using System.Collections.Generic;
using System.Linq;
using System.Windows;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Threading;
using ytLive.Models;
using ytLive.Services.Audio;
using ytLive.Services.Compositor;

namespace ytLive.Services;

/// <summary>
/// The native alert box (OBS-style celebration zone, no third party). Owns the
/// event queue and the animation clock: <see cref="ChatEventKind"/> events from
/// the chat feed are enqueued one-at-a-time and played through a celebration
/// animation (<see cref="AlertRenderer"/>) OR — when the alert-box video is
/// configured and resolves — through a decoded clip. Frames are served to the
/// stream compositor via <see cref="RenderFrame"/> and mirrored to the preview
/// via <see cref="UpdatePreview"/>. Idle = transparent (null frame); playback is
/// advanced by a 33ms dispatch ticker. The clock is exposed as
/// <see cref="Advance"/> so tests drive playback deterministically without the
/// timer. Ordinary chat rows (<see cref="ChatEventKind.None"/>) never enqueue —
/// a subscriber mention is a chat row, not an alert.
///
/// TASK 47 (Stream Alerts video): a video-backed alert replaces the animation
/// while a clip decodes (<see cref="IAlertClipDecoder"/>, one per play). The
/// clip plays at its own media pace; the layer applies a ~300ms fade-in/out
/// alpha envelope to the frames AND the audio samples (freeze-frame fade-out on
/// the tail), clips the alert to the clip length, and forwards the scaled audio
/// to the mixer's alert ring via <paramref name="audioSink"/> (no duck). The
/// per-source config (path/default/ticker/volume) is resolved through
/// <paramref name="clipPathResolver"/>; the ticker strip is served via
/// <see cref="AlertTickerFrame"/>.
/// </summary>
public sealed class AlertOverlayLayer : IDisposable
{
    /// <summary>The fade-in/out ramp length (video alpha AND audio gain). Measured
    /// against a real clip in the AlertLayerVideoTests unit; keep the ramp short
    /// enough to read as a "pop-in" on stream (see ai.md).</summary>
    internal const double FadeDurationSeconds = 0.30;

    private static readonly TimeSpan TickInterval = TimeSpan.FromMilliseconds(33);

    private readonly AlertRenderer _renderer;
    private readonly Func<string, int, int, IAlertClipDecoder>? _clipDecoderFactory;
    private readonly Func<Source, string?>? _clipPathResolver;
    private readonly Action<AudioSample>? _audioSink;
    private readonly Queue<ChatMessage> _queue = new();
    private readonly DispatcherTimer? _ticker;

    private ChatMessage? _current;
    private Source? _currentBox;
    private IAlertClipDecoder? _clip;
    private VideoFrame? _latestClipFrame;
    private bool _clipEof;
    private double _clipEofElapsed;
    private int _clipWidth;
    private int _clipHeight;
    private string? _tickerText;
    private double _elapsed;
    private IEnumerable<Scene>? _scenes;

    private int _contentVersion;
    private int _frameVersion = -1;
    private string? _frameKey;
    private VideoFrame? _cachedFrame;

    public AlertOverlayLayer(
        AlertRenderer renderer,
        Func<string, int, int, IAlertClipDecoder>? clipDecoderFactory = null,
        Func<Source, string?>? clipPathResolver = null,
        Action<AudioSample>? audioSink = null)
    {
        _renderer = renderer;
        _clipDecoderFactory = clipDecoderFactory;
        _clipPathResolver = clipPathResolver;
        _audioSink = audioSink;
        if (Application.Current != null)
        {
            _ticker = new DispatcherTimer { Interval = TickInterval };
            _ticker.Tick += (_, _) =>
            {
                Advance(TickInterval.TotalSeconds);
                RefreshAlertPreviews();
            };
        }
    }

