<?php

    require_once( ABSPATH . '/wp-includes/shortcodes.php' );


    function custom_registration_function() {
        if (isset($_POST['submit'])) {
            registration_validation(
                $_POST['username'],
                $_POST['password'],
                $_POST['email'],
                $_POST['website'],
                $_POST['fname'],
                $_POST['lname'],
                $_POST['nickname'],
                $_POST['bio']
            );

            // sanitize user form input
            global $username, $password, $email, $website, $first_name, $last_name, $nickname, $bio;
            $username   =   sanitize_user($_POST['username']);
            $password   =   esc_attr($_POST['password']);
            $email      =   sanitize_email($_POST['email']);
            $website    =   esc_url($_POST['website']);
            $first_name =   sanitize_text_field($_POST['fname']);
            $last_name  =   sanitize_text_field($_POST['lname']);
            $nickname   =   sanitize_text_field($_POST['nickname']);
            $bio        =   esc_textarea($_POST['bio']);

            // call @function complete_registration to create the user
            // only when no WP_error is found
            complete_registration(
                $username,
                $password,
                $email,
                $website,
                $first_name,
                $last_name,
                $nickname,
                $bio
            );
        }

        registration_form(
                $username,
                $password,
                $email,
                $website,
                $first_name,
                $last_name,
                $nickname,
                $bio
            );
    }

    function registration_form( $username, $password, $email, $website, $first_name, $last_name, $nickname, $bio ) {
        echo '
        <style>
        div {
            margin-bottom:2px;
        }

        input{
            margin-bottom:4px;
        }
        </style>
        ';

        echo '
        <form action="' . $_SERVER['REQUEST_URI'] . '" method="post">
        <div>
        <label for="username">Username <strong>*</strong></label>
        <input type="text" name="username" value="' . (isset($_POST['username']) ? $username : null) . '">
        </div>

        <div>
        <label for="password">Password <strong>*</strong></label>
        <input type="password" name="password" value="' . (isset($_POST['password']) ? $password : null) . '">
        </div>

        <div>
        <label for="email">Email <strong>*</strong></label>
        <input type="text" name="email" value="' . (isset($_POST['email']) ? $email : null) . '">
        </div>

        <div>
        <label for="website">Website</label>
        <input type="text" name="website" value="' . (isset($_POST['website']) ? $website : null) . '">
        </div>

        <div>
        <label for="firstname">First Name</label>
        <input type="text" name="fname" value="' . (isset($_POST['fname']) ? $first_name : null) . '">
        </div>

        <div>
        <label for="website">Last Name</label>
        <input type="text" name="lname" value="' . (isset($_POST['lname']) ? $last_name : null) . '">
        </div>

        <div>
        <label for="nickname">Nickname</label>
        <input type="text" name="nickname" value="' . (isset($_POST['nickname']) ? $nickname : null) . '">
        </div>

        <div>
        <label for="bio">About / Bio</label>
        <textarea name="bio">' . (isset($_POST['bio']) ? $bio : null) . '</textarea>
        </div>
        <input type="submit" name="submit" value="Register"/>
        </form>
        ';
    }

    function registration_validation( $username, $password, $email, $website, $first_name, $last_name, $nickname, $bio )  {
        global $reg_errors;
        $reg_errors = new WP_Error;

        if ( empty( $username ) || empty( $password ) || empty( $email ) ) {
            $reg_errors->add('field', 'Required form field is missing');
        }

        if ( strlen( $username ) < 4 ) {
            $reg_errors->add('username_length', 'Username too short. At least 4 characters is required');
        }

        if ( username_exists( $username ) )
            $reg_errors->add('user_name', 'Sorry, that username already exists!');

        if ( !validate_username( $username ) ) {
            $reg_errors->add('username_invalid', 'Sorry, the username you entered is not valid');
        }

        if ( strlen( $password ) < 5 ) {
            $reg_errors->add('password', 'Password length must be greater than 5');
        }

        if ( !is_email( $email ) ) {
            $reg_errors->add('email_invalid', 'Email is not valid');
        }

        if ( email_exists( $email ) ) {
            $reg_errors->add('email', 'Email Already in use');
        }

        if ( !empty( $website ) ) {
            if ( !filter_var($website, FILTER_VALIDATE_URL) ) {
                $reg_errors->add('website', 'Website is not a valid URL');
            }
        }

        if ( is_wp_error( $reg_errors ) ) {

            foreach ( $reg_errors->get_error_messages() as $error ) {
                echo '<div>';
                echo '<strong>ERROR</strong>:';
                echo $error . '<br/>';

                echo '</div>';
            }
        }
    }

    function complete_registration() {
        global $reg_errors, $username, $password, $email, $website, $first_name, $last_name, $nickname, $bio;
        if ( count($reg_errors->get_error_messages()) < 1 ) {
            $userdata = array(
                'user_login'    =>  $username,
                'user_email'    =>  $email,
                'user_pass'     =>  $password,
                'user_url'      =>  $website,
                'first_name'    =>  $first_name,
                'last_name'     =>  $last_name,
                'nickname'      =>  $nickname,
                'description'   =>  $bio,
            );
            $user = wp_insert_user( $userdata );
            echo 'Registration complete. Goto <a href="' . get_site_url() . '/wp-login.php">login page</a>.';
        }
    }

    // Register a new shortcode: [cr_custom_registration]
    add_shortcode('cr_custom_registration', 'custom_registration_shortcode');

    // The callback function that will replace [book]
    function custom_registration_shortcode() {
        ob_start();
        custom_registration_function();
        return ob_get_clean();
    }