using UIKit;
using VoiceCat.Audio;
using VoiceCat.Core;
using Voicecat.V1;
using Channel = Voicecat.V1.Channel;

namespace VoiceCat.iOS;

internal sealed record ChatEntry(DateTime Timestamp, string Sender, string Text, bool Private);
internal sealed record ActivityEntry(DateTime Timestamp, string Text);

internal sealed class AppModel
{
    internal static AppModel Shared { get; } = new();
    private readonly IosStorage storage = new();
    private readonly List<ServerProfile> profiles = [];
    private readonly List<ChatEntry> messages = [];
    private readonly List<ActivityEntry> activity = [];
    private readonly IosSettings settings = new();
    private readonly EventFeedback feedback;
    private CancellationTokenSource? lifetime;
    private VoiceCatClient? client;
    private TaskCompletionSource<bool>? identityDecision;
    private ServerProfile? connectedProfile;
    private int reconnectAttempt;
    private bool explicitDisconnect;
    private uint microphoneStream;
    private BroadcastAudioPump? broadcast;
    private Timer? levelTimer;
    private bool lastTalking;
    private bool restoringVoice;
    private uint restoreChannel;
    private bool restoreMuted;
    private bool restoreDeafened;
    private bool backgrounded;

    internal event Action? Changed;
    internal event Action<ServerIdentityChallenge>? IdentityRequested;
    internal IReadOnlyList<ServerProfile> Profiles => profiles;
    internal IReadOnlyList<ChatEntry> Messages => messages;
    internal IReadOnlyList<ActivityEntry> Activity => activity;
    internal IosSettings Settings => settings;
    internal VoiceCatClient? Client => client;
    internal bool IsConnected => client?.State == ClientConnectionState.Connected;
    internal bool IsConnecting { get; private set; }
    internal bool VoiceJoined => microphoneStream != 0;
    internal bool ScreenSharing => broadcast?.IsActive == true;
    internal bool IsBackgrounded => backgrounded;
    internal float MicrophoneLevel { get; private set; }
    internal string Status { get; private set; } = "Not connected";
    internal uint CurrentChannelId { get; private set; }
    internal uint SelfUserId => client?.Authentication?.Self.Id ?? 0;
    internal IReadOnlyList<Channel> Channels => client?.Channels ?? [];
    internal IReadOnlyList<User> Users => client?.Users ?? [];

    private AppModel() { feedback = new(settings); }
    internal void Load() { profiles.Clear(); profiles.AddRange(storage.LoadProfiles()); settings.Load(); IosAudioRouter.Shared.Load(); Notify(); }
    internal void Save() { storage.SaveProfiles(profiles); settings.Save(); }

    internal void DidEnterBackground()
    {
        backgrounded = true; Save();
        // Do not stop or rebuild AVAudioEngine here. With the `audio` background mode and an
        // active PlayAndRecord session, capture, playback, media UDP, and screen-ring draining
        // remain live while the scene is backgrounded or the device is locked.
    }

    internal void WillEnterForeground()
    {
        backgrounded = false;
        IosAudioRouter.Shared.Recover("foreground");
    }

    internal void DidBecomeActive()
    {
        backgrounded = false;
        IosAudioRouter.Shared.EnsureAudio("active scene");
        Notify();
    }

    internal void UpsertProfile(ServerProfile profile, string? password)
    {
        int index = profiles.FindIndex(item => item.Id == profile.Id);
        if (index < 0) profiles.Add(profile); else profiles[index] = profile;
        if (!string.IsNullOrEmpty(password)) storage.SavePassword(profile.Id, password);
        Save(); Notify();
    }

    internal void RemoveProfile(ServerProfile profile)
    {
        storage.RemovePassword(profile.Id); profiles.RemoveAll(item => item.Id == profile.Id); Save(); Notify();
    }