    /// <summary>Production entry from the chat feed: enqueue one event. Messages
    /// arrive on the chat poller thread, so this marshals to the UI thread (same
    /// rule as <see cref="ChatOverlayLayer.OnMessageReceived"/>) — the preview
    /// writes create WPF <see cref="WriteableBitmap"/> instances, and creating a
    /// DependencySource off the UI thread crashes the WPF binding engine
    /// (ArgumentException "Must create DependencySource on same Thread").</summary>
    public void OnMessageReceived(ChatMessage message, IEnumerable<Scene> scenes)
    {
        var app = Application.Current;
        if (app != null && !app.Dispatcher.CheckAccess())
        {
            app.Dispatcher.Invoke(() => Ingest(message, scenes));
            return;
        }
        Ingest(message, scenes);
    }

    private void Ingest(ChatMessage message, IEnumerable<Scene> scenes)
    {
        _scenes = scenes;
        Enqueue(message);
        _ticker?.Start();
        RefreshAlertPreviews();
    }

    /// <summary>Queue an event (pure — also the test seam). Chat rows carry
    /// <see cref="ChatEventKind.None"/> and are ignored: no alert for a mention.</summary>
    public void Enqueue(ChatMessage message)
    {
        if (message.Kind == ChatEventKind.None) return;
        if (_queue.Count >= 10) return; // back-to-back floods drop the tail, never stall playback
        _queue.Enqueue(message);
        if (_current == null)
        {
            _current = _queue.Dequeue();
            _elapsed = 0;
            BeginClip();
        }
        _contentVersion++;
    }

    /// <summary>Advance the playback clock (the ticker's beat — and the test seam;
    /// tests call this directly and never start the timer). Draining the queue to
    /// nothing stops the ticker and leaves the box transparent.</summary>
    public void Advance(double deltaSeconds)
    {
        // Video-backed alert: duration is clip-driven. The clip plays at media
        // pace; once it EOFs the last frame sweeps through the fade-out before
        // the alert moves on (a hard cut at EOF would pop, not fade).
        if (_clip != null)
        {
            _elapsed += deltaSeconds;
            if (_clipEof && _elapsed - _clipEofElapsed >= FadeDurationSeconds)
            {
                _clipEof = false;
                StopClip();
                _current = null;
                _elapsed = 0;
                AdvanceToNext();
            }
            _contentVersion++;
            return;
        }

        if (_current == null)
        {
            if (_queue.Count == 0) return;
            _current = _queue.Dequeue();
            _elapsed = 0;
            BeginClip();
            _contentVersion++;
            return;
        }

        _elapsed += deltaSeconds;
        if (_elapsed >= DurationOf(_current))
        {
            _current = null;
            _elapsed = 0;
            AdvanceToNext();
        }
        _contentVersion++;
    }

    /// <summary>Whether an alert is currently playing or queued.</summary>
    public bool IsPlaying => _current != null || _queue.Count > 0;

    /// <summary>The live-output frame for one AlertBox element: the decoded clip
    /// frame (faded) while a clip is active, else the animation frame, null
    /// (transparent) when idle.</summary>
    public VideoFrame? RenderFrame(Source alertBox)
    {
        if (_current == null)
        {
            _frameKey = null;
            return null;
        }

        if (_clip != null)
            return RenderClipFrame(alertBox);

        var width = (int)Math.Max(1, alertBox.Width);
        var height = (int)Math.Max(1, alertBox.Height);
        var key = $"{width}x{height}|{_current.Id}|{Progress()}";

        if (_frameKey == key && _frameVersion == _contentVersion)
            return _cachedFrame;

        var app = Application.Current;
        if (app != null && !app.Dispatcher.CheckAccess())
        {
            var capturedKey = key;
            var capturedVersion = _contentVersion;
            return app.Dispatcher.Invoke(() =>
            {
                if (_frameKey == capturedKey && _frameVersion == capturedVersion)
                    return _cachedFrame;
                return RenderCore(alertBox, width, height, capturedKey, capturedVersion);
            });
        }

