// Pure vanilla JS – no Svelte imports
const BASE = import.meta.env.VITE_API_URL ?? 'http://localhost:8000';

export const chatStore = (() => {
  let chatId = $state(null);          // null until first message
  let messages = $state([]);
  let input = $state('');
  let loading = $state(false);

  /* ── helpers ── */
  async function createChat() {
    const res = await fetch(`${BASE}/chats`, { method: 'POST' });
    const { id } = await res.json();
    return id;
  }

  async function sendUserMessage(text) {
    await fetch(`${BASE}/chats/${chatId}/messages`, {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ message: text })
    });
  }

  function streamAssistantReply() {
    const source = new EventSource(`${BASE}/chats/${chatId}/stream`);
    let botMsg = { id: Date.now(), text: '', me: false, sender: 'bot' };
    messages = [...messages, botMsg];

    source.onmessage = (ev) => {
      console.log(ev.data);
      if (ev.data === '[DONE]') {
        source.close();
        loading = false;
        return;
      }
      
      messages = messages.map((m, i) =>
        i === messages.length - 1 ? { ...m, text: m.text + ev.data } : m
      );
    };

    source.onerror = () => {
      source.close();
      loading = false;
    };
  }

  async function send() {
    const text = input.trim();
    if (!text || loading) return;

    // add user bubble immediately
    messages = [...messages, { id: Date.now(), text, me: true, sender: 'user' }];
    input = '';
    loading = true;

    try {
      if (!chatId) chatId = await createChat();
      await sendUserMessage(text);
      streamAssistantReply();
    } catch {
      messages = [
        ...messages,
        { id: Date.now(), text: 'Sorry, something went wrong.', me: false, sender: 'bot' }
      ];
      loading = false;
    }
  }

  function handleKey(e) {
    if (e.key === 'Enter' && !e.shiftKey) {
      e.preventDefault();
      send();
    }
  }

  return {
    get messages() { return messages; },
    get input() { return input; },
    set input(v) { input = v; },
    get loading() { return loading; },
    send,
    handleKey
  };
})();