Adds input attributes like minimums or maximums to WooCommerce Measurement Price Calculator inputs

wc_mpc_add_input_attributes.php

<?php // only copy this line if needed
/**
 * These snippets work together to let you set attributes for WooCommerce Measurement Price Calculator inputs
 * You can use post custom fields to set attributes like min, max, and step for a given measurement
 * 
 * Example: if you want to limit width, name a field `mpc_width` -- format: `mpc_{measurementName}`
 * The field value should be a comma-separated list of attributes, like min = 0, max = 10, step = 1
 */

/**
 * Modify MPC inputs to add field attributes from product custom fields
 * 
 * The product custom field must have a key that uses the measurement name,
 *   such as `mpc_width`, `mpc_length`, `mpc_volume`, etc.
 */
function sv_wc_measurement_price_calculator_input_min_max() {

	// bail unless we're on a product page and MPC is active
	if ( ! ( is_product() && class_exists( 'WC_Price_Calculator_Product' ) ) ) {
		return;
	}

	global $product;
	
	// bail unless the calculator is enabled for this product, this is also why we hook
	// into the footer scripts, since this isn't available immediately at page load
	if ( ! WC_Price_Calculator_Product::calculator_enabled( $product ) ) {
		return;
	}

	// get the possible measurements for the current calculator set up
	$settings = new WC_Price_Calculator_Settings( $product );
	$measurements = $settings->get_calculator_measurements();

	// get any rules we should add based on which measurements are enabled, +
	// which custom fields exist
	$rules = sv_mpc_generate_attributes_js( $product, $measurements );

	wc_enqueue_js( $rules );
	
}
add_action( 'wp_print_footer_scripts', 'sv_wc_measurement_price_calculator_input_min_max' );


/**
 * Helper function to generate javascript rules to add to the product page
 * 
 * @param \WC_Product $product global product object
 * @param array $measurements the enabled measurements for this product
 * @return string the rules (in jQuery) to apply to the product
 */
function sv_mpc_generate_attributes_js( $product, $measurements ) {

	$rules = array();
	
	foreach( $measurements as $measurement ) {

		// get the custom field for this measurement in array form
		$vals = sv_mpc_generate_calculator_input_limits( $product, 'mpc_' . $measurement->get_name() );
		
		// break for this measurement if it doesn't have a custom field
		if ( empty( $vals ) ) {
			continue;
		}
		
		// we have a value, so build a jQuery rule to change the input atts
		$id = '#' . $measurement->get_name() . '_needed';
		$rules[] = "$('" . $id . "').attr({ type: 'number', min: '" . esc_attr( $vals['min'] ) . "', max: '" . esc_attr( $vals['max'] ) . "', step: '" . esc_attr( $vals['step'] ) . "' }).addClass('input-text');";
	}
	
	// give back a string rules, one per line
	return implode( "\n", $rules );
}


/**
 * Helper function to generate an associative array from the custom field string
 * 
 * @param \WC_Product $product global product object
 * @param string $meta_key the meta key for the post meta to retrieve
 * @return array the meta key values as an associative array
 */
function sv_mpc_generate_calculator_input_limits( $product, $meta_key ) {

	// get the meta field, bail if it's not set
	$meta_values = get_post_meta( $product->id, $meta_key, true );
	if ( empty( $meta_values ) ) {
		return array();
	}

	// turn this into a messy array ( [0] => 'key = value') for now
	$meta_values = array_map( 'trim', explode( ',', $meta_values ) );
	$new_values = array();

	// break each string into an associative array like 'key' => 'value'
	foreach ( $meta_values as $value ) {

		$piece = explode ( '=', $value );
		$piece[0] = sanitize_text_field( $piece[0] );
		$piece[1] = floatval( trim( $piece[1] ) );
		
		$new_values[ $piece[0] ] = $piece[1];
	}
	
	// return the new associative array for this field
	return $new_values;
}