        return RenderCore(alertBox, width, height, key, _contentVersion);
    }

    /// <summary>The global ticker strip for the stream output (top edge, full
    /// master width): a marquee of "viewer — event" while an alert is playing
    /// and the config has the ticker on, else null. Pure byte-math per call so
    /// the frame pump can read it on any thread (the text strip is rasterized
    /// once on the UI thread and cached).</summary>
    public VideoFrame? AlertTickerFrame
    {
        get
        {
            if (_current == null || string.IsNullOrWhiteSpace(_tickerText)) return null;
            return AlertTickerRenderer.Render(_tickerText!, _elapsed);
        }
    }

    private VideoFrame? RenderClipFrame(Source alertBox)
    {
        var frame = _latestClipFrame;
        if (frame == null) return null;

        var w = (int)Math.Max(1, alertBox.Width);
        var h = (int)Math.Max(1, alertBox.Height);
        if (frame.Width != w || frame.Height != h)
            frame = StretchMath.BilinearScale(frame, w, h);

        var fade = FadeAt();
        if (fade >= 1.0) return frame;

        // Straight-alpha source-over on the compositor side: scale the source
        // alpha by the envelope so the clip blends out (a 680x200 copy per fade
        // tick is trivial; outside the ramps fade==1 returns the raw frame).
        var copy = new byte[frame.BgraPixels.Length];
        Buffer.BlockCopy(frame.BgraPixels, 0, copy, 0, copy.Length);
        var a = (byte)(fade * 255 + 0.5);
        for (var i = 3; i < copy.Length; i += 4)
            copy[i] = (byte)((copy[i] * a) >> 8);
        return new VideoFrame(frame.Width, frame.Height, copy);
    }

    private double FadeAt()
    {
        if (_clip == null) return 1.0;
        if (_clipEof)
            return Math.Clamp(1.0 - (_elapsed - _clipEofElapsed) / FadeDurationSeconds, 0.0, 1.0);
        return Math.Clamp(_elapsed / FadeDurationSeconds, 0.0, 1.0);
    }

    private void BeginClip()
    {
        StopClip();
        _tickerText = null;
        if (_current == null) return;

        var box = _scenes?.SelectMany(s => s.Elements).OfType<Source>()
            .FirstOrDefault(s => s.Type == SourceType.AlertBox);
        _currentBox = box;
        if (box != null && box.AlertShowTicker)
            _tickerText = ComposeTicker(_current);

        if (box == null || _clipDecoderFactory == null) return;
        var path = _clipPathResolver?.Invoke(box);
        if (string.IsNullOrWhiteSpace(path)) return;

        _clipWidth = (int)Math.Max(1, box.Width);
        _clipHeight = (int)Math.Max(1, box.Height);
        try
        {
            _clip = _clipDecoderFactory(path, _clipWidth, _clipHeight);
            _clip.FrameAvailable += OnClipFrame;
            _clip.AudioReady += OnClipAudio;
            _clip.Completed += OnClipCompleted;
            _clip.Start();
        }
        catch
        {
            StopClip(); // decode setup failed (bad path) — fall back to animations
        }
    }

    private void StopClip()
    {
        var clip = _clip;
        _clip = null;
        _latestClipFrame = null;
        _clipEof = false;
        if (clip == null) return;
        clip.FrameAvailable -= OnClipFrame;
        clip.AudioReady -= OnClipAudio;
        clip.Completed -= OnClipCompleted;
        try { clip.Stop(); } catch { /* already stopped */ }
        clip.Dispose();
    }

    private void OnClipFrame(VideoFrame frame) => _latestClipFrame = frame;

    private void OnClipCompleted()
    {
        _clipEof = true;
        _clipEofElapsed = _elapsed;
    }

    private void OnClipAudio(AudioSample sample)
    {
        if (_audioSink == null) return;
        var volume = (float)Math.Clamp(_currentBox?.AlertVideoVolume ?? 1.0, 0.0, 1.0);
        if (volume <= 0f) return;
        var fade = FadeAt();
        if (fade <= 0.0) return;

        var data = sample.Samples;
        if (fade < 1.0 || Math.Abs(volume - 1f) > 0.001f)
        {
            data = new float[data.Length];
            var gain = volume * (float)fade;
            for (var i = 0; i < sample.Samples.Length; i++)
                data[i] = sample.Samples[i] * gain;
        }
        _audioSink(new AudioSample(data, sample.SampleRate, sample.Channels));
    }

