using System;
using System.Collections.Concurrent;
using System.IO;
using System.Linq;
using System.Net.Http;
using System.Threading;
using System.Threading.Tasks;
using Jellyfin.Plugin.Jellypod.Models;
using Microsoft.Extensions.Logging;

namespace Jellyfin.Plugin.Jellypod.Services;

/// <summary>
/// Service for downloading podcast episodes.
/// </summary>
public sealed class PodcastDownloadService : IPodcastDownloadService, IDisposable
{
    private readonly ILogger<PodcastDownloadService> _logger;
    private readonly IHttpClientFactory _httpClientFactory;
    private readonly IPodcastStorageService _storageService;
    private readonly ConcurrentQueue<(Podcast Podcast, Episode Episode)> _downloadQueue = new();
    private readonly SemaphoreSlim _downloadSemaphore;
    private int _isProcessing;

    /// <summary>
    /// Initializes a new instance of the <see cref="PodcastDownloadService"/> class.
    /// </summary>
    /// <param name="logger">Logger instance.</param>
    /// <param name="httpClientFactory">HTTP client factory.</param>
    /// <param name="storageService">Storage service.</param>
    public PodcastDownloadService(
        ILogger<PodcastDownloadService> logger,
        IHttpClientFactory httpClientFactory,
        IPodcastStorageService storageService)
    {
        _logger = logger;
        _httpClientFactory = httpClientFactory;
        _storageService = storageService;

        var maxConcurrent = Plugin.Instance?.Configuration?.MaxConcurrentDownloads ?? 2;
        _downloadSemaphore = new SemaphoreSlim(maxConcurrent, maxConcurrent);
    }

    /// <inheritdoc />
    public Task QueueDownloadAsync(Podcast podcast, Episode episode)
    {
        _downloadQueue.Enqueue((podcast, episode));
        _logger.LogDebug("Queued download: {PodcastTitle} - {EpisodeTitle}", podcast.Title, episode.Title);

        // Start processing if not already running
        if (Interlocked.CompareExchange(ref _isProcessing, 1, 0) == 0)
        {
            _ = ProcessQueueAsync();
        }

        return Task.CompletedTask;
    }

    /// <inheritdoc />
    public async Task<string> DownloadEpisodeAsync(
        Podcast podcast,
        Episode episode,
        IProgress<double>? progress = null,
        CancellationToken cancellationToken = default)
    {
        var filePath = _storageService.GetEpisodeFilePath(podcast, episode);
        var directory = Path.GetDirectoryName(filePath);

        if (!string.IsNullOrEmpty(directory))
        {
            Directory.CreateDirectory(directory);
        }

        _logger.LogInformation("Downloading episode: {Title} to {Path}", episode.Title, filePath);

        try
        {
            episode.Status = EpisodeStatus.Downloading;

            var httpClient = _httpClientFactory.CreateClient("Jellypod");
            using var response = await httpClient.GetAsync(
                episode.AudioUrl,
                HttpCompletionOption.ResponseHeadersRead,
                cancellationToken).ConfigureAwait(false);

            response.EnsureSuccessStatusCode();

            var totalBytes = response.Content.Headers.ContentLength ?? -1;

            var contentStream = await response.Content.ReadAsStreamAsync(cancellationToken).ConfigureAwait(false);
            long totalRead;
            try
            {
                var fileStream = new FileStream(filePath, FileMode.Create, FileAccess.Write, FileShare.None, 81920, true);
                try
                {
                    var buffer = new byte[81920];
                    totalRead = 0L;
                    int bytesRead;

                    while ((bytesRead = await contentStream.ReadAsync(buffer, cancellationToken).ConfigureAwait(false)) > 0)
                    {
                        await fileStream.WriteAsync(buffer.AsMemory(0, bytesRead), cancellationToken).ConfigureAwait(false);
                        totalRead += bytesRead;

