const http  = require("http");
const Redis = require("ioredis");

const redis   = new Redis({ host: process.env.REDIS_HOST || "data_jobs",
                            port: Number(process.env.REDIS_PORT || 6379) });
const JOBS    = process.env.JOB_QUEUE    || "grist:jobs";
const RESULTS = process.env.RESULT_QUEUE || "grist:results";
const ALLOW_ORIGIN = process.env.ALLOW_ORIGIN || "https://map.arenos.danielnagel.at";

http.createServer(async (req, res) => {

  // ---- CORS Header immer mitsenden ----
  res.setHeader("Access-Control-Allow-Origin", ALLOW_ORIGIN);
  res.setHeader("Vary", "Origin");

  // Preflight (OPTIONS) beantworten
  if (req.method === "OPTIONS") {
    res.setHeader("Access-Control-Allow-Methods", "GET, POST, OPTIONS");
    res.setHeader("Access-Control-Allow-Headers", "Content-Type, Authorization");
    // wenn du Auth/Cookies brauchst:
    // res.setHeader("Access-Control-Allow-Credentials", "true");
    res.statusCode = 204;
    return res.end();
  }
  // -------------------------------------


  if (req.method === "POST" && req.url === "/job") {
    const stream = await readJsonBody(req);                  // JSON Stream vom Client. mit readJsonBody() wieder zurück in JSON.
    await redis.lpush(JOBS, JSON.stringify(stream));         // Job in Queue. Als String in Redis eintragen. Der Worker nimmt dann den String.
    const reply = await redis.blpop(RESULTS, 30);            // auf Antwort warten

    const value = reply[1];                                   // Worker-Response
    res.writeHead(200, {"content-type":"application/json"});
    try { 
      JSON.parse(value); res.end(value);    //Prüfen für JSON
    } catch { 
      res.end(JSON.stringify({    //Fallback damit es sicher ein JSON ist.
        ok:true, 
        data:value
      })); 
    }
  }

  //mit curl http://192.168.0.104:8080/health kann man checken ob das Gateway überhaupt arbeitet.
  if (req.method === "GET" && req.url === "/health") {
    res.writeHead(200, { "content-type":"text/plain" });
    return res.end("ok");
  }

  res.writeHead(404, { "content-type":"text/plain" });
  res.end("not found");
  
}).listen(8080, "0.0.0.0", () => console.log("[gateway] listening 8080"));


//DataStream in Json zurückverwandeln.
function readJsonBody(req){
  return new Promise((resolve) => {
    let buf = "";
    req.on("data", c => buf += c);
    req.on("end",  () => resolve(buf ? JSON.parse(buf) : null));
  });
}