Source

File: wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php

protected function prepare_links( $post ) {
		$base = sprintf( '%s/%s', $this->namespace, $this->rest_base );

		// Entity meta.
		$links = array(
			'self'       => array(
				'href' => rest_url( trailingslashit( $base ) . $post->ID ),
			),
			'collection' => array(
				'href' => rest_url( $base ),
			),
			'about'      => array(
				'href' => rest_url( 'wp/v2/types/' . $this->post_type ),
			),
		);

		if ( ( in_array( $post->post_type, array( 'post', 'page' ), true ) || post_type_supports( $post->post_type, 'author' ) )
			&& ! empty( $post->post_author ) ) {
			$links['author'] = array(
				'href'       => rest_url( 'wp/v2/users/' . $post->post_author ),
				'embeddable' => true,
			);
		}

		if ( in_array( $post->post_type, array( 'post', 'page' ), true ) || post_type_supports( $post->post_type, 'comments' ) ) {
			$replies_url = rest_url( 'wp/v2/comments' );
			$replies_url = add_query_arg( 'post', $post->ID, $replies_url );

			$links['replies'] = array(
				'href'       => $replies_url,
				'embeddable' => true,
			);
		}

		if ( in_array( $post->post_type, array( 'post', 'page' ), true ) || post_type_supports( $post->post_type, 'revisions' ) ) {
			$revisions       = wp_get_post_revisions( $post->ID, array( 'fields' => 'ids' ) );
			$revisions_count = count( $revisions );

			$links['version-history'] = array(
				'href'  => rest_url( trailingslashit( $base ) . $post->ID . '/revisions' ),
				'count' => $revisions_count,
			);

			if ( $revisions_count > 0 ) {
				$last_revision = array_shift( $revisions );

				$links['predecessor-version'] = array(
					'href' => rest_url( trailingslashit( $base ) . $post->ID . '/revisions/' . $last_revision ),
					'id'   => $last_revision,
				);
			}
		}

		$post_type_obj = get_post_type_object( $post->post_type );

		if ( $post_type_obj->hierarchical && ! empty( $post->post_parent ) ) {
			$links['up'] = array(
				'href'       => rest_url( trailingslashit( $base ) . (int) $post->post_parent ),
				'embeddable' => true,
			);
		}

		// If we have a featured media, add that.
		$featured_media = get_post_thumbnail_id( $post->ID );
		if ( $featured_media ) {
			$image_url = rest_url( 'wp/v2/media/' . $featured_media );

			$links['https://api.w.org/featuredmedia'] = array(
				'href'       => $image_url,
				'embeddable' => true,
			);
		}

		if ( ! in_array( $post->post_type, array( 'attachment', 'nav_menu_item', 'revision' ), true ) ) {
			$attachments_url = rest_url( 'wp/v2/media' );
			$attachments_url = add_query_arg( 'parent', $post->ID, $attachments_url );

			$links['https://api.w.org/attachment'] = array(
				'href' => $attachments_url,
			);
		}

		$taxonomies = get_object_taxonomies( $post->post_type );

		if ( ! empty( $taxonomies ) ) {
			$links['https://api.w.org/term'] = array();

			foreach ( $taxonomies as $tax ) {
				$taxonomy_obj = get_taxonomy( $tax );

				// Skip taxonomies that are not public.
				if ( empty( $taxonomy_obj->show_in_rest ) ) {
					continue;
				}

				$tax_base = ! empty( $taxonomy_obj->rest_base ) ? $taxonomy_obj->rest_base : $tax;

				$terms_url = add_query_arg(
					'post',
					$post->ID,
					rest_url( 'wp/v2/' . $tax_base )
				);

				$links['https://api.w.org/term'][] = array(
					'href'       => $terms_url,
					'taxonomy'   => $tax,
					'embeddable' => true,
				);
			}
		}

		return $links;
	}