Refactoring event channel subscription to send events correctly

Author: DoumanAsh

include/plugins/audioplayers.h

@@ -38,4 +38,13 @@ void audio_player_set_source_url(struct audio_player *self, char *url);
 
 bool audio_player_is_id(struct audio_player *self, char *id);
 
+const char* audio_player_subscribe_channel_name(const struct audio_player *self);
+
+///Asks to subscribe to channel events
+///
+///`value` - Indicates whether to subscribe or unsubscribe
+///
+///Returns `true` if player uses `channel`, otherwise returns `false
+bool audio_player_set_subscription_status(struct audio_player *self, const char *channel, bool value);
+
 #endif  // AUDIOPLAYERS_H_

src/plugins/audioplayers/player.c

@@ -1,11 +1,13 @@
+#define _GNU_SOURCE
+
 #include <stdio.h>
+#include <stdbool.h>
 
 #include "gst/gst.h"
 #include "gst/gstelementfactory.h"
 #include "gst/gstmessage.h"
 #include "gst/gstsegment.h"
 #include "platformchannel.h"
-#include "pluginregistry.h"
 
 #include <flutter-pi.h>
 #include <plugins/audioplayers.h>
@@ -30,7 +32,9 @@ struct audio_player {
 
     char *url;
     char *player_id;
-	char event_channel_name[128];
+    char *event_channel_name;
+
+    _Atomic bool event_subscribed;
 };
 
 // Private Class functions
@@ -75,22 +79,6 @@ static void audio_player_source_setup(GstElement *playbin, GstElement *source, G
     }
 }
 
-static int on_receive_event_ch(char *channel, struct platch_obj *object, FlutterPlatformMessageResponseHandle *responsehandle) {
-    //TODO: Do we need any more setup to send events to dart code?
-    (void)channel;
-    if (strcmp(object->method, "listen") == 0) {
-        LOG_DEBUG("%s: listen()\n", channel);
-        platch_respond_success_std(responsehandle, NULL);
-    } else if (strcmp(object->method, "cancel") == 0) {
-        LOG_DEBUG("%s: cancel()\n", channel);
-        platch_respond_success_std(responsehandle, NULL);
-    } else {
-        return platch_respond_not_implemented(responsehandle);
-    }
-
-    return 0;
-}
-
 struct audio_player *audio_player_new(char *player_id, char *channel) {
     GPollFD fd;
     sd_event_source *busfd_event_source;
@@ -101,11 +89,13 @@ struct audio_player *audio_player_new(char *player_id, char *channel) {
     }
 
     self->url = NULL;
+    self->source = NULL;
     self->is_initialized = false;
     self->is_playing = false;
     self->is_looping = false;
     self->is_seek_completed = false;
     self->playback_rate = 1.0;
+    self->event_subscribed = false;
 
     gst_init(NULL, NULL);
     self->playbin = gst_element_factory_make("playbin", NULL);
@@ -154,23 +144,10 @@ struct audio_player *audio_player_new(char *player_id, char *channel) {
 
     // audioplayers player event channel clang:
     // <local>/events/<player_id>
-    int ok = snprintf(
-        self->event_channel_name,
-        sizeof(self->event_channel_name),
-        "%s/events/%s",
-        channel,
-        player_id
-    );
-    DEBUG_ASSERT_MSG(ok < sizeof(self->event_channel_name), "event channel name overflow");
-
-    // set a receiver on the videoEvents event channel
-    ok = plugin_registry_set_receiver(
-        self->event_channel_name,
-        kStandardMethodCall,
-        on_receive_event_ch
-    );
+    asprintf(&self->event_channel_name, "%s/events/%s", channel, player_id);
+    DEBUG_ASSERT_MSG(self->event_channel_name != NULL, "event channel name OEM");
 
-    if (ok != 0) {
+    if (self->event_channel_name == NULL) {
         goto deinit_player_id;
     }
 
@@ -293,6 +270,10 @@ void audio_player_set_playback(struct audio_player *self, int64_t seekTo, double
 }
 
 void audio_player_on_media_error(struct audio_player *self, GError *error, gchar *debug) {
+    if (!self->event_subscribed) {
+        return;
+    }
+
     char error_code[16] = {0};
     snprintf(error_code, sizeof(error_code), "%d", error->code);
     // clang-format off
@@ -335,6 +316,10 @@ void audio_player_on_media_state_change(struct audio_player *self, GstObject *sr
 }
 
 void audio_player_on_prepared(struct audio_player *self, bool value) {
+    if (!self->event_subscribed) {
+        return;
+    }
+
     // clang-format off
     platch_send_success_event_std(
         self->event_channel_name,
@@ -347,6 +332,10 @@ void audio_player_on_prepared(struct audio_player *self, bool value) {
 }
 
 void audio_player_on_position_update(struct audio_player *self) {
+    if (!self->event_subscribed) {
+        return;
+    }
+
     // clang-format off
     platch_send_success_event_std(
         self->event_channel_name,
@@ -359,6 +348,9 @@ void audio_player_on_position_update(struct audio_player *self) {
 }
 
