<?php

namespace KTXC\Logger;

use Psr\Log\LoggerInterface;
use Psr\Log\LogLevel;

/**
 * PSR-3 logger that writes to stderr using the journald/systemd SD_JOURNAL_PREFIX
 * format: a syslog-priority number wrapped in angle brackets followed by the message.
 *
 * journald automatically parses the "<N>" prefix and maps it to the corresponding
 * log priority, so log entries appear in the journal with the correct severity.
 *
 * Format: <priority>LEVEL [channel] interpolated-message {"context":"key",...}
 */
class SystemdLogger implements LoggerInterface
{
    /** Maps PSR-3 levels to RFC 5424 / syslog priority numbers */
    private const PRIORITY = [
        LogLevel::EMERGENCY => 0,
        LogLevel::ALERT     => 1,
        LogLevel::CRITICAL  => 2,
        LogLevel::ERROR     => 3,
        LogLevel::WARNING   => 4,
        LogLevel::NOTICE    => 5,
        LogLevel::INFO      => 6,
        LogLevel::DEBUG     => 7,
    ];

    /** @var resource */
    private $stderr;

    public function __construct(private readonly string $channel = 'app')
    {
        $this->stderr = fopen('php://stderr', 'w');
    }

    public function __destruct()
    {
        if (is_resource($this->stderr)) {
            fclose($this->stderr);
        }
    }

    public function emergency($message, array $context = []): void { $this->log(LogLevel::EMERGENCY, $message, $context); }
    public function alert($message, array $context = []): void      { $this->log(LogLevel::ALERT,     $message, $context); }
    public function critical($message, array $context = []): void   { $this->log(LogLevel::CRITICAL,  $message, $context); }
    public function error($message, array $context = []): void      { $this->log(LogLevel::ERROR,     $message, $context); }
    public function warning($message, array $context = []): void    { $this->log(LogLevel::WARNING,   $message, $context); }
    public function notice($message, array $context = []): void     { $this->log(LogLevel::NOTICE,    $message, $context); }
    public function info($message, array $context = []): void       { $this->log(LogLevel::INFO,      $message, $context); }
    public function debug($message, array $context = []): void      { $this->log(LogLevel::DEBUG,     $message, $context); }

    public function log($level, $message, array $context = []): void
    {
        // Extract tenant id injected by TenantAwareLogger; default to 'system'.
        $tenantId = isset($context['__tenant']) && is_string($context['__tenant'])
            ? $context['__tenant']
            : 'system';
        unset($context['__tenant']);

        $level    = strtolower((string) $level);
        $priority = self::PRIORITY[$level] ?? 7;

        $interpolated = $this->interpolate((string) $message, $context);
        $contextStr   = empty($context) ? '' : ' ' . $this->encodeContext($context);

        $line = sprintf(
            "<%d>%s [%s] [%s] %s%s\n",
            $priority,
            strtoupper($level),
            $this->channel,
            $tenantId,
            $interpolated,
            $contextStr,
        );

        fwrite($this->stderr, $line);
    }

    private function interpolate(string $message, array $context): string
    {
        if (!str_contains($message, '{')) {
            return $message;
        }
        $replace = [];
        foreach ($context as $key => $val) {
            if (!is_array($val) && !is_object($val)) {
                $replace['{' . $key . '}'] = (string) $val;
            }
        }
        return strtr($message, $replace);
    }

    private function encodeContext(array $context): string
    {
        $clean = [];
        foreach ($context as $k => $v) {
            if ($v instanceof \Throwable) {
                $clean[$k] = ['type' => get_class($v), 'message' => $v->getMessage()];
            } elseif (is_resource($v)) {
                $clean[$k] = 'resource(' . get_resource_type($v) . ')';
            } elseif (is_object($v)) {
                $clean[$k] = method_exists($v, '__toString') ? (string) $v : ['object' => get_class($v)];
            } else {
                $clean[$k] = $v;
            }
        }
        return json_encode($clean, JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE) ?: '{}';
    }
}