    internal async Task ConnectAsync(ServerProfile profile, string? suppliedPassword = null, bool restoring = false)
    {
        if (IsConnecting || IsConnected) return;
        explicitDisconnect = false; IsConnecting = true; connectedProfile = profile;
        Status = restoring ? "Reconnecting…" : "Connecting…"; Notify();
        lifetime?.Cancel(); lifetime?.Dispose(); lifetime = new();
        VoiceCatClient next = new("VoiceCat-iOS", "0.0.1", storage.TofuPath);
        client = next;
        try
        {
            await next.ConnectAsync(profile.Host, profile.Port, ConfirmIdentityAsync, lifetime.Token);
            AuthResult auth = profile.Authentication == ServerAuthentication.Guest
                ? await next.AuthenticateGuestAsync(profile.Nickname ?? "iOS User", lifetime.Token)
                : await next.AuthenticateUserAsync(profile.Username!, suppliedPassword ?? storage.LoadPassword(profile) ?? "", lifetime.Token);
            if (!auth.Ok) throw new InvalidOperationException(auth.Error);
            CurrentChannelId = auth.Self.ChannelId; reconnectAttempt = 0; IsConnecting = false; Status = "Connected";
            ApplyAudioSettings(next);
            IosAudioEngine.Shared.StartListening(next);
            broadcast = new(); broadcast.Changed += BroadcastChanged; broadcast.Start(next);
            _ = PumpEventsAsync(next, lifetime.Token);
            levelTimer?.Dispose(); levelTimer = new(_ => PollAudio(), null, 50, 50);
            feedback.Play(SoundEvent.Login); feedback.Speak(restoring ? "Reconnected" : "Connected");
            if (restoring && restoreChannel != 0) await RestoreSessionAsync(next);
            Notify();
        }
        catch (Exception exception)
        {
            IsConnecting = false; Status = exception.Message; Notify();
            await next.DisposeAsync(); if (ReferenceEquals(client, next)) client = null;
            if (restoring && !explicitDisconnect) ScheduleReconnect();
            else throw;
        }
    }

    private ValueTask<bool> ConfirmIdentityAsync(ServerIdentityChallenge challenge, CancellationToken token)
    {
        identityDecision = new(TaskCreationOptions.RunContinuationsAsynchronously);
        token.Register(() => identityDecision.TrySetCanceled(token));
        UIApplication.SharedApplication.BeginInvokeOnMainThread(() => IdentityRequested?.Invoke(challenge));
        return new(identityDecision.Task);
    }

    internal void ResolveIdentity(bool accepted) { identityDecision?.TrySetResult(accepted); identityDecision = null; }

    private async Task PumpEventsAsync(VoiceCatClient owner, CancellationToken token)
    {
        try
        {
            await foreach (Envelope envelope in owner.ReadEventsAsync(token))
            {
                if (envelope.JoinChannelResult?.Ok == true) CurrentChannelId = envelope.JoinChannelResult.ChannelId;
                if (envelope.JoinChannelResult is { Ok: false } joinFailure) AddActivity("Join failed: " + joinFailure.Error);
                if (envelope.TextMessage is { } text)
                {
                    User? sender = owner.Users.FirstOrDefault(user => user.Id == text.SenderId);
                    messages.Add(new(DateTime.Now, sender?.Nickname ?? $"User {text.SenderId}", text.Body, text.Scope == TextScope.TextPrivate));
                    if (messages.Count > 500) messages.RemoveAt(0);
                    bool self = text.SenderId == SelfUserId;
                    feedback.Play(text.Scope == TextScope.TextPrivate
                        ? self ? SoundEvent.PrivateSent : SoundEvent.PrivateReceived
                        : self ? SoundEvent.ChannelSent : SoundEvent.ChannelReceived);
                    if (!self) feedback.Speak(text.Scope == TextScope.TextPrivate ? $"Private message from {sender?.Nickname}: {text.Body}" : $"{sender?.Nickname}: {text.Body}");
                }
                if (envelope.UserEvent is { } userEvent) HandleUserEvent(owner, userEvent);
                if (envelope.StreamState is { } streamState) AddActivity($"{Name(owner, streamState.UserId)} {(streamState.Talking ? "started" : "stopped")} talking");
                if (envelope.StreamAnnounceResult?.Ok == false) AddActivity("Stream failed: " + envelope.StreamAnnounceResult.Error);
                if (envelope.GenericResult is { Ok: false } result) AddActivity("Operation failed: " + result.Message);
                if (envelope.Disconnect is { } disconnected) AddActivity("Disconnected: " + disconnected.Reason);
                UIApplication.SharedApplication.BeginInvokeOnMainThread(Notify);
            }
        }
        catch (OperationCanceledException) { }
        finally
        {
            if (ReferenceEquals(client, owner) && !explicitDisconnect)
            {
                CaptureRestoreState(owner); await StopSessionResourcesAsync(); client = null; Status = "Connection lost";
                feedback.Play(SoundEvent.ConnectionLost); feedback.Speak("Connection lost, reconnecting"); UIApplication.SharedApplication.BeginInvokeOnMainThread(Notify);
                ScheduleReconnect();
            }
        }
    }

