<?php
/**
* WooCommerce Variations Add to Cart JS-free
* Determines the variation ID for the user's chosen attributes on variable items server-side, so that users can shop without Javascript enabled.
* @author Jacob Eva, Liberated Embedded Systems, liberatedsystems.co.uk
* @version 1
*/


/*
Plugin Name: LES Variations Add-to-Cart JS-free
Plugin URI: https://git.liberatedsystems.co.uk
Description: This plugin determines the variation ID for a product from the server side, allowing users to shop without Javascript enabled. Inspiration taken from eggplant studios' variations add to cart plugin (www.eggplantstudios.ca).
Version: 1.0.0
Author: Jacob Eva
License: GPLv2 or later
License URI: http://www.gnu.org/licenses/gpl-2.0.html
*/

/* 
 * Get variation ID function, uses an array of the attributes to construct an
 * SQL query that can determine the correct variation ID to return, so that the
 * product can be added to the user's cart
*/
function get_variation_id( $attributes, $product_id ) {
    global $wpdb;

    $select_from_sql = "
        SELECT p.ID
        FROM {$wpdb->prefix}posts as p
    ";

    $join_sql = "
        JOIN {$wpdb->prefix}postmeta as pm ON p.ID = pm.post_id
    ";

    $where_sql = "
        WHERE pm.meta_key = %s
        AND pm.meta_value LIKE %s
    ";

    $parent_sql = "
        AND p.post_parent = %s
    ";

    // add additional attributes to JOIN if there are more than 1
    for ( $x = 2; $x < count( array_keys($attributes) ) + 1; $x++ ) {
        $join_sql = $join_sql . "
        JOIN {$wpdb->prefix}postmeta as pm{$x} ON p.ID = pm{$x}.post_id
        ";
    }

    // add additional attributes to AND section if there are more than 1
    for ( $x = 2; $x < count( array_keys($attributes) ) + 1; $x++ ) {
        $where_sql = $where_sql . "
        AND pm{$x}.meta_key = %s
        AND pm{$x}.meta_value LIKE %s
        ";
    }
    
    // merge attribute arrays into one for use in prepared statement
    $parameters = array();

    for ( $x = 0; $x < count ( array_keys($attributes) ); $x++ ) {
        $parameters[] = array_keys($attributes)[$x];
        $parameters[] = array_values($attributes)[$x];
    }
    $parameters[] = $product_id;

    $sql = $select_from_sql . $join_sql . $where_sql . $parent_sql;

    return $wpdb->get_var($wpdb->prepare($sql, $parameters));
}


add_filter( 'woocommerce_add_to_cart_handler', 'les_add_to_cart_handler');
/*
 * Override function to change type of variable product, so custom function is
 * called to handle it 
*/
function les_add_to_cart_handler( $type ) {
    if ( $type === "variable" || $type === "variation" ) {
        return "les_variation";
    }
    else {
        return $type;
    }
}

add_action( 'woocommerce_add_to_cart_handler_les_variation', 'les_add_variation_to_cart', 10, 2 );
/* 
 * Add to cart function, created to allow shopping without JS
*/
function les_add_variation_to_cart() {
    global $woocommerce;
    $added_products = 0;

    $product_id = (int) $_POST['product_id'];

    $quantity = (int) $_POST['quantity'];

    $product = wc_get_product( $product_id );

    // do nothing if attributes were not sent
    $attributes_valid = false;

    // if the user has JS enabled and / or has already set the variation ID
    // themselves
    if ( ! empty( $_POST['variation_id'] ) ) {
        $variation_id = $_POST['variation_id'];
    }

    else {
        // create array with all attribute keys
        $attributes = array();
        $attr_exp = "/attribute.+/";
        foreach (array_keys($_POST) as $field)
        {
            if ( preg_match($attr_exp, $field) ) {
                $attributes[$field] = $_POST[$field];
            }
        }


        // if there are attributes, process them to get the variation id
        if ( ! empty( $attributes ) ) {
            $variation_id = get_variation_id( $attributes, $product_id );
        }
    }

    $passed_validation = apply_filters( 'woocommerce_add_to_cart_validation', true, $product_id, $quantity, $variation_id, $attributes );

    if ( ! $passed_validation ) {
        return false;
    }

    if( (int) $_POST['quantity'] > 0 ) {
        // if no variation id was found for product
        if ( empty( $variation_id ) ) {
            /* translators: 1: product link, 2: product name */
            wc_add_notice( sprintf( __( 'Please choose product options by visiting <a href="%1$s" title="%2$s">%2$s</a>.', 'woocommerce' ), esc_url( get_permalink( $product_id ) ), esc_html( $product->get_name() ) ), 'error' );
            return false;
        }
        else {
            $added_to_cart = $woocommerce->cart->add_to_cart(
                    $_POST['product_id'],   // string $product_id
                    $_POST['quantity'],     // string $quantity = 1
                    (int) $variation_id,    // integer $variation_id = ''
                    false // no attributes
            );
            $added_products ++;

            if ( $added_to_cart ) { 
                wp_safe_redirect( wc_get_cart_url() );
            }
            return $added_to_cart;
        }
    }
}