using System;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Text.Json;
using System.Threading;
using System.Threading.Tasks;
using Jellyfin.Plugin.Jellypod.Models;
using MediaBrowser.Common.Configuration;
using Microsoft.Extensions.Logging;

namespace Jellyfin.Plugin.Jellypod.Services;

/// <summary>
/// Service for storing and retrieving podcast data.
/// </summary>
public sealed class PodcastStorageService : IPodcastStorageService, IDisposable
{
    private static readonly JsonSerializerOptions JsonOptions = new()
    {
        WriteIndented = true,
        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
        PropertyNameCaseInsensitive = true
    };

    private readonly ILogger<PodcastStorageService> _logger;
    private readonly IApplicationPaths _applicationPaths;
    private readonly SemaphoreSlim _dbLock = new(1, 1);
    private PodcastDatabase? _cache;

    /// <summary>
    /// Initializes a new instance of the <see cref="PodcastStorageService"/> class.
    /// </summary>
    /// <param name="logger">Logger instance.</param>
    /// <param name="applicationPaths">Application paths.</param>
    public PodcastStorageService(ILogger<PodcastStorageService> logger, IApplicationPaths applicationPaths)
    {
        _logger = logger;
        _applicationPaths = applicationPaths;
        _logger.LogInformation("Jellypod database path: {Path}", DatabasePath);
        _logger.LogInformation("PluginConfigurationsPath: {Path}", applicationPaths.PluginConfigurationsPath);
    }

    private string DatabasePath => Path.Combine(
        _applicationPaths.PluginConfigurationsPath,
        "Jellypod",
        "podcasts.json");

    /// <inheritdoc />
    public async Task<IReadOnlyList<Podcast>> GetAllPodcastsAsync()
    {
        var db = await LoadDatabaseAsync().ConfigureAwait(false);
        return db.Podcasts.ToList();
    }

    /// <inheritdoc />
    public async Task<Podcast?> GetPodcastAsync(Guid id)
    {
        var db = await LoadDatabaseAsync().ConfigureAwait(false);
        return db.Podcasts.FirstOrDefault(p => p.Id == id);
    }

    /// <inheritdoc />
    public async Task AddPodcastAsync(Podcast podcast)
    {
        await _dbLock.WaitAsync().ConfigureAwait(false);
        try
        {
            var db = await LoadDatabaseInternalAsync().ConfigureAwait(false);
            db.Podcasts.Add(podcast);
            await SaveDatabaseInternalAsync(db).ConfigureAwait(false);
            _logger.LogInformation("Added podcast: {Title}", podcast.Title);
        }
        finally
        {
            _dbLock.Release();
        }
    }

    /// <inheritdoc />
    public async Task UpdatePodcastAsync(Podcast podcast)
    {
        await _dbLock.WaitAsync().ConfigureAwait(false);
        try
        {
            var db = await LoadDatabaseInternalAsync().ConfigureAwait(false);
            var existing = db.Podcasts.FirstOrDefault(p => p.Id == podcast.Id);
            if (existing != null)
            {
                var index = db.Podcasts.IndexOf(existing);
                db.Podcasts[index] = podcast;
                await SaveDatabaseInternalAsync(db).ConfigureAwait(false);
                _logger.LogDebug("Updated podcast: {Title}", podcast.Title);
            }
        }
        finally
        {
            _dbLock.Release();
        }
    }

    /// <inheritdoc />
    public async Task DeletePodcastAsync(Guid id)
    {
        await _dbLock.WaitAsync().ConfigureAwait(false);
        try
        {
            var db = await LoadDatabaseInternalAsync().ConfigureAwait(false);
            var podcast = db.Podcasts.FirstOrDefault(p => p.Id == id);
            if (podcast != null)
            {
                db.Podcasts.Remove(podcast);
                await SaveDatabaseInternalAsync(db).ConfigureAwait(false);
                _logger.LogInformation("Deleted podcast: {Title}", podcast.Title);
            }
        }
        finally
        {
            _dbLock.Release();
        }
    }

