Function to generate a random discount code for Easy Digital Downloads

edd-generate-discount.php

<?php
/**
 * Generate a random discount code that matches the given criteria.
 *
 * Samples:
 *  - generate_discount( 10, 'percent', '+7days', 'HI-^^^^' );
 *  - generate_discount( 5, 'flat', '', '********' );
 *
 * @param int    $amount  The discount code value.
 * @param string $type    The type, either [flat|percent].
 * @param string $expires A (relative) date string like "+7days", or empty for
 *                        no expiration.
 * @param string $pattern A string that describes the length/pattern of the code.
 *                        "*" is replaced with a random uppercase letter or digit.
 *                        "?" is replaced with a random uppercase/lowercase letter.
 *                        "." is replaced with a random lowercase letter.
 *                        "#" is replaced with a random uppercase letter.
 *                        "^" is replaced with a random uppercase hexadecimal digit.
 *                        "+" is replaced with a random digit.
 * @param string $name    Optional, internal coupon name.
 *
 * @return string The newly generated code.
 */
function generate_discount(
	int $amount = 10,
	string $type = 'flat',
	string $expires = '',
	string $pattern = '^^^^-^^^^',
	string $name = ''
) : string {
	if ( ! is_callable( 'edd_store_discount' ) ) {
		return '';
	}

	if ( $expires ) {
		if ( is_numeric( $expires ) ) {
			$exp_date = gmdate( 'm/d/Y', $expires );
		} else {
			$exp_date = gmdate( 'm/d/Y', strtotime( $expires ) );
		}
	} else {
		$exp_date = '';
	}

	do {
		$coupon_code = generate_coupon_code( $pattern );

		$exists = edd_get_discount_by_code( $coupon_code );
	} while ( $exists );

	$meta = [
		'name'              => $name ? $name : $coupon_code,
		'code'              => $coupon_code,
		'type'              => $type,
		'amount'            => $amount,
		'excluded_products' => [],
		'expiration'        => $exp_date,
		'is_not_global'     => false,
		'is_single_use'     => true,
		'max_uses'          => '1',
		'min_price'         => '',
		'product_condition' => '',
		'product_reqs'      => [],
		'start'             => '',
		'uses'              => '',
	];

	// EDD will set its own defaults in the edd_store_discount() so let's filter out
	// empty defaults. We just keep them here for easier reference.
	$meta = array_filter( $meta );

	// EDD takes a $details array which has some different keys than the meta, let's
	// map the keys to the expected format.
	$edd_post_keys = [
		'max_uses'          => 'max',
		'product_reqs'      => 'products',
		'excluded_products' => 'excluded-products',
		'is_not_global'     => 'not_global',
		'is_single_use'     => 'use_once',
	];

	foreach ( $meta as $key => $value ) {
		$mod_key = $edd_post_keys[ $key ];

		if ( $mod_key ) {
			$meta[ $mod_key ] = $value;
		}
	}

	edd_store_discount( $meta );

	return $coupon_code;
}


/**
 * Generates a random coupon code.
 *
 * @param string $pattern    The pattern - @see generate_discount() for details.
 * @param int    $min_length Minimum length of the code.
 *
 * @return string The random coupon code.
 */
function generate_coupon_code( $pattern, $min_length = 6 ) {
	$pattern = preg_replace( '/[^a-zA-Z0-9_\-.*#+^?]/', '*', $pattern );
	while ( strlen( $pattern ) < 6 ) {
		$pattern .= '*';
	}

	$pattern_len  = strlen( $pattern );
	$num_chars    = '0123456789';
	$lower_chars  = 'abcdefghijklmnopqrstuvwxyz';
	$upper_chars  = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
	$letter_chars = $lower_chars . $upper_chars;
	$hex_chars    = 'ABCDEF0123456789';
	$all_chars    = $num_chars . $upper_chars;

	$coupon_code = '';
	for ( $i = 0; $i < $pattern_len; $i ++ ) {
		$char = $pattern[ $i ];

		if ( '*' === $char ) {
			$pool = $all_chars;
		} elseif ( '^' === $char ) {
			$pool = $hex_chars;
		} elseif ( '?' === $char ) {
			$pool = $letter_chars;
		} elseif ( '.' === $char ) {
			$pool = $lower_chars;
		} elseif ( '#' === $char ) {
			$pool = $upper_chars;
		} elseif ( '+' === $char ) {
			$pool = $num_chars;
		} else {
			$pool = false;
		}

		if ( $pool ) {
			$char = $pool[ wp_rand( 0, strlen( $pool ) - 1 ) ];
		}
		$coupon_code .= $char;
	}

	return $coupon_code;
}