    internal async Task JoinChannelAsync(uint channelId, string password = "")
    {
        VoiceCatClient active = client ?? throw new InvalidOperationException("Not connected.");
        Envelope response = await active.RequestAsync(new() { JoinChannel = new() { ChannelId = channelId, Password = password } });
        if (response.JoinChannelResult?.Ok != true) throw new InvalidOperationException(response.JoinChannelResult?.Error ?? "Join failed.");
        CurrentChannelId = channelId; Notify();
    }

    internal void SendText(string body, uint targetUser = 0)
    {
        if (string.IsNullOrWhiteSpace(body)) return;
        (client ?? throw new InvalidOperationException("Not connected.")).Send(new()
        {
            TextMessage = new() { Scope = targetUser == 0 ? TextScope.TextChannel : TextScope.TextPrivate,
                TargetId = targetUser == 0 ? CurrentChannelId : targetUser, Body = body.Trim(), ClientMsgId = Guid.NewGuid().ToString("N") }
        });
    }

    internal async Task ToggleVoiceAsync()
    {
        VoiceCatClient active = client ?? throw new InvalidOperationException("Not connected.");
        if (microphoneStream != 0)
        {
            IosAudioEngine.Shared.StopMicrophone(); active.StopStream(microphoneStream); microphoneStream = 0;
            await active.SubscribeVoiceAsync(false); MicrophoneLevel = 0; feedback.Play(SoundEvent.VoiceOff); Notify(); return;
        }
        if (AVFoundation.AVCaptureDevice.GetAuthorizationStatus(AVFoundation.AVAuthorizationMediaType.Audio) == AVFoundation.AVAuthorizationStatus.NotDetermined)
            await AVFoundation.AVCaptureDevice.RequestAccessForMediaTypeAsync(AVFoundation.AVAuthorizationMediaType.Audio);
        VoiceSubscriptionResult subscribed = await active.SubscribeVoiceAsync();
        if (!subscribed.Ok) throw new InvalidOperationException(subscribed.Error);
        int channels = IosAudioRouter.Shared.CaptureChannels;
        StreamInfo stream = await active.StartStreamAsync(StreamKind.StreamMic, "Microphone", channels);
        microphoneStream = stream.StreamId; IosAudioEngine.Shared.StartMicrophone(stream.StreamId, channels); feedback.Play(SoundEvent.VoiceOn); Notify();
    }

    internal void ToggleScreenAudio()
    {
        if (!OperatingSystem.IsIOSVersionAtLeast(27)) throw new PlatformNotSupportedException("Use the ReplayKit broadcast picker on this iOS version.");
        if (ScreenSharing) { IosScreenCapture.Stop(); broadcast?.RequestStop(); }
        else
        {
            if (!IsConnected || CurrentChannelId == 0) throw new InvalidOperationException("Connect and join a channel before sharing screen audio.");
            IosScreenCapture.Present();
        }
    }

    internal void SetSelfAudio(bool muted, bool deafened) { client?.SetSelfAudioState(muted, deafened); Notify(); }
    internal void SetPushToTalk(bool active)
    {
        if (client is null) return; client.Audio.PushToTalk = active;
        if (active) feedback.Play(SoundEvent.PushToTalk); Notify();
    }
    internal void ApplyVoiceSettings()
    {
        if (client is { } active) ApplyAudioSettings(active); settings.Save(); Notify();
    }

    internal async Task<GenericResult> RunAdminAsync(Func<VoiceCatClient, Task<GenericResult>> action)
    {
        GenericResult result = await action(client ?? throw new InvalidOperationException("Not connected."));
        AddActivity(result.Ok ? (string.IsNullOrEmpty(result.Message) ? "Operation completed." : result.Message) : "Operation failed: " + result.Message);
        Notify(); return result;
    }

