vue-wp/plugins/cia-endpoints/includes/formats.php

<?php
function make_taxonomy_endpoint_for( $terms ) {
    $type_slugs = [];
    foreach ($terms as $type_slug):
        array_push($type_slugs, $type_slug->slug);
    endforeach;
    return $type_slugs;
}


function default_post_format( $item, $include_content ) {
    $filtered = [];
    $filtered[id] = $item->ID;
    $filtered[slug] = $item->post_name;
    $filtered[type] = $item->post_type;
    $filtered[title] = $item->post_title;
    $filtered[excerpt] = $item->post_excerpt;
    $filtered[date] = $item->post_date;
    if(!$filtered[excerpt]) {
        $filtered[excerpt] = get_the_excerpt($item);
    }
    if($include_content) $filtered[content] = $item->post_content;

    $filtered[featured] = get_the_post_thumbnail_url($item);
    if(!$filtered[featured]) {
        $thumbnailId = get_post_meta( $item->ID, '_thumbnail_id', true );
        $filtered[featured] = get_post($thumbnailId)->guid;
    }

    // Materials + type endpoints
    // if($item->post_type === 'artist' || $item->post_type === 'event' || $item->post_type === 'exhibition') {
    $posts_with_type = ['artist', 'exhbition', 'event'];
    if( in_array($item->post_type, $posts_with_type) ) {
        $filtered[materials] = make_taxonomy_endpoint_for( get_the_terms( $item, 'material' ) );
        $filtered[subtypes] = make_taxonomy_endpoint_for( get_the_terms( $item, $item->post_type . '_type' ) );
    }

    // Custom fields endpoint
    if($item->post_type === 'episode') $filtered[credits] = get_post_meta( $item->ID, 'credits', true );

    if($item->post_type === 'artist') $filtered[sortname] = get_post_meta( $item->ID, 'artist-sort-name', true );

    if($item->post_type === 'event') {
        $filtered[start] = get_post_meta( $item->ID, 'event-start-time', true );
        $filtered[end] = get_post_meta( $item->ID, 'event-end-time', true );
    }
    if($item->post_type === 'exhibition') {
        $filtered[start] = get_post_meta( $item->ID, 'exhibit-start-date', true );
        $filtered[end] = get_post_meta( $item->ID, 'exhibit-end-date', true );
    }

    // Post categories and tags (store just the slugs)
    if($item->post_type === 'post') {
        $filtered[categories] = make_taxonomy_endpoint_for(get_the_terms( $item, 'category' ));
        $filtered[tags] = make_taxonomy_endpoint_for(get_the_terms( $item, 'post_tag' ));
    }

    return $filtered;
}

?>