src/app/api/upload/route.ts

// POST /api/upload — accept multipart file upload, store via saveArtifact, return Artifact.
import { NextRequest, NextResponse } from "next/server";
import { saveArtifact, artifactId } from "@/server/storage";
import type { Artifact } from "@/lib/types";

export const dynamic = "force-dynamic";

const ALLOWED_EXTENSIONS = new Set([".fasta", ".pdb", ".csv", ".nwk"]);
const MAX_FILE_SIZE = 50 * 1024 * 1024; // 50 MB

function extFromName(name: string): string {
  const idx = name.lastIndexOf(".");
  return idx >= 0 ? name.slice(idx).toLowerCase() : "";
}

function mimeFromExt(ext: string): string {
  const map: Record<string, string> = {
    ".fasta": "chemical/seq-aa-fasta",
    ".pdb": "chemical/x-pdb",
    ".csv": "text/csv",
    ".nwk": "text/x-newick",
  };
  return map[ext] || "application/octet-stream";
}

export async function POST(req: NextRequest): Promise<NextResponse> {
  try {
    const formData = await req.formData();
    const file = formData.get("file");
    const taskIdParam = formData.get("taskId");

    if (!file || !(file instanceof File)) {
      return NextResponse.json(
        { error: "Missing file in multipart body" },
        { status: 400 },
      );
    }

    if (!taskIdParam || typeof taskIdParam !== "string") {
      return NextResponse.json(
        { error: "Missing taskId in multipart body" },
        { status: 400 },
      );
    }

    const ext = extFromName(file.name);
    if (!ALLOWED_EXTENSIONS.has(ext)) {
      return NextResponse.json(
        { error: `File extension "${ext}" not allowed. Accepted: ${Array.from(ALLOWED_EXTENSIONS).join(", ")}` },
        { status: 400 },
      );
    }

    if (file.size > MAX_FILE_SIZE) {
      return NextResponse.json(
        { error: `File too large (${(file.size / 1024 / 1024).toFixed(1)} MB). Max: 50 MB` },
        { status: 400 },
      );
    }

    const id = artifactId();
    const artifact: Artifact = {
      id,
      name: file.name,
      bytes: file.size,
      mime: mimeFromExt(ext),
      url: `/api/artifacts/${id}`,
      createdAt: Date.now(),
    };

    const buffer = Buffer.from(await file.arrayBuffer());
    await saveArtifact(taskIdParam, artifact, buffer);

    return NextResponse.json({ artifact }, { status: 201 });
  } catch (err) {
    const message = err instanceof Error ? err.message : "unknown error";
    return NextResponse.json({ error: message }, { status: 500 });
  }
}