import Foundation
import Network
import VoiceCatCore

struct PendingIdentity: Identifiable {
    let id = UUID()
    let displayText: String
    let tofuStatus: VoiceCatTofuStatus
}

@Observable
@MainActor
final class AppState {
    var servers: [SavedServer] = ServerListStore.shared.load()
    var session: SessionState?

    // Connect-flow state
    var isConnecting = false
    var connectStatus = ""
    var showAddServer = false
    var editingServer: SavedServer?
    var showPasswordPrompt = false
    var pendingIdentity: PendingIdentity?

    private var connectingClient: VoiceCatClient?
    private(set) var connectingServer: SavedServer?
    private var identityHandled = false

    /// Retained after authentication so an interrupted session can be restored.
    private var connectedServer: SavedServer?

    // MARK: - Reconnect state

    /// Distinguishes an explicit disconnect from a transport failure.
    private var userInitiatedDisconnect = false

    private struct LastSession {
        let server: SavedServer
        let channelId: UInt32
        let voiceSubscribed: Bool
        let micMuted: Bool
        let deafened: Bool
    }
    private var lastSession: LastSession?

    private var reconnectAttempt = 0

    private var reconnectTask: Task<Void, Never>?

    /// Detects interface changes before TCP keepalive notices a dead path.
    private var pathMonitor: NWPathMonitor?
    private let pathQueue = DispatchQueue(label: "cat.voice.network.path")

    private var lastPathSignature: String?

    // MARK: - Server list management

    func addServer(_ server: SavedServer, password: String?) {
        if let pw = password, !pw.isEmpty {
            ServerListStore.shared.savePassword(pw, tag: server.keychainTag)
        }
        servers.append(server)
        ServerListStore.shared.save(servers)
    }

    func updateServer(_ server: SavedServer, password: String?) {
        if let pw = password, !pw.isEmpty {
            ServerListStore.shared.savePassword(pw, tag: server.keychainTag)
        }
        if let idx = servers.firstIndex(where: { $0.id == server.id }) {
            servers[idx] = server
        }
        ServerListStore.shared.save(servers)
    }

    func removeServer(_ server: SavedServer) {
        ServerListStore.shared.deletePassword(tag: server.keychainTag)
        servers.removeAll(where: { $0.id == server.id })
        ServerListStore.shared.save(servers)
    }

    // MARK: - Connect flow

    func connectTo(_ server: SavedServer) {
        connectTo(server, restoring: nil)
    }

    private func connectTo(_ server: SavedServer, restoring: LastSession?) {
        guard !isConnecting else { return }
        isConnecting = true
        connectStatus = (restoring != nil) ? "Reconnecting…" : "Connecting…"
        connectingServer = server
        identityHandled = false
        userInitiatedDisconnect = false

        // Releasing the wrapper joins the core's I/O thread before freeing native strings.
        connectingClient = nil

        let config = VoiceCatConfig(
            clientName: "VoiceCat-iOS",
            clientVersion: "0.0.1",
            logLevel: .info,
            tofuStorePath: ServerListStore.shared.tofuStorePath)
        let client = VoiceCatClient(config: config)
        connectingClient = client

        client.onEvent = { [weak self] ev in
            Task { @MainActor [weak self] in
                self?.handleConnectEvent(ev, server: server, restoring: restoring)
            }
        }
        // Authentication can start audio, so select the external path before connecting.
        client.setExternalPlayback(true)
        client.connect(host: server.host, port: server.port)

        switch server.authMode {
        case .guest:
            let nick = (server.nickname?.isEmpty == false) ? server.nickname! : "iOS User"
            client.authenticateGuest(nick)
        case .password:
            let savedPw = ServerListStore.shared.loadPassword(tag: server.keychainTag)
            if let pw = savedPw, !pw.isEmpty {
                client.authenticateUser(server.savedUsername, password: pw)
            } else {
                showPasswordPrompt = true
            }
        }
    }

    func disconnect() {
        // Set before disconnect so its event cannot arm reconnect.
        userInitiatedDisconnect = true
        cancelReconnect()
        lastSession = nil
        session?.leaveVoice()
        session?.client.disconnect()
        IOSAudioEngine.shared.stop()
        AudioSessionManager.shared.deactivateSession()
        session = nil
        connectingClient?.disconnect()
        connectingClient = nil
        connectingServer = nil
        connectedServer = nil
        isConnecting = false
        connectStatus = ""
        showPasswordPrompt = false
        pendingIdentity = nil
    }

