import Foundation
#if os(macOS)
import AppKit
#endif

@MainActor
final class UpdateViewModel: ObservableObject {
    struct StatusAlert: Identifiable {
        let id = UUID()
        let title: String
        let message: String
    }

    @Published var availableRelease: ReleaseInfo?
    @Published var latestFetchedRelease: ReleaseInfo?
    @Published var statusAlert: StatusAlert?
    @Published var isChecking = false

    private let service: UpdateService
    private let userDefaults: UserDefaults
    private let autoCheckKey = "autoCheckUpdates"
    private let includePrereleaseKey = "includePrereleaseUpdates"

    init(service: UpdateService = UpdateService(), userDefaults: UserDefaults = .standard) {
        self.service = service
        self.userDefaults = userDefaults
        registerDefaultsIfNeeded()
    }

    func startAutomaticCheckIfNeeded() {
        if userDefaults.bool(forKey: autoCheckKey) {
            checkForUpdates(userInitiated: false)
        }
    }

    func checkForUpdates(userInitiated: Bool) {
        guard !isChecking else { return }
        isChecking = true

        Task {
            do {
                let release = try await service.fetchLatestRelease(includePrerelease: userDefaults.bool(forKey: includePrereleaseKey))
                handle(release: release, userInitiated: userInitiated)
            } catch {
                if userInitiated {
                    statusAlert = StatusAlert(
                        title: "Update Check Failed",
                        message: error.localizedDescription
                    )
                }
            }
            self.isChecking = false
        }
    }

    func openReleaseNotes() {
        guard let releaseURL = availableRelease?.releaseURL ?? latestFetchedRelease?.releaseURL else { return }
        #if os(macOS)
        NSWorkspace.shared.open(releaseURL)
        #endif
    }

    func downloadLatest() {
        let release = availableRelease ?? latestFetchedRelease
        availableRelease = nil
        guard let downloadURL = release?.downloadURL else { return }
        #if os(macOS)
        NSWorkspace.shared.open(downloadURL)
        #endif
    }

    private func handle(release: ReleaseInfo, userInitiated: Bool) {
        let currentVersion = VersionNumber(
            Bundle.main.infoDictionary?["CFBundleShortVersionString"] as? String ?? "0.0.0"
        )

        latestFetchedRelease = release

        if release.version > currentVersion {
            availableRelease = release
        } else if userInitiated {
            statusAlert = StatusAlert(
                title: "You're Up To Date",
                message: "iKeyMon \(currentVersion.rawValue) is the latest version."
            )
        }
    }

    private func registerDefaultsIfNeeded() {
        userDefaults.register(defaults: [
            autoCheckKey: true,
            includePrereleaseKey: true
        ])
    }
}