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

  // Cached probe result for the current URL so click-handlers know which
  // action to dispatch without round-tripping again.
  let currentProbe = null;
  // Bumped on every evaluate(): a probe that answers after the operator has
  // navigated on is for a page they've left, and must not repaint the chip.
  let generation = 0;
  let lastUrl = window.location.href;

  evaluate();

  // SPA navigation. Patreon, SubscribeStar and above all Discord change
  // channel/page without a reload. Patching history.pushState from here never
  // worked: a content script runs in an isolated world, so the page's own
  // pushState is not the function we'd replace. Polling the URL is the one
  // signal that sees every navigation, and costs a string compare.
  window.addEventListener('popstate', () => onUrlMaybeChanged());
  setInterval(onUrlMaybeChanged, 500);

  function onUrlMaybeChanged() {
    if (window.location.href === lastUrl) return;
    lastUrl = window.location.href;
    closePanel();
    evaluate();
  }

  async function evaluate() {
    const mine = ++generation;
    const url = window.location.href;
    const platform = getPlatformFromUrl(url);
    const onArtist = platform && isArtistPage(url, platform);
    if (!onArtist) {
      removeButton();
      currentProbe = null;
      return;
    }
    // Ask the backend what state the URL is in BEFORE drawing the button, so
    // the chip renders the right state on first paint instead of flashing the
    // generic "Add" copy and updating afterwards.
    let probe;
    try {
      probe = await browser.runtime.sendMessage({ type: 'PROBE_SOURCE', url });
    } catch (e) {
      probe = { error: e?.message || 'probe failed' };
    }
    if (mine !== generation) return;
    currentProbe = probe;
    if (probe?.state === 'unknown_platform') {
      removeButton();
      return;
    }
    renderButton(probe);
  }

  function removeButton() {
    document.getElementById('fc-add-source-btn')?.remove();
    closePanel();
  }

  function renderButton(probe) {
    let btn = document.getElementById('fc-add-source-btn');
    if (!btn) {
      btn = document.createElement('button');
      btn.id = 'fc-add-source-btn';
      btn.addEventListener('click', onClick);
      document.body.appendChild(btn);
    }
    // Reset state classes so re-renders (SPA navigation) don't stack.
    btn.className = 'fc-add-source-btn';
    btn.classList.add(`fc-add-source-btn--${chipState(probe)}`);
    btn.textContent = chipLabel(probe, PLATFORMS[probe?.platform]?.name || probe?.platform || '');
    btn.disabled = false;
  }

  async function onClick() {
    const btn = document.getElementById('fc-add-source-btn');
    if (!btn) return;
    const probe = currentProbe;

    if (probe?.state === 'source_match') {
      await openArtist(btn, probe.artist?.slug);
      return;
    }
    // A Discord URL names a channel, not a creator — ask which artist.
    if (probe?.platform === 'discord') {
      if (document.getElementById('fc-discord-panel')) closePanel();
      else openDiscordPanel(probe);
      return;
    }
    await add(btn, { url: window.location.href });
  }

  async function openArtist(btn, slug) {
    btn.disabled = true;
    const original = btn.textContent;
    btn.textContent = 'Opening…';
    try {
      const r = await browser.runtime.sendMessage({ type: 'OPEN_ARTIST_PAGE', slug });
      if (r?.error) showToast(`Error: ${r.error}`, 'error');
    } catch (e) {
      showToast(`Error: ${e.message}`, 'error');
    } finally {
      btn.disabled = false;
      btn.textContent = original;
    }
  }

  // One add, shared by the one-click chip and the Discord panel. Resolves
  // true on success.
  async function add(btn, request) {
    btn.disabled = true;
    const original = btn.textContent;
    btn.textContent = 'Adding…';
    try {
      const r = await browser.runtime.sendMessage({ type: 'ADD_AS_SOURCE', ...request });
      if (r?.error) {
        showToast(`Error: ${r.error}`, 'error');
        return false;
      }
      const verb = r.created_source ? 'Added to' : 'Already a source for';
      showToast(`${verb} ${r.artist?.name || 'artist'} (${r.source?.platform || ''})`, 'success');
      // Re-probe so the chip flips green without waiting for a navigation.
      evaluate();
      return true;
    } catch (e) {
      showToast(`Error: ${e.message}`, 'error');
      return false;
    } finally {
      btn.disabled = false;
      btn.textContent = original;
    }
  }

  // ---- Discord Add panel ----
  // Where: this channel or the whole server. Who: the suggested artist, one
  // found by search, or a new one by name. Built with createElement only —
  // server, channel and artist names are other people's text.

