/**
 * Flynn Chat Page
 *
 * Session selector, message input, streaming tool events,
 * and markdown-rendered responses.
 */

/* global marked, hljs */

let _currentSession = null;
let _sending = false;
let _elements = {};

function escapeHtml(text) {
  const div = document.createElement('div');
  div.textContent = text;
  return div.innerHTML;
}

function renderMarkdown(text) {
  try {
    if (typeof marked !== 'undefined') {
      return marked.parse(text);
    }
  } catch {
    // Fall through to plain text
  }
  return `<p>${escapeHtml(text)}</p>`;
}

function highlightCode() {
  if (typeof hljs !== 'undefined') {
    document.querySelectorAll('.chat-messages pre code').forEach(block => {
      hljs.highlightElement(block);
    });
  }
}

function createMessageEl(role, content) {
  const div = document.createElement('div');
  div.className = `message ${role}`;

  if (role === 'assistant') {
    div.innerHTML = renderMarkdown(content);
    setTimeout(highlightCode, 0);
  } else {
    div.textContent = content;
  }
  return div;
}

function createToolEventEl(event, data) {
  const group = document.createElement('div');
  group.className = 'tool-event-group';

  const header = document.createElement('div');
  header.className = 'tool-event-header';

  if (event === 'tool_start') {
    header.innerHTML = `<span class="spinner"></span> <strong>${escapeHtml(data.tool)}</strong>`;
  } else if (event === 'tool_end') {
    const icon = data.result?.success ? '&#10003;' : '&#10007;';
    const cls = data.result?.success ? 'status-ok' : 'status-error';
    header.innerHTML = `<span class="${cls}">${icon}</span> <strong>${escapeHtml(data.tool)}</strong>`;
  }

  header.addEventListener('click', () => {
    body.classList.toggle('open');
  });

  const body = document.createElement('div');
  body.className = 'tool-event-body';

  if (event === 'tool_start' && data.args) {
    body.textContent = JSON.stringify(data.args, null, 2);
  } else if (event === 'tool_end' && data.result) {
    body.textContent = data.result.output || data.result.error || '(no output)';
  }

  group.appendChild(header);
  group.appendChild(body);
  return group;
}

function scrollToBottom() {
  const msgs = _elements.messages;
  if (msgs) {
    msgs.scrollTop = msgs.scrollHeight;
  }
}

async function loadSessions(client) {
  const select = _elements.sessionSelect;
  if (!select) return;

  try {
    const result = await client.call('sessions.list');
    const sessions = result.sessions ?? [];

    // Preserve current selection
    const current = _currentSession;
    select.innerHTML = '';

    if (sessions.length === 0) {
      const opt = document.createElement('option');
      opt.value = '';
      opt.textContent = 'No sessions';
      select.appendChild(opt);
    } else {
      for (const s of sessions) {
        const opt = document.createElement('option');
        opt.value = s.id;
        opt.textContent = `${s.id} (${s.messageCount} msgs)`;
        if (s.id === current) opt.selected = true;
        select.appendChild(opt);
      }
    }

    // Update current session
    _currentSession = select.value || null;
  } catch {
    // Ignore — sessions may not be available
  }
}

async function loadHistory(client) {
  const msgs = _elements.messages;
  if (!msgs || !_currentSession) return;

  msgs.innerHTML = '';

  try {
    const result = await client.call('sessions.history', { sessionId: _currentSession });
    const messages = result.messages ?? [];

    for (const msg of messages) {
      const role = msg.role ?? 'assistant';
      const content = msg.content ?? msg.text ?? '';
      msgs.appendChild(createMessageEl(role, content));
    }

    scrollToBottom();
  } catch {
    msgs.innerHTML = '<div class="empty-state">Could not load history</div>';
  }
}

async function sendMessage(client) {
  const input = _elements.input;
  const text = input?.value?.trim();
  if (!text || _sending) return;

  _sending = true;
  _elements.sendBtn.disabled = true;
  input.value = '';

  // Show user message
  _elements.messages.appendChild(createMessageEl('user', text));
  scrollToBottom();

