// ---------------------------------------------------------------------------
// Health checks for all dashboard services.
// Reads the service URLs from script.js (single source of truth), pings each
// one in parallel and writes health.json. Scheduled every minute by cron.
//
// Status classification:
//   online  - got any HTTP response below 500 (401/404 still means "up")
//   error   - server responded with 5xx
//   offline - timeout / connection refused / DNS failure
// TLS certificate validity is ignored (reachability check only).
// ---------------------------------------------------------------------------

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

const OUT_FILE = process.env.OUT_FILE || "/usr/share/nginx/html/health.json";
const TIMEOUT = parseInt(process.env.HEALTH_TIMEOUT || "5000", 10);

// Reachability only — don't fail on self-signed certificates.
const httpAgent = new http.Agent({ rejectUnauthorized: false });
const httpsAgent = new https.Agent({ rejectUnauthorized: false });

function serviceUrls() {
  const candidates = [
    process.env.SERVICES_JS,
    "/usr/share/nginx/html/script.js",
    path.join(__dirname, "..", "script.js"),
  ].filter(Boolean);
  for (const p of candidates) {
    try {
      const src = fs.readFileSync(p, "utf8");
      const urls = [...src.matchAll(/url: *"(https?:\/\/[^"]+)"/g)].map((m) => m[1]);
      if (urls.length) return [...new Set(urls)];
    } catch {
      // try next candidate
    }
  }
  return [];
}

function checkUrl(url) {
  return new Promise((resolve) => {
    const started = Date.now();
    let settled = false;
    const done = (result) => {
      if (settled) return;
      settled = true;
      resolve(result);
    };

    let req;
    try {
      const u = new URL(url);
      const client = u.protocol === "https:" ? https : http;
      req = client.request(
        u,
        {
          method: "GET",
          agent: u.protocol === "https:" ? httpsAgent : httpAgent,
          timeout: TIMEOUT,
        },
        (res) => {
          const code = res.statusCode;
          res.destroy(); // response headers are all we need
          done({
            status: code >= 500 ? "error" : "online",
            code,
            latencyMs: Date.now() - started,
            error: null,
          });
        }
      );
    } catch (e) {
      return done({ status: "offline", code: null, latencyMs: null, error: e.message });
    }

    req.on("timeout", () => {
      req.destroy();
      done({ status: "offline", code: null, latencyMs: null, error: "Timeout" });
    });
    req.on("error", (e) => {
      done({ status: "offline", code: null, latencyMs: null, error: e.message });
    });
    req.end();
  });
}

async function main() {
  const urls = serviceUrls();
  if (urls.length === 0) {
    console.error("No service URLs found — is script.js available?");
    process.exit(1);
  }

  const results = await Promise.all(urls.map(async (u) => [u, await checkUrl(u)]));
  const services = Object.fromEntries(results);

  const payload = { updatedAt: new Date().toISOString(), services };
  fs.writeFileSync(OUT_FILE, JSON.stringify(payload, null, 2));

  const count = (s) => results.filter(([, r]) => r.status === s).length;
  console.log(`Health: ${urls.length} services — ${count("online")} online, ${count("error")} error, ${count("offline")} offline`);
}

main().catch((err) => {
  console.error(err);
  process.exit(1);
});