WordPress bulk actions in plugins, starterkit example

<?php
/*
Plugin Name: Bulk
Plugin URI: http://mac-blog.org.ua/
Description: Test for bulk actions via ajax.
Author: Marchenko Alexandr
Version: None
Author URI: http://mac-blog.org.ua/
*/

//add example admin page, and register hook to enqueue needed scripts and styles
function bulk_admin_menu() {
    $page = add_menu_page('Bulk Page Title', 'Bulk Menu Title', 'manage_options', 'bulk_page_slug', 'bulk_page_handler');
    add_action('admin_print_scripts-' . $page, 'bulk_admin_print_scripts');
}
add_action('admin_menu', 'bulk_admin_menu');

//register and enqueue needed scripts and styles here
function bulk_admin_print_scripts() {
    wp_enqueue_script('jquery');
}

//page handler is simple function that renders page
function bulk_page_handler() {
    //here is our nonce, we will use it in bulk_process function to check that request is maded from this page
    $_ajax_nonce = wp_create_nonce(basename(__FILE__));

    //here is page actualy, u can do somthing like: include_once 'bulk_page.php'; and move all this code to bulk_page.php file
    //include_once 'bulk_page.php';
    ?>
<div class="wrap">
    <!--
        Here is our simple form, it just contains one input to configure number of actions
        but form may be as big as u want
    -->
    <div id="bulk_form">
        <input type="number" name="bulk_count" id="bulk_count" placeholder="number of iterations..." required>
        <input id="bulk_submit" type="submit" value="Submit">
    </div>
    <!--
        #bulk_process will be used to show process metrics, just for example
    -->
    <div id="bulk_process" style="display:none">
        <table cellspacing="0" cellpadding="5" border="1">
            <tr>
                <th>success</th>
                <th>total</th>
                <th>success</th>
                <th>fail</th>
                <th>current</th>
                <th>remainded</th>
                <th>percentage</th>
                <th>start</th>
                <th>elapsed</th>
                <th>remainded</th>
                <th>per item</th>
                <th>message</th>
            </tr>
        </table>
    </div>
</div>

<script>
jQuery(document).ready(function($) {
    //some process metrics variables, might be usefull for creating nice interface
    var bulk_actions_total = 0;
    var bulk_actions_success = 0;
    var bulk_actions_fail = 0;
    var bulk_actions_current = 0;
    var bulk_actions_remainded = 0;
    var bulk_actions_complete_percentage = 0;
    var bulk_actions_time_start = 0;
    var bulk_actions_time_elapsed = 0;
    var bulk_actions_time_remainded = 0;
    var bulk_actions_time_per_item = 0;

    //This function called as many times as you input
    //it just call php bulk_process() function via ajax
    //recursively until all actions will be done
    function bulk_process() {
        //recalculate most important metric values
        bulk_actions_current = bulk_actions_current + 1;
        bulk_actions_remainded = bulk_actions_remainded - 1;

        //check if we are done
        if(bulk_actions_remainded < 0) return bulk_finish();

        //make another request
        $.ajax({
            type: 'POST',
            dataType: 'json',
            url: ajaxurl, //this is Wordpress variable
            data: {
                action: 'bulk_process', //action name, add_action('wp_ajax_[bulk_process]', 'bulk_process');
                _ajax_nonce: '<?php echo $_ajax_nonce?>', //our nonce, defined in bulk_page_handler function
                bulk_nonce: $('bulk_nonce').val(), //and there can be as much data as u want, it will be accessible in php via $_POST
                index: bulk_actions_current,
                //...
                bulk_count: $('bulk_count').val()
            },
            success: function(response) {
                //in both cases of success and failure we call bulk_update function
                //to notify user about changes, also we are going to recursion
                bulk_update(response, response.success); //notice, response.success coming from php, and can be false
                bulk_process();
            },
            error: function(response) {
                bulk_update(response, false); //there is some network error or something else
                bulk_process();
            }
        });
    }

    //this function call after every action is done
    function bulk_update(response, success) {
        calculateMetrics(success);

        $('#bulk_process table').append('<tr><td>' + success + '</td><td>' + bulk_actions_total + '</td><td>' + bulk_actions_success + '</td><td>' + bulk_actions_fail + '</td><td>' + bulk_actions_current + '</td><td>' + bulk_actions_remainded + '</td><td>' + bulk_actions_complete_percentage + '%</td><td>' + bulk_actions_time_start + '</td><td>' + humanReadableTime(bulk_actions_time_elapsed) + '</td><td>' + humanReadableTime(bulk_actions_time_remainded) + '</td><td>' + humanReadableTime(bulk_actions_time_per_item) + '</td><td>' + response.message + '</td></tr>');

        console.log(
            response,
            success,
            bulk_actions_total,
            bulk_actions_success,
            bulk_actions_fail,
            bulk_actions_current,
            bulk_actions_remainded,
            bulk_actions_complete_percentage,
            bulk_actions_time_start,
            bulk_actions_time_elapsed,
            bulk_actions_time_remainded,
            bulk_actions_time_per_item
        );
    }

