(function () {
  "use strict";

  const messagesEl = document.getElementById("messages");
  const formEl = document.getElementById("composer");
  const inputEl = document.getElementById("input");
  const sendEl = document.getElementById("send");

  const SESSION_KEY = "bookly_session_id";
  let sessionId = sessionStorage.getItem(SESSION_KEY);
  if (!sessionId) {
    sessionId = crypto.randomUUID();
    sessionStorage.setItem(SESSION_KEY, sessionId);
  }

  const GREETING =
    "Hi! I'm the Bookly support assistant. I can help you check on an order, start a return, or answer questions about shipping, returns, or password reset. How can I help today?";

  function appendMessage(role, text) {
    const el = document.createElement("div");
    el.className = "message message--" + role;
    el.textContent = text;
    messagesEl.appendChild(el);
    messagesEl.scrollTop = messagesEl.scrollHeight;
    return el;
  }

  function appendTypingIndicator() {
    const el = document.createElement("div");
    el.className = "message message--assistant message--typing";
    el.setAttribute("aria-label", "Assistant is typing");
    el.innerHTML = "<span></span><span></span><span></span>";
    messagesEl.appendChild(el);
    messagesEl.scrollTop = messagesEl.scrollHeight;
    return el;
  }

  async function sendMessage(text) {
    const response = await fetch("/api/chat", {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify({ session_id: sessionId, message: text }),
    });
    if (!response.ok) {
      throw new Error("Server returned " + response.status);
    }
    const data = await response.json();
    return data.reply;
  }

  formEl.addEventListener("submit", async function (event) {
    event.preventDefault();
    const text = inputEl.value.trim();
    if (!text) return;

    appendMessage("user", text);
    inputEl.value = "";
    inputEl.disabled = true;
    sendEl.disabled = true;

    const typing = appendTypingIndicator();
    try {
      const reply = await sendMessage(text);
      typing.remove();
      appendMessage("assistant", reply);
    } catch (err) {
      typing.remove();
      appendMessage(
        "assistant",
        "Sorry, I couldn't reach the server. Please try again in a moment."
      );
      console.error(err);
    } finally {
      inputEl.disabled = false;
      sendEl.disabled = false;
      inputEl.focus();
    }
  });

  appendMessage("assistant", GREETING);
  inputEl.focus();
})();