<?php
/**
 * Calculates a weighted health score from site-check results.
 *
 * @package advanced-analytics
 *
 * @since 4.9.0
 */

declare(strict_types=1);

namespace ADVAN\Checks;

// Exit if accessed directly.
if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

if ( ! class_exists( 'ADVAN\Checks\Score_Calculator' ) ) {

	/**
	 * Converts an array of check results into category and overall health scores.
	 *
	 * All methods are static — no instantiation required.
	 *
	 * @since 4.9.0
	 */
	class Score_Calculator {

		/**
		 * Score multipliers by status.
		 *
		 *  pass    => full weight credited
		 *  warning => half weight credited
		 *  fail    => zero weight credited (deducted amount depends on severity)
		 *
		 * @since 4.9.0
		 */
		private const STATUS_MULTIPLIER = array(
			'pass'    => 1.0,
			'info'    => 1.0,
			'warning' => 0.5,
			'fail'    => 0.0,
		);

		/**
		 * Additional penalty applied on top of zero credit for fails.
		 * High-severity failures push the score below neutral.
		 *
		 * @since 4.9.0
		 */
		private const SEVERITY_PENALTY = array(
			'high'   => 0.3,
			'medium' => 0.1,
			'low'    => 0.0,
		);

		// ------------------------------------------------------------------
		// Public API
		// ------------------------------------------------------------------

		/**
		 * Calculate scores from the full Scanner::run_all() result set.
		 *
		 * @param array $all_results  Associative array with keys 'security', 'speed', 'resources'.
		 *
		 * @return array{
		 *   overall: int,
		 *   security: int,
		 *   speed: int,
		 *   resources: int,
		 *   counts: array{pass: int, warning: int, fail: int, total: int}
		 * }
		 *
		 * @since 4.9.0
		 */
		public static function calculate( array $all_results ): array {
			$flat = array_merge(
				$all_results['security'] ?? array(),
				$all_results['speed'] ?? array(),
				$all_results['resources'] ?? array()
			);

			return array(
				'overall'   => static::score_results( $flat ),
				'security'  => static::score_results( $all_results['security'] ?? array() ),
				'speed'     => static::score_results( $all_results['speed'] ?? array() ),
				'resources' => static::score_results( $all_results['resources'] ?? array() ),
				'counts'    => static::count_statuses( $flat ),
			);
		}

		// ------------------------------------------------------------------
		// Internal helpers
		// ------------------------------------------------------------------

		/**
		 * Compute a 0-100 integer score for a flat list of check results.
		 *
		 * @param array[] $results List of check results, each with keys 'status', 'weight', and optionally 'severity'.
		 *
		 * @return int
		 *
		 * @since 4.9.0
		 */
		private static function score_results( array $results ): int {
			if ( empty( $results ) ) {
				return 100;
			}

			$max_points    = 0.0;
			$earned_points = 0.0;

			foreach ( $results as $result ) {
				$weight   = (float) ( $result['weight'] ?? 5 );
				$status   = $result['status'] ?? 'pass';
				$severity = $result['severity'] ?? 'low';

				$max_points += $weight;

				$multiplier = self::STATUS_MULTIPLIER[ $status ] ?? 0.0;
				$penalty    = ( 'fail' === $status )
				? ( self::SEVERITY_PENALTY[ $severity ] ?? 0.0 )
				: 0.0;

				$earned_points += $weight * max( 0.0, $multiplier - $penalty );
			}

			if ( $max_points <= 0.0 ) {
				return 100;
			}

			return (int) round( ( $earned_points / $max_points ) * 100 );
		}

		/**
		 * Count pass / warning / fail across a flat result list.
		 *
		 * @param array[] $results List of check results, each with keys 'status', 'weight', and optionally 'severity'.
		 *
		 * @return array{pass: int, warning: int, fail: int, total: int}
		 *
		 * @since 4.9.0
		 */
		private static function count_statuses( array $results ): array {
			$counts = array(
				'pass'    => 0,
				'info'    => 0,
				'warning' => 0,
				'fail'    => 0,
			);
			foreach ( $results as $result ) {
				$status = $result['status'] ?? 'pass';
				if ( isset( $counts[ $status ] ) ) {
					++$counts[ $status ];
				}
			}
			$counts['total'] = array_sum( $counts );
			return $counts;
		}
	}
}