// KI-Chat client: sends messages, streams assistant tokens over SSE.
// Tailwind CDN is loaded via the head partial; this file only handles logic.
(function () {
  const boot = window.__CHAT_BOOT__ || {};
  let activeId = boot.activeId || null;
  const log = document.getElementById('chatLog');
  const form = document.getElementById('chatForm');
  const input = document.getElementById('chatInput');
  const sendBtn = document.getElementById('sendBtn');
  const newThreadBtn = document.getElementById('newThreadBtn');
  const threadList = document.getElementById('threadList');
  let sending = false;

  function escapeHtml(s) {
    const d = document.createElement('div');
    d.textContent = s == null ? '' : String(s);
    return d.innerHTML;
  }

  function scrollBottom() {
    if (log) log.scrollTop = log.scrollHeight;
  }

  function emptyState(msg) {
    log.innerHTML =
      '<div class="h-full flex items-center justify-center text-gray-400 text-sm text-center px-6">' +
      escapeHtml(msg) + '</div>';
  }

  function addBubble(role, content) {
    if (log && log.querySelector('.h-full')) log.innerHTML = '';
    const wrap = document.createElement('div');
    wrap.className = 'flex ' + (role === 'user' ? 'justify-end' : 'justify-start');
    const bubble = document.createElement('div');
    bubble.className = 'max-w-[80%] rounded-lg px-3 py-2 text-sm chat-msg ' +
      (role === 'user' ? 'bg-blue-600 text-white' : 'bg-gray-100 dark:bg-gray-700 text-gray-800 dark:text-gray-100');
    bubble.textContent = content;
    wrap.appendChild(bubble);
    log.appendChild(wrap);
    scrollBottom();
    return bubble;
  }

  function typingIndicator() {
    if (log && log.querySelector('.h-full')) log.innerHTML = '';
    const wrap = document.createElement('div');
    wrap.className = 'flex justify-start';
    wrap.id = 'typing';
    wrap.innerHTML = '<div class="rounded-lg px-3 py-2 bg-gray-100 dark:bg-gray-700 text-gray-500 flex gap-1">' +
      '<span class="typing-dot"></span><span class="typing-dot"></span><span class="typing-dot"></span></div>';
    log.appendChild(wrap);
    scrollBottom();
    return wrap;
  }

  function prependThread(id, titel) {
    if (!threadList) return;
    const empty = threadList.querySelector('li.text-center');
    if (empty) empty.remove();
    const li = document.createElement('li');
    li.innerHTML = '<a href="/chat?thread=' + encodeURIComponent(id) + '" data-thread="' + id +
      '" class="block px-3 py-2 text-sm text-gray-700 dark:text-gray-200 hover:bg-gray-50 dark:hover:bg-gray-700/40 bg-blue-50 dark:bg-gray-700">' +
      '<div class="truncate font-medium">' + escapeHtml(titel || '(neuer Chat)') + '</div>' +
      '<div class="text-[11px] text-gray-400">gerade</div></a>';
    threadList.insertBefore(li, threadList.firstChild);
  }

  function enableInput() {
    input.disabled = false;
    sendBtn.disabled = false;
  }

  async function createThread() {
    const res = await fetch('/chat/api/threads', {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ titel: '' }),
    });
    if (!res.ok) throw new Error('Thread konnte nicht angelegt werden.');
    const data = await res.json();
    activeId = data.id;
    document.getElementById('activeThread').value = activeId;
    prependThread(activeId, data.titel);
    enableInput();
    history.replaceState(null, '', '/chat?thread=' + activeId);
    return activeId;
  }

  // Parse the SSE response body stream. `onEvent` is called with each parsed
  // data object. Returns when the stream closes or errors.
  async function consumeSSE(res, onEvent) {
    const reader = res.body.getReader();
    const decoder = new TextDecoder();
    let buffer = '';
    while (true) {
      const { done, value } = await reader.read();
      if (done) break;
      buffer += decoder.decode(value, { stream: true });
      let sep;
      while ((sep = buffer.indexOf('\n\n')) >= 0) {
        const block = buffer.slice(0, sep);
        buffer = buffer.slice(sep + 2);
        for (const line of block.split('\n')) {
          if (!line.startsWith('data:')) continue;
          const payload = line.slice(5).trim();
          if (!payload) continue;
          try { onEvent(JSON.parse(payload)); } catch (e) { /* ignore */ }
        }
      }
    }
  }

  async function sendMessage(text) {
    if (sending || !text.trim()) return;
    sending = true;
    sendBtn.disabled = true;

    if (!activeId) {
      try { await createThread(); }
      catch (e) { sending = false; sendBtn.disabled = false; alert(e.message); return; }
    }

    addBubble('user', text);
    input.value = '';
    input.style.height = 'auto';
    const typing = typingIndicator();
    let assistantBubble = null;
    let assistantText = '';

    try {
      const res = await fetch('/chat/api/threads/' + activeId + '/messages', {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ content: text }),
      });
      if (!res.ok || !res.body) {
        let msg = 'Senden fehlgeschlagen (' + res.status + ')';
        try { const j = await res.json(); msg = j.error || msg; } catch (e) {}
        throw new Error(msg);
      }

      await consumeSSE(res, (ev) => {
        if (ev.type === 'token') {
          if (!assistantBubble) {
            if (typing) typing.remove();
            assistantBubble = addBubble('assistant', '');
          }
          assistantText += ev.content;
          assistantBubble.textContent = assistantText;
          scrollBottom();
        } else if (ev.type === 'done') {
          if (assistantBubble && ev.content) {
            assistantBubble.textContent = ev.content;
          } else if (!assistantBubble) {
            if (typing) typing.remove();
            addBubble('assistant', ev.content || '(keine Antwort)');
          }
          scrollBottom();
        } else if (ev.type === 'error') {
          if (typing) typing.remove();
          if (!assistantBubble) addBubble('assistant', 'Fehler: ' + ev.message);
          else assistantBubble.textContent += '\n[Fehler: ' + ev.message + ']';
        }
      });
    } catch (err) {
      if (typing) typing.remove();
      addBubble('assistant', 'Fehler: ' + (err.message || 'unbekannt'));
    } finally {
      if (typing && typing.parentNode) typing.remove();
      sending = false;
      sendBtn.disabled = false;
      input.focus();
    }
  }

  // Auto-grow the textarea; Enter sends, Shift+Enter inserts a newline.
  if (input) {
    input.addEventListener('input', () => {
      input.style.height = 'auto';
      input.style.height = Math.min(input.scrollHeight, 160) + 'px';
    });
    input.addEventListener('keydown', (e) => {
      if (e.key === 'Enter' && !e.shiftKey) {
        e.preventDefault();
        sendMessage(input.value);
      }
    });
  }

  if (form) {
    form.addEventListener('submit', (e) => {
      e.preventDefault();
      sendMessage(input.value);
    });
  }

  if (newThreadBtn) {
    newThreadBtn.addEventListener('click', () => {
      window.location.href = '/chat';
    });
  }

  scrollBottom();
  if (input && !input.disabled) input.focus();
})();