    //we will call this function at the end of our bulk actions
    function bulk_finish() {

        console.log('FINISH');
    }

    //here we are attaching to submit button click event and starting bulk process
    $('#bulk_submit').click(function(event){
        event.preventDefault();

        //get and validate number of actions
        var count = parseInt($('#bulk_count').val());
        if(!count) {
            alert('Please enter number');
            return false;
        }

        //define start metric values
        bulk_actions_total = count;
        bulk_actions_remainded = count;
        bulk_actions_time_start = new Date();

        //start bull process
        bulk_process();

        $('#bulk_form').hide();
        $('#bulk_process').show();

        return false;
    });

    //helper function, must be called every time to get apropriate metrics
    function calculateMetrics(success) {
        if(success) {
            bulk_actions_success = bulk_actions_success + 1;
        } else {
            bulk_actions_fail = bulk_actions_fail + 1;
        }

        bulk_actions_complete_percentage = Math.round(bulk_actions_current / (bulk_actions_total / 100));
        bulk_actions_time_elapsed = (new Date()).getTime() - bulk_actions_time_start.getTime();
        bulk_actions_time_elapsed = bulk_actions_time_elapsed / 1000;
        bulk_actions_time_per_item = bulk_actions_time_elapsed / bulk_actions_current;
        bulk_actions_time_remainded = bulk_actions_remainded * bulk_actions_time_per_item;
    }

    //helper function to display nice time text
    function humanReadableTime(seconds) {
        // 1, 2, 5 - period label
        var periods = [
            ['&#1089;&#1077;&#1082;&#1091;&#1085;&#1076;&#1072;', '&#1089;&#1077;&#1082;&#1091;&#1088;&#1085;&#1076;&#1099;', '&#1089;&#1077;&#1082;&#1091;&#1085;&#1076;'], //1 second, 2 seconds, 5 seconds
            ['&#1084;&#1080;&#1085;&#1091;&#1090;&#1072;', '&#1084;&#1080;&#1085;&#1091;&#1090;&#1099;', '&#1084;&#1080;&#1085;&#1091;&#1090;'], //min
            ['&#1095;&#1072;&#1089;', '&#1095;&#1072;&#1089;&#1072;', '&#1095;&#1072;&#1089;&#1086;&#1074;'], //hour
            ['&#1076;&#1077;&#1085;&#1100;', '&#1076;&#1085;&#1103;', '&#1076;&#1085;&#1077;&#1081;'], //day
            ['&#1085;&#1077;&#1076;&#1077;&#1083;&#1103;', '&#1085;&#1077;&#1076;&#1077;&#1083;&#1080;', '&#1085;&#1077;&#1076;&#1077;&#1083;&#1100;'], //week
            ['&#1084;&#1077;&#1089;&#1103;&#1094;', '&#1084;&#1077;&#1089;&#1103;&#1094;&#1072;', '&#1084;&#1077;&#1089;&#1103;&#1094;&#1077;&#1074;'], //month
            ['&#1075;&#1086;&#1076;', '&#1075;&#1086;&#1076;&#1072;', '&#1083;&#1077;&#1090;'], //year
        ];

        var lengths = [60, 60, 24, 7, 4.35, 12];

        for(var i = 0; seconds >= lengths[i]; i++) {
            seconds = seconds / lengths[i];
        }

        seconds = Math.round(seconds);

        var cases = [2, 0, 1, 1, 1, 2];
        var text = periods[i][(seconds%100>4 && seconds%100<20)? 2: cases[Math.min(seconds%10, 5)]];
        return seconds + ' ' + text;
    }
});
</script>
    <?php
}

// our ajax handler, all data accessible via $_POST
function bulk_process() {
    //check correct nonce (setted in bulk_page_handler function)
    check_ajax_referer(basename(__FILE__));
    //try to turn off error reporting
    @error_reporting(0);
    //we are going to retrieve json response
    header('Content-type: application/json');

    try {

        //TODO: do something heavy weight here
        //throw exceptions on error
        if($_POST['index'] == 2) throw new Exception('Wrong id');
        //fill $response variable at the end
        sleep(rand(1, 3));

        $response = array(
            'success' => true,
            'message' => $_POST['index'] . ' - done'
        );

    } catch(Exception $ex) {
        $response = array(
            'success' => false,
            'message' => $ex->getMessage()
        );
    }

    //echoing response
    echo json_encode($response);
    //do not forget about this die()
    die();
}
//notice how we registering our handler
//wp_ajax_[bulk_process] - where [bulk_process] will be action name in javascript
add_action('wp_ajax_bulk_process', 'bulk_process');