<?php
namespace ILJ\Helper;

/**
 * Custom Fields
 *
 * This class represents a collection of custom field names, this is an abstract representation
 * which will be used in filters.
 *
 * @package ILJ\Helper
 * @since   2.23.5
 */
class Custom_Fields {

	/**
	 * A list of custom field names.
	 *
	 * @var array<string>
	 */
	private $fields;

	/**
	 *  Boolean to represent if the custom fields have a regex field.
	 *
	 * @var boolean $has_regex_custom_field
	 */
	private $has_regex_custom_field;

	/**
	 * Constructor for CustomFields
	 *
	 * @param array<string> $fields                 A list of custom field names.
	 * @param boolean       $has_regex_custom_field Boolean to represent if the custom fields have a regex field.
	 */
	private function __construct($fields, $has_regex_custom_field) {
		$this->fields = $fields;
		$this->has_regex_custom_field = $has_regex_custom_field;
	}

	/**
	 * Returns true if it has custom field.
	 *
	 * @return bool
	 */
	public function has_regex_custom_field() {
		return $this->has_regex_custom_field;
	}

	/**
	 * Construct the instance from a list of custom field names.
	 *
	 * @param array<string> $fields A list of custom field names.
	 *
	 * @return Custom_Fields
	 */
	public static function from_custom_field_names($fields) {
		foreach ($fields as $field) {
			if (Regex_Custom_Field::is_valid_rule($field)) {
				return new Custom_Fields($fields, true);
			}
		}
		return new Custom_Fields($fields, false);
	}

	/**
	 * Expands the custom fields based on the post context, this is only needed if it has regex
	 * custom fields.
	 *
	 * @param int $post_id The post id.
	 *
	 * @return array
	 */
	public function expand_post_custom_fields($post_id) {
		if (!$this->has_regex_custom_field()) {
			return $this->fields;
		}
		$result = array();
		$regex_fields = array();
		foreach ($this->fields as $field) {
			if (!Regex_Custom_Field::is_valid_rule($field)) {
				$result[] = $field;
			} else {
				$regex_fields[] = Regex_Custom_Field::from($field);
			}
		}

		return array_merge($result, $this->expand_regex_post_custom_fields($regex_fields, $post_id));
	}

	/**
	 * Expands the custom fields based on the term context, this is only needed if it has regex
	 * custom fields.
	 *
	 * @param int $term_id The term id.
	 *
	 * @return array
	 */
	public function expand_term_custom_fields($term_id) {
		if (!$this->has_regex_custom_field()) {
			return $this->fields;
		}
		$result = array();
		$regex_fields = array();
		foreach ($this->fields as $field) {
			if (!Regex_Custom_Field::is_valid_rule($field)) {
				$result[] = $field;
			} else {
				$regex_fields[] = Regex_Custom_Field::from($field);
			}
		}
		return array_merge($result, $this->expand_regex_term_custom_fields($regex_fields, $term_id));
	}

	/**
	 * Applies the regex rules and expands the custom post fields.
	 *
	 * @param array<Regex_Custom_Field> $regex_fields
	 * @param int                       $post_id
	 *
	 * @return array
	 */
	private function expand_regex_post_custom_fields($regex_fields, $post_id) {
		global $wpdb;
		$query = "SELECT DISTINCT meta_key FROM {$wpdb->postmeta} WHERE post_id=%d AND (";
		$query .= join('OR', array_fill(0, count($regex_fields), ' meta_key LIKE %s '));
		$names = array_map(function ($field) {
			return $field->get_escaped_sql_like_clause();
		}, $regex_fields);

		$query .= ' )';

		// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching, WordPress.DB.PreparedSQL.NotPrepared -- Direct query necessary and caching is not applicable for dynamic data.
		$data = $wpdb->get_results($wpdb->prepare($query, array_merge(array($post_id), $names)), ARRAY_N);
		return array_map(function ($item) {
			return $item[0];
		}, $data);
	}


	/**
	 * Applies the regex rules and expands the custom term fields.
	 *
	 * @param array<Regex_Custom_Field> $regex_fields
	 * @param int                       $term_id
	 *
	 * @return array
	 */
	private function expand_regex_term_custom_fields($regex_fields, $term_id) {
		global $wpdb;
		$query = "SELECT DISTINCT meta_key FROM {$wpdb->termmeta} WHERE term_id=%d AND (";
		$query .= join('OR', array_fill(0, count($regex_fields), ' meta_key LIKE %s '));
		$names = array_map(function ($field) {
			return $field->get_escaped_sql_like_clause();
		}, $regex_fields);

		$query .= ' )';

		// phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared, WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Direct query necessary and caching is not applicable for dynamic data.
		$data = $wpdb->get_results($wpdb->prepare($query, array_merge(array($term_id), $names)), ARRAY_N);
		return array_map(function ($item) {
			return $item[0];
		}, $data);
	}
}