    // MARK: - Auth actions (called from prompt sheets)

    func authenticateUser(username: String, password: String) {
        connectingClient?.authenticateUser(username, password: password)
        showPasswordPrompt = false
    }

    func confirmServerIdentity(accept: Bool) {
        connectingClient?.confirmServerIdentity(accept: accept)
        pendingIdentity = nil
        if !accept { cancelConnect() }
    }

    func cancelConnect() {
        // User explicitly cancelled — no reconnect for the resulting .disconnected event.
        userInitiatedDisconnect = true
        cancelReconnect()
        lastSession = nil
        connectingClient?.disconnect()
        connectingClient = nil
        connectingServer = nil
        connectedServer = nil
        isConnecting = false
        connectStatus = ""
        showPasswordPrompt = false
        pendingIdentity = nil
    }

    // MARK: - Reconnect orchestration

    private func cancelReconnect() {
        reconnectTask?.cancel()
        reconnectTask = nil
        stopPathMonitor()
    }

    /// Schedules the next reconnect with exponential backoff capped at 30 seconds.
    private func scheduleReconnect() {
        guard !userInitiatedDisconnect, let last = lastSession else { return }
        reconnectTask?.cancel()
        reconnectAttempt = max(1, reconnectAttempt + 1)
        let delaySec = min(pow(2.0, Double(reconnectAttempt - 1)), 30.0)
        connectStatus = "Reconnecting (attempt \(reconnectAttempt))…"

        startPathMonitor()

        let task = Task { [weak self, last] in
            guard let self else { return }
            try? await Task.sleep(nanoseconds: UInt64(delaySec * 1_000_000_000))
            if Task.isCancelled { return }
            guard !self.userInitiatedDisconnect else { return }
            guard self.lastSession != nil else { return }
            guard self.session == nil else { return }
            self.connectTo(last.server, restoring: last)
        }
        reconnectTask = task
    }

    private func startPathMonitor() {
        guard pathMonitor == nil else { return }
        let monitor = NWPathMonitor()
        monitor.pathUpdateHandler = { [weak self] path in
            Task { @MainActor [weak self] in
                guard let self else { return }
                guard !self.userInitiatedDisconnect else { return }
                let sig = Self.pathSignature(path)
                let prevSig = self.lastPathSignature
                self.lastPathSignature = sig
                if prevSig == nil { return }

                if self.session != nil {
                    if path.status != .satisfied || sig != prevSig {
                        self.proactiveReconnect()
                    }
                } else if self.lastSession != nil {
                    if path.status == .satisfied {
                        self.reconnectAttempt = 0
                        self.scheduleReconnect()
                    }
                }
            }
        }
        monitor.start(queue: pathQueue)
        pathMonitor = monitor
    }

    private func stopPathMonitor() {
        pathMonitor?.cancel()
        pathMonitor = nil
        lastPathSignature = nil
    }

    private static func pathSignature(_ path: NWPath) -> String {
        guard path.status == .satisfied else { return "unsatisfied" }
        var parts: [String] = []
        if path.usesInterfaceType(.wifi)           { parts.append("wifi") }
        if path.usesInterfaceType(.cellular)       { parts.append("cellular") }
        if path.usesInterfaceType(.wiredEthernet)  { parts.append("wired") }
        if path.usesInterfaceType(.other)          { parts.append("other") }
        return parts.isEmpty ? "none" : parts.sorted().joined(separator: "+")
    }

    // MARK: - Live-session disconnect (called by SessionState)

    /// Receives disconnects after `SessionState` takes ownership of authenticated events.
    func onLiveSessionDisconnected() {
        guard !userInitiatedDisconnect else { return }
        teardownLiveSessionAndReconnect(sound: false)
    }

    private func proactiveReconnect() {
        guard !userInitiatedDisconnect else { return }
        guard session != nil else { return }
        teardownLiveSessionAndReconnect(sound: true)
    }

    private func teardownLiveSessionAndReconnect(sound: Bool) {
        if let s = session, let srv = connectedServer {
            lastSession = LastSession(
                server: srv,
                channelId: s.currentChannelId,
                voiceSubscribed: s.voiceState.voiceSubscribed,
                micMuted: s.voiceState.selfMuted,
                deafened: s.voiceState.selfDeafened)
        }
        IOSAudioEngine.shared.stop()
        AudioSessionManager.shared.deactivateSession()
        session = nil
        isConnecting = false
        connectingClient = nil
        connectedServer = nil
        if sound {
            EventFeedback.shared.play(.connectionLost)
            EventFeedback.shared.speak("Network changed — reconnecting")
        }
        reconnectAttempt = 0
        scheduleReconnect()
    }