    private void AdvanceToNext()
    {
        if (_queue.Count > 0)
        {
            _current = _queue.Dequeue();
            _elapsed = 0;
            BeginClip();
        }
        else
        {
            _ticker?.Stop();
        }
    }

    private VideoFrame? RenderCore(Source alertBox, int width, int height, string key, int version)
    {
        _frameKey = key;
        _frameVersion = version;
        if (_current == null) return _cachedFrame = null;
        return _cachedFrame = _renderer.Render(_current, Progress(), width, height);
    }

    private double Progress()
    {
        if (_current == null) return 0;
        return Math.Clamp(_elapsed / DurationOf(_current), 0.0, 1.0);
    }

    private static double DurationOf(ChatMessage m) => m.Kind switch
    {
        ChatEventKind.SuperChat => 4.6,
        ChatEventKind.SuperSticker => 4.2,
        ChatEventKind.NewMember => 4.0,
        ChatEventKind.MemberGift => 5.0,
        ChatEventKind.GiftReceived => 4.4,
        ChatEventKind.MemberMilestone => 4.8,
        _ => 4.0,
    };

    private static string ComposeTicker(ChatMessage m)
    {
        var label = m.Kind switch
        {
            ChatEventKind.SuperChat => "Super Chat",
            ChatEventKind.SuperSticker => "Super Sticker",
            ChatEventKind.NewMember => "New Member",
            ChatEventKind.MemberGift => "Membership Gift",
            ChatEventKind.GiftReceived => "Gifted Membership",
            ChatEventKind.MemberMilestone => "Member Milestone",
            _ => "Stream Alert",
        };
        var amount = m.Kind is ChatEventKind.SuperChat or ChatEventKind.SuperSticker
            && m.SuperChatDisplayString is { Length: > 0 } s
                ? $" · {s}"
                : "";
        return $"{m.AuthorName} — {label}{amount}";
    }

    /// <summary>Render the current state onto one AlertBox preview (mirrors chat):
    /// the playing frame, or null when idle so the source shows nothing until an
    /// event actually fires.</summary>
    public void UpdatePreview(Source alertBox)
    {
        try
        {
            var frame = RenderFrame(alertBox);
            if (frame == null)
            {
                alertBox.VideoImageSource = null;
                return;
            }
            var width = (int)Math.Max(1, alertBox.Width);
            var height = (int)Math.Max(1, alertBox.Height);
            var bitmap = new WriteableBitmap(width, height, 96, 96, PixelFormats.Bgra32, null);
            bitmap.WritePixels(new Int32Rect(0, 0, width, height), frame.BgraPixels, frame.Stride, 0);
            alertBox.VideoImageSource = bitmap;
        }
        catch (Exception ex)
        {
            System.Diagnostics.Debug.WriteLine($"Alert preview failed: {ex.Message}");
        }
    }

    /// <summary>Wire property-change subscriptions for all AlertBox sources across
    /// every scene (geometry changes re-render), and clear/reset their previews.</summary>
    public void UpdateConfiguredBoxes(IEnumerable<Scene> scenes)
    {
        _scenes = scenes;
        foreach (var scene in scenes)
        foreach (var alertBox in scene.Elements.OfType<Source>().Where(s => s.Type == SourceType.AlertBox))
        {
            alertBox.PropertyChanged += (_, e) =>
            {
                if (e.PropertyName is nameof(Source.Width) or nameof(Source.Height))
                    UpdatePreview(alertBox);
            };
            UpdatePreview(alertBox);
        }
    }

    private void RefreshAlertPreviews()
    {
        if (_scenes == null) return;
        foreach (var alertBox in _scenes.SelectMany(s => s.Elements).OfType<Source>()
                     .Where(s => s.Type == SourceType.AlertBox))
            UpdatePreview(alertBox);
    }

    public void Dispose()
    {
        _ticker?.Stop();
        _queue.Clear();
        _current = null;
        StopClip();
    }
}