Build on HighChat

function useHighChat(apiKey) {
  const convId = useRef(null);
  const [reply, setReply] = useState("");

  async function send(message) {
    setReply("");
    const res = await fetch("https://app.highchat.am/v1/chat", {
      method: "POST",
      headers: { "content-type": "application/json", authorization: `Bearer ${apiKey}` },
      body: JSON.stringify({ conversation_id: convId.current, message }),
    });
    const reader = res.body.getReader();
    const dec = new TextDecoder();
    let buf = "", ev = "";
    for (;;) {
      const { value, done } = await reader.read();
      if (done) break;
      buf += dec.decode(value, { stream: true });
      const lines = buf.split("\n"); buf = lines.pop();
      for (const l of lines) {
        if (l.startsWith("event:")) ev = l.slice(6).trim();
        else if (l.startsWith("data:")) {
          const d = JSON.parse(l.slice(5).trim());
          if (ev === "meta") convId.current = d.conversation_id;
          else if (ev === "delta") setReply((r) => r + d.text);
        }
      }
    }
  }
  return { reply, send };
}

func send(_ message: String) async throws {
  var req = URLRequest(url: URL(string: "https://app.highchat.am/v1/chat")!)
  req.httpMethod = "POST"
  req.setValue("Bearer hc_xxx", forHTTPHeaderField: "Authorization")
  req.setValue("application/json", forHTTPHeaderField: "Content-Type")
  req.httpBody = try JSONSerialization.data(withJSONObject: [
    "message": message, "conversation_id": conversationId as Any
  ])

  let (bytes, _) = try await URLSession.shared.bytes(for: req)
  var event = ""
  for try await line in bytes.lines {
    if line.hasPrefix("event:") { event = String(line.dropFirst(6)).trimmingCharacters(in: .whitespaces) }
    else if line.hasPrefix("data:") {
      let json = String(line.dropFirst(5)).trimmingCharacters(in: .whitespaces)
      let d = (try? JSONSerialization.jsonObject(with: Data(json.utf8))) as? [String: Any] ?? [:]
      if event == "meta" { conversationId = d["conversation_id"] as? String }
      else if event == "delta" { appendToBubble(d["text"] as? String ?? "") }
    }
  }
}

val body = """{"message":${JSONObject.quote(message)},"conversation_id":${
  conversationId?.let { JSONObject.quote(it) } ?: "null"}}"""
val req = Request.Builder()
  .url("https://app.highchat.am/v1/chat")
  .addHeader("Authorization", "Bearer hc_xxx")
  .post(body.toRequestBody("application/json".toMediaType()))
  .build()

client.newCall(req).execute().use { res ->
  val src = res.body!!.source()
  var event = ""
  while (!src.exhausted()) {
    val line = src.readUtf8Line() ?: break
    when {
      line.startsWith("event:") -> event = line.substring(6).trim()
      line.startsWith("data:")  -> {
        val d = JSONObject(line.substring(5).trim())
        when (event) {
          "meta"  -> conversationId = d.optString("conversation_id")
          "delta" -> appendToBubble(d.optString("text"))
        }
      }
    }
  }
}

// Keep the key on YOUR server; your app talks to your backend.
app.post("/chat", async (req, res) => {
  const upstream = await fetch("https://app.highchat.am/v1/chat", {
    method: "POST",
    headers: { "content-type": "application/json",
               authorization: `Bearer ${process.env.HIGHCHAT_KEY}` },
    body: JSON.stringify(req.body),
  });
  res.setHeader("content-type", "text/event-stream");
  upstream.body.pipe(res);   // stream SSE straight through
});