command: make playlist writable

DOCS/interface-changes/writable-playlist.txt

@@ -0,0 +1 @@
+- make `playlist` property writable

DOCS/man/input.rst

@@ -3029,7 +3029,7 @@ Property list
     the entries. Unavailable if the file was not originally associated with a
     playlist in some way.
 
-``playlist``
+``playlist`` (RW)
     Playlist, current entry marked. Currently, the raw property value is
     useless.
 
@@ -3081,6 +3081,39 @@ Property list
                 "title"     MPV_FORMAT_STRING (optional)
                 "id"        MPV_FORMAT_INT64
 
+    Writing this property is also possible using the following format:
+
+    ::
+
+        MPV_FORMAT_NODE_ARRAY (the new playlist)
+            MPV_FORMAT_STRING (entry from filename)
+
+            MPV_FORMAT_INT64 (take existing entry at index, counts from 0)
+
+            MPV_FORMAT_NODE_MAP (take existing entry from id)
+                "id"        MPV_FORMAT_INT64
+                "current"   MPV_FORMAT_FLAG (optional)
+                "title"     MPV_FORMAT_STRING|MPV_FORMAT_NONE (optional)
+
+            MPV_FORMAT_NODE_MAP (entry from filename)
+                "filename"  MPV_FORMAT_STRING
+                "current"   MPV_FORMAT_FLAG (optional)
+                "title"     MPV_FORMAT_STRING|MPV_FORMAT_NONE (optional)
+
+    .. admonition:: Lua examples
+
+        ``mp.set_property_native("playlist", {1, 0})``
+
+        Swap the first two entries and remove the rest.
+
+        ``mp.set_property_native("playlist", {{filename="foo", current=true}})``
+
+        Replace playlist with a single entry and start playing.
+
+        ``mp.set_property_native("playlist", {1, {id=2}, "bar"})``
+
+        Various ways to specify an entry.
+
 ``track-list``
     List of audio/video/sub tracks, current entry marked. Currently, the raw
     property value is useless.

common/playlist.c

@@ -23,10 +23,15 @@
 #include "misc/random.h"
 #include "mpv_talloc.h"
 #include "options/path.h"
+#include "misc/khash.h"
 
 #include "demux/demux.h"
 #include "stream/stream.h"
 
+KHASH_MAP_INIT_INT64(playlist_id_map, int)
+
+typedef khash_t(playlist_id_map) playlist_id_map_t;
+
 struct playlist_entry *playlist_entry_new(const char *filename)
 {
     struct playlist_entry *e = talloc_zero(NULL, struct playlist_entry);
@@ -89,6 +94,16 @@ void playlist_entry_unref(struct playlist_entry *e)
     }
 }
 
+void playlist_entry_remove(struct playlist_entry *entry)
+{
+    entry->pl = NULL;
+    entry->pl_index = -1;
+    ta_set_parent(entry, NULL);
+
+    entry->removed = true;
+    playlist_entry_unref(entry);
+}
+
 void playlist_remove(struct playlist *pl, struct playlist_entry *entry)
 {
     assert(pl && entry->pl == pl);
@@ -101,12 +116,7 @@ void playlist_remove(struct playlist *pl, struct playlist_entry *entry)
     MP_TARRAY_REMOVE_AT(pl->entries, pl->num_entries, entry->pl_index);
     playlist_update_indexes(pl, entry->pl_index, -1);
 
-    entry->pl = NULL;
-    entry->pl_index = -1;
-    ta_set_parent(entry, NULL);
-
-    entry->removed = true;
-    playlist_entry_unref(entry);
+    playlist_entry_remove(entry);
 }
 
 void playlist_clear(struct playlist *pl)
@@ -456,3 +466,30 @@ void playlist_set_current(struct playlist *pl)
         }
     }
 }
+
+playlist_id_map_t *playlist_build_id_map(const struct playlist *pl)
+{
+    khash_t(playlist_id_map) *h = kh_init(playlist_id_map);
+    for (int i = 0; i < pl->num_entries; ++i) {
+        struct playlist_entry *e = pl->entries[i];
+        int absent;
+        khint_t k = kh_put(playlist_id_map, h, e->id, &absent);
+        kh_val(h, k) = i;
+    }
+    return h;
+}
+
+void playlist_destroy_id_map(playlist_id_map_t *h)
+{
+    kh_destroy(playlist_id_map, h);
+}
+
+struct playlist_entry *playlist_entry_from_id(struct playlist *pl, const playlist_id_map_t *h, uint64_t id)
+{
+    khint_t k = kh_get(playlist_id_map, h, id);
+    if (k == kh_end(h))
+        return NULL;
+
+    int index = kh_val(h, k);
+    return pl->entries[index];
+}

common/playlist.h

@@ -19,8 +19,11 @@
 #define MPLAYER_PLAYLIST_H
 
 #include <stdbool.h>
+
 #include "misc/bstr.h"
 
+typedef struct kh_playlist_id_map_s playlist_id_map_t;
+
 struct playlist_param {
     bstr name, value;
 };
@@ -127,4 +130,10 @@ void playlist_entry_unref(struct playlist_entry *e);
 
 void playlist_set_current(struct playlist *pl);
 
+playlist_id_map_t *playlist_build_id_map(const struct playlist *pl);
+void playlist_destroy_id_map(playlist_id_map_t *h);
+struct playlist_entry *playlist_entry_from_id(struct playlist *pl, const playlist_id_map_t *h, uint64_t id);
+
+void playlist_entry_remove(struct playlist_entry *entry);
+
 #endif