command: add playlist-next-playlist and playlist-prev-playlist

playlist-prev-playlist goes to the beginning of the previous playlist
because this seems more useful and symmetrical to
playlist-next-playlist. It does not go to the beginning when the current
playlist-path starts with the previous playlist-path, e.g. with mpv
--loop-playlist foo/, which expands to foo/{1..9}.zip, the current
playlist path foo/1.zip beings with the playlist-path foo/ of {2..9}.zip
and thus playlist-prev-playlist goes to 9.zip rather than to 2.zip.

Closes mpv-player#12495.

DOCS/interface-changes.rst

@@ -93,6 +93,7 @@ Interface changes
     - remove `--scale-cutoff`, `--cscale-cutoff`, `--dscale-cutoff`, `--tscale-cutoff`
     - remove `--scaler-lut-size`
     - deprecate shared-script-properties (user-data is a replacement)
+    - add `playlist-next-playlist` and `playlist-prev-playlist` commands
  --- mpv 0.36.0 ---
     - add `--target-contrast`
     - Target luminance value is now also applied when ICC profile is used.

DOCS/man/input.rst

@@ -422,6 +422,13 @@ Remember to quote string arguments in input.conf (see `Flat command syntax`_).
     force
         Terminate playback if the first file is being played.
 
+``playlist-next-playlist``
+    Go to the next entry on the playlist with a different ``playlist-path``.
+
+``playlist-prev-playlist``
+    Go to the first of the previous entries on the playlist with a different
+    ``playlist-path``.
+
 ``playlist-play-index <integer|current|none>``
     Start (or restart) playback of the given playlist index. In addition to the
     0-based playlist entry index, it supports the following values:

common/playlist.c

@@ -214,6 +214,74 @@ struct playlist_entry *playlist_entry_get_rel(struct playlist_entry *e,
     return playlist_entry_from_index(e->pl, e->pl_index + direction);
 }
 
+struct playlist_entry *playlist_get_first_in_next_playlist(struct playlist *pl,
+                                                           int direction)
+{
+    struct playlist_entry *entry = playlist_get_next(pl, direction);
+    if (!entry)
+        return NULL;
+
+    while (entry && entry->playlist_path &&
+           strcmp(entry->playlist_path, pl->current->playlist_path) == 0)
+        entry = playlist_entry_get_rel(entry, direction);
+
+    if (direction < 0)
+        entry = playlist_get_first_in_same_playlist(entry,
+                                                    pl->current->playlist_path);
+
+    return entry;
+}
+
+struct playlist_entry *playlist_get_first_in_same_playlist(
+    struct playlist_entry *entry, char *current_playlist_path)
+{
+    void *tmp = talloc_new(NULL);
+
+    if (!entry || !entry->playlist_path)
+        goto exit;
+
+    // Don't go to the beginning of the playlist when the current playlist-path
+    // starts with the previous playlist-path, e.g. with mpv --loop-playlist
+    // archive_dir/, which expands to archive_dir/{1..9}.zip, the current
+    // playlist path "archive_dir/1.zip" beings with the playlist-path
+    // "archive_dir/" of {2..9}.zip, so go to 9.zip instead of 2.zip. But
+    // playlist-prev-playlist from e.g. the directory "foobar" to the directory
+    // "foo" should still go to the first entry in "foo/", and this should all
+    // work whether mpv's arguments have trailing slashes or not, e.g. in the
+    // first example:
+    // mpv archive_dir results in the playlist-paths "archive_dir/1.zip" and
+    // "archive_dir"
+    // mpv archive_dir/ in "archive_dir/1.zip" and "archive_dir/"
+    // mpv archive_dir// in "archive_dir//1.zip" and "archive_dir//"
+    // Always adding a separator to entry->playlist_path to fix the foobar foo
+    // case would break the previous 2 cases instead. Stripping the separator
+    // from entry->playlist_path if present and appending it again makes this
+    // work in all cases.
+    char* playlist_path = talloc_strdup(tmp, entry->playlist_path);
+    mp_path_strip_trailing_separator(playlist_path);
+    if (bstr_startswith(bstr0(current_playlist_path),
+                        bstr0(talloc_strdup_append(playlist_path, "/")))
+#if HAVE_DOS_PATHS
+        ||
+        bstr_startswith(bstr0(current_playlist_path),
+                        bstr0(talloc_strdup_append(playlist_path, "\\")))
+#endif
+       )
+        goto exit;
+
+    struct playlist_entry *prev = playlist_entry_get_rel(entry, -1);
+
+    while (prev && prev->playlist_path &&
+           strcmp(prev->playlist_path, entry->playlist_path) == 0) {
+        entry = prev;
+        prev = playlist_entry_get_rel(entry, -1);
+    }
+
+exit:
+    talloc_free(tmp);
+    return entry;
+}
+
 void playlist_add_base_path(struct playlist *pl, bstr base_path)
 {
     if (base_path.len == 0 || bstrcmp0(base_path, ".") == 0)

