Implementation of a filter query containing AND and OR statement

args.php

<?php

use WPGraphQL\Type\WPInputObjectType;
use WPGraphQL\Types;

include_once('types.php');

add_filter( 'graphql_input_fields', function ( $fields, $type_name, $config ) {
	if ( $type_name === 'RootQueryToProductConnectionWhereArgs' ) {

		$fields['filterQuery'] = [
			'description' => 'A filter query',
			'type' => WPGraphQL\Types::list_of(
				new WPInputObjectType( [
					'name' => 'relation',
					'fields' => function() {
						return [
							'OR' => [
							'name' => 'OR',
							'type' => WPGraphQL\Types::list_of( product_filter_type('OR') )
							],
							'AND' => [
							'name' => 'AND',
							'type' => WPGraphQL\Types::list_of(product_filter_type('AND'))
							]
						];
					}
				] )
			),
		];

	}

	return $fields;

}, 10, 3 );

fields.php

<?php 

include_once('types.php');
include_once('args.php');

// ADD FILTERQUERY ARGUMENT TO PRODUCT TYPE
add_filter( 'graphql_map_input_fields_to_product_query', function( $query_args, $where_args, $source ) {

	if(isset($where_args['filterQuery']) && !empty($where_args['filterQuery'])) {

		$tax_query = ['relation' => 'AND'];

		foreach ($where_args['filterQuery'] as $filter) {
			foreach ($filter as $relation => $filter_args) {
				foreach ($filter_args as $filter_arg) {
					array_push($tax_query,
						array(
							'relation' => $relation,
							array(
								'taxonomy' => $filter_arg['taxonomy'],
								'field'    => 'slug',
								'terms'    => $filter_arg['terms'],
								'operator' => 'IN',
							)
						)
					);
				}
			}
		}

		$query_args['tax_query'] = $tax_query;

	}

	return $query_args;

}, 10, 3);

types.php

<?php

use WPGraphQL\Type\WPEnumType;
use WPGraphQL\Type\WPInputObjectType;
use WPGraphQL\Types;

function product_taxonomy_enum() {

	$taxonomy_args = array(
		'TYPE' => 'product_type',
		'CATEGORY' => 'product_cat',
		'TAG' => 'product_tag',
		'BRAND' => 'product_brand',
	);

	$values = [];

	foreach ($taxonomy_args as $key => $taxonomy) {
		$values[$key] = array(
			'name' => $key,
			'value' => $taxonomy
		);
	}

  // Add attributes to enum values
  $attributes = wc_get_attribute_taxonomy_names();
	foreach ($attributes as $attribute) {
		$attr_key = strtoupper($attribute);
		$values[$attr_key] = array(
			'name' => $attr_key,
			'value' => $attribute
		);
	}

	return $values;
}

// The allowed format of the filter query
function product_filter_type($type_name) {

	$filter_type = new WPInputObjectType( [
		'name' => $type_name . 'filterArray',
		'fields' => function() use ( $type_name ) {
			return [
				'taxonomy' => [
					'type' => new WPEnumType( [
						'name' =>  $type_name . 'taxonomy',
						'description' => __( 'Which field to select taxonomy term by.', 'beleco-market' ),
						'values' => product_taxonomy_enum()
					] ),
				],
				'terms' => [
				'type' => WPGraphQL\Types::list_of( WPGraphQL\Types::string() ),
				'description' => __( 'A list of term slugs', 'beleco-market' ),
				],
			];
		}
	] );

	return $filter_type;
}