtons
            }
            .padding(.horizontal)
            .padding(.bottom, 32)
        }
        .navigationTitle(session.workoutType.displayName)
        .navigationBarTitleDisplayMode(.inline)
    }

    private var sessionHeader: some View {
        VStack(spacing: 12) {
            Image(systemName: session.workoutType.icon)
                .font(.system(size: 48))
                .foregroundColor(session.workoutType.color)

            VStack(spacing: 4) {
                Text(session.title)
                    .font(.title2)
                    .fontWeight(.bold)
                Text(session.dayOfWeek.displayName)
                    .font(.subheadline)
                    .foregroundColor(.secondary)
            }

            HStack(spacing: 24) {
                if let distance = session.targetDistanceKm {
                    metricCard(value: "\(distance)", label: "Target km", icon: "figure.run")
                }
                if let duration = session.targetDurationMinutes {
                    metricCard(value: "\(duration)", label: "Target min", icon: "clock")
                }
                if let pace = session.targetPaceMinPerKm {
                    metricCard(value: "\(Int(pace)):00", label: "Pace /km", icon: "speedometer")
                }
            }
        }
        .padding()
        .frame(maxWidth: .infinity)
        .background(Color.secondary.opacity(0.1))
        .cornerRadius(12)
    }

    private func metricCard(value: String, label: String, icon: String) -> some View {
        VStack(spacing: 4) {
            Image(systemName: icon)
                .font(.system(size: 18))
                .foregroundColor(session.workoutType.color)
            Text(value)
                .font(.title3)
                .fontWeight(.bold)
            Text(label)
                .font(.caption)
                .foregroundColor(.secondary)
        }
    }

    private var metricsSection: some View {
        VStack(alignment: .leading, spacing: 12) {
            Text("Current Session")
                .font(.headline)

            HStack(spacing: 16) {
                currentMetric(value: "\(formatElapsed(elapsedSeconds))", label: "Elapsed", icon: "stopwatch")
                currentMetric(value: "0.0", label: "Distance", icon: "route")
                currentMetric(value: "--:--", label: "Pace", icon: "speedometer")
            }
        }
    }

    private func currentMetric(value: String, label: String, icon: String) -> some View {
        VStack(spacing: 4) {
            Image(systemName: icon)
                .font(.system(size: 16))
                .foregroundColor(.blue)
            Text(value)
                .font(.title3)
                .fontWeight(.bold)
            Text(label)
                .font(.caption)
                .foregroundColor(.secondary)
        }
        .frame(maxWidth: .infinity)
        .padding(.vertical, 10)
        .background(Color.blue.opacity(0.08))
        .cornerRadius(10)
    }

    private var workoutInstructions: some View {
        VStack(alignment: .leading, spacing: 8) {
            Text("Instructions")
                .font(.headline)
            Text(session.description)
                .font(.subheadline)
                .foregroundColor(.secondary)

            if session.intensity != .veryEasy {
                HStack {
                    Text("Intensity")
                    Spacer()
                    HStack(spacing: 2) {
                        ForEach(1...5, id: \.self) { i in
                            Circle()
                                .fill(i <= sessionIntensityLevel ? session.workoutType.color : Color.secondary.opacity(0.2))
                                .frame(width: 8, height: 8)
                        }
                    }
                }
                .font(.caption)
            }
        }
    }

    private var sessionIntensityLevel: Int {
        switch session.intensity {
        case .veryEasy: return 1
        case .easy: return 2
        case .moderate: return 3
        case .hard: return 4
        case .veryHard: return 5
        }
    }

    private var actionButtons: some View {
        VStack(spacing: 12) {
            if isRunning {
                Button {
                    isRunning = false
                    Task {
                        await viewModel.updateSessionStatus(sessionId: session.id, status: .completed)
                    }
                } label: {
                    Text("Finish Workout")
                        .font(.headline)
                        .frame(maxWidth: .infinity)
                        .padding()
                        .background(Color.blue)
                        .foregroundColor(.white)
                        .cornerRadius(10)
                }

                Button {
                    isRunning = false
                    Task {
                        await viewModel.updateSessionStatus(sessionId: session.id, status: .skipped)
                    }
                } label: {
                    Text("Skip Session")
                        .font(.headline)
                        .frame(maxWidth: .infinity)
                        .padding()
                        .background(Color.orange.opacity(0.15))
                        .foregroundColor(.orange)
                        .cornerRadius(10)
                }
            } else {
                Button {
                    isRunning = true
                } label: {
                    Text("Start Workout")
                        .font(.headline)
                        .frame(maxWidth: .infinity)
                        .padding()
                        .background(session.workoutType.color)
                        .foregroundColor(.white)
                        .cornerRadius(10)
                }
            }
        }
    }

    private func formatElapsed(_ seconds: Int) -> String {
        let mins = seconds / 60
        let secs = seconds % 60
        return String(format: "%d:%02d", mins, secs)
    }
}

#Preview {
    NavigationView {
        WorkoutSessionView(session: sampleSession)
    }
}

private var sampleSession: DailySession {
    DailySession(
        id: "1",
        dayOfWeek: .monday,
        workoutType: .easyRun,
        title: "Easy Recovery Run",
        description: "Keep the pace comfortable. Focus on maintaining good form and breathing rhythm.",
        targetDistanceKm: 5.0,
        targetDurationMinutes: 30,
        targetPaceMinPerKm: 6,
        intensity: .easy,
        status: .pending
    )
}