import { NextRequest, NextResponse } from "next/server";
import { basename } from "node:path";
import { readUploadBuffer, resolveUploadPath } from "@/lib/chat-store";

function guessContentType(fileName: string) {
  const lower = fileName.toLowerCase();

  if (lower.endsWith(".png")) return "image/png";
  if (lower.endsWith(".jpg") || lower.endsWith(".jpeg")) return "image/jpeg";
  if (lower.endsWith(".gif")) return "image/gif";
  if (lower.endsWith(".webp")) return "image/webp";
  if (lower.endsWith(".svg")) return "image/svg+xml";
  if (lower.endsWith(".pdf")) return "application/pdf";
  if (lower.endsWith(".txt")) return "text/plain; charset=utf-8";
  if (lower.endsWith(".zip")) return "application/zip";
  if (lower.endsWith(".rar")) return "application/vnd.rar";
  if (lower.endsWith(".doc")) return "application/msword";
  if (lower.endsWith(".docx")) {
    return "application/vnd.openxmlformats-officedocument.wordprocessingml.document";
  }
  if (lower.endsWith(".xls")) return "application/vnd.ms-excel";
  if (lower.endsWith(".xlsx")) {
    return "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
  }

  return "application/octet-stream";
}

export async function GET(
  request: NextRequest,
  context: { params: Promise<{ storageKey: string }> }
) {
  const { storageKey } = await context.params;
  const safeStorageKey = basename(storageKey);

  try {
    const fileBuffer = await readUploadBuffer(safeStorageKey);
    const contentType = guessContentType(safeStorageKey);
    const download = request.nextUrl.searchParams.get("download") === "1";

    return new NextResponse(fileBuffer, {
      headers: {
        "Content-Type": contentType,
        "Content-Disposition": `${download ? "attachment" : "inline"}; filename="${encodeURIComponent(safeStorageKey)}"`,
        "Cache-Control": "private, max-age=31536000, immutable"
      }
    });
  } catch {
    return NextResponse.json({ error: "文件不存在" }, { status: 404 });
  }
}