TOOLS/lua/autoload: avoid unnecessary playlist manipulation, performance

We used to sort the playlist with playlist-move after every loadfile.
Instead, append all files in order and call playlist-move once to move
the only entry we don't control the position of.
Don't fetch every playlist item separately, reuse native property.
We used to pick up on new files added to the directory, but only when
playing an entry at the edge of the playlist due to an early return.
New files are now added to the playlist on every file change.
This still works as expected and doesn't load duplicate files on
shuffled playlists or playlists with files manually added after autoload

33% faster on average for my test directory with 1371 files.

TOOLS/lua/autoload.lua

@@ -68,12 +68,11 @@ if o.videos then EXTENSIONS = SetUnion(EXTENSIONS, EXTENSIONS_VIDEO) end
 if o.audio then EXTENSIONS = SetUnion(EXTENSIONS, EXTENSIONS_AUDIO) end
 if o.images then EXTENSIONS = SetUnion(EXTENSIONS, EXTENSIONS_IMAGES) end
 
-function add_files_at(index, files)
+function add_files(files)
-    index = index - 1
     local oldcount = mp.get_property_number("playlist-count", 1)
     for i = 1, #files do
-        mp.commandv("loadfile", files[i], "append")
+        mp.commandv("loadfile", files[i][1], "append")
-        mp.commandv("playlist-move", oldcount + i - 1, index + i - 1)
+        mp.commandv("playlist-move", oldcount + i - 1, files[i][2])
     end
 end
 
@@ -116,11 +115,10 @@ end
 
 local autoloaded = nil
 
-function get_playlist_filenames()
+function get_playlist_filenames(playlist)
     local filenames = {}
-    for n = 0, pl_count - 1, 1 do
+    for i = 1, #playlist do
-        local filename = mp.get_property('playlist/'..n..'/filename')
+        local _, file = utils.split_path(playlist[i].filename)
-        local _, file = utils.split_path(filename)
         filenames[file] = true
     end
     return filenames
@@ -190,32 +188,43 @@ function find_and_add_entries()
     msg.trace("current file position in files: "..current)
 
     local append = {[-1] = {}, [1] = {}}
-    local filenames = get_playlist_filenames()
+    local filenames = get_playlist_filenames(pl)
     for direction = -1, 1, 2 do -- 2 iterations, with direction = -1 and +1
         for i = 1, MAXENTRIES do
-            local file = files[current + i * direction]
+            local pos = current + i * direction
+            local file = files[pos]
             if file == nil or file[1] == "." then
                 break
             end
 
             local filepath = dir .. file
             -- skip files already in playlist
-            if filenames[file] then break end
+            if not filenames[file] then
-
+                if direction == -1 then
-            if direction == -1 then
-                if pl_current == 1 then -- never add additional entries in the middle
                     msg.info("Prepending " .. file)
-                    table.insert(append[-1], 1, filepath)
+                    table.insert(append[-1], 1, {filepath, pos - 1})
+                else
+                    msg.info("Adding " .. file)
+                    if pl_count > 1 then
+                        table.insert(append[1], {filepath, pos - 1})
+                    else
+                        mp.commandv("loadfile", filepath, "append")
+                    end
                 end
-            else
-                msg.info("Adding " .. file)
-                table.insert(append[1], filepath)
             end
         end
+        if pl_count == 1 and direction == -1 and #append[-1] > 0 then
+            for i = 1, #append[-1] do
+                mp.commandv("loadfile", append[-1][i][1], "append")
+            end
+            mp.commandv("playlist-move", 0, current)
+        end
     end
 
-    add_files_at(pl_current + 1, append[1])
+    if pl_count > 1 then
-    add_files_at(pl_current, append[-1])
+        add_files(append[1])
+        add_files(append[-1])
+    end
 end
 
 mp.register_event("start-file", find_and_add_entries)