import { readdir, readFile } from "node:fs/promises";
import { join } from "node:path";
import { zipSync } from "fflate";

export const archivePath = "downloads/questiongraph-library.zip";

export async function createLibraryArchive(root) {
  const files = {};
  async function collect(directory, prefix) {
    for (const entry of await readdir(directory, { withFileTypes: true })) {
      const path = join(directory, entry.name);
      const name = prefix + "/" + entry.name;
      if (entry.isDirectory()) await collect(path, name);
      else if (entry.isFile() && /\.(ts|tsx|json)$/.test(entry.name))
        files[name] = new Uint8Array(await readFile(path));
    }
  }
  await collect(join(root, "src/lib"), "questiongraph/lib");
  files["questiongraph/README.md"] = new Uint8Array(await readFile(join(root, "scripts/library-README.md")));
  return zipSync(files, { level: 6 });
}

// Build-time asset generation keeps the ZIP in sync with the shipped source.
// Dev requests generate it afresh; no generated ZIP is committed.
export function libraryDownload() {
  let root;
  let base;
  return {
    name: "questiongraph-library-download",
    configResolved(config) { root = config.root; base = config.base; },
    configureServer(server) {
      server.middlewares.use(async (request, response, next) => {
        const pathname = (request.url ?? "").split("?")[0];
        if (pathname !== "/" + archivePath && pathname !== base + archivePath) return next();
        if (request.method !== "GET" && request.method !== "HEAD") {
          response.statusCode = 405; response.setHeader("Allow", "GET, HEAD"); response.end(); return;
        }
        try {
          const archive = await createLibraryArchive(root);
          response.setHeader("Content-Type", "application/zip");
          response.setHeader("Content-Disposition", 'attachment; filename="questiongraph-library.zip"');
          response.setHeader("Cache-Control", "no-store");
          response.setHeader("Content-Length", archive.length);
          response.end(request.method === "HEAD" ? undefined : Buffer.from(archive));
        } catch (error) { next(error); }
      });
    },
    async generateBundle() {
      this.emitFile({ type: "asset", fileName: archivePath, source: await createLibraryArchive(root) });
    },
  };
}