                        if (totalBytes > 0)
                        {
                            progress?.Report((double)totalRead / totalBytes * 100);
                        }
                    }
                }
                finally
                {
                    await fileStream.DisposeAsync().ConfigureAwait(false);
                }
            }
            finally
            {
                await contentStream.DisposeAsync().ConfigureAwait(false);
            }

            episode.LocalFilePath = filePath;
            episode.Status = EpisodeStatus.Downloaded;
            episode.DownloadedDate = DateTime.UtcNow;
            episode.FileSizeBytes = totalRead;

            _logger.LogInformation("Downloaded episode: {Title} ({Size} bytes)", episode.Title, totalRead);

            // Update the podcast in storage
            await _storageService.UpdatePodcastAsync(podcast).ConfigureAwait(false);

            return filePath;
        }
        catch (Exception ex)
        {
            episode.Status = EpisodeStatus.Error;
            _logger.LogError(ex, "Failed to download episode: {Title}", episode.Title);
            throw;
        }
    }

    /// <inheritdoc />
    public Task DeleteEpisodeFileAsync(Episode episode)
    {
        if (string.IsNullOrEmpty(episode.LocalFilePath))
        {
            return Task.CompletedTask;
        }

        try
        {
            if (File.Exists(episode.LocalFilePath))
            {
                File.Delete(episode.LocalFilePath);
                _logger.LogInformation("Deleted episode file: {Path}", episode.LocalFilePath);
            }

            episode.LocalFilePath = null;
            episode.Status = EpisodeStatus.Available;
            episode.DownloadedDate = null;
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Failed to delete episode file: {Path}", episode.LocalFilePath);
        }

        return Task.CompletedTask;
    }

    /// <inheritdoc />
    public async Task DownloadPodcastArtworkAsync(Podcast podcast, CancellationToken cancellationToken = default)
    {
        if (string.IsNullOrEmpty(podcast.ImageUrl))
        {
            return;
        }

        var config = Plugin.Instance?.Configuration;
        if (config?.CreatePodcastFolders != true)
        {
            return;
        }

        var basePath = _storageService.GetStoragePath();
        var podcastFolder = Path.Combine(basePath, SanitizeFileName(podcast.Title));
        var artworkPath = Path.Combine(podcastFolder, "folder.jpg");

        if (File.Exists(artworkPath))
        {
            return;
        }

        try
        {
            Directory.CreateDirectory(podcastFolder);

            var httpClient = _httpClientFactory.CreateClient("Jellypod");
            var imageBytes = await httpClient.GetByteArrayAsync(podcast.ImageUrl, cancellationToken).ConfigureAwait(false);
            await File.WriteAllBytesAsync(artworkPath, imageBytes, cancellationToken).ConfigureAwait(false);

            _logger.LogInformation("Downloaded artwork for podcast: {Title}", podcast.Title);
        }
        catch (Exception ex)
        {
            _logger.LogWarning(ex, "Failed to download artwork for podcast: {Title}", podcast.Title);
        }
    }

    private async Task ProcessQueueAsync()
    {
        try
        {
            while (_downloadQueue.TryDequeue(out var item))
            {
                await _downloadSemaphore.WaitAsync().ConfigureAwait(false);
                try
                {
                    await DownloadEpisodeAsync(item.Podcast, item.Episode).ConfigureAwait(false);
                }
                catch (Exception ex)
                {
                    _logger.LogError(ex, "Failed to process queued download: {Title}", item.Episode.Title);
                }
                finally
                {
                    _downloadSemaphore.Release();
                }
            }
        }
        finally
        {
            Interlocked.Exchange(ref _isProcessing, 0);
        }
    }

    private static string SanitizeFileName(string name)
    {
        var invalidChars = Path.GetInvalidFileNameChars();
        var result = new string(name.Where(c => !invalidChars.Contains(c)).ToArray());
        return result.Length > 100 ? result.Substring(0, 100).Trim() : result.Trim();
    }

    /// <inheritdoc />
    public void Dispose()
    {
        _downloadSemaphore.Dispose();
    }
}