const http = require("http");
const { URL } = require("url");

const targetBase = process.env.MEMOS_UPSTREAM || "http://memos:5230";
const listenPort = Number(process.env.PORT || 8080);

function shouldRewrite(pathname) {
  return /^\/api\/v1\/users\/[^/]+\/settings$/.test(pathname);
}

function filterSettingsPayload(buffer) {
  const payload = JSON.parse(buffer.toString("utf8"));
  if (!Array.isArray(payload.settings)) {
    return buffer;
  }

  const settings = payload.settings.filter((item) => {
    const name = String((item && item.name) || "");
    return !name.endsWith("/unknown");
  });

  return Buffer.from(
    JSON.stringify({
      ...payload,
      settings,
      totalSize: settings.length,
    }),
    "utf8",
  );
}

const server = http.createServer((req, res) => {
  const upstreamUrl = new URL(req.url, targetBase);
  const headers = { ...req.headers };
  headers.host = upstreamUrl.host;

  const upstreamReq = http.request(
    upstreamUrl,
    {
      method: req.method,
      headers,
    },
    (upstreamRes) => {
      const pathname = upstreamUrl.pathname;
      const contentType = String(upstreamRes.headers["content-type"] || "");
      const canRewrite = shouldRewrite(pathname) && contentType.includes("application/json");

      if (!canRewrite) {
        res.writeHead(upstreamRes.statusCode || 502, upstreamRes.headers);
        upstreamRes.pipe(res);
        return;
      }

      const chunks = [];
      upstreamRes.on("data", (chunk) => chunks.push(chunk));
      upstreamRes.on("end", () => {
        try {
          const body = filterSettingsPayload(Buffer.concat(chunks));
          const responseHeaders = { ...upstreamRes.headers };
          responseHeaders["content-length"] = String(body.length);
          delete responseHeaders["content-encoding"];

          res.writeHead(upstreamRes.statusCode || 200, responseHeaders);
          res.end(body);
        } catch (error) {
          res.writeHead(502, { "content-type": "text/plain; charset=utf-8" });
          res.end(`memos proxy rewrite failed: ${error.message}`);
        }
      });
    },
  );

  upstreamReq.on("error", (error) => {
    res.writeHead(502, { "content-type": "text/plain; charset=utf-8" });
    res.end(`memos upstream error: ${error.message}`);
  });

  req.pipe(upstreamReq);
});

server.listen(listenPort, "0.0.0.0");