<?php

namespace KTXC\Logger;

use Psr\Log\LogLevel;

/**
 * Maps PSR-3 log level strings to integer severity values.
 *
 * Lower integer = higher severity (matches RFC 5424 / syslog convention):
 *   emergency = 0, alert = 1, critical = 2, error = 3,
 *   warning = 4, notice = 5, info = 6, debug = 7
 */
class LogLevelSeverity
{
    private const MAP = [
        LogLevel::EMERGENCY => 0,
        LogLevel::ALERT     => 1,
        LogLevel::CRITICAL  => 2,
        LogLevel::ERROR     => 3,
        LogLevel::WARNING   => 4,
        LogLevel::NOTICE    => 5,
        LogLevel::INFO      => 6,
        LogLevel::DEBUG     => 7,
    ];

    /**
     * Returns the integer severity for a PSR-3 level string.
     *
     * @throws \InvalidArgumentException for unknown level strings
     */
    public static function severity(string $level): int
    {
        $normalized = strtolower($level);

        if (!array_key_exists($normalized, self::MAP)) {
            throw new \InvalidArgumentException(
                sprintf(
                    'Unknown log level "%s". Valid levels are: %s.',
                    $level,
                    implode(', ', array_keys(self::MAP))
                )
            );
        }

        return self::MAP[$normalized];
    }

    /**
     * Validates that a level string is a known PSR-3 level.
     *
     * @throws \InvalidArgumentException for unknown level strings
     */
    public static function validate(string $level): void
    {
        self::severity($level); // throws on unknown
    }

    /**
     * Returns all valid PSR-3 level strings ordered from most to least severe.
     *
     * @return string[]
     */
    public static function levels(): array
    {
        return array_keys(self::MAP);
    }
}