  function el(tag, props = {}, children = []) {
    const node = document.createElement(tag);
    const { class: className, text, ...rest } = props;
    if (className) node.className = className;
    if (text != null) node.textContent = text;
    Object.assign(node, rest);
    for (const c of children) node.appendChild(c);
    return node;
  }

  function closePanel() {
    document.getElementById('fc-discord-panel')?.remove();
  }

  function openDiscordPanel(probe) {
    closePanel();
    const d = probe.discord || {};
    const choice = discordPanelDefaults(probe);

    const scopeRow = (value, label, disabled) => {
      const input = el('input', {
        type: 'radio', name: 'fc-discord-scope', value,
        checked: choice.scope === value, disabled,
      });
      input.addEventListener('change', () => { choice.scope = value; refresh(); });
      return el('label', { class: 'fc-panel__radio' }, [input, el('span', { text: label })]);
    };

    // The artist field is an autocomplete over FC's artists: it searches as
    // soon as the panel opens (with the prefilled name) and on every keystroke,
    // lists the matches under the field, fills in the rest of the top match as
    // you type (Tab or Enter accepts it, typing on replaces it), and picks an
    // artist whose name IS the text, spacing and case aside, without being
    // asked. ↑/↓ walk the list; the last row creates a new artist instead.
    const nameInput = el('input', {
      type: 'text', class: 'fc-panel__input', value: choice.artistName,
      placeholder: 'Search artists or type a new name',
      autocomplete: 'off', spellcheck: false,
      role: 'combobox',
    });
    nameInput.setAttribute('aria-autocomplete', 'both');
    nameInput.setAttribute('aria-expanded', 'false');
    const results = el('div', { class: 'fc-panel__results', role: 'listbox' });
    const hint = el('div', { class: 'fc-panel__hint' });
    const addBtn = el('button', { class: 'fc-panel__btn fc-panel__btn--primary', text: 'Add' });
    const cancelBtn = el('button', { class: 'fc-panel__btn', text: 'Cancel' });

    const panel = el('div', { id: 'fc-discord-panel', class: 'fc-panel' }, [
      el('div', { class: 'fc-panel__title', text: 'Add Discord source' }),
      el('div', { class: 'fc-panel__sub', text: serverLabel(d) }),
      el('div', { class: 'fc-panel__label', text: 'Follow' }),
      scopeRow('channel', d.channel_id ? channelLabel(d) : 'this channel', !d.channel_id),
      scopeRow('server', `Every channel in ${serverLabel(d)}`, false),
      el('div', { class: 'fc-panel__label', text: 'Artist' }),
      el('div', { class: 'fc-panel__combo' }, [nameInput, results]),
      hint,
      el('div', { class: 'fc-panel__actions' }, [cancelBtn, addBtn]),
    ]);

    // Search state: the rows on screen, which one ↑/↓ has highlighted (-1 =
    // none), and whether the list is open.
    let rows = [];
    let active = -1;
    let listOpen = false;

    function refresh() {
      const req = discordAddRequest(choice);
      addBtn.disabled = !req;
      if (!req) hint.textContent = 'Pick an artist or type a name.';
      else if (req.artistId != null) hint.textContent = `✓ Connects to ${choice.artist.name}, already in FabledCurator.`;
      else hint.textContent = `Creates a new artist “${req.artistName}”.`;
      hint.classList.toggle('fc-panel__hint--match', !!req && req.artistId != null);
    }

    function pick(artist) {
      choice.artist = artist ? { id: artist.id, name: artist.name } : null;
      if (artist) {
        choice.artistName = artist.name;
        nameInput.value = artist.name;
      }
      closeList();
      refresh();
    }

    function closeList() {
      listOpen = false;
      active = -1;
      results.replaceChildren();
      nameInput.setAttribute('aria-expanded', 'false');
    }