  // Create placeholder for assistant response
  const placeholder = document.createElement('div');
  placeholder.className = 'message assistant streaming-cursor';
  placeholder.innerHTML = '<span class="text-muted">Thinking...</span>';
  _elements.messages.appendChild(placeholder);
  scrollToBottom();

  try {
    const stream = client.stream('agent.send', { message: text });

    stream.on('tool_start', (data) => {
      const el = createToolEventEl('tool_start', data);
      _elements.messages.insertBefore(el, placeholder);
      scrollToBottom();
    });

    stream.on('tool_end', (data) => {
      // Replace the last tool_start spinner with completion marker
      const events = _elements.messages.querySelectorAll('.tool-event-group');
      const last = events[events.length - 1];
      if (last) {
        const header = last.querySelector('.tool-event-header');
        if (header && data.tool) {
          const icon = data.result?.success !== false ? '&#10003;' : '&#10007;';
          const cls = data.result?.success !== false ? 'status-ok' : 'status-error';
          header.innerHTML = `<span class="${cls}">${icon}</span> <strong>${escapeHtml(data.tool)}</strong>`;
        }
        // Add result body
        const body = last.querySelector('.tool-event-body');
        if (body && data.result) {
          body.textContent = data.result.output || data.result.error || '(no output)';
        }
      }
      scrollToBottom();
    });

    const done = await stream.result;
    // Replace placeholder with actual response
    placeholder.classList.remove('streaming-cursor');
    const content = done?.content ?? done?.text ?? '(no response)';
    placeholder.innerHTML = renderMarkdown(content);
    setTimeout(highlightCode, 0);
  } catch (err) {
    placeholder.classList.remove('streaming-cursor');
    placeholder.className = 'message error';
    placeholder.textContent = `Error: ${err.message}`;
  } finally {
    _sending = false;
    if (_elements.sendBtn) _elements.sendBtn.disabled = false;
    scrollToBottom();
  }
}

export const ChatPage = {
  async render(el, client) {
    el.innerHTML = `
      <div class="chat-layout">
        <div class="chat-header">
          <select id="chat-session-select"></select>
          <button id="chat-new-session" class="btn btn-secondary">+ New Session</button>
          <button id="chat-load-history" class="btn btn-secondary">Load History</button>
        </div>
        <div class="chat-messages" id="chat-messages"></div>
        <div class="chat-input">
          <textarea id="chat-input" placeholder="Type a message..." rows="1"></textarea>
          <button id="chat-send" class="btn btn-primary">Send</button>
        </div>
      </div>
    `;

    _elements = {
      sessionSelect: el.querySelector('#chat-session-select'),
      messages: el.querySelector('#chat-messages'),
      input: el.querySelector('#chat-input'),
      sendBtn: el.querySelector('#chat-send'),
    };

    // Load sessions into dropdown
    await loadSessions(client);

    // Event: session change
    _elements.sessionSelect.addEventListener('change', () => {
      _currentSession = _elements.sessionSelect.value || null;
    });

    // Event: new session
    el.querySelector('#chat-new-session').addEventListener('click', async () => {
      try {
        const result = await client.call('sessions.create');
        _currentSession = result.sessionId;
        await loadSessions(client);
        _elements.messages.innerHTML = '';
      } catch (err) {
        _elements.messages.innerHTML = `<div class="empty-state">Failed to create session: ${err.message}</div>`;
      }
    });

    // Event: load history
    el.querySelector('#chat-load-history').addEventListener('click', () => {
      loadHistory(client);
    });

    // Event: send message
    _elements.sendBtn.addEventListener('click', () => sendMessage(client));

    // Event: Enter to send (Shift+Enter for newline)
    _elements.input.addEventListener('keydown', (e) => {
      if (e.key === 'Enter' && !e.shiftKey) {
        e.preventDefault();
        sendMessage(client);
      }
    });

    // Auto-resize textarea
    _elements.input.addEventListener('input', () => {
      const ta = _elements.input;
      ta.style.height = 'auto';
      ta.style.height = Math.min(ta.scrollHeight, 150) + 'px';
    });

    // If there's a current session, show welcome
    if (!_currentSession) {
      _elements.messages.innerHTML = '<div class="empty-state">Select a session or create a new one to start chatting</div>';
    }
  },

  teardown() {
    _currentSession = null;
    _sending = false;
    _elements = {};
  },
};