    internal async Task DisconnectAsync()
    {
        explicitDisconnect = true; lifetime?.Cancel(); await StopSessionResourcesAsync();
        VoiceCatClient? old = client; client = null; microphoneStream = 0; IsConnecting = false; Status = "Not connected"; Notify();
        if (old is not null) await old.DisposeAsync(); feedback.Play(SoundEvent.Logout); feedback.Speak("Disconnected");
    }

    private void ScheduleReconnect()
    {
        ServerProfile? profile = connectedProfile; if (profile is null || explicitDisconnect) return;
        int delay = Math.Min(1 << Math.Min(reconnectAttempt++, 5), 30);
        _ = Task.Run(async () => { try { await Task.Delay(TimeSpan.FromSeconds(delay), lifetime?.Token ?? default); await ConnectAsync(profile, restoring: true); } catch { } });
    }

    private void Notify() => Changed?.Invoke();

    private void ApplyAudioSettings(VoiceCatClient owner)
    {
        owner.Audio.InputMode = settings.InputMode; owner.Audio.VadThreshold = settings.VadThreshold;
        owner.Audio.InputGain = settings.InputGain; owner.Audio.OutputGain = settings.OutputGain;
        owner.Audio.InputNoiseReduction = settings.InputNoiseReduction;
    }

    private void PollAudio()
    {
        VoiceCatClient? owner = client; uint stream = microphoneStream; if (owner is null || stream == 0) return;
        (float level, bool talking) = owner.Audio.GetLocalLevel(stream); MicrophoneLevel = level;
        if (talking != lastTalking) { lastTalking = talking; owner.PublishStreamState(stream, talking); feedback.Play(talking ? SoundEvent.VoiceStart : SoundEvent.VoiceStop); }
        UIApplication.SharedApplication.BeginInvokeOnMainThread(Notify);
    }

    private void HandleUserEvent(VoiceCatClient owner, UserEvent value)
    {
        string name = value.User?.Nickname ?? Name(owner, value.LeftId);
        if (value.Kind == UserEvent.Types.Kind.Joined && value.User?.ChannelId == CurrentChannelId && value.User.Id != SelfUserId)
        { AddActivity($"{name} joined"); feedback.Play(SoundEvent.ChannelJoin); feedback.Speak($"{name} joined"); }
        else if (value.Kind == UserEvent.Types.Kind.Left)
        { AddActivity($"{name} left"); feedback.Play(SoundEvent.ChannelLeave); feedback.Speak($"{name} left"); }
        User? self = owner.Users.FirstOrDefault(user => user.Id == SelfUserId); if (self is not null) CurrentChannelId = self.ChannelId;
    }

    private void AddActivity(string text) { activity.Add(new(DateTime.Now, text)); if (activity.Count > 500) activity.RemoveAt(0); }
    private static string Name(VoiceCatClient owner, uint id) => owner.Users.FirstOrDefault(user => user.Id == id)?.Nickname ?? $"User {id}";
    private void BroadcastChanged() => UIApplication.SharedApplication.BeginInvokeOnMainThread(Notify);

    private void CaptureRestoreState(VoiceCatClient owner)
    {
        restoreChannel = CurrentChannelId; restoringVoice = microphoneStream != 0;
        restoreMuted = owner.Audio.MicMuted; restoreDeafened = owner.Audio.Deafened;
    }

    private async Task RestoreSessionAsync(VoiceCatClient owner)
    {
        Envelope joined = await owner.RequestAsync(new() { JoinChannel = new() { ChannelId = restoreChannel } });
        if (joined.JoinChannelResult?.Ok != true) { AddActivity("Could not restore the previous channel."); return; }
        CurrentChannelId = restoreChannel;
        if (restoringVoice) await ToggleVoiceAsync();
        owner.SetSelfAudioState(restoreMuted, restoreDeafened); AddActivity($"Restored to channel {restoreChannel}{(restoringVoice ? " with voice" : "")}");
    }

    private async Task StopSessionResourcesAsync()
    {
        levelTimer?.Dispose(); levelTimer = null; IosAudioEngine.Shared.Stop(); microphoneStream = 0; MicrophoneLevel = 0;
        if (broadcast is { } pump) { broadcast = null; pump.Changed -= BroadcastChanged; await pump.DisposeAsync(); }
    }
}