using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Threading;
using System.Threading.Tasks;
using System.Xml;
using Microsoft.Extensions.Logging;

namespace Jellyfin.Plugin.CinemaTrailers4Jellyfins.Services
{
    /// <summary>
    /// Produces the placeholder "fake movie" file and its NFO that sit alongside each
    /// downloaded trailer. Jellyfin scans the fake movie as a normal library item (its
    /// metadata locked via the NFO so it never queries TMDB) and picks up the adjacent
    /// "-trailer.mp4" as that item's local trailer — exactly what a Cinema Mode / trailer
    /// pre-roll plugin consumes.
    /// </summary>
    public class FakeMovieService
    {
        private const string MasterFileName = "master.mp4";
        private readonly ILogger<FakeMovieService> _logger;
        private readonly SemaphoreSlim _masterLock = new(1, 1);

        public FakeMovieService(ILogger<FakeMovieService> logger)
        {
            _logger = logger;
        }

        private static string MasterFilePath =>
            Path.Combine(Plugin.Instance.DataFolderPath, "fake-movie", MasterFileName);

        /// <summary>
        /// Copies the master fake-movie file to <paramref name="destinationPath"/>,
        /// generating the master via ffmpeg first if it doesn't exist yet.
        /// </summary>
        public async Task<bool> CopyFakeMovieAsync(string destinationPath, CancellationToken ct)
        {
            if (!await EnsureMasterFileAsync(ct).ConfigureAwait(false))
                return false;

            try
            {
                Directory.CreateDirectory(Path.GetDirectoryName(destinationPath)!);
                File.Copy(MasterFilePath, destinationPath, overwrite: true);
                return true;
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "|CinemaTrailers4Jellyfins| Failed to copy fake movie file to {Path}", destinationPath);
                return false;
            }
        }

        /// <summary>
        /// Writes a minimal Jellyfin/Kodi-compatible movie NFO with &lt;lockdata&gt;true&lt;/lockdata&gt;
        /// so Jellyfin never tries to refresh metadata for the fake entry from TMDB.
        /// </summary>
        public void WriteNfo(string nfoPath, string title, int? year, IReadOnlyList<string>? genres = null, string? mpaa = null, IReadOnlyList<string>? tags = null)
        {
            var settings = new XmlWriterSettings { Indent = true };
            using var writer = XmlWriter.Create(nfoPath, settings);
            writer.WriteStartDocument();
            writer.WriteStartElement("movie");
            writer.WriteElementString("title", title);
            if (year.HasValue)
                writer.WriteElementString("year", year.Value.ToString());
            if (genres != null)
                foreach (var genre in genres)
                    writer.WriteElementString("genre", genre);
            if (!string.IsNullOrWhiteSpace(mpaa))
                writer.WriteElementString("mpaa", mpaa);
            if (tags != null)
                foreach (var tag in tags)
                    writer.WriteElementString("tag", tag);
            writer.WriteElementString("lockdata", "true");
            writer.WriteEndElement();
            writer.WriteEndDocument();
        }

        // Generates a few seconds of black video with silent audio — just enough for
        // Jellyfin to recognize the file as a valid playable video. Built once and reused
        // by copying, rather than regenerated per trailer.
        private async Task<bool> EnsureMasterFileAsync(CancellationToken ct)
        {
            if (File.Exists(MasterFilePath))
                return true;

            await _masterLock.WaitAsync(ct).ConfigureAwait(false);
            try
            {
                if (File.Exists(MasterFilePath))
                    return true;

                Directory.CreateDirectory(Path.GetDirectoryName(MasterFilePath)!);

                var tempPath = MasterFilePath + ".tmp";
                if (File.Exists(tempPath)) File.Delete(tempPath);

                _logger.LogInformation("|CinemaTrailers4Jellyfins| Generating master fake-movie file via ffmpeg at {Path}", MasterFilePath);

                var args = string.Join(" ",
                    "-y",
                    "-f lavfi -i \"color=c=black:s=640x360:r=24:d=3\"",
                    "-f lavfi -i \"anullsrc=channel_layout=stereo:sample_rate=44100\"",
                    "-shortest",
                    "-c:v libx264 -tune stillimage -pix_fmt yuv420p",
                    "-c:a aac -b:a 64k",
                    "-f mp4",
                    $"\"{tempPath}\"");

                // Prefer Jellyfin's bundled ffmpeg; fall back to whatever is on PATH.
                var ffmpegPath = File.Exists("/usr/lib/jellyfin-ffmpeg/ffmpeg")
                    ? "/usr/lib/jellyfin-ffmpeg/ffmpeg"
                    : "ffmpeg";

                using var process = new Process
                {
                    StartInfo = new ProcessStartInfo
                    {
                        FileName = ffmpegPath,
                        Arguments = args,
                        RedirectStandardOutput = true,
                        RedirectStandardError = true,
                        UseShellExecute = false,
                        CreateNoWindow = true,
                    }
                };

                process.Start();
                await process.WaitForExitAsync(ct).ConfigureAwait(false);

                if (process.ExitCode != 0 || !File.Exists(tempPath))
                {
                    var stderr = await process.StandardError.ReadToEndAsync(ct).ConfigureAwait(false);
                    _logger.LogError(
                        "|CinemaTrailers4Jellyfins| ffmpeg failed to generate the master fake-movie file (exit code {Code}): {Error}",
                        process.ExitCode, stderr);
                    if (File.Exists(tempPath)) File.Delete(tempPath);
                    return false;
                }

                File.Move(tempPath, MasterFilePath, overwrite: true);
                _logger.LogInformation("|CinemaTrailers4Jellyfins| Master fake-movie file generated at {Path}", MasterFilePath);
                return true;
            }
            catch (OperationCanceledException)
            {
                throw;
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "|CinemaTrailers4Jellyfins| Failed to generate the master fake-movie file.");
                return false;
            }
            finally
            {
                _masterLock.Release();
            }
        }
    }
}