myCRED Points to MarketPress Coupon

/**
 * Convert myCRED Points into MarketPress Coupon
 * This shortcode will present a form where users can
 * convert points into MarketPress coupons.
 * @version 1.0
 */
add_shortcode( 'mycred_to_mpress_coupon', 'mycred_pro_render_points_to_marketpress_coupon' );
function mycred_pro_render_points_to_marketpress_coupon( $atts, $content = NULL ) {
    // Users must be logged in
    if ( ! is_user_logged_in() )
        return 'You must be logged in to generate store coupons.';

    // myCRED must be enabled
    if ( ! function_exists( 'mycred_get_settings' ) )
        return 'myCRED must be enabled to use this shortcode';

    // Load myCRED
    $mycred = mycred_get_settings();

    // Prep
    $error = $code = false;
    $output = '';
    $user_id = get_current_user_id();

    // No need to show this for excluded users
    if ( $mycred->exclude_user( $user_id ) ) return;

    $balance = $mycred->get_users_balance( $user_id );

    // Form submission
    if ( isset( $_POST['mycred_to_mark'] ) && wp_verify_nonce( $_POST['mycred_to_mark']['token'], 'points-to-market-coupon' ) ) {

        // Make sure amounts are always positive
        $amount = abs( $_POST['mycred_to_mark']['amount'] );

        // Assumes 1 point = 1 currency. You would need to apply an
        // exchange rate here before we continue on.

        // Make sure amount is not zero
        if ( $amount == $mycred->zero() )
            $error = 'Amount can not be zero';

        // Make sure user has enough points
        if ( $amount > $balance )
            $error = 'Insufficient Funds. Please try a lower amount';

        // If no errors
        if ( $error === false ) {

            // In this example coupons are valid for 30 days
            // You can change this to a specific date or change
            // the number of days. We need a unix timestamp.
            $expires = strtotime( '+ 30 days' );

            // In this exmaple we will want users to be able to use
            // the generated coupon right away but you can change thi
            // to any unix timestamp as long as it is befor the expire date.
            $start = time();

            // Create MarketPress Coupon
            $code = wp_generate_password( 12, false, false );
            $code = strtoupper( $code );
            $coupon = array(
                'discount_type' => 'amt',
                'discount'      => $amount,
                'start'         => $start,
                'end'           => $expires,
                'uses'          => 1
            );

            // Save
            $coupons = get_option( 'mp_coupons', array() );
            $coupons[ $code ] = $coupon;
            update_option( 'mp_coupons', $coupons );

            // Deduct points from user
            $mycred->add_creds(
                'points_to_coupon',
                $user_id,
                0-$amount,
                '%plural% conversion into store coupon',
                $new_coupon_id,
                array( 'code' => $code )
            );

            $balance = $balance-$amount;
            $balance = $mycred->number( $balance );
        }

    }

    // Show users current balance
    $output .= '
<p>Your current balance is: ' . $mycred->format_creds( $balance ) . '</p>';

    // Error
    if ( $error !== false )
        $output .= '<p style="color:red;">' . $error . '</p>';

    // Success
    elseif ( $code !== false )
        $output .= '<p>Your coupon code is: <strong>' . $code . '</strong></p>';

    // The form for those who have points
    if ( $balance > $mycred->zero() )
        $output .= '
<form action="" method="post">
    <input type="hidden" name="mycred_to_mark[token]" value="' . wp_create_nonce( 'points-to-market-coupon' ) . '" />
    <label>Amount</label>
    <input type="text" size="5" name="mycred_to_mark[amount]" value="" />
    <input type="submit" name="submit" value="Create Coupon" />
</form>';

    // Not enough points
    else
        $output .= '<p>Not enough points to create coupons.</p>';

    return $output;
}