(function () {
  if (window.__fc_addsource_injected) return;
  window.__fc_addsource_injected = true;

  evaluate();

  const reEval = () => evaluate();
  window.addEventListener('popstate', reEval);
  const origPush = history.pushState;
  history.pushState = function () { origPush.apply(this, arguments); reEval(); };

  function evaluate() {
    const platform = getPlatformFromUrl(window.location.href);
    const onArtist = platform && isArtistPage(window.location.href, platform);
    let btn = document.getElementById('fc-add-source-btn');
    if (onArtist && !btn) injectButton();
    else if (!onArtist && btn) btn.remove();
  }

  function injectButton() {
    const btn = document.createElement('button');
    btn.id = 'fc-add-source-btn';
    btn.className = 'fc-add-source-btn';
    btn.textContent = '+ Add to FabledCurator';
    btn.addEventListener('click', onClick);
    document.body.appendChild(btn);
  }

  async function onClick() {
    const btn = document.getElementById('fc-add-source-btn');
    btn.disabled = true;
    const original = btn.textContent;
    btn.textContent = 'Adding…';
    try {
      const r = await browser.runtime.sendMessage({
        type: 'ADD_AS_SOURCE',
        url: window.location.href,
      });
      if (r.error) {
        showToast(`Error: ${r.error}`, 'error');
      } else {
        const verb = r.created_source ? 'Added' : 'Already a source for';
        showToast(`${verb} ${r.artist?.name || 'artist'} (${r.source?.platform || ''})`, 'success');
      }
    } catch (e) {
      showToast(`Error: ${e.message}`, 'error');
    } finally {
      btn.disabled = false;
      btn.textContent = original;
    }
  }

  function showToast(text, kind) {
    const t = document.createElement('div');
    t.className = `fc-toast fc-toast--${kind}`;
    t.textContent = text;
    document.body.appendChild(t);
    setTimeout(() => t.remove(), 4000);
  }
})();