//
//  ServicesMAStoreManager.swift
//  Mobile Music Assistant
//
//  Created by Sven Hanold on 09.04.26.
//

import StoreKit
import OSLog
import SwiftUI

private let logger = Logger(subsystem: "com.musicassistant.mobile", category: "StoreManager")

enum PurchaseResult: Equatable {
    case success(Product)
    case cancelled
    case failed(String)
}

@Observable @MainActor final class MAStoreManager {
    var products: [Product] = []
    var purchaseResult: PurchaseResult?
    var isPurchasing = false
    var loadError: String?

    private static let productIDs: Set<String> = [
        "donatesong",
        "donatealbum",
        "donateanthology"
    ]

    // MARK: - Nudge / Supporter tracking keys
    private static let firstLaunchKey      = "ma_firstLaunchDate"
    private static let lastKeyDateKey      = "ma_lastNudgeOrPurchaseDate"
    private static let hasEverSupportedKey = "ma_hasEverSupported"
    private let defaults = UserDefaults.standard

    private var updateListenerTask: Task<Void, Never>?

    init() {
        // Persist first-launch date on very first run
        _ = firstLaunchDate
        updateListenerTask = listenForTransactions()
    }

    // MARK: - Supporter state

    /// True once the user has completed at least one donation.
    var hasEverSupported: Bool {
        defaults.bool(forKey: Self.hasEverSupportedKey)
    }

    // MARK: - Nudge logic

    /// The date the app was first launched (written once, then read-only).
    var firstLaunchDate: Date {
        if let date = defaults.object(forKey: Self.firstLaunchKey) as? Date { return date }
        let now = Date()
        defaults.set(now, forKey: Self.firstLaunchKey)
        return now
    }

    /// True when the nudge sheet should be presented.
    /// Rules:
    ///  - First show: ≥ 3 days after install and never shown/purchased before.
    ///  - Repeat:     ≥ 6 months since last nudge dismissal OR last purchase.
    var shouldShowNudge: Bool {
        let threeDays: TimeInterval = 3 * 24 * 3600
        let sixMonths: TimeInterval = 6 * 30 * 24 * 3600
        guard Date().timeIntervalSince(firstLaunchDate) >= threeDays else { return false }
        guard let last = defaults.object(forKey: Self.lastKeyDateKey) as? Date else { return true }
        return Date().timeIntervalSince(last) >= sixMonths
    }

    /// Call when the nudge sheet is dismissed (regardless of purchase outcome).
    func recordNudgeShown() {
        defaults.set(Date(), forKey: Self.lastKeyDateKey)
    }

    /// Records a successful purchase: sets supporter flag and resets the nudge clock.
    private func recordPurchase() {
        defaults.set(true, forKey: Self.hasEverSupportedKey)
        defaults.set(Date(), forKey: Self.lastKeyDateKey)
    }

    func loadProducts() async {
        loadError = nil
        do {
            let fetched = try await Product.products(for: Self.productIDs)
            products = fetched.sorted { $0.price < $1.price }
            if fetched.isEmpty {
                loadError = "No products returned. Make sure the StoreKit configuration is active in the scheme (Edit Scheme → Run → Options → StoreKit Configuration)."
                logger.warning("Product.products(for:) returned 0 results for IDs: \(Self.productIDs)")
            }
        } catch {
            loadError = error.localizedDescription
            logger.error("Failed to load products: \(error.localizedDescription)")
        }
    }

    func purchase(_ product: Product) async {
        isPurchasing = true
        defer { isPurchasing = false }

        do {
            let result = try await product.purchase()
            switch result {
            case .success(let verification):
                let transaction = try checkVerified(verification)
                await transaction.finish()
                recordPurchase()
                purchaseResult = .success(product)
            case .userCancelled:
                purchaseResult = .cancelled
            case .pending:
                break
            @unknown default:
                break
            }
        } catch {
            purchaseResult = .failed(error.localizedDescription)
        }
    }

    private func checkVerified<T>(_ result: VerificationResult<T>) throws -> T {
        switch result {
        case .unverified(_, let error):
            throw error
        case .verified(let value):
            return value
        }
    }

    private func listenForTransactions() -> Task<Void, Never> {
        Task(priority: .background) { [weak self] in
            for await result in Transaction.updates {
                do {
                    let transaction = try self?.checkVerified(result)
                    await transaction?.finish()
                } catch {
                    logger.error("Transaction verification failed: \(error.localizedDescription)")
                }
            }
        }
    }

    // MARK: - Helpers

    func iconName(for product: Product) -> String {
        switch product.id {
        case "donatesong":      return "music.note"
        case "donatealbum":     return "opticaldisc"
        case "donateanthology": return "music.note.list"
        default:                return "heart.fill"
        }
    }

    func tierName(for product: Product) -> LocalizedStringKey {
        switch product.id {
        case "donatesong":      return "Song"
        case "donatealbum":     return "Album"
        case "donateanthology": return "Anthology"
        default:                return LocalizedStringKey(product.displayName)
        }
    }
}