<?php

namespace App\Http\Controllers\Api;

use App\Http\Controllers\Controller;
use Illuminate\Http\JsonResponse;
use Illuminate\Http\Request;

class SystemLogController extends Controller
{
    private const MAX_LINES = 5000;

    private const DEFAULT_LINES = 400;

    /** 仅允许 laravel.log 与 laravel-YYYY-MM-DD.log */
    private function isAllowedBasename(string $name): bool
    {
        return (bool) preg_match('/^laravel(-\d{4}-\d{2}-\d{2})?\.log$/', $name);
    }

    public function index(Request $request): JsonResponse
    {
        abort_unless($request->user()?->isSuperAdmin(), 403, '仅超级管理员可查看系统日志');

        $logsDir = storage_path('logs');
        $files = $this->listLogFiles($logsDir);

        $requested = basename((string) $request->query('file', ''));
        $selected = '';
        if ($requested !== '' && $requested !== '.' && $this->isAllowedBasename($requested)) {
            $candidate = $logsDir.DIRECTORY_SEPARATOR.$requested;
            if (is_file($candidate)) {
                $selected = $requested;
            }
        }
        if ($selected === '' && $files !== []) {
            $selected = $files[0]['name'];
        }

        $linesParam = (int) $request->query('lines', self::DEFAULT_LINES);
        $lines = max(50, min(self::MAX_LINES, $linesParam));

        $linesPayload = [];
        $error = null;

        if ($selected !== '') {
            $fullPath = $logsDir.DIRECTORY_SEPARATOR.$selected;
            if (! is_file($fullPath) || ! is_readable($fullPath)) {
                $error = '日志文件不可读';
            } else {
                $linesPayload = $this->tailLines($fullPath, $lines);
            }
        }

        return response()->json([
            'files' => $files,
            'file' => $selected,
            'lines' => $linesPayload,
            'lines_requested' => $lines,
            'error' => $error,
        ]);
    }

    /**
     * @return array<int, array{name: string, size_bytes: int, modified_at: string}>
     */
    private function listLogFiles(string $logsDir): array
    {
        if (! is_dir($logsDir)) {
            return [];
        }

        $pattern = $logsDir.DIRECTORY_SEPARATOR.'laravel*.log';
        $paths = glob($pattern) ?: [];

        $files = [];
        foreach ($paths as $full) {
            $base = basename($full);
            if (! $this->isAllowedBasename($base)) {
                continue;
            }
            $mtime = @filemtime($full);
            $size = @filesize($full);
            $files[] = [
                'name' => $base,
                'size_bytes' => $size !== false ? $size : 0,
                'modified_at' => $mtime ? date('c', $mtime) : '',
            ];
        }

        usort($files, static function (array $a, array $b): int {
            return strcmp($b['modified_at'], $a['modified_at']);
        });

        return array_values($files);
    }

    /**
     * @return array<int, string>
     */
    private function tailLines(string $path, int $maxLines): array
    {
        $size = filesize($path);
        if ($size === false || $size === 0) {
            return [];
        }

        $maxLines = max(1, min(self::MAX_LINES, $maxLines));
        $chunk = min($size, 262144);

        while ($chunk <= $size) {
            $start = $size - $chunk;
            $data = file_get_contents($path, false, null, $start, $chunk);
            if ($data === false) {
                return [];
            }
            if ($start > 0) {
                $firstNl = strpos($data, "\n");
                if ($firstNl !== false) {
                    $data = substr($data, $firstNl + 1);
                }
            }

            $parts = preg_split('/\r\n|\r|\n/', $data);
            if ($parts === false) {
                $parts = [];
            }

            if (count($parts) >= $maxLines || $chunk >= $size) {
                return array_values(array_slice($parts, -$maxLines));
            }

            $chunk = min($size, $chunk * 2);
        }

        return [];
    }
}