/* static/script.js */
function chatApp() {
  return {
    // ------------------------------
    // State
    // ------------------------------
    messages: [],               // {id, role, content}
    userInput: '',
    loading: false,
    dark: false,                // dark‑mode flag

    // ------------------------------
    // Init – runs once when component mounts
    // ------------------------------
    init() {
      // Detect system dark‑mode preference
      this.dark = window.matchMedia('(prefers-color-scheme: dark)').matches;
      this.applyDarkMode();

      // Listen for changes (e.g., user switches OS theme)
      window.matchMedia('(prefers-color-scheme: dark)').addEventListener('change', e => {
        this.dark = e.matches;
        this.applyDarkMode();
      });
    },

    // ------------------------------
    // Dark‑mode helper
    // ------------------------------
    toggleDark() {
      this.dark = !this.dark;
      this.applyDarkMode();
    },
    applyDarkMode() {
      if (this.dark) {
        document.documentElement.classList.add('dark');
      } else {
        document.documentElement.classList.remove('dark');
      }
    },

    // ------------------------------
    // Auto‑grow textarea
    // ------------------------------
    autoResize(event) {
      const el = event.target;
      el.style.height = 'auto';
      el.style.height = `${el.scrollHeight}px`;
    },

    // ------------------------------
    // Send a message to the back‑end
    // ------------------------------
    async sendMessage() {
      const content = this.userInput.trim();
      if (!content) return;

      // 1️⃣  Add user bubble
      const userMsg = {
        id: Date.now(),
        role: 'user',
        content: this.escapeHtml(content).replace(/\n/g, '<br>')
      };
      this.messages.push(userMsg);
      this.userInput = '';
      this.scrollToBottom();

      // 2️⃣  Show loading indicator
      this.loading = true;

      // 3️⃣  Call the OpenAI‑compatible endpoint
      try {
        const response = await fetch('/v1/chat/completions', {
          method: 'POST',
          headers: { 'Content-Type': 'application/json' },
          body: JSON.stringify({
            model: 'qwen2.5-1.5b-instruct',
            messages: [
              // Keep the whole conversation – the model can handle a few turns
              ...this.messages.map(m => ({
                role: m.role,
                content: this.stripHtml(m.content)   // plain text for the model
              }))
            ],
            temperature: 0.7,
            max_tokens: 512,
            top_p: 0.9,
            stream: false   // set true later if you implement SSE streaming
          })
        });

        if (!response.ok) {
          const err = await response.json();
          throw new Error(err.detail || 'API error');
        }

        const data = await response.json();
        const assistant = data.choices[0].message.content;

        // 4️⃣  Add assistant bubble
        const assistantMsg = {
          id: Date.now() + 1,
          role: 'assistant',
          content: this.escapeHtml(assistant).replace(/\n/g, '<br>')
        };
        this.messages.push(assistantMsg);
        this.scrollToBottom();
      } catch (e) {
        console.error(e);
        const errMsg = {
          id: Date.now() + 1,
          role: 'assistant',
          content: `<span class="text-red-500">⚠️ ${this.escapeHtml(e.message)}</span>`
        };
        this.messages.push(errMsg);
        this.scrollToBottom();
      } finally {
        this.loading = false;
      }
    },

    // ------------------------------
    // Helpers
    // ------------------------------
    scrollToBottom() {
      this.$nextTick(() => {
        const chat = document.getElementById('chat-window');
        chat.scrollTop = chat.scrollHeight;
      });
    },

    // Escape HTML to avoid XSS when we later render raw strings
    escapeHtml(str) {
      const div = document.createElement('div');
      div.appendChild(document.createTextNode(str));
      return div.innerHTML;
    },

    // Strip HTML tags – used when sending the prompt to the model
    stripHtml(html) {
      const div = document.createElement('div');
      div.innerHTML = html;
      return div.textContent || div.innerText || '';
    }
  };
}