<?php
/*
Plugin Name:  Simple AJAX test 2018-05-22
Author:       Kevin Meredith
Description:  Pluggin to test client site AJAX request
Version:      1
*/

// disable direct file access
if ( ! defined( 'ABSPATH' ) ) {
    exit;
}

function load_js() {

    wp_enqueue_script('ajax_test', plugin_dir_url( __FILE__ ) . 'ajax_test.js', array('jquery'), null, true );

     $test_nonce = wp_create_nonce('test_nonce');
    wp_localize_script(
        'ajax_test',
        'wbs_ajax_obj',
        array(
            'ajax_url' => admin_url( 'admin-ajax.php' ),
            'nonce'    => $test_nonce,
        )
    );
    error_log('Load JS TEST SITE');
    // wp_localize_script is used to send an array of php values to javascript
    // it embeds values in the HTML so that be used by java script
}
add_action( 'wp_enqueue_scripts', 'load_js' );

function test_ajax_process_request() {
    error_log('test_ajax_process_request() has been called');
    // first check if data is being sent and that it is the data we want
    //check_ajax_referer( $action, $query_arg, $die )
    if ( check_ajax_referer( 'test_nonce', 'js_nonce', false) ) {
        // 1st parameter is the were the nonce is stored in the $_POST array or what the nonce from field name
        // 2nd parameter is the name of the nonce which is set up in wp_create_nonce()
        // 3rd parameter is die, if true and nonce fails they function will return false
        $ran = rand(0, 100);
      $return_string = 'string from JS: "'.$_POST["from_js"].'" random number from server: '.$ran.' nonce: '.$_POST["js_nonce"].' TEST SITE';
      error_log($return_string);
      echo $return_string;
        die();
    }else{
      $return_string = 'nonce fail (ajax_test.php)';
        echo ($return_string);
      error_log($return_string);
        die();
    }
}
add_action('wp_ajax_test_ajax', 'test_ajax_process_request');
add_action('wp_ajax_nopriv_test_ajax', 'test_ajax_process_request');

var $ = jQuery.noConflict();

$( document ).ready(function() {

    console.log('Nonce: '+wbs_ajax_obj.nonce+' from ajax_test.js');

    $.ajax({
      type:"POST",
      url: wbs_ajax_obj.ajax_url, // 'https://lomokev.com/ajaxtest'
      data: {
          action: "test_ajax", // name of the wordpress hook that will trigger function so in this case wp_ajax_nopriv_test_ajax and wp_ajax_test_ajax'
          js_nonce: wbs_ajax_obj.nonce,
          from_js: 'value of from_js from ajax_test.js'
      },
      success:function(data){
        console.log(data);
      },
      error: function(errorThrown){
          console.log(Object.values(errorThrown));
      }

    });

    // if it's a 404 the error says "error"
    // but this says "Bad Request"

});