<?php

declare(strict_types=1);

namespace App\Services\Logging;

/**
 * LogViewerService
 *
 * - Listet Log-Dateien im konfigurierten Logging-Verzeichnis.
 * - Liest performant die letzten N Zeilen (Tail), ohne komplette Datei zu laden.
 * - Parst das LoggingService-Format:
 *   "[YYYY-MM-DD HH:MM:SS] LEVEL   message {json}"
 */
class LogViewerService
{
    private string $logDir;

    /**
     * @param array<string, mixed> $loggingConfig Teilkonfiguration "logging" aus config.php
     */
    public function __construct(array $loggingConfig)
    {
        $baseDir = $loggingConfig['log_dir'] ?? (__DIR__ . '/../../../public/logs');
        $this->logDir = rtrim((string)$baseDir, DIRECTORY_SEPARATOR);
    }

    /**
     * @return array<int, array{name:string, size:int, mtime:int}>
     */
    public function listLogFiles(): array
    {
        $result = [];

        if (is_dir($this->logDir) === false) {
            return $result;
        }

        $entries = @scandir($this->logDir);
        if ($entries === false) {
            return $result;
        }

        foreach ($entries as $name) {
            if ($name === '.' || $name === '..') {
                continue;
            }

            // Nur normale Dateien, keine Unterordner.
            $fullPath = $this->logDir . DIRECTORY_SEPARATOR . $name;
            if (is_file($fullPath) === false) {
                continue;
            }

            // Safety: nur "logartige" Dateien anzeigen.
            $lower = strtolower($name);
            if (
                str_ends_with($lower, '.log') === false
                && str_ends_with($lower, '.txt') === false
            ) {
                continue;
            }

            $size = @filesize($fullPath);
            $mtime = @filemtime($fullPath);

            $result[] = [
                'name' => $name,
                'size' => is_int($size) ? $size : 0,
                'mtime' => is_int($mtime) ? $mtime : 0,
            ];
        }

        // Neueste zuerst
        usort(
            $result,
            static function (array $a, array $b): int {
                return ($b['mtime'] ?? 0) <=> ($a['mtime'] ?? 0);
            }
        );

        return $result;
    }

    /**
     * Liefert Metadaten zur ausgewählten Datei (oder null wenn ungültig).
     *
     * @return array{name:string, size:int, mtime:int}|null
     */
    public function getFileMeta(string $fileName): ?array
    {
        $path = $this->resolveLogFilePath($fileName);
        if ($path === null) {
            return null;
        }

        $size = @filesize($path);
        $mtime = @filemtime($path);

        return [
            'name' => basename($path),
            'size' => is_int($size) ? $size : 0,
            'mtime' => is_int($mtime) ? $mtime : 0,
        ];
    }

    /**
     * @param string $fileName
     * @param int $maxLines
     * @param string|null $levelFilter  z.B. "ERROR"|"WARNING"|"INFO"|"DEBUG"|null
     * @param string|null $search       Freitextsuche in message/context/raw
     *
     * @return array<int, array{
     *   ts:string|null,
     *   level:string|null,
     *   message:string,
     *   context:array<string,mixed>|null,
     *   raw:string
     * }>
     */
    public function getEntries(string $fileName, int $maxLines = 200, ?string $levelFilter = null, ?string $search = null): array
    {
        $path = $this->resolveLogFilePath($fileName);
        if ($path === null) {
            return [];
        }

        $lines = $this->tailLines($path, $maxLines);

        $entries = [];
        foreach ($lines as $line) {
            $parsed = $this->parseLine($line);

            if ($levelFilter !== null && $levelFilter !== '') {
                $lvl = strtoupper((string)($parsed['level'] ?? ''));
                if ($lvl !== strtoupper($levelFilter)) {
                    continue;
                }
            }

            if ($search !== null && $search !== '') {
                $haystack = $parsed['raw'] . ' ' . $parsed['message'];

                if (is_array($parsed['context'])) {
                    $haystack .= ' ' . (string)json_encode($parsed['context'], JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES);
                }

                if (mb_stripos($haystack, $search) === false) {
                    continue;
                }
            }

            $entries[] = $parsed;
        }

        return $entries;
    }

    /**
     * @return string|null Vollständiger Pfad oder null, wenn ungültig/Traversal
     */
    private function resolveLogFilePath(string $fileName): ?string
    {
        $fileName = trim($fileName);
        if ($fileName === '') {
            return null;
        }

