// ── Shareable Timer Manager ───────────────────────────────────
// Create shareable timer links: chronom.ind/t/abc123
// iOS Universal Links → open app directly
// Web fallback → PWA timer page

import Foundation
import Combine

@MainActor
final class ShareableTimerManager: ObservableObject {
    static let shared = ShareableTimerManager()

    @Published var sharedTimers: [SharedTimer] = []

    private let storageKey = "chronomind-shared-timers"
    private let baseURL = "https://chronomind.app/t/"

    private init() {
        loadSharedTimers()
    }

    // MARK: - Create Shareable Link

    func createShareableLink(for timer: CMTimer) -> SharedTimer {
        let shareCode = generateShareCode()
        let shared = SharedTimer(
            code: shareCode,
            label: timer.label,
            type: timer.type,
            durationSeconds: timer.duration ?? 0,
            urgency: timer.urgency,
            cascadePreset: timer.cascade.preset,
            category: timer.category,
            createdBy: nil, // anonymized
            createdAt: Date(),
            expiresAt: Calendar.current.date(byAdding: .day, value: 30, to: Date())!
        )

        sharedTimers.append(shared)
        saveSharedTimers()

        return shared
    }

    /// Full shareable URL
    func shareURL(for shared: SharedTimer) -> URL {
        URL(string: "\(baseURL)\(shared.code)")!
    }

    /// Share text for messaging
    func shareText(for shared: SharedTimer) -> String {
        let url = shareURL(for: shared)
        return "Check out my \(shared.label) timer on ChronoMind: \(url.absoluteString)"
    }

    // MARK: - Import from Link

    /// Parse a share link and create a timer from it
    func importFromURL(_ url: URL) -> CMTimer? {
        guard let code = extractShareCode(from: url) else { return nil }
        return importFromCode(code)
    }

    func importFromCode(_ code: String) -> CMTimer? {
        // Look up in local shared timers first
        guard let shared = sharedTimers.first(where: { $0.code == code }) else {
            // In production, fetch from server
            return nil
        }

        guard !shared.isExpired else { return nil }

        // Create timer from shared data
        switch shared.type {
        case .countdown:
            return createCountdown(CreateCountdownParams(
                label: shared.label,
                durationSeconds: shared.durationSeconds,
                urgency: shared.urgency,
                cascade: CascadeConfig(preset: shared.cascadePreset, intervals: []),
                category: shared.category
            ))
        case .alarm:
            // Alarm needs a target time — set to duration from now
            return createAlarm(CreateAlarmParams(
                label: shared.label,
                targetTime: Date().addingTimeInterval(shared.durationSeconds),
                urgency: shared.urgency,
                cascade: CascadeConfig(preset: shared.cascadePreset, intervals: [])
            ))
        case .pomodoro:
            let workMinutes = Int(shared.durationSeconds / 60)
            return createPomodoro(CreatePomodoroParams(
                label: shared.label,
                config: PomodoroConfig(
                    workMinutes: workMinutes,
                    breakMinutes: 5,
                    longBreakMinutes: 15,
                    rounds: 4
                )
            ))
        case .event:
            // Events need a target date — set to duration from now
            return createAlarm(CreateAlarmParams(
                label: shared.label,
                targetTime: Date().addingTimeInterval(shared.durationSeconds),
                urgency: shared.urgency,
                cascade: CascadeConfig(preset: shared.cascadePreset, intervals: [])
            ))
        }
    }

    // MARK: - URL Handling

    func extractShareCode(from url: URL) -> String? {
        let path = url.path
        // Handle: chronom.ind/t/abc123 or chronomind.app/t/abc123
        if path.hasPrefix("/t/") {
            return String(path.dropFirst(3))
        }
        return nil
    }

    func canHandleURL(_ url: URL) -> Bool {
        let host = url.host ?? ""
        return (host == "chronomind.app" || host == "chronom.ind") && url.path.hasPrefix("/t/")
    }

    // MARK: - Manage Shared Timers

    func revokeShare(_ code: String) {
        sharedTimers.removeAll { $0.code == code }
        saveSharedTimers()
    }

    func cleanExpired() {
        sharedTimers.removeAll { $0.isExpired }
        saveSharedTimers()
    }

    // MARK: - Private

    private func generateShareCode() -> String {
        // 8-character alphanumeric code
        let chars = "abcdefghijklmnopqrstuvwxyz0123456789"
        return String((0..<8).map { _ in chars.randomElement()! })
    }

    private func loadSharedTimers() {
        guard let data = UserDefaults.standard.data(forKey: storageKey),
              let decoded = try? JSONDecoder().decode([SharedTimer].self, from: data) else { return }
        sharedTimers = decoded
    }

    private func saveSharedTimers() {
        if let data = try? JSONEncoder().encode(sharedTimers) {
            UserDefaults.standard.set(data, forKey: storageKey)
        }
    }
}

// MARK: - Shared Timer Model

struct SharedTimer: Codable, Identifiable {
    let code: String
    let label: String
    let type: CMTimerType
    let durationSeconds: TimeInterval
    let urgency: UrgencyLevel
    let cascadePreset: CascadePreset
    let category: String?
    let createdBy: String?
    let createdAt: Date
    let expiresAt: Date

    var id: String { code }

    var isExpired: Bool {
        Date() > expiresAt
    }

    var shareURL: URL {
        URL(string: "https://chronomind.app/t/\(code)")!
    }
}