    /// <inheritdoc />
    public string GetEpisodeFilePath(Podcast podcast, Episode episode)
    {
        var basePath = GetStoragePath();
        var config = Plugin.Instance?.Configuration;

        var safePodcastTitle = SanitizeFileName(podcast.Title);
        var safeEpisodeTitle = SanitizeFileName(episode.Title);
        var extension = GetAudioExtension(episode.AudioUrl);

        // Format: YYYY-MM-DD - Episode Title.mp3
        var datePrefix = episode.PublishedDate.ToString("yyyy-MM-dd", CultureInfo.InvariantCulture);
        var fileName = $"{datePrefix} - {safeEpisodeTitle}{extension}";

        if (config?.CreatePodcastFolders == true)
        {
            return Path.Combine(basePath, safePodcastTitle, fileName);
        }

        return Path.Combine(basePath, $"{safePodcastTitle} - {fileName}");
    }

    /// <inheritdoc />
    public string GetStoragePath()
    {
        var config = Plugin.Instance?.Configuration;

        if (!string.IsNullOrEmpty(config?.PodcastStoragePath))
        {
            return config.PodcastStoragePath;
        }

        return Path.Combine(_applicationPaths.DataPath, "Podcasts");
    }

    private async Task<PodcastDatabase> LoadDatabaseAsync()
    {
        await _dbLock.WaitAsync().ConfigureAwait(false);
        try
        {
            return await LoadDatabaseInternalAsync().ConfigureAwait(false);
        }
        finally
        {
            _dbLock.Release();
        }
    }

    private async Task<PodcastDatabase> LoadDatabaseInternalAsync()
    {
        if (_cache != null)
        {
            return _cache;
        }

        if (!File.Exists(DatabasePath))
        {
            _logger.LogWarning("Database file does not exist at {Path}", DatabasePath);
            _cache = new PodcastDatabase();
            return _cache;
        }

        try
        {
            _logger.LogInformation("Loading database from {Path}", DatabasePath);
            var json = await File.ReadAllTextAsync(DatabasePath).ConfigureAwait(false);
            _logger.LogInformation("Read {Length} characters from database file", json.Length);
            _cache = JsonSerializer.Deserialize<PodcastDatabase>(json, JsonOptions) ?? new PodcastDatabase();
            _logger.LogInformation("Loaded {Count} podcasts from database", _cache.Podcasts.Count);
            return _cache;
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Failed to load podcast database, starting fresh");
            _cache = new PodcastDatabase();
            return _cache;
        }
    }

    private async Task SaveDatabaseInternalAsync(PodcastDatabase db)
    {
        try
        {
            var directory = Path.GetDirectoryName(DatabasePath);
            if (!string.IsNullOrEmpty(directory))
            {
                Directory.CreateDirectory(directory);
            }

            db.LastSaved = DateTime.UtcNow;
            var json = JsonSerializer.Serialize(db, JsonOptions);
            await File.WriteAllTextAsync(DatabasePath, json).ConfigureAwait(false);
            _cache = db;
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Failed to save podcast database");
            throw;
        }
    }

    private static string SanitizeFileName(string name)
    {
        var invalidChars = Path.GetInvalidFileNameChars();
        var result = new string(name.Where(c => !invalidChars.Contains(c)).ToArray());

        // Limit length
        if (result.Length > 100)
        {
            result = result.Substring(0, 100);
        }

        return result.Trim();
    }

    private static string GetAudioExtension(string url)
    {
        try
        {
            var uri = new Uri(url);
            var path = uri.AbsolutePath;
            var extension = Path.GetExtension(path);

            if (!string.IsNullOrEmpty(extension) &&
                (extension.Equals(".mp3", StringComparison.OrdinalIgnoreCase) ||
                 extension.Equals(".m4a", StringComparison.OrdinalIgnoreCase) ||
                 extension.Equals(".ogg", StringComparison.OrdinalIgnoreCase) ||
                 extension.Equals(".opus", StringComparison.OrdinalIgnoreCase)))
            {
                return extension.ToLowerInvariant();
            }
        }
        catch
        {
            // Ignore URL parsing errors
        }

        return ".mp3";
    }

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