(() => {
  const introMessage =
    "Witaj, jestem twoim wirtualnym agentem Krzak.org, w czym mogę Ci pomóc?";
  const baseReplies = [
    "Niestety, nie umiem jeszcze tego zrobić",
    "Nie jestem pewien o co Ci chodzi",
  ];
  const offerFrom = [
    "pedałów",
    "pajaca",
    "noży",
    "gwoździ",
    "przypraw",
    "słoika",
    "słoików",
    "tabletek",
    "spreju",
    "narzędzi",
    "samolotu",
    "ostrzałki",
    "szafki",
    "pojemnika",
    "pojemników",
    "ładowarki",
    "ładowarek",
    "wieszaków",
    "wieszaka",
    "półki",
    "półek",
    "ryby",
  ];
  const offerTo = [
    "gwoździ",
    "roweru",
    "krojenia cebuli",
    "pedałów",
    "latania",
    "łatania",
    "podatków",
    "sprzątania",
    "wyrywania zębów",
    "zmywarki",
    "śmieci",
    "krojenia chleba",
    "krojenia ogórków",
    "krojenia pomidorów",
    "krojenia cebuli",
    "krojenia ogórków",
    "krojenia pomidorów",
    "jedzenia",
    "picia",
    "kuchni",
    "książek",
    "ryb",
  ];

  const chatRoot = document.createElement("div");
  chatRoot.className = "ai-chat";
  chatRoot.innerHTML = `
        <button class="ai-chat__fab" type="button" aria-expanded="false" aria-controls="ai-chat-panel">AI chat</button>
        <section class="ai-chat__panel" id="ai-chat-panel" aria-hidden="true">
            <header class="ai-chat__header">
                <strong>Agent Krzak.org</strong>
                <button class="ai-chat__close" type="button" aria-label="Close chat">x</button>
            </header>
            <div class="ai-chat__messages"></div>
            <form class="ai-chat__form">
                <input class="ai-chat__input" type="text" placeholder="Napisz wiadomość..." autocomplete="off" />
                <button class="ai-chat__send" type="submit">Wyslij</button>
            </form>
        </section>
    `;
  document.body.appendChild(chatRoot);

  const fab = chatRoot.querySelector(".ai-chat__fab");
  const panel = chatRoot.querySelector(".ai-chat__panel");
  const closeBtn = chatRoot.querySelector(".ai-chat__close");
  const messages = chatRoot.querySelector(".ai-chat__messages");
  const form = chatRoot.querySelector(".ai-chat__form");
  const input = chatRoot.querySelector(".ai-chat__input");
  const sendBtn = chatRoot.querySelector(".ai-chat__send");
  const backToTop = document.getElementById("back-to-top");
  const viewport = window.visualViewport;

  function addMessage(text, fromUser) {
    const bubble = document.createElement("p");
    bubble.className = fromUser
      ? "ai-chat__bubble ai-chat__bubble--user"
      : "ai-chat__bubble";
    bubble.textContent = text;
    messages.appendChild(bubble);
    messages.scrollTop = messages.scrollHeight;
  }

  function openChat() {
    panel.classList.add("is-open");
    panel.setAttribute("aria-hidden", "false");
    fab.setAttribute("aria-expanded", "true");
    if (!messages.hasChildNodes()) {
      addMessage(introMessage, false);
    }
    input.focus();
    syncKeyboardOffset();
  }

  function closeChat() {
    panel.classList.remove("is-open");
    panel.setAttribute("aria-hidden", "true");
    fab.setAttribute("aria-expanded", "false");
    syncKeyboardOffset();
  }

  function randomItem(items) {
    return items[Math.floor(Math.random() * items.length)];
  }

  function buildReply() {
    return `${randomItem(baseReplies)}, ale mogę Ci zaoferować kupno ${randomItem(offerFrom)} do ${randomItem(offerTo)}.`;
  }

  function syncChatPosition() {
    if (!backToTop) {
      chatRoot.classList.remove("ai-chat--raised");
      return;
    }
    chatRoot.classList.toggle(
      "ai-chat--raised",
      backToTop.classList.contains("visible"),
    );
  }

  function syncKeyboardOffset() {
    if (!viewport) {
      chatRoot.style.setProperty("--ai-chat-keyboard-offset", "0px");
      return;
    }
    const offset = Math.max(
      0,
      Math.round(window.innerHeight - viewport.height - viewport.offsetTop),
    );
    chatRoot.style.setProperty("--ai-chat-keyboard-offset", `${offset}px`);
  }

  fab.addEventListener("click", () => {
    if (panel.classList.contains("is-open")) {
      closeChat();
      return;
    }
    openChat();
  });

  closeBtn.addEventListener("click", closeChat);
  sendBtn.addEventListener("pointerdown", (event) => {
    // Keep focus on the input so mobile keyboards stay open after sending.
    event.preventDefault();
  });

  form.addEventListener("submit", (event) => {
    event.preventDefault();
    const text = input.value.trim();
    if (!text) {
      return;
    }
    addMessage(text, true);
    addMessage(buildReply(), false);
    input.value = "";
    input.focus({ preventScroll: true });
  });

  if (backToTop) {
    const observer = new MutationObserver(syncChatPosition);
    observer.observe(backToTop, {
      attributes: true,
      attributeFilter: ["class"],
    });
    window.addEventListener("resize", syncChatPosition);
  }
  if (viewport) {
    viewport.addEventListener("resize", syncKeyboardOffset);
    viewport.addEventListener("scroll", syncKeyboardOffset);
  }
  window.addEventListener("resize", syncKeyboardOffset);
  syncChatPosition();
  syncKeyboardOffset();
})();