common/playlist.h

@@ -97,6 +97,10 @@ struct playlist_entry *playlist_get_last(struct playlist *pl);
 struct playlist_entry *playlist_get_next(struct playlist *pl, int direction);
 struct playlist_entry *playlist_entry_get_rel(struct playlist_entry *e,
                                               int direction);
+struct playlist_entry *playlist_get_first_in_next_playlist(struct playlist *pl,
+                                                           int direction);
+struct playlist_entry *playlist_get_first_in_same_playlist(
+    struct playlist_entry *entry, char *current_playlist_path);
 void playlist_add_base_path(struct playlist *pl, bstr base_path);
 void playlist_set_stream_flags(struct playlist *pl, int flags);
 int64_t playlist_transfer_entries(struct playlist *pl, struct playlist *source_pl);

player/command.c

@@ -5321,6 +5321,45 @@ static void cmd_playlist_next_prev(void *p)
         mpctx->add_osd_seek_info |= OSD_SEEK_INFO_CURRENT_FILE;
 }
 
+static void cmd_playlist_next_prev_playlist(void *p)
+{
+    struct mp_cmd_ctx *cmd = p;
+    struct MPContext *mpctx = cmd->mpctx;
+    int direction = *(int *)cmd->priv;
+
+    struct playlist_entry *entry =
+        playlist_get_first_in_next_playlist(mpctx->playlist, direction);
+
+    if (!entry && mpctx->opts->loop_times != 1 && mpctx->playlist->current) {
+        entry = direction > 0 ? playlist_get_first(mpctx->playlist)
+                              : playlist_get_last(mpctx->playlist);
+
+        if (entry && entry->playlist_path &&
+            strcmp(entry->playlist_path,
+                   mpctx->playlist->current->playlist_path) == 0)
+            entry = NULL;
+
+        if (direction > 0 && entry && mpctx->opts->loop_times > 1) {
+            mpctx->opts->loop_times--;
+            m_config_notify_change_opt_ptr(mpctx->mconfig,
+                                           &mpctx->opts->loop_times);
+        }
+
+        if (direction < 0)
+            entry = playlist_get_first_in_same_playlist(
+                        entry, mpctx->playlist->current->playlist_path);
+    }
+
+    if (!entry) {
+        cmd->success = false;
+        return;
+    }
+
+    mp_set_playlist_entry(mpctx, entry);
+    if (cmd->on_osd & MP_ON_OSD_MSG)
+        mpctx->add_osd_seek_info |= OSD_SEEK_INFO_CURRENT_FILE;
+}
+
 static void cmd_playlist_play_index(void *p)
 {
     struct mp_cmd_ctx *cmd = p;
@@ -6372,6 +6411,10 @@ const struct mp_cmd_def mp_cmds[] = {
         },
         .priv = &(const int){-1},
     },
+    { "playlist-next-playlist", cmd_playlist_next_prev_playlist,
+        .priv = &(const int){1} },
+    { "playlist-prev-playlist", cmd_playlist_next_prev_playlist,
+        .priv = &(const int){-1} },
     { "playlist-play-index", cmd_playlist_play_index,
         {
             {"index", OPT_CHOICE(v.i, {"current", -2}, {"none", -1}),