    function renderList() {
      const typed = nameInput.value.trim();
      const exact = exactArtistMatch(typed, rows);
      const items = rows.map((a, i) => {
        const row = el('button', { type: 'button', class: 'fc-panel__result', role: 'option' }, [
          el('span', { text: a.name }),
        ]);
        if (choice.artist && choice.artist.id === a.id) {
          row.appendChild(el('span', { class: 'fc-panel__result-tag', text: 'selected' }));
        }
        row.classList.toggle('fc-panel__result--active', i === active);
        // mousedown, not click: it fires before the input's blur closes the list.
        row.addEventListener('mousedown', (e) => { e.preventDefault(); pick(a); });
        return row;
      });
      if (typed && !exact) {
        const i = rows.length;
        const create = el('button', { type: 'button', class: 'fc-panel__result fc-panel__result--new', role: 'option',
          text: `+ New artist “${typed}”` });
        create.classList.toggle('fc-panel__result--active', i === active);
        create.addEventListener('mousedown', (e) => { e.preventDefault(); pick(null); choice.artistName = typed; refresh(); });
        items.push(create);
      }
      if (typed && !rows.length) {
        items.unshift(el('div', { class: 'fc-panel__empty', text: 'No FabledCurator artist matches.' }));
      }
      results.replaceChildren(...items);
      listOpen = items.length > 0;
      nameInput.setAttribute('aria-expanded', String(listOpen));
      results.querySelector('.fc-panel__result--active')?.scrollIntoView({ block: 'nearest' });
    }

    let debounce = null;
    let searchSeq = 0;
    // `autofill` is false for deletions: filling the name back in as you
    // backspace would make it impossible to delete.
    function search(autofill) {
      clearTimeout(debounce);
      const q = nameInput.value.trim();
      if (!q) { rows = []; closeList(); return; }
      debounce = setTimeout(async () => {
        const mine = ++searchSeq;
        let r;
        try {
          r = await browser.runtime.sendMessage({ type: 'SEARCH_ARTISTS', q });
        } catch {
          return;
        }
        // Stale: a later keystroke has its own search coming.
        if (mine !== searchSeq || r?.error || nameInput.value.trim() !== q) return;
        rows = r.artists || [];
        active = -1;
        const exact = exactArtistMatch(q, rows);
        if (exact && !choice.artist) {
          choice.artist = { id: exact.id, name: exact.name };
        } else if (autofill && document.activeElement === nameInput) {
          const hit = inlineCompletion(nameInput.value, rows);
          const caret = nameInput.value.length;
          if (hit && nameInput.selectionStart === caret) {
            nameInput.value = nameInput.value + hit.name.slice(caret);
            nameInput.setSelectionRange(caret, hit.name.length);
            choice.artist = { id: hit.id, name: hit.name };
            choice.artistName = hit.name;
          }
        }
        renderList();
        refresh();
      }, 150);
    }

    nameInput.addEventListener('input', (e) => {
      choice.artistName = nameInput.value;
      // Any edit un-picks: the artist is whatever the field now says.
      choice.artist = null;
      refresh();
      search(!String(e.inputType || '').startsWith('delete'));
    });
    nameInput.addEventListener('focus', () => { if (rows.length) renderList(); });
    nameInput.addEventListener('blur', () => closeList());

    // Keep Discord's global shortcuts from eating keystrokes meant for us.
    panel.addEventListener('keydown', (e) => {
      e.stopPropagation();
      const count = results.querySelectorAll('.fc-panel__result').length;
      if (e.target === nameInput && listOpen && count) {
        if (e.key === 'ArrowDown' || e.key === 'ArrowUp') {
          e.preventDefault();
          active = e.key === 'ArrowDown' ? (active + 1) % count : (active <= 0 ? count - 1 : active - 1);
          renderList();
          return;
        }
        if ((e.key === 'Enter' || e.key === 'Tab') && active >= 0) {
          e.preventDefault();
          results.querySelectorAll('.fc-panel__result')[active]
            .dispatchEvent(new MouseEvent('mousedown', { cancelable: true }));
          return;
        }
        if ((e.key === 'Tab' || e.key === 'Enter') && choice.artist
            && nameInput.selectionEnd > nameInput.selectionStart) {
          // Accept the inline autofill — Enter too, but only to accept: the
          // add itself takes a second Enter, once the hint names the artist.
          e.preventDefault();
          pick(choice.artist);
          return;
        }
      }
      if (e.key === 'Escape') {
        if (listOpen) closeList();
        else closePanel();
        return;
      }
      if (e.key === 'Enter' && e.target === nameInput && !addBtn.disabled) addBtn.click();
    });

    cancelBtn.addEventListener('click', closePanel);
    addBtn.addEventListener('click', async () => {
      const req = discordAddRequest(choice);
      if (!req) return;
      const btn = document.getElementById('fc-add-source-btn');
      addBtn.disabled = true;
      const ok = await add(btn || addBtn, req);
      if (ok) closePanel();
      else refresh();
    });

    document.body.appendChild(panel);
    refresh();
    nameInput.focus();
    nameInput.select();
    // Search what the field opens with — the server's name, usually — so an
    // artist it already matches is picked before the operator types anything.
    if (!choice.artist && nameInput.value.trim()) search(false);
  }

  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);
  }
})();