[Bugfix] prevent duplicate videos from being downloaded if the video's name changes (#396)

* Added methods for deleting outdated files

* Hooked up outdated file deletion to media download worker

lib/pinchflat/downloading/media_download_worker.ex

@@ -12,6 +12,7 @@ defmodule Pinchflat.Downloading.MediaDownloadWorker do
   alias Pinchflat.Tasks
   alias Pinchflat.Repo
   alias Pinchflat.Media
+  alias Pinchflat.Media.FileDeletion
   alias Pinchflat.Downloading.MediaDownloader
 
   alias Pinchflat.Lifecycle.UserScripts.CommandRunner, as: UserScriptRunner
@@ -85,6 +86,7 @@ defmodule Pinchflat.Downloading.MediaDownloadWorker do
             media_redownloaded_at: get_redownloaded_at(is_quality_upgrade)
           })
 
+        :ok = FileDeletion.delete_outdated_files(media_item, updated_media_item)
         run_user_script(:media_downloaded, updated_media_item)
 
         :ok

lib/pinchflat/media/file_deletion.ex

@@ -0,0 +1,54 @@
+defmodule Pinchflat.Media.FileDeletion do
+  @moduledoc """
+  Functions for deleting files that are no longer needed by media items.
+  """
+
+  alias Pinchflat.Utils.MapUtils
+  alias Pinchflat.Media.MediaItem
+  alias Pinchflat.Utils.FilesystemUtils, as: FSUtils
+
+  @doc """
+  Deletes files that are no longer needed by a media item.
+
+  This means that if a media item has been updated, the old and new versions
+  can be passed and any files that are no longer needed will be deleted.
+
+  An example is a video that gets its quality upgraded and its name changes
+  between original download and re-download. The old file will exist on-disk
+  with the old name but the database entry will point to the new file. This
+  function can be used to delete the old file in this case.
+
+  Returns :ok
+  """
+  def delete_outdated_files(old_media_item, new_media_item) do
+    non_subtitle_keys = MediaItem.filepath_attributes() -- [:subtitle_filepaths]
+
+    old_non_subtitles = Map.take(old_media_item, non_subtitle_keys)
+    old_subtitles = MapUtils.from_nested_list(old_media_item.subtitle_filepaths)
+    new_non_subtitles = Map.take(new_media_item, non_subtitle_keys)
+    new_subtitles = MapUtils.from_nested_list(new_media_item.subtitle_filepaths)
+
+    handle_file_deletion(old_non_subtitles, new_non_subtitles)
+    handle_file_deletion(old_subtitles, new_subtitles)
+
+    :ok
+  end
+
+  defp handle_file_deletion(old_attributes, new_attributes) do
+    # The logic:
+    #   - A file should only be deleted if it exists and the new file is different
+    #   - The new attributes are the ones we're interested in keeping
+    #   - If the old attributes have a key that doesn't exist in the new attributes, don't touch it.
+    #     This is good for archiving but may be unpopular for other users so this may change.
+
+    Enum.each(new_attributes, fn {key, new_filepath} ->
+      old_filepath = Map.get(old_attributes, key)
+      files_have_changed = old_filepath && new_filepath && old_filepath != new_filepath
+      files_exist_on_disk = files_have_changed && File.exists?(old_filepath) && File.exists?(new_filepath)
+
+      if files_exist_on_disk && !FSUtils.filepaths_reference_same_file?(old_filepath, new_filepath) do
+        FSUtils.delete_file_and_remove_empty_directories(old_filepath)
+      end
+    end)
+  end
+end

lib/pinchflat/utils/filesystem_utils.ex

@@ -20,6 +20,24 @@ defmodule Pinchflat.Utils.FilesystemUtils do
     end
   end
 
+  @doc """
+  Checks if two filepaths reference the same file.
+
+  Useful if you have a relative and absolute filepath and want to be sure they're the same file.
+  Also works with symlinks.
+
+  Returns boolean()
+  """
+  def filepaths_reference_same_file?(filepath_1, filepath_2) do
+    {:ok, stat_1} = File.stat(filepath_1)
+    {:ok, stat_2} = File.stat(filepath_2)
+
+    identifier_1 = "#{stat_1.major_device}:#{stat_1.minor_device}:#{stat_1.inode}"
+    identifier_2 = "#{stat_2.major_device}:#{stat_2.minor_device}:#{stat_2.inode}"
+
+    identifier_1 == identifier_2
+  end
+
   @doc """
   Generates a temporary file and returns its path. The file is empty and has the given type.
   Generates all the directories in the path if they don't exist.

lib/pinchflat/utils/map_utils.ex

@@ -0,0 +1,17 @@
+defmodule Pinchflat.Utils.MapUtils do
+  @moduledoc """
+  Utility methods for working with maps
+  """
+
+  @doc """
+  Converts a nested list of 2-element tuples or lists into a map.
+
+  Returns map()
+  """
+  def from_nested_list(list) do
+    Enum.reduce(list, %{}, fn
+      [key, value], acc -> Map.put(acc, key, value)
+      {key, value}, acc -> Map.put(acc, key, value)
+    end)
+  end
+end