import AVFoundation
import os
import VoiceCatCore

private let logger = Logger(subsystem: "cat.voice.VoiceCatiOS", category: "AudioSessionManager")

@MainActor
final class AudioSessionManager {
    static let shared = AudioSessionManager()

    weak var client: VoiceCatClient?

    func configure() {
        // Load stored audio routing preferences and apply them before any audio session
        // activation. IOSAudioRouter drives all iOS audio route selection via AVAudioSession;
        // miniaudio (the core) does NOT touch AVAudioSession on iOS.
        IOSAudioRouter.shared.loadStoredPreferences()
        IOSAudioRouter.shared.applyConfiguration()
        IOSAudioRouter.shared.refreshRoutes()

        NotificationCenter.default.addObserver(
            self, selector: #selector(handleInterruption),
            name: AVAudioSession.interruptionNotification, object: nil)
        NotificationCenter.default.addObserver(
            self, selector: #selector(handleRouteChange),
            name: AVAudioSession.routeChangeNotification, object: nil)
    }

    func activateForStreaming() throws {
        // Re-apply the routing configuration before activating, in case the user changed
        // settings since the last apply. The core (miniaudio) will open whatever route
        // AVAudioSession has established.
        IOSAudioRouter.shared.applyConfiguration()
        try AVAudioSession.sharedInstance().setActive(true, options: [])
    }

    func deactivateAfterStreaming() {
        try? AVAudioSession.sharedInstance().setActive(false,
            options: .notifyOthersOnDeactivation)
    }

    @objc private func handleInterruption(_ notification: Notification) {
        guard let info = notification.userInfo,
              let typeValue = info[AVAudioSessionInterruptionTypeKey] as? UInt,
              let type = AVAudioSession.InterruptionType(rawValue: typeValue)
        else { return }

        switch type {
        case .began:
            client?.audioSuspend()
        case .ended:
            let optionsValue = info[AVAudioSessionInterruptionOptionKey] as? UInt ?? 0
            let options = AVAudioSession.InterruptionOptions(rawValue: optionsValue)
            if options.contains(.shouldResume) {
                try? AVAudioSession.sharedInstance().setActive(true)
                client?.audioResume()
            }
        @unknown default: break
        }
    }

    @objc private func handleRouteChange(_ notification: Notification) {
        guard let info = notification.userInfo,
              let reasonValue = info[AVAudioSessionRouteChangeReasonKey] as? UInt,
              let reason = AVAudioSession.RouteChangeReason(rawValue: reasonValue)
        else {
            logger.warning("routeChange — unknown reason, refreshing only")
            IOSAudioRouter.shared.refreshRoutes()
            NotificationCenter.default.post(name: .voiceCatDeviceListChanged, object: nil)
            return
        }

        logger.info("routeChange reason=\(self.reasonLabel(reason))")

        // Re-apply preferences ONLY on external device plug/unplug. Do NOT re-apply on
        // .categoryChange / .routeConfigurationChange — those are triggered by our own
        // applyConfiguration() calls (setCategory, setPreferredInput, etc.), and re-applying
        // would create an infinite notification loop:
        //   handleRouteChange → applyConfiguration → setCategory → routeChange → ...
        // That loop burns CPU and cycles the audio session on/off — the "glitching" bug.
        // IOSAudioRouter.applyConfiguration() also has a re-entrancy guard for synchronous
        // notifications, but the reason check here is the primary defense.
        if reason == .oldDeviceUnavailable || reason == .newDeviceAvailable {
            logger.info("routeChange — external device change, re-applying config")
            IOSAudioRouter.shared.applyConfiguration()
        }

        IOSAudioRouter.shared.refreshRoutes()
        NotificationCenter.default.post(name: .voiceCatDeviceListChanged, object: nil)
    }

    private func reasonLabel(_ reason: AVAudioSession.RouteChangeReason) -> String {
        switch reason {
        case .oldDeviceUnavailable: return "oldDeviceUnavailable"
        case .newDeviceAvailable: return "newDeviceAvailable"
        case .categoryChange: return "categoryChange"
        case .override: return "override"
        case .wakeFromSleep: return "wakeFromSleep"
        case .noSuitableRouteForCategory: return "noSuitableRouteForCategory"
        case .routeConfigurationChange: return "routeConfigurationChange"
        @unknown default: return "unknown"
        }
    }
}

extension Notification.Name {
    static let voiceCatDeviceListChanged = Notification.Name("cat.voice.deviceListChanged")
}