<?php
/**
 * Financial severity badges.
 *
 * @package Kayvandra\MarginBeacon
 */

declare(strict_types=1);

namespace Kayvandra\MarginBeacon\Domain\Risk;

/**
 * Merchant-facing financial severity values stored in risk_badge.
 */
final class Severity {

	const CRITICAL = 'critical';
	const HIGH     = 'high';
	const WARNING  = 'warning';
	const SAFE     = 'safe';
	const UNKNOWN  = 'unknown';

	/**
	 * Worst-first priority (lower index = worse).
	 *
	 * @return string[]
	 */
	public static function priority_order() {
		return array(
			self::CRITICAL,
			self::HIGH,
			self::WARNING,
			self::SAFE,
		);
	}

	/**
	 * Numeric rank for worst-line selection (lower = worse).
	 * Unknown must beat Safe (PRD: Unknown outranks Safe for worst-line tracking).
	 *
	 * @param string|null $severity Severity.
	 * @return int
	 */
	public static function rank( $severity ) {
		$order = array(
			self::CRITICAL => 0,
			self::HIGH     => 1,
			self::WARNING  => 2,
			self::UNKNOWN  => 3,
			self::SAFE     => 4,
		);
		$key   = (string) $severity;
		return isset( $order[ $key ] ) ? $order[ $key ] : 99;
	}

	/**
	 * Whether $candidate is strictly worse than $current for worst-line tracking.
	 *
	 * @param string|null $candidate Candidate severity.
	 * @param string|null $current   Current worst.
	 * @return bool
	 */
	public static function is_worse_than( $candidate, $current ) {
		if ( null === $current ) {
			return null !== $candidate;
		}
		if ( null === $candidate ) {
			return false;
		}
		return self::rank( $candidate ) < self::rank( $current );
	}

	/**
	 * Pick the worse of two known severities. Unknown never upgrades Safe away
	 * from known risk, and never replaces Critical/High/Warning.
	 *
	 * @param string|null $a First.
	 * @param string|null $b Second.
	 * @return string|null
	 */
	public static function worst( $a, $b ) {
		if ( null === $a ) {
			return $b;
		}
		if ( null === $b ) {
			return $a;
		}

		$known_risk = array( self::CRITICAL, self::HIGH, self::WARNING );
		$a_risk     = in_array( $a, $known_risk, true );
		$b_risk     = in_array( $b, $known_risk, true );
		$known_all  = self::priority_order();
		$a_known    = in_array( $a, $known_all, true );
		$b_known    = in_array( $b, $known_all, true );

		if ( $a_known && $b_known ) {
			return array_search( $a, $known_all, true ) <= array_search( $b, $known_all, true ) ? $a : $b;
		}

		// Known Critical/High/Warning beats Unknown; Unknown beats Safe.
		if ( $a_risk && self::UNKNOWN === $b ) {
			return $a;
		}
		if ( $b_risk && self::UNKNOWN === $a ) {
			return $b;
		}
		if ( self::SAFE === $a && self::UNKNOWN === $b ) {
			return self::UNKNOWN;
		}
		if ( self::SAFE === $b && self::UNKNOWN === $a ) {
			return self::UNKNOWN;
		}
		if ( self::UNKNOWN === $a || self::UNKNOWN === $b ) {
			return self::UNKNOWN;
		}

		return $a;
	}

	/**
	 * Merchant-facing translated label (never rely on ucfirst of the slug).
	 *
	 * @param string|null $severity Severity slug.
	 * @return string
	 */
	public static function label( $severity ) {
		switch ( (string) $severity ) {
			case self::CRITICAL:
				return __( 'Critical', 'marginbeacon' );
			case self::HIGH:
				return __( 'High', 'marginbeacon' );
			case self::WARNING:
				return __( 'Warning', 'marginbeacon' );
			case self::SAFE:
				return __( 'Safe', 'marginbeacon' );
			case self::UNKNOWN:
				return __( 'Unknown', 'marginbeacon' );
			default:
				return $severity ? (string) $severity : '';
		}
	}

	/**
	 * Prevent instantiation.
	 */
	private function __construct() {}
}