// static/js/slashAutocomplete.js
// Lightweight popup that surfaces the existing /command registry as users
// type. Reads COMMANDS from slashCommands.js — no command logic lives here.

import { COMMANDS, LEGACY_ALIASES } from './slashCommands.js';

const POPUP_ID = 'slash-autocomplete';
const MAX_VISIBLE = 12;

// Flatten the registry into a searchable list of leaf entries. Each entry is
// either a top-level command or a "cmd sub" pair (so subcommands get their
// own row when relevant — /toggle web, /chats new, etc).
// Commands intentionally excluded from the autocomplete popup (pure easter
// eggs with no productivity value, or internal machinery).
const EXCLUDED = new Set(['flip','roll','8ball','fortune','odyssey','ascii']);

// Important legacy aliases to promote to their own rows in the popup. These
// are the short forms people will actually type (/new, /clear, /web, etc.)
// rather than the full /chats new, /toggle web equivalents.
const PROMOTED_ALIASES = new Set([
  'new','clear','rename','fork','export','archive','favorite','unfavorite',
  'web','bash','research','doc',
  'memories','forget',
]);

function _flatten() {
  const out = [];
  const seen = new Set();

  // 1. Top-level commands and their subcommands from COMMANDS
  for (const [name, def] of Object.entries(COMMANDS)) {
    if (EXCLUDED.has(name)) continue;
    if (def.hidden) continue;
    if (def.handler) {
      seen.add(`/${name}`);
      out.push({
        token: `/${name}`,
        aliases: (def.alias || []).map(a => `/${a}`),
        category: def.category || '',
        help: def.help || '',
        usage: def.usage || '',
      });
    }
    if (def.subs) {
      for (const [sub, sdef] of Object.entries(def.subs)) {
        if (sub.startsWith('_')) continue;
        if (sdef.hidden) continue;
        const tok = `/${name} ${sub}`;
        seen.add(tok);
        out.push({
          token: tok,
          aliases: (sdef.alias || []).map(a => `/${name} ${a}`),
          category: def.category || '',
          help: sdef.help || '',
          usage: sdef.usage || '',
        });
      }
    }
  }

  // 2. Promoted legacy aliases (/new, /clear, /web …) as convenient short rows
  if (LEGACY_ALIASES) {
    for (const [alias, { parent, sub }] of Object.entries(LEGACY_ALIASES)) {
      if (!PROMOTED_ALIASES.has(alias)) continue;
      const tok = `/${alias}`;
      if (seen.has(tok)) continue;
      const parentDef = COMMANDS[parent];
      const subDef = parentDef?.subs?.[sub];
      if (!subDef) continue;
      seen.add(tok);
      out.push({
        token: tok,
        aliases: [],
        category: parentDef.category || '',
        help: subDef.help || '',
        usage: tok,
      });
    }
  }

  return out;
}

function _scoreMatch(entry, query) {
  // query already starts with "/". Match against token + aliases. Prefix wins
  // over substring; alias match scores slightly lower than token match.
  const q = query.toLowerCase();
  const t = entry.token.toLowerCase();
  if (t === q) return 1000;
  if (t.startsWith(q)) return 500 + (50 - Math.min(50, t.length - q.length));
  for (const a of entry.aliases) {
    const al = a.toLowerCase();
    if (al === q) return 900;
    if (al.startsWith(q)) return 400;
  }
  if (t.includes(q)) return 100;
  if (entry.help.toLowerCase().includes(q.slice(1))) return 25;  // help text
  return 0;
}

function _ensurePopup(textarea) {
  let el = document.getElementById(POPUP_ID);
  if (el) return el;
  el = document.createElement('div');
  el.id = POPUP_ID;
  el.className = 'slash-autocomplete-popup';
  el.setAttribute('role', 'listbox');
  el.setAttribute('aria-label', 'Slash commands');
  document.body.appendChild(el);
  return el;
}

function _position(popup, textarea) {
  const r = textarea.getBoundingClientRect();
  const maxH = Math.min(window.innerHeight * 0.5, 360);
  popup.style.maxHeight = maxH + 'px';
  // Anchor above the textarea, left-aligned with it
  popup.style.left = Math.round(r.left) + 'px';
  popup.style.width = Math.max(280, Math.round(Math.min(r.width, 520))) + 'px';
  // Place above when there's enough room, otherwise below.
  const aboveSpace = r.top;
  if (aboveSpace > maxH + 20) {
    popup.style.bottom = (window.innerHeight - r.top + 6) + 'px';
    popup.style.top = '';
  } else {
    popup.style.top = (r.bottom + 6) + 'px';
    popup.style.bottom = '';
  }
}

