"""
Widget JS generator.

Produces a self-contained, framework-agnostic JavaScript bundle served at
GET /widget.js.  Embed on any page with:

    <script
      src="https://api.yoursite.com/widget.js"
      data-chatbot="<chatbot-id>">
    </script>

Works on vanilla HTML, WordPress, Webflow, Shopify, Next.js (_document),
and any framework where you control the HTML shell.

For React/Vue projects that want a native component, host-side devs can call
  window.Contexta.open() / .close() / .toggle()
from their own button, or await the dedicated npm package (@contexta/widget).

Design decisions
----------------
- All CSS is ID-scoped (#ctxa-*) to avoid colliding with host-page styles.
- The iframe src is set lazily on first open — zero network cost until use.
- document.currentScript is captured synchronously (before any async code)
  so it works even when the host page has many script tags.
- z-index 2147483647 is the highest a browser will honour.
- sandbox attribute restricts the iframe while still allowing forms/popups.
"""

_TEMPLATE = r"""(function () {
  'use strict';

  /* ── Double-init guard ─────────────────────────────────────────────── */
  if (window.__ctxa) return;

  /* ── Read chatbot ID from <script data-chatbot="..."> ──────────────── */
  var _cur = document.currentScript;
  var _id  = _cur && _cur.getAttribute('data-chatbot');
  if (!_id) {
    var _all = document.querySelectorAll('script[data-chatbot]');
    if (_all.length) _id = _all[_all.length - 1].getAttribute('data-chatbot');
  }
  if (!_id) {
    console.warn('[Contexta] widget loaded but no data-chatbot attribute found.');
    return;
  }

  var _base = '__APP_URL__';
  var _url  = _base + '/chat/' + _id;

  /* ── Styles ─────────────────────────────────────────────────────────── */
  var _css = [
    '#ctxa-btn{',
      'position:fixed;bottom:24px;right:24px;',
      'width:56px;height:56px;border-radius:50%;',
      'background:linear-gradient(135deg,#6366f1,#4f46e5);',
      'border:none;cursor:pointer;padding:0;',
      'box-shadow:0 4px 20px rgba(99,102,241,.45);',
      'display:flex;align-items:center;justify-content:center;',
      'z-index:2147483646;',
      'transition:transform .2s ease,box-shadow .2s ease;',
      'outline:none;',
    '}',
    '#ctxa-btn:hover{transform:scale(1.1);box-shadow:0 6px 28px rgba(99,102,241,.55)}',
    '#ctxa-btn:focus-visible{outline:2px solid #6366f1;outline-offset:3px}',

    /* Icon animations */
    '#ctxa-ico-chat,#ctxa-ico-x{position:absolute;transition:opacity .15s ease,transform .2s ease}',
    '#ctxa-ico-x{opacity:0;transform:rotate(-90deg)}',
    '#ctxa-btn.open #ctxa-ico-chat{opacity:0;transform:rotate(90deg)}',
    '#ctxa-btn.open #ctxa-ico-x{opacity:1;transform:rotate(0)}',

    /* Panel */
    '#ctxa-panel{',
      'position:fixed;bottom:92px;right:24px;',
      'width:380px;height:600px;',
      'max-height:calc(100dvh - 120px);',
      'border-radius:20px;overflow:hidden;background:#fff;',
      'box-shadow:0 20px 60px rgba(0,0,0,.18),0 0 0 1px rgba(0,0,0,.07);',
      'z-index:2147483647;',
      'opacity:0;transform:translateY(12px) scale(.97);pointer-events:none;',
      'transition:opacity .22s cubic-bezier(.4,0,.2,1),transform .22s cubic-bezier(.4,0,.2,1);',
    '}',
    '#ctxa-panel.open{opacity:1;transform:translateY(0) scale(1);pointer-events:all}',
    '#ctxa-frame{width:100%;height:100%;border:none;display:block;background:#fff}',

    /* Mobile: full-screen */
    '@media(max-width:480px){',
      '#ctxa-panel{bottom:0;right:0;left:0;width:100%;height:100%;',
        'max-height:100dvh;border-radius:0;box-shadow:none}',
      '#ctxa-btn{bottom:16px;right:16px}',
    '}',
  ].join('');

  var _style = document.createElement('style');
  _style.textContent = _css;
  document.head.appendChild(_style);

  /* ── Button ─────────────────────────────────────────────────────────── */
  var _btn = document.createElement('button');
  _btn.id = 'ctxa-btn';
  _btn.setAttribute('aria-label', 'Open chat');
  _btn.setAttribute('aria-expanded', 'false');
  _btn.innerHTML = (
    '<svg id="ctxa-ico-chat" width="24" height="24" viewBox="0 0 24 24" fill="none">' +
      '<path d="M12 2C6.477 2 2 6.2 2 11.4c0 2.8 1.26 5.3 3.26 7.04L4 22l4.2-1.75' +
             'A11.1 11.1 0 0 0 12 20.8c5.523 0 10-4.2 10-9.4S17.523 2 12 2z" fill="white"/>' +
    '</svg>' +
    '<svg id="ctxa-ico-x" width="20" height="20" viewBox="0 0 24 24" fill="none">' +
      '<path d="M18 6L6 18M6 6l12 12" stroke="white" stroke-width="2.5"' +
             ' stroke-linecap="round" stroke-linejoin="round"/>' +
    '</svg>'
  );

  /* ── Panel + lazy iframe ─────────────────────────────────────────────── */
  var _panel = document.createElement('div');
  _panel.id = 'ctxa-panel';
  _panel.setAttribute('role', 'dialog');
  _panel.setAttribute('aria-label', 'Chat');

  var _frame = document.createElement('iframe');
  _frame.id = 'ctxa-frame';
  _frame.title = 'Contexta chat';
  _frame.setAttribute('allow', 'clipboard-write');
  /* sandbox: scripts + same-origin needed for the React app to run */
  _frame.setAttribute('sandbox',
    'allow-scripts allow-same-origin allow-forms allow-popups allow-top-navigation-by-user-activation'
  );
  _panel.appendChild(_frame);

  /* ── Mount after DOM ready ───────────────────────────────────────────── */
  function _mount() {
    document.body.appendChild(_btn);
    document.body.appendChild(_panel);
  }
  if (document.readyState === 'loading') {
    document.addEventListener('DOMContentLoaded', _mount);
  } else {
    _mount();
  }

  /* ── Open / Close ────────────────────────────────────────────────────── */
  var _isOpen = false;
  var _loaded = false;

  function _open() {
    if (!_loaded) { _frame.src = _url; _loaded = true; }
    _isOpen = true;
    _panel.classList.add('open');
    _btn.classList.add('open');
    _btn.setAttribute('aria-expanded', 'true');
    _btn.setAttribute('aria-label', 'Close chat');
  }

  function _close() {
    _isOpen = false;
    _panel.classList.remove('open');
    _btn.classList.remove('open');
    _btn.setAttribute('aria-expanded', 'false');
    _btn.setAttribute('aria-label', 'Open chat');
  }

  _btn.addEventListener('click', function () { _isOpen ? _close() : _open(); });

  document.addEventListener('keydown', function (e) {
    if (e.key === 'Escape' && _isOpen) _close();
  });

  /* ── Public API ──────────────────────────────────────────────────────── */
  window.__ctxa = true;
  window.Contexta = {
    open:   _open,
    close:  _close,
    toggle: function () { _isOpen ? _close() : _open(); },
  };

}());
"""


def generate_widget_js(app_url: str) -> str:
    """Return the widget bundle with the frontend app URL baked in."""
    return _TEMPLATE.replace('__APP_URL__', app_url.rstrip('/'))