Playlist logn EDL paths, or give up

Some ytdl Youtube EDLs can be even 150 kilobytes long, which is much
too much for commandline and even playlist files (mpv can handle 8k
characters on one line).

If a file path (url) is over 8k characters long, use original path
(url) and permit the use of ytdl. This will be slow, but it will work.
If a file path is over 1k characters long (but less than 8k), save it
to a temporary playlist and play that. 1k may be too long for
Windows commandline; I didn't really check.

src/thumbnailer_server.lua

@@ -6,8 +6,11 @@ function skip_nil(tbl)
     return n
 end
 
-function create_thumbnail_mpv(file_path, timestamp, size, output_path)
-    local ytdl_disabled = mp.get_property_native("ytdl") == false or thumbnailer_options.remote_direct_stream
+function create_thumbnail_mpv(file_path, timestamp, size, output_path, options)
+    options = options or {}
+
+    local ytdl_disabled = not options.enable_ytdl and (mp.get_property_native("ytdl") == false
+                                                       or thumbnailer_options.remote_direct_stream)
 
     local profile_arg = nil
     if thumbnailer_options.mpv_profile ~= "" then
@@ -81,8 +84,8 @@ function check_output(ret, output_path, is_mpv)
     else
         if ret.error or ret.status ~= 0 then
             msg.error("Thumbnailing command failed!")
-            msg.error(ret.error)
-            msg.error(ret.stdout)
+            msg.error("mpv process error:", ret.error)
+            msg.error("Process stdout:", ret.stdout)
             if is_mpv then
                 msg.error("Debug log:", log_path)
             end
@@ -131,6 +134,7 @@ function do_worker_job(state_json_string, frames_json_string)
 
     local file_duration = mp.get_property_native("duration")
     local file_path = mp.get_property_native("path")
+    local extra_worker_options = {}
 
     if thumb_state.is_remote then
         thumbnail_func = create_thumbnail_mpv
@@ -142,7 +146,33 @@ function do_worker_job(state_json_string, frames_json_string)
         end
     end
 
-    msg.debug(("Generating %d thumbnails @ %dx%d"):format(#thumbnail_indexes, thumb_state.thumbnail_size.w, thumb_state.thumbnail_size.h))
+    -- edl:// urls can get LONG. In which case, save the path (URL)
+    -- to a temporary file and use that instead.
+    local thumbnail_directory = split_path(thumb_state.thumbnail_template)
+    local playlist_filename = join_paths(thumbnail_directory, "playlist" .. mp.get_script_name() .. ".txt")
+    local edl_playlist_used = false
+
+    if #file_path > 8000 then
+        -- Path is too long for a playlist - just pass the original URL to
+        -- workers and allow ytdl
+        extra_worker_options.enable_ytdl = true
+        file_path = mp.get_property_native("path")
+        msg.warn("Falling back to original URL and ytdl due to LONG source path. This will be slow.")
+
+    elseif #file_path > 1024 then
+        local playlist_file = io.open(playlist_filename, "wb")
+        if not playlist_file then
+            msg.error(("Tried to write a playlist to %s but couldn't!"):format(playlist_file))
+            return
+        end
+
+        playlist_file:write(file_path .. "\n")
+        playlist_file:close()
+
+        file_path = "--playlist=" .. playlist_filename
+        edl_playlist_used = true
+        msg.warn("Using playlist workaround due to long source path")
+    end
 
     local generate_thumbnail_for_index = function(thumbnail_index)
         local thumbnail_path = thumb_state.thumbnail_template:format(thumbnail_index)
@@ -170,7 +200,7 @@ function do_worker_job(state_json_string, frames_json_string)
         end
 
         if need_thumbnail_generation then
-            local ret = thumbnail_func(file_path, timestamp, thumb_state.thumbnail_size, thumbnail_path)
+            local ret = thumbnail_func(file_path, timestamp, thumb_state.thumbnail_size, thumbnail_path, extra_worker_options)
             local success = check_output(ret, thumbnail_path, thumbnail_func == create_thumbnail_mpv)
 
             if success == nil then
@@ -216,6 +246,17 @@ function do_worker_job(state_json_string, frames_json_string)
         local bail = generate_thumbnail_for_index(thumbnail_index)
         if bail then return end
     end
+
+    msg.debug(("Generating %d thumbnails @ %dx%d for %q"):format(
+        #thumbnail_indexes,
+        thumb_state.thumbnail_size.w,
+        thumb_state.thumbnail_size.h,
+        file_path))
+
+    -- Remove playlist file if it was used as a workaround
+    if edl_playlist_used then
+        os.remove(playlist_filename)
+    end
 end
 
 -- Set up listeners and keybinds