Initial commit: CinemaTrailers4Jellyfins plugin

Adapted from Trailers4Jellyfin: keeps TMDB/YouTube trailer downloading,
the scheduled task, language/source/date filters, and trailer rotation,
but drops cinema-mode/IIntroProvider entirely. Each trailer now ships in
its own fake-movie folder (placeholder video + locked NFO + trailer) for
use with a Cinema Mode / trailer pre-roll plugin.

Jellyfin.Plugin.CinemaTrailers4Jellyfins/Services/FakeMovieService.cs

@@ -0,0 +1,147 @@
+using System;
+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)
+        {
+            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());
+            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",
+                    $"\"{tempPath}\"");
+
+                using var process = new Process
+                {
+                    StartInfo = new ProcessStartInfo
+                    {
+                        FileName = "ffmpeg",
+                        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. Is ffmpeg installed and on PATH?");
+                return false;
+            }
+            finally
+            {
+                _masterLock.Release();
+            }
+        }
+    }
+}