import Foundation

enum SystemPlayerAction { case play, pause, next, previous, seek, volume }

@MainActor
final class SystemPlayerTransport {
    private var busy = false

    func send(_ action: SystemPlayerAction, value: Double? = nil, sessionID: String) async throws -> MediaState {
        guard !busy else { throw BridgeError.message("Предыдущая команда ещё выполняется.") }
        busy = true
        defer { busy = false }
        let saved = try SystemPlayerCredentials.load(sessionID)
        let client = BridgeClient(saved, timeout: 5)
        defer { client.close() }
        return try await Self.execute(action, value: value, client: client) {
            let current = try SystemPlayerCredentials.load(sessionID)
            guard current.endpoint == saved.endpoint, current.fingerprint == saved.fingerprint, current.token == saved.token else {
                throw BridgeError.unauthorized
            }
        }
    }

    static func execute(_ action: SystemPlayerAction, value: Double? = nil, client: BridgeClient,
                        validate: () throws -> Void = {}) async throws -> MediaState {
        let state = try await client.state()
        try validate()
        let command = try command(action, value: value, state: state)
        do { try await client.command(command) }
        catch {
            if error is URLError { throw BridgeError.message("Результат команды неизвестен. Откройте плеер перед повтором.") }
            throw error
        }
        do { return try await client.state() }
        catch {
            if case BridgeError.unauthorized = error { throw error }
            throw BridgeError.message("Команда выполнена, но новый трек не получен. Откройте приложение для обновления.")
        }
    }

    static func command(_ action: SystemPlayerAction, value: Double?, state: MediaState) throws -> Command {
        switch action {
        case .play where state.hasSession && state.capabilities.play: return Command(type: "play", value: nil)
        case .pause where state.hasSession && state.capabilities.pause: return Command(type: "pause", value: nil)
        case .next where state.hasSession && state.capabilities.next: return Command(type: "next", value: nil)
        case .previous where state.hasSession && state.capabilities.previous: return Command(type: "previous", value: nil)
        case .seek where state.hasSession && state.capabilities.seek && state.maxSeekSeconds > state.minSeekSeconds:
            guard let value, value.isFinite else { throw BridgeError.message("Некорректная позиция трека.") }
            return Command(type: "seek", value: min(state.maxSeekSeconds, max(state.minSeekSeconds, state.startSeconds + value)))
        case .volume where state.volume != nil:
            guard let value, value.isFinite else { throw BridgeError.message("Некорректная громкость.") }
            return Command(type: "volume", value: min(1, max(0, value)))
        default: throw BridgeError.message("Плеер на ПК не поддерживает эту команду.")
        }
    }
}