import { NextRequest, NextResponse } from 'next/server'
import { readFile } from 'fs/promises'
import { existsSync } from 'fs'
import path from 'path'
import { getUploadsDir } from '@/lib/forge-data'

const MIME_MAP: Record<string, string> = {
  // Images — 浏览器直接渲染
  '.png': 'image/png',
  '.jpg': 'image/jpeg',
  '.jpeg': 'image/jpeg',
  '.gif': 'image/gif',
  '.webp': 'image/webp',
  '.bmp': 'image/bmp',
  '.svg': 'image/svg+xml',
  // Documents — 下载（部分浏览器内置 PDF 预览）
  '.pdf': 'application/pdf',
  '.doc': 'application/msword',
  '.docx': 'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
  '.xls': 'application/vnd.ms-excel',
  '.xlsx': 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
  '.ppt': 'application/vnd.ms-powerpoint',
  '.pptx': 'application/vnd.openxmlformats-officedocument.presentationml.presentation',
  // Text / web / data — 浏览器显示源码；html/htm 渲染成网页
  '.txt': 'text/plain; charset=utf-8',
  '.md': 'text/markdown; charset=utf-8',
  '.csv': 'text/csv; charset=utf-8',
  '.json': 'application/json; charset=utf-8',
  '.html': 'text/html; charset=utf-8',
  '.htm': 'text/html; charset=utf-8',
  '.xml': 'text/xml; charset=utf-8',
  '.yaml': 'text/yaml; charset=utf-8',
  '.yml': 'text/yaml; charset=utf-8',
  '.css': 'text/css; charset=utf-8',
  '.js': 'text/javascript; charset=utf-8',
  // Archives — 下载
  '.zip': 'application/zip',
  '.tar': 'application/x-tar',
  '.gz': 'application/gzip',
}

// GET /api/upload/:filename — serve uploaded file
export async function GET(_req: NextRequest, { params }: { params: Promise<{ filename: string }> }) {
  const UPLOAD_DIR = getUploadsDir()
  const { filename } = await params

  // Prevent path traversal
  if (filename.includes('..') || filename.includes('/')) {
    return NextResponse.json({ error: 'Invalid filename' }, { status: 400 })
  }

  const filePath = path.join(UPLOAD_DIR, filename)
  if (!existsSync(filePath)) {
    return NextResponse.json({ error: 'File not found' }, { status: 404 })
  }

  const buffer = await readFile(filePath)
  const ext = path.extname(filename).toLowerCase()
  const contentType = MIME_MAP[ext] || 'application/octet-stream'

  return new Response(buffer, {
    headers: {
      'Content-Type': contentType,
      'Cache-Control': 'public, max-age=31536000, immutable',
    },
  })
}