A custom WP JSON API SearchWP endpoint

api.php

<?php
/*
 * Register custom API endpoints
 *
 * NOTE: Will be accessable at: https://example.com/wp-json/fuxt/v1/search?term=Netflix&engine=work
 */
function add_fuxt_api_routes()
{
    // Sitemap
    register_rest_route("fuxt/v1", "/search", [
        [
            "methods" => "GET",
            "callback" => "fuxt_search_get",
            "args" => ["term", "engine", "page", "per_page"],
            "permission_callback" => "__return_true",
        ],
    ]);
}
add_action("rest_api_init", "add_fuxt_api_routes");

/**
 * GET an array of posts that match the search term
 *
 * @return array of Post objects
 */
function fuxt_search_get($request)
{
    // Setup inputs
    $term = $request->get_param("term") ?? "";
    $engine = $request->get_param("engine") ?? "default";
    $page = $request->get_param("page") ?? 1;
    $per_page = $request->get_param("per_page") ?? -1;

    // Our default SearchWP args
    $search_args = [
        "s" => $term,
        "engine" => $engine,
        "posts_per_page" => $per_page,
        "page" => $page,
        "fields" => "all",
    ];

    // Example: Limit an engine to specific sub-pages of a page
    /*
    if ($engine == "our_work") {
        $args = [
            'post_type' => ['page'],
            'post_parent__in' => [32], // Our Work
            'fields' => 'ids',
            'posts_per_page' => -1,
        ];
        $page_ids = get_posts($args);
        $search_args['post__in'] = $page_ids;
    }
	*/

    // Do a new WP Search.
    // SEE: https://searchwp.com/documentation/classes/swp_query/
    $search = new SWP_Query($search_args);
    $results = $search->get_posts();

    // Build out post objects with any extra data needed
    $posts = array_map(function ($post_obj) {
        // Convert object to array for manipulation
        $array = (array) $post_obj;

        // Add data to reponse
        $array["meta"] = get_fields($post_obj->ID);
        $array["featured_image"] = custom_build_repsponsive_image(
            get_post_thumbnail_id($post_obj->ID)
        );

        // Add data to mimic WP-GQL
        $array["ID"] = "post-" . $post_obj->ID;
        $array["database_id"] = $post_obj->ID;
        $array["uri"] = wp_make_link_relative(get_permalink($post_obj->ID));

        return camelCaseKeys($array);
    }, $results);

    return new WP_REST_Response($posts, 200);
}

/**
 * Utility function to build an image in the same format <wp-image> expects it from WP-GQL
 *
 * @param int $attachment_id The WordPress attachment ID
 * @param string $size The WordPress image size keyword
 */
function custom_build_repsponsive_image(
    $attachment_id,
    $size = "fullscreen-xlarge"
) {
    $attachment = get_post($attachment_id);
    $attachment_data = wp_get_attachment_image_src($attachment_id, $size);
    $attachment_data_small = wp_get_attachment_image_src(
        $attachment_id,
        "fullscreen-small"
    );

    // Build image details array
    $media_details = [
        "height" => $attachment_data[2],
        "width" => $attachment_data[1],
    ];

    // Add ACF image meta data
    $acf_image_meta = [
        "videoUrl" => $attachment->videoUrl,
        "primaryColor" => $attachment->primaryColor,
        "focalPointY" => $attachment->focal_point_x,
        "focalPointX" => $attachment->focal_point_y,
        "blurhash" => $attachment->blurhash,
    ];

    // Build base image data
    $image = [
        "sourceUrl" => $attachment_data[0],
        "sizes" => wp_calculate_image_sizes(
            $size,
            $attachment_data[0],
            null,
            $attachment->ID
        ),
        "srcSet" => wp_get_attachment_image_srcset($attachment->ID, $size),
        "src" => $attachment_data_small[0],
        "id" => "attachment-" . $attachment->ID,
        "databaseId" => $attachment->ID,
        "title" => $attachment->post_title,
        "altText" => $attachment->_wp_attachment_image_alt,
        "caption" => $attachment->post_excerpt,
        "mediaDetails" => $media_details,
        "imageMeta" => $acf_image_meta,
    ];

    return $image;
}

/**
 * Utility function to recursively camelCase all keys in an array
 */
function camelCaseKeys($array)
{
    $finalArray = [];

    foreach ($array as $key => $value):
        // If key is all uppercase, make all lower case. ID => id
        if ($key == strtoupper($key)) {
            $key = strtolower($key);
        }
        
        // Remove post_ from all keys to match WP_GQL
        $key = str_replace("post_", "", $key);

	// Let's convert key into camelCase
        if (strpos($key, "_")) {
            $key = lcfirst(str_replace("_", "", ucwords($key, "_")));
        }

        // Recursive if key's value contains another array
        if (is_array($value)) {
            $finalArray[$key] = camelCaseKeys($value);
        } else {
            $finalArray[$key] = $value;
        }
    endforeach;

    return $finalArray;
}