    // MARK: - Connect event handler

    private func handleConnectEvent(_ ev: VoiceCatEvent, server: SavedServer,
                                    restoring: LastSession?) {
        switch ev.type {
        case .connectionState:
            switch ev.connectionState {
            case .connecting:        connectStatus = (restoring != nil) ? "Reconnecting…" : "Connecting…"
            case .tlsHandshake:      connectStatus = "TLS handshake…"
            case .authenticating:    connectStatus = "Authenticating…"
            case .verifyingIdentity: connectStatus = "Verifying server identity…"
            case .connected:        connectStatus = "Connected"
            default: break
            }
        case .serverIdentity:
            guard !identityHandled else { break }
            let tofuStatus = ev.tofuStatus ?? .firstConnect
            if tofuStatus == .matched {
                connectingClient?.confirmServerIdentity(accept: true)
            } else {
                identityHandled = true
                let displayText = connectingClient?.getServerIdentityDisplay() ?? ""
                pendingIdentity = PendingIdentity(displayText: displayText, tofuStatus: tofuStatus)
            }
        case .authResult:
            if ev.result == .ok {
                guard let client = connectingClient else { break }
                let perms = client.getPermissions()
                let newSession = SessionState(client: client, selfUserId: ev.userId, permissions: perms)
                newSession.appState = self
                connectingClient = nil
                isConnecting = false
                connectStatus = ""
                showPasswordPrompt = false
                connectedServer = server
                self.session = newSession
                EventFeedback.shared.play(.login)
                EventFeedback.shared.speak(restoring != nil ? "Reconnected" : "Connected")
                // External-playback mode was enabled before connect() so the core never opens a
                // miniaudio device on iOS (the single ordering rule of the unified audio path).
                // Now activate the session and start the engine in listening mode so remote audio
                // plays the moment someone talks, even before we join voice (no "can't hear anyone").
                do {
                    try AudioSessionManager.shared.ensureSessionActive()
                } catch {
                    print("Audio session activate on connect failed: \(error)")
                }
                IOSAudioEngine.shared.startListening(client: client)
                // The path monitor runs the whole time we're connected so a network change fires
                // proactiveReconnect immediately instead of waiting for the C core's TCP keepalive
                // timeout (~30-60 s on a hard Wi-Fi drop). It stays armed across reconnects and is
                // stopped only on user-initiated disconnect.
                startPathMonitor()

                // Reconnect restore: rejoin the prior channel and re-enable voice/mic if they
                // were on. The session is fresh (server auto-places us in Lobby), so the restore
                // is driven through SessionState.requestRestore, which issues a JoinChannel then
                // (on the resulting .joinResult) re-arms voice + mute/deafen. A successful auth
                // means the server is reachable, so the backoff counter resets and `lastSession`
                // clears; the path monitor keeps watching for the next change.
                if let restoring {
                    newSession.requestRestore(channelId: restoring.channelId,
                                              voiceSubscribed: restoring.voiceSubscribed,
                                              micMuted: restoring.micMuted,
                                              deafened: restoring.deafened)
                    reconnectAttempt = 0
                    lastSession = nil
                }
            } else {
                connectStatus = "Auth failed: \(ev.result.description)"
                showPasswordPrompt = true
            }
        case .disconnected:
            // This handler runs ONLY during the connecting phase — after auth success
            // `SessionState.init` overwrites `client.onEvent`, so a live-session disconnect
            // reaches `SessionState.handleEvent` and comes back via
            // `onLiveSessionDisconnected`, not here. Two outcomes for this branch:
            //   - A reconnect's connecting phase failed (`lastSession != nil`, set by a prior
            //     teardown) → re-arm `scheduleReconnect` so the backoff loop continues.
            //   - A fresh connect failed before auth (`lastSession == nil`) → show the error, do
            //     not auto-reconnect (the user should retry manually once the server is reachable).
            connectingClient = nil
            isConnecting = false
            IOSAudioEngine.shared.stop()
            AudioSessionManager.shared.deactivateSession()

            if userInitiatedDisconnect {
                connectStatus = ""
                showPasswordPrompt = false
                pendingIdentity = nil
                lastSession = nil
                connectedServer = nil
                cancelReconnect()
            } else if lastSession != nil {
                // Mid-reconnect drop — keep the backoff loop going.
                EventFeedback.shared.play(.connectionLost)
                EventFeedback.shared.speak("Connection lost — reconnecting")
                scheduleReconnect()
            } else {
                // Fresh connect failed before auth. Surface the reason; no auto-reconnect.
                connectStatus = ev.text ?? "Disconnected"
                showPasswordPrompt = false
                pendingIdentity = nil
                connectedServer = nil
                cancelReconnect()
            }
        case .error:
            connectStatus = ev.text ?? "Unknown error"
            // Errors don't disconnect us; the .disconnected event handles teardown/reconnect.
        default:
            break
        }
    }
}