 void audio_player_on_duration_update(struct audio_player *self) {
+    if (!self->event_subscribed) {
+        return;
+    }
     // clang-format off
     platch_send_success_event_std(
         self->event_channel_name,
@@ -371,28 +363,32 @@ void audio_player_on_duration_update(struct audio_player *self) {
 }
 void audio_player_on_seek_completed(struct audio_player *self) {
     audio_player_on_position_update(self);
-    // clang-format off
-    platch_send_success_event_std(
-        self->event_channel_name,
-        &STDMAP2(
-            STDSTRING("event"), STDSTRING("audio.onSeekComplete"),
-            STDSTRING("value"), STDBOOL(true)
-        )
-    );
-    // clang-format on
+
+    if (self->event_subscribed) {
+        // clang-format off
+        platch_send_success_event_std(
+            self->event_channel_name,
+            &STDMAP2(
+                STDSTRING("event"), STDSTRING("audio.onSeekComplete"),
+                STDSTRING("value"), STDBOOL(true)
+            )
+        );
+        // clang-format on
+    }
     self->is_seek_completed = true;
 }
 void audio_player_on_playback_ended(struct audio_player *self) {
-    // clang-format off
-    platch_send_success_event_std(
-        self->event_channel_name,
-        &STDMAP2(
-            STDSTRING("event"), STDSTRING("audio.onComplete"),
-            STDSTRING("value"), STDBOOL(true)
-        )
-    );
-
-    // clang-format on
+    if (self->event_subscribed) {
+        // clang-format off
+        platch_send_success_event_std(
+            self->event_channel_name,
+            &STDMAP2(
+                STDSTRING("event"), STDSTRING("audio.onComplete"),
+                STDSTRING("value"), STDBOOL(true)
+            )
+        );
+        // clang-format on
+    }
 
     if (audio_player_get_looping(self)) {
         audio_player_play(self);
@@ -482,14 +478,15 @@ void audio_player_destroy(struct audio_player *self) {
         self->url = NULL;
     }
 
-
     if (self->player_id != NULL) {
         free(self->player_id);
         self->player_id = NULL;
     }
 
-    plugin_registry_remove_receiver(self->event_channel_name);
-    self->event_channel_name[0] = 0;
+    if (self->event_channel_name != NULL) {
+        free(self->event_channel_name);
+        self->event_channel_name = NULL;;
+    }
 
     free(self);
 }
@@ -572,3 +569,16 @@ void audio_player_set_source_url(struct audio_player *self, char *url) {
 bool audio_player_is_id(struct audio_player *self, char *player_id) {
     return strcmp(self->player_id, player_id) == 0;
 }
+
+const char* audio_player_subscribe_channel_name(const struct audio_player *self) {
+    return self->event_channel_name;
+}
+
+bool audio_player_set_subscription_status(struct audio_player *self, const char *channel, bool value) {
+    if (strcmp(self->event_channel_name, channel) == 0) {
+        self->event_subscribed = value;
+        return true;
+    } else {
+        return false;
+    }
+}

src/plugins/audioplayers/plugin.c

@@ -195,6 +195,38 @@ static int on_global_method_call(char *channel, struct platch_obj *object, Flutt
     return platch_respond_success_std(responsehandle, &STDBOOL(true));
 }
 
+static int on_receive_event_ch(char *channel, struct platch_obj *object, FlutterPlatformMessageResponseHandle *responsehandle) {
+    struct audio_player *player;
+
+    if (strcmp(object->method, "listen") == 0) {
+        LOG_DEBUG("%s: listen()\n", channel);
+
+        for_each_pointer_in_cpset(&plugin.players, player) {
+            if (audio_player_set_subscription_status(player, channel, true)) {
+                return platch_respond_success_std(responsehandle, NULL);
+            }
+        }
+
+        LOG_ERROR("%s: player not found\n", channel);
+        return platch_respond_not_implemented(responsehandle);
+    } else if (strcmp(object->method, "cancel") == 0) {
+        LOG_DEBUG("%s: cancel()\n", channel);
+
+        for_each_pointer_in_cpset(&plugin.players, player) {
+            if (audio_player_set_subscription_status(player, channel, false)) {
+                return platch_respond_success_std(responsehandle, NULL);
+            }
+        }
+
+        LOG_ERROR("%s: player not found\n", channel);
+        return platch_respond_not_implemented(responsehandle);
+    } else {
+        return platch_respond_not_implemented(responsehandle);
+    }
+
+    return 0;
+}
+
 enum plugin_init_result audioplayers_plugin_init(struct flutterpi *flutterpi, void **userdata_out) {
     (void) userdata_out;
     int ok;
@@ -249,12 +281,33 @@ static struct audio_player *audioplayers_linux_plugin_get_player(char *player_id
         }
     }
 
+    LOG_DEBUG("Create player(id=%s)\n", player_id);
     player = audio_player_new(player_id, AUDIOPLAYERS_LOCAL_CHANNEL);
+
+    if (player == NULL) {
+        LOG_ERROR("player(id=%s) cannot be created", player_id);
+        return NULL;
+    }
+
+    const char* event_channel = audio_player_subscribe_channel_name(player);
+    // set a receiver on the videoEvents event channel
+    int ok = plugin_registry_set_receiver(
+        event_channel,
+        kStandardMethodCall,
+        on_receive_event_ch
+    );
+    if (ok != 0) {
+        LOG_ERROR("Cannot set player receiver for event channel: %s\n", event_channel);
+        audio_player_destroy(player);
+        return NULL;
+    }
+
     cpset_put_locked(&plugin.players, player);
     return player;
 }
 
 static void audioplayers_linux_plugin_dispose_player(struct audio_player *player) {
+    plugin_registry_remove_receiver(audio_player_subscribe_channel_name(player));
     audio_player_destroy(player);
     cpset_remove_locked(&plugin.players, player);
 }