function _render(popup, items, selectedIdx, query) {
  if (!items.length) {
    popup.innerHTML = `<div class="slash-ac-empty">No commands match <code>${_esc(query)}</code></div>`;
    return;
  }
  // Group by category for the headers
  let html = '';
  let lastCat = null;
  for (let i = 0; i < items.length; i++) {
    const it = items[i];
    if (it.category !== lastCat) {
      html += `<div class="slash-ac-cat">${_esc(it.category || 'Other')}</div>`;
      lastCat = it.category;
    }
    const sel = i === selectedIdx ? ' slash-ac-row-sel' : '';
    const usage = it.usage && it.usage !== it.token ? ` <span class="slash-ac-usage">${_esc(it.usage)}</span>` : '';
    html += `<div class="slash-ac-row${sel}" role="option" data-idx="${i}" data-token="${_esc(it.token)}">`
         +    `<span class="slash-ac-token">${_esc(it.token)}</span>`
         +    `<span class="slash-ac-help">${_esc(it.help)}</span>`
         +    usage
         + `</div>`;
  }
  popup.innerHTML = html;
  // Scroll selected into view
  const selEl = popup.querySelector('.slash-ac-row-sel');
  if (selEl) selEl.scrollIntoView({ block: 'nearest' });
}

function _esc(s) {
  return String(s).replace(/[&<>"']/g, c => ({ '&':'&amp;','<':'&lt;','>':'&gt;','"':'&quot;','\'':'&#39;' }[c]));
}

export function initSlashAutocomplete(textarea) {
  if (!textarea || textarea._slashAcWired) return;
  textarea._slashAcWired = true;

  const all = _flatten();
  let popup = null;
  let visible = false;
  let items = [];
  let selectedIdx = 0;

  const hide = () => {
    if (!visible) return;
    visible = false;
    if (popup) popup.style.display = 'none';
  };

  const show = () => {
    if (!popup) popup = _ensurePopup(textarea);
    visible = true;
    popup.style.display = 'block';
    _position(popup, textarea);
  };

  const refresh = () => {
    const v = textarea.value;
    // Only trigger when the message starts with "/" (no leading space) and
    // contains at most one space after the command (so subcommands work).
    // If the user has moved past the slash command (newline, longer prose),
    // the menu hides — we don't autocomplete mid-sentence.
    if (!v.startsWith('/') || v.includes('\n')) { hide(); return; }
    const query = v.trim();
    items = all
      .map(e => ({ e, s: _scoreMatch(e, query) }))
      .filter(x => x.s > 0)
      .sort((a, b) => b.s - a.s)
      .slice(0, MAX_VISIBLE)
      .map(x => x.e);
    if (!items.length && query.length > 1) { hide(); return; }
    if (!items.length) {
      // Just "/" with no matches — fall back to showing everything up to MAX_VISIBLE
      items = all.slice(0, MAX_VISIBLE);
    }
    selectedIdx = 0;
    show();
    _render(popup, items, selectedIdx, query);
  };

  const insert = (token) => {
    textarea.value = token + ' ';
    textarea.dispatchEvent(new Event('input', { bubbles: true }));
    textarea.focus();
    const len = textarea.value.length;
    textarea.setSelectionRange(len, len);
    hide();
  };

  textarea.addEventListener('input', refresh);
  textarea.addEventListener('focus', () => { if (textarea.value.startsWith('/')) refresh(); });
  textarea.addEventListener('blur', () => { setTimeout(hide, 120); });  // delay so click works

  textarea.addEventListener('keydown', (e) => {
    if (!visible || !items.length) return;
    if (e.key === 'ArrowDown') {
      e.preventDefault();
      selectedIdx = (selectedIdx + 1) % items.length;
      _render(popup, items, selectedIdx, textarea.value);
    } else if (e.key === 'ArrowUp') {
      e.preventDefault();
      selectedIdx = (selectedIdx - 1 + items.length) % items.length;
      _render(popup, items, selectedIdx, textarea.value);
    } else if (e.key === 'Tab' || (e.key === 'Enter' && !e.shiftKey)) {
      // Tab always inserts. Enter inserts only when the user hasn't already
      // typed a full command + args — i.e. the popup is still in completion
      // mode, not in "ready to submit a typed-out command" mode.
      const v = textarea.value.trim();
      const exactHit = items.find(it => it.token === v || it.aliases.includes(v));
      if (e.key === 'Enter' && exactHit) {
        // User typed the whole command — let the normal submit path handle it
        hide();
        return;
      }
      e.preventDefault();
      insert(items[selectedIdx].token);
    } else if (e.key === 'Escape') {
      e.preventDefault();
      hide();
    }
  });

  // Re-position on window resize / scroll
  window.addEventListener('resize', () => { if (visible) _position(popup, textarea); });

  // Click handler on the popup (delegated)
  document.addEventListener('mousedown', (e) => {
    if (!visible || !popup) return;
    const row = e.target.closest?.('.slash-ac-row');
    if (row && popup.contains(row)) {
      e.preventDefault();
      const tok = row.dataset.token;
      if (tok) insert(tok);
    }
  });
}

export default { initSlashAutocomplete };
