<?php

namespace Glovario\Rules;

use Glovario\Locale\LocaleManager;
use Glovario\Repository\RuleRepository;

defined( 'ABSPATH' ) || exit;

/**
 * Selects a variable's alternative value from its enabled rules.
 *
 * The engine evaluates date and language conditions. Audience and content
 * conditions (login state, roles, post types, post IDs) are evaluated by an
 * extension; without one, rules that use them are ignored rather than applied
 * to the wrong visitors.
 */
final class RuleEngine {
	private $rules;
	private $locales;

	public function __construct( RuleRepository $rules, ?LocaleManager $locales = null ) {
		$this->rules   = $rules;
		$this->locales = $locales;
	}

	public function resolve( $base_value, $variable, $context ) {
		if ( empty( $variable['id'] ) || ( isset( $variable['scope'] ) && 'site' !== $variable['scope'] ) ) {
			return $base_value;
		}
		foreach ( $this->rules->for_variable( $variable['id'], true ) as $rule ) {
			if ( $this->matches( $rule['conditions'], $context ) ) {
				return apply_filters( 'glovario_rule_alternative_value', $rule['alternative_value'], $rule, $variable, $context );
			}
		}
		return $base_value;
	}

	public function matches( $conditions, $context ) {
		$conditions = wp_parse_args(
			is_array( $conditions ) ? $conditions : array(),
			array(
				'version'    => 1,
				'date'       => array(),
				'auth'       => 'everyone',
				'roles'      => array(),
				'post_types' => array(),
				'post_ids'   => array(),
				'locales'    => array(),
			)
		);

		if ( self::has_audience_conditions( $conditions ) && ! apply_filters( 'glovario_rule_audience_conditions_supported', false ) ) {
			return false;
		}

		$date = is_array( $conditions['date'] ) ? $conditions['date'] : array();
		$now  = isset( $context['timestamp'] ) ? (int) $context['timestamp'] : time();
		// An unreadable date (only possible through corrupted data) never matches.
		$from  = empty( $date['from'] ) ? null : self::site_timestamp( $date['from'] );
		$until = empty( $date['until'] ) ? null : self::site_timestamp( $date['until'] );
		if ( ! empty( $date['from'] ) && ( null === $from || $now < $from ) ) {
			return false;
		}
		if ( ! empty( $date['until'] ) && ( null === $until || $now > $until ) ) {
			return false;
		}

		if ( ! empty( $conditions['locales'] ) ) {
			$locale       = sanitize_locale_name( (string) apply_filters( 'glovario_current_locale', $context['locale'] ?? determine_locale(), $context ) );
			$rule_locales = array_values( (array) $conditions['locales'] );
			/**
			 * Short-circuits language matching.
			 *
			 * @param bool|null $matches      Null to use the two-language matching below.
			 * @param array     $rule_locales Locales stored on the rule.
			 * @param string    $locale       Locale of the current request.
			 * @param array     $context      Resolution context.
			 */
			$matches = apply_filters( 'glovario_rule_locale_match', null, $rule_locales, $locale, $context );
			if ( ! ( null === $matches ? $this->matches_language( $rule_locales, $locale ) : $matches ) ) {
				return false;
			}
		}

		return (bool) apply_filters( 'glovario_rule_conditions_match', true, $conditions, $context );
	}

	/**
	 * A language rule applies when it names one language, that language is the
	 * default or the second language, and it is the language of the request.
	 * Rules for several languages, or for other languages, are kept but ignored.
	 *
	 * @param array  $rule_locales Locales stored on the rule.
	 * @param string $locale       Locale of the current request.
	 * @return bool
	 */
	private function matches_language( $rule_locales, $locale ) {
		if ( 1 !== count( $rule_locales ) || sanitize_locale_name( (string) $rule_locales[0] ) !== $locale ) {
			return false;
		}
		if ( ! $this->locales ) {
			return true;
		}
		$settings = $this->locales->settings();
		return $locale === $settings['default_locale'] || ( '' !== $settings['second_locale'] && $locale === $settings['second_locale'] );
	}

	/**
	 * Whether a rule uses audience or content conditions.
	 *
	 * @param array $conditions Rule conditions.
	 * @return bool
	 */
	public static function has_audience_conditions( $conditions ) {
		$auth = $conditions['auth'] ?? 'everyone';
		return ( '' !== $auth && 'everyone' !== $auth ) || ! empty( $conditions['roles'] ) || ! empty( $conditions['post_types'] ) || ! empty( $conditions['post_ids'] );
	}

	/**
	 * Convert a rule date (site timezone) to a Unix timestamp.
	 *
	 * @param string $value Date such as 2026-12-24T00:00.
	 * @return int|null Null when the date cannot be read.
	 */
	public static function site_timestamp( $value ) {
		try {
			$date = new \DateTimeImmutable( (string) $value, wp_timezone() );
			return $date->getTimestamp();
		} catch ( \Exception $exception ) {
			return null;
		}
	}
}