<?php

namespace App\Services;

class Fingerprinter
{
    /**
     * Compute a fingerprint hash for grouping events into issues.
     *
     * If the payload contains a custom `fingerprint` array (Sentry SDK standard),
     * that takes precedence. Otherwise we derive one from exception type, a
     * sanitized message, and the top stacktrace frames.
     */
    public function compute(array $payload): string
    {
        if (! empty($payload['fingerprint']) && is_array($payload['fingerprint'])) {
            return $this->hash($payload['fingerprint']);
        }

        $parts = [];

        $exception = $this->extractPrimaryException($payload);

        if ($exception) {
            $parts[] = $exception['type'] ?? '';
            $parts[] = $this->sanitizeMessage($exception['value'] ?? '');
            $parts = array_merge($parts, $this->topFrames($exception, 5));
        } else {
            $parts[] = $payload['message'] ?? $payload['logentry']['message'] ?? 'unknown';
        }

        return $this->hash($parts);
    }

    public function extractPrimaryException(array $payload): ?array
    {
        $exceptions = $payload['exception']['values'] ?? [];

        return end($exceptions) ?: null;
    }

    /**
     * Strip variable parts (numbers, UUIDs, hex strings) so that
     * "User 42 not found" and "User 99 not found" group together.
     */
    private function sanitizeMessage(string $message): string
    {
        $message = preg_replace(
            '/[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}/i',
            '{uuid}',
            $message,
        );

        $message = preg_replace('/\b[0-9a-f]{24,}\b/i', '{hash}', $message);

        $message = preg_replace('/\b\d+\b/', '{n}', $message);

        return $message;
    }

    /**
     * Return file+function strings from the top N stacktrace frames.
     */
    private function topFrames(array $exception, int $limit): array
    {
        $frames = $exception['stacktrace']['frames'] ?? [];

        $frames = array_reverse($frames);
        $frames = array_slice($frames, 0, $limit);

        $parts = [];
        foreach ($frames as $frame) {
            $file = $frame['filename'] ?? $frame['abs_path'] ?? '';
            $function = $frame['function'] ?? '';
            $parts[] = "{$file}:{$function}";
        }

        return $parts;
    }

    private function hash(array $parts): string
    {
        return md5(implode("\x00", $parts));
    }
}