import SwiftUI
import AlarmKit
import Observation

@Observable
@MainActor
final class TimerStore {
    var timeRemaining: TimeInterval = 25 * 60  // 25 min Pomodoro
    var isRunning = false
    var session: Session?
    
    private var timer: Task<Void, Never>?
    private let service = TimerService()
}

struct TimerView: View {
    @State private var store = TimerStore()
    
    var body: some View {
        NavigationStack {
            VStack(spacing: 40) {
                Text(timeString(from: store.timeRemaining))
                    .font(.system(size: 80, weight: .bold, design: .rounded))
                    .foregroundStyle(.primary)
                
                VStack(spacing: 20) {
                    Button(store.isRunning ? "Pause" : "Start") {
                        toggleTimer()
                    }
                    .buttonStyle(.borderedProminent)
                    .controlSize(.large)
                    
                    Button("Reset") {
                        resetTimer()
                    }
                    .buttonStyle(.bordered)
                }
                
                Spacer()
            }
            .padding()
            .navigationTitle("Pomodoro Timer")
            .sheet(isPresented: .constant(store.isRunning)) {
                // Optional: Session summary sheet with AI
                Text("Timer active!")
            }
        }
        .glassEffect()  // Liquid Glass for the nav stack
    }
    
    private func toggleTimer() {
        if store.isRunning {
            store.timer?.cancel()
            store.timer = nil
            store.isRunning = false
            // Save session to SwiftData
            store.session = Session(duration: store.timeRemaining, completed: true)
        } else {
            store.isRunning = true
            store.timer = Task {
                while store.timeRemaining > 0 && !Task.isCancelled {
                    try? await Task.sleep(for: .seconds(1))
                    store.timeRemaining -= 1
                }
                if !Task.isCancelled {
                    // Alarm via AlarmKit
                    await store.service.scheduleAlarm(for: store.timeRemaining)
                    store.isRunning = false
                }
            }
        }
    }
    
    private func resetTimer() {
        store.timer?.cancel()
        store.timeRemaining = 25 * 60
        store.isRunning = false
    }
    
    private func timeString(from timeInterval: TimeInterval) -> String {
        let minutes = Int(timeInterval) / 60
        let seconds = Int(timeInterval) % 60
        return String(format: "%02d:%02d", minutes, seconds)
    }
}

#Preview {
    TimerView()
}