        // Keine Pfade erlauben, nur Dateiname
        $fileName = basename($fileName);

        $candidate = $this->logDir . DIRECTORY_SEPARATOR . $fileName;

        $realDir = realpath($this->logDir);
        $realFile = realpath($candidate);

        if ($realDir === false || $realFile === false) {
            return null;
        }

        // Muss innerhalb des Log-Verzeichnisses liegen
        $realDirNorm = rtrim($realDir, DIRECTORY_SEPARATOR) . DIRECTORY_SEPARATOR;
        $realFileNorm = $realFile;

        if (str_starts_with($realFileNorm, $realDirNorm) === false) {
            return null;
        }

        if (is_file($realFileNorm) === false) {
            return null;
        }

        return $realFileNorm;
    }

    /**
     * Tail-Implementierung: liest die letzten $maxLines Zeilen.
     *
     * @return array<int, string>
     */
    private function tailLines(string $filePath, int $maxLines): array
    {
        $maxLines = max(1, min(2000, $maxLines));

        $fh = @fopen($filePath, 'rb');
        if ($fh === false) {
            return [];
        }

        $chunkSize = 8192;
        $buffer = '';
        $pos = -1;
        $linesFound = 0;

        // ans Ende springen
        @fseek($fh, 0, SEEK_END);
        $fileSize = (int)@ftell($fh);
        if ($fileSize <= 0) {
            @fclose($fh);
            return [];
        }

        while ($linesFound <= $maxLines && -$pos < $fileSize) {
            $readSize = $chunkSize;
            if (-$pos + $chunkSize > $fileSize) {
                $readSize = $fileSize - (-$pos);
            }

            @fseek($fh, $pos - $readSize + 1, SEEK_END);
            $chunk = (string)@fread($fh, $readSize);

            $buffer = $chunk . $buffer;
            $linesFound = substr_count($buffer, "\n");

            $pos -= $readSize;
        }

        @fclose($fh);

        $lines = preg_split("/\r\n|\n|\r/", $buffer);
        if (is_array($lines) === false) {
            return [];
        }

        // ggf. letzte leere Zeile raus
        if (end($lines) === '') {
            array_pop($lines);
        }

        // letzte maxLines
        $lines = array_slice($lines, -$maxLines);

        // Leere Zeilen am Anfang/Ende tolerieren, aber nicht komplett aufblasen
        $clean = [];
        foreach ($lines as $line) {
            $line = (string)$line;
            if ($line === '') {
                continue;
            }
            $clean[] = $line;
        }

        return $clean;
    }

    /**
     * @return array{
     *   ts:string|null,
     *   level:string|null,
     *   message:string,
     *   context:array<string,mixed>|null,
     *   raw:string
     * }
     */
    private function parseLine(string $line): array
    {
        $raw = $line;

        $ts = null;
        $level = null;
        $message = $line;
        $context = null;

        // Basis: [timestamp] LEVEL ...
        if (preg_match('/^\[(?<ts>[0-9\-:\s]{19})\]\s+(?<lvl>[A-Z]+)\s+(?<rest>.*)$/', $line, $m) === 1) {
            $ts = (string)$m['ts'];
            $level = (string)$m['lvl'];
            $rest = (string)$m['rest'];

            // Versuch: Context ist am Ende ein JSON-Objekt, das mit "{" beginnt und mit "}" endet.
            $ctxCandidate = null;

            $lastBracePos = strrpos($rest, '{');
            if ($lastBracePos !== false) {
                $maybeJson = substr($rest, $lastBracePos);
                $maybeJson = trim($maybeJson);

                if ($maybeJson !== '' && str_starts_with($maybeJson, '{') && str_ends_with($maybeJson, '}')) {
                    $decoded = json_decode($maybeJson, true);
                    if (is_array($decoded)) {
                        $ctxCandidate = $decoded;
                        $rest = trim(substr($rest, 0, $lastBracePos));
                    }
                }
            }

            $context = $ctxCandidate;
            $message = $rest;
        }

        return [
            'ts' => $ts,
            'level' => $level,
            'message' => $message,
            'context' => $context,
            'raw' => $raw,
        ];
    }
}