datasets.php

<?php

$EMPTY_SPACE_FILE = kg_get_space_file_path("default").".hidden";

add_action("wp_ajax_get_space", "kg_get_space"); // Fires only for logged-in-users
add_action("wp_ajax_nopriv_get_space", 'kg_get_space' ); // Fires for everyone
function kg_get_space() {
    $file_path = kg_get_space_file_path($_POST["space"]);

    // If it doesn't exist, create new empty space
    if (!file_exists($file_path)) {
        kg_create_empty_space($file_path);
    }

    $content = file_get_contents($file_path);
    echo $content;

    wp_die();
}

add_action("wp_ajax_list_spaces", "kg_list_spaces"); // Fires only for logged-in-users
function kg_list_spaces() {
    $spaces = kg_get_list_of_spaces();
    $payload = array("spaces" => $spaces);

    echo json_encode($payload);

    wp_die();
}

add_action("wp_ajax_update_space", "kg_update_space"); // Fires only for logged-in-users
//add_action("wp_ajax_nopriv_update_space", 'update_space' ); // Fires for everyone
function kg_update_space() {
    // Check user capabilities
    if (current_user_can("edit_posts")) {
        // Use json encoding.
        $graph = stripslashes($_POST["graph"]);

        kg_store_new_graph($graph, $_POST["space"]);

        wp_die();
    } else {
        echo "Insufficient permissions!";
    }
}

function kg_store_new_graph($graph, $space_id) {
    $file_path = kg_get_space_file_path($space_id);
    $result = file_put_contents($file_path, $graph);

    //echo print_r($_POST);
    echo "Saved file at ";
    echo $file_path;
    echo " ";
    echo $result;
}

function kg_get_space_file_path($space_id) {
    return __DIR__."/".$space_id.".json";
}

function kg_get_list_of_spaces() {
    $all_files = scandir(__DIR__);

    if ($all_files == false) {
        return [];
    }

    $spaces = [];

    foreach ($all_files as $file) {
        if (endsWith($file, ".json")) {
            $spaces[] = substr($file, 0, -strlen(".json"));
        }
    }

    return $spaces;
}

function kg_create_empty_space($file_path) {
    // Don't do anything, if it exists
    if (file_exists($file_path)) {
        return;
    }

    // Read and copy default empty graph from default file
    global $EMPTY_SPACE_FILE;
    $empty_graph = file_get_contents($EMPTY_SPACE_FILE);
    file_put_contents($file_path, $empty_graph);
}

function endsWith( $haystack, $needle ) {
    # Source: https://stackoverflow.com/a/834355/7376120
    $length = strlen( $needle );
    if( !$length ) {
        return true;
    }
    return substr( $haystack, -$length ) === $needle;
}