//
//  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"
    ]

    private var updateListenerTask: Task<Void, Never>?

    init() {
        updateListenerTask = listenForTransactions()
    }

    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()
                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)
        }
    }
}