using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using System.Diagnostics;

namespace Evergreen.Health.Application.Health.Integrations.MiAirX;

/// <summary>Demo 音乐任务由服务端持续驱动，页面关闭后仍按体质曲目循环渐弱播放。</summary>
public sealed class TcmMusicTransitionService : IHostedService
{
    private readonly MiAirXClient _miAirX;
    private readonly TcmMusicOptions _options;
    private readonly ILogger<TcmMusicTransitionService> _logger;
    private readonly SemaphoreSlim _operationLock = new(1, 1);
    private CancellationTokenSource? _activeCancellation;
    private Task? _activeTask;

    public TcmMusicTransitionService(
        IHttpClientFactory httpClientFactory,
        IOptions<MiAirXOptions> miAirXOptions,
        IOptions<TcmMusicOptions> musicOptions,
        ILogger<TcmMusicTransitionService> logger)
    {
        _miAirX = new MiAirXClient(httpClientFactory.CreateClient(nameof(TcmMusicTransitionService)), miAirXOptions);
        _options = musicOptions.Value;
        _logger = logger;
    }

    public Task StartAsync(CancellationToken cancellationToken) => Task.CompletedTask;

    public async Task StopAsync(CancellationToken cancellationToken)
    {
        try { await StopMusicAsync(cancellationToken); }
        catch (Exception exception) when (exception is not OperationCanceledException)
        {
            _logger.LogWarning(exception, "应用退出时未能停止助眠音乐");
        }
    }

    public bool HasPlayableTracks(string constitutionCode)
        => _miAirX.IsConfigured &&
           _options.Tracks.TryGetValue(constitutionCode, out var tracks) && tracks.Count > 0 &&
           tracks.All(track => IsValidTrack(track));

    public async Task StartForConstitutionAsync(string constitutionCode, CancellationToken cancellationToken)
    {
        if (!HasPlayableTracks(constitutionCode))
            throw new InvalidOperationException($"{constitutionCode} 的体质音乐 OSS URL 尚未配置完整");
        if (_options.StartVolume is < 1 or > 100 || _options.FadeStepSeconds is < 1 or > 60)
            throw new InvalidOperationException("体质音乐渐弱参数无效");

        var tracks = _options.Tracks[constitutionCode].ToArray();
        await _operationLock.WaitAsync(cancellationToken);
        try
        {
            await CancelCurrentLoopAsync();
            await _miAirX.SetVolumeAsync(_options.StartVolume, cancellationToken);
            await _miAirX.PlayUrlAsync(tracks[0].Url, cancellationToken);
            _activeCancellation = new CancellationTokenSource();
            _activeTask = RunFadeAsync(tracks, constitutionCode, _activeCancellation.Token);
        }
        finally { _operationLock.Release(); }
    }

    public async Task PlayTestMusicAsync(CancellationToken cancellationToken)
    {
        await _operationLock.WaitAsync(cancellationToken);
        try
        {
            await CancelCurrentLoopAsync();
            await _miAirX.PlayAsync(cancellationToken);
        }
        finally { _operationLock.Release(); }
    }

    public async Task SetManualVolumeAsync(int volume, CancellationToken cancellationToken)
    {
        await _operationLock.WaitAsync(cancellationToken);
        try
        {
            // 手动调音量接管当前播放，避免下一次自动渐弱立刻覆盖用户选择。
            await CancelCurrentLoopAsync();
            await _miAirX.SetVolumeAsync(volume, cancellationToken);
        }
        finally { _operationLock.Release(); }
    }

    public async Task StopMusicAsync(CancellationToken cancellationToken)
    {
        await _operationLock.WaitAsync(cancellationToken);
        try
        {
            await CancelCurrentLoopAsync();
            await _miAirX.StopAsync(cancellationToken);
        }
        finally { _operationLock.Release(); }
    }

    private async Task RunFadeAsync(
        IReadOnlyList<TcmMusicTrackOptions> tracks,
        string constitutionCode,
        CancellationToken cancellationToken)
    {
        var clock = Stopwatch.StartNew();
        var currentVolume = _options.StartVolume;
        var nextFadeSecond = (double)_options.FadeStepSeconds;
        var trackStartSecond = 0d;
        var trackIndex = 0;
        try
        {
            while (true)
            {
                await Task.Delay(TimeSpan.FromSeconds(1), cancellationToken);
                var elapsed = clock.Elapsed.TotalSeconds;
                while (elapsed >= nextFadeSecond && currentVolume > 0)
                {
                    currentVolume--;
                    await _miAirX.SetVolumeAsync(currentVolume, cancellationToken);
                    nextFadeSecond += _options.FadeStepSeconds;
                }

                if (currentVolume == 0)
                {
                    await _miAirX.StopAsync(cancellationToken);
                    _logger.LogInformation("体质 {ConstitutionCode} 的助眠音乐已渐弱至 0 并停止", constitutionCode);
                    return;
                }

                if (elapsed - trackStartSecond < tracks[trackIndex].DurationSeconds) continue;
                trackIndex = (trackIndex + 1) % tracks.Count;
                await _miAirX.PlayUrlAsync(tracks[trackIndex].Url, cancellationToken);
                trackStartSecond = clock.Elapsed.TotalSeconds;
                _logger.LogInformation("体质 {ConstitutionCode} 循环播放 {Track}，继承音量 {Volume}",
                    constitutionCode, tracks[trackIndex].Title, currentVolume);
            }
        }
        catch (OperationCanceledException) when (cancellationToken.IsCancellationRequested) { }
        catch (Exception exception)
        {
            _logger.LogWarning(exception, "体质音乐渐弱或续播中断");
            try { await _miAirX.StopAsync(CancellationToken.None); }
            catch (Exception stopException) { _logger.LogWarning(stopException, "体质音乐中断后停止音箱失败"); }
        }
    }

    private async Task CancelCurrentLoopAsync()
    {
        var cancellation = _activeCancellation;
        var task = _activeTask;
        _activeCancellation = null;
        _activeTask = null;
        if (cancellation is null) return;
        cancellation.Cancel();
        try { if (task is not null) await task; }
        finally { cancellation.Dispose(); }
    }

    private static bool IsValidTrack(TcmMusicTrackOptions track)
        => track.DurationSeconds > 0 &&
           Uri.TryCreate(track.Url, UriKind.Absolute, out var uri) &&
           uri.Scheme is "http" or "https";
}