BP_REST_Messages_Endpoint::bp_rest_messages_get_avatars( int $thread_id, int $user_id )

	public function bp_rest_messages_get_avatars( $thread_id, $user_id = 0 ) {
		global $wpdb;

		if ( empty( $user_id ) ) {
			$user_id = bp_loggedin_user_id();
		}

		$avatar_urls      = array();
		$avatars_user_ids = array();
		$thread_messages  = BP_Messages_Thread::get_messages( $thread_id, null, 99999999 );
		$recepients       = BP_Messages_Thread::get_recipients_for_thread( $thread_id );

		if ( count( $recepients ) > 2 ) {
			foreach ( $thread_messages as $message ) {
				if ( $message->sender_id !== $user_id ) {

					if ( count( $avatars_user_ids ) >= 2 ) {
						continue;
					}

					if ( ! in_array( $message->sender_id, $avatars_user_ids ) ) {
						$avatars_user_ids[] = $message->sender_id;
					}
				}
			}
		} else {
			unset( $recepients[ $user_id ] );
			$avatars_user_ids[] = current( $recepients )->user_id;
		}

		if ( count( $recepients ) > 2 && count( $avatars_user_ids ) < 2 ) {
			unset( $recepients[ $user_id ] );
			if ( count( $avatars_user_ids ) === 0 ) {
				$avatars_user_ids = array_slice( array_keys( $recepients ), 0, 2 );
			} else {
				unset( $recepients[ $avatars_user_ids[0] ] );
				$avatars_user_ids = array_merge( $avatars_user_ids, array_slice( array_keys( $recepients ), 0, 1 ) );
			}
		}

		if ( ! empty( $avatars_user_ids ) ) {
			$avatars_user_ids = array_reverse( $avatars_user_ids );
			foreach ( (array) $avatars_user_ids as $avatar_user_id ) {
				$avatar_urls[] = array(
					'full'  => bp_core_fetch_avatar(
						array(
							'item_id' => $avatar_user_id,
							'html'    => false,
							'type'    => 'full',
							'object'  => 'user',
						)
					),
					'thumb' => bp_core_fetch_avatar(
						array(
							'item_id' => $avatar_user_id,
							'html'    => false,
							'object'  => 'user',
						)
					),
				);
			}
		}

		$first_message    = end( $thread_messages );
		$first_message_id = ( ! empty( $first_message ) ? $first_message->id : false );
		$group_id         = ( isset( $first_message_id ) ) ? (int) bp_messages_get_meta( $first_message_id, 'group_id', true ) : 0;
		if ( ! empty( $first_message_id ) && ! empty( $group_id ) ) {
			$message_from  = bp_messages_get_meta( $first_message_id, 'message_from', true ); // group
			$message_users = bp_messages_get_meta( $first_message_id, 'group_message_users', true ); // all - individual
			$message_type  = bp_messages_get_meta( $first_message_id, 'group_message_type', true ); // open - private

			if ( 'group' === $message_from && 'all' === $message_users && 'open' === $message_type ) {
				if ( bp_is_active( 'groups' ) ) {
					$group_name   = bp_get_group_name( groups_get_group( $group_id ) );
					$group_avatar = array(
						'thumb' => bp_core_fetch_avatar(
							array(
								'html'    => false,
								'object'  => 'group',
								'item_id' => $group_id,
								'type'    => 'thumb',
							)
						),
						'full'  => bp_core_fetch_avatar(
							array(
								'html'    => false,
								'object'  => 'group',
								'item_id' => $group_id,
								'type'    => 'full',
							)
						),
					);
				} else {
					$prefix                   = apply_filters( 'bp_core_get_table_prefix', $wpdb->base_prefix );
					$groups_table             = $prefix . 'bp_groups';
					$group_name               = $wpdb->get_var( "SELECT `name` FROM `{$groups_table}` WHERE `id` = '{$group_id}';" ); // db call ok; no-cache ok;
					$group_avatar             = buddypress()->plugin_url . 'bp-core/images/mystery-group.png';
					$legacy_group_avatar_name = '-groupavatar-full';
					$legacy_user_avatar_name  = '-avatar2';

					if ( ! empty( $group_name ) ) {
						$directory         = 'group-avatars';
						$avatar_size       = '-bpfull';
						$avatar_folder_dir = bp_core_avatar_upload_path() . '/' . $directory . '/' . $group_id;
						$avatar_folder_url = bp_core_avatar_url() . '/' . $directory . '/' . $group_id;

						$avatar = bp_core_get_group_avatar( $legacy_user_avatar_name, $legacy_group_avatar_name, $avatar_size, $avatar_folder_dir, $avatar_folder_url );
						if ( '' !== $avatar ) {
							$group_avatar = array(
								'thumb' => $avatar,
								'full'  => $avatar,
							);
						}
					}
				}

				if ( ! empty( $group_avatar ) ) {
					$avatar_urls = array( $group_avatar );
				}
			}
		}

		return apply_filters( 'bp_rest_messages_get_avatars', $avatar_urls, $thread_id, $user_id );
	}