// 기본 실행 (페이지 로드시 전체 document)
class IpAutoComplete {
  /**
   * @param {HTMLElement|string} input
   * @param {HTMLElement|string} panel
   * @param {string[]} ipArray
   * @param {object} opts
   */
  constructor(input, panel, ipArray = [], opts = {}) {
    this.inputEl = typeof input === 'string' ? document.querySelector(input) : input;
    this.panelEl = typeof panel === 'string' ? document.querySelector(panel) : panel;
    if (!this.inputEl || !this.panelEl) throw new Error('Invalid input/panel element');

    this.opts = Object.assign({
      validateIPv4: true,
      enforceListOnly: false,
      previewOnFocus: true,   // 포커스 시 상위 N개 미리보기
      previewCount: 30,       // 미리보기 개수
      resultLimit: 1000       // 너무 많을 때 렌더 최대치(성능 안전장치)
    }, opts);

    this.errorEl = document.getElementById('ipError');
    this.ipv4Re  = /^(25[0-5]|2[0-4]\d|[01]?\d\d?)(\.(25[0-5]|2[0-4]\d|[01]?\d\d?)){3}$/;
    this.setArray(ipArray);

    // 상태
    this.activeIndex = -1;

    // 이벤트
    this.onInput   = this._handleInput.bind(this);
    this.onChange  = this._handleChange.bind(this);
    this.onFocus   = this._handleFocus.bind(this);
    this.onKeydown = this._handleKeydown.bind(this);
    this.onClickOutside = this._handleClickOutside.bind(this);

    this.inputEl.addEventListener('input', this.onInput);
    this.inputEl.addEventListener('change', this.onChange);
    this.inputEl.addEventListener('focus', this.onFocus);
    this.inputEl.addEventListener('keydown', this.onKeydown);
    document.addEventListener('mousedown', this.onClickOutside);
  }

  destroy(){
    this.inputEl.removeEventListener('input', this.onInput);
    this.inputEl.removeEventListener('change', this.onChange);
    this.inputEl.removeEventListener('focus', this.onFocus);
    this.inputEl.removeEventListener('keydown', this.onKeydown);
    document.removeEventListener('mousedown', this.onClickOutside);
    this.hidePanel();
  }

  setArray(arr){ this.ipArray = Array.from(new Set((arr||[]).filter(Boolean))); }

  _handleInput(e){
    const q = (e.target.value||'').trim();
    this._filterAndRender(q);
    this._checkIPv4(q);
  }

  _handleChange(){
    const v = (this.inputEl.value||'').trim();
    this._checkIPv4(v);
    if (this.opts.enforceListOnly && v && !this.ipArray.includes(v)) {
      this._setError('❌ 목록에 없는 IP입니다.');
    }
  }

  _handleFocus(){
    if (!this.inputEl.value && this.opts.previewOnFocus) {
      this._renderPanel(this.ipArray.slice(0, this.opts.resultLimit));
      this.showPanel();
    }
  }

  _handleKeydown(e){
    if (this.panelEl.hidden) return;
    const items = this._items();
    if (!items.length) return;

    if (e.key === 'ArrowDown'){ e.preventDefault(); this._move(1); }
    else if (e.key === 'ArrowUp'){ e.preventDefault(); this._move(-1); }
    else if (e.key === 'Enter'){
      if (this.activeIndex >= 0){ e.preventDefault(); this._pick(items[this.activeIndex].dataset.value); }
    } else if (e.key === 'Escape'){ this.hidePanel(); }
  }

  _handleClickOutside(e){
    if (!this.inputEl.closest('.ac-wrap')?.contains(e.target)) this.hidePanel();
  }

  _filterAndRender(query){
    if (!query){
      this.hidePanel();
      return;
    }
    const q = query.toLowerCase();
    let results = this.ipArray.filter(ip => ip.toLowerCase().includes(q));
    if (this.opts.resultLimit > 0) results = results.slice(0, this.opts.resultLimit);
    if (results.length){ this._renderPanel(results); this.showPanel(); }
    else { this.hidePanel(); }
  }

  _renderPanel(list){
    this.panelEl.innerHTML = '';
    this.activeIndex = -1;

    const frag = document.createDocumentFragment();
    list.forEach((ip) => {
      const item = document.createElement('div');
      item.className = 'ac-item';
      item.textContent = ip;
      item.dataset.value = ip;
      item.addEventListener('mousedown', (ev) => { ev.preventDefault(); this._pick(ip); });
      frag.appendChild(item);
    });
    this.panelEl.appendChild(frag);
  }

  _items(){ return Array.from(this.panelEl.querySelectorAll('.ac-item')); }

  _move(delta){
    const items = this._items();
    if (!items.length) return;
    this.activeIndex = (this.activeIndex + delta + items.length) % items.length;
    items.forEach(el => el.classList.remove('active'));
    const el = items[this.activeIndex];
    el.classList.add('active');
    el.scrollIntoView({ block: 'nearest' });
  }

  _pick(value){
    this.inputEl.value = value;
    this.hidePanel();
    this._checkIPv4(value);
  }

  showPanel(){ this.panelEl.hidden = false; }
  hidePanel(){ this.panelEl.hidden = true; this.activeIndex = -1; }

  _checkIPv4(val){
    if (!this.opts.validateIPv4 || !val){ this._setError(''); return; }
    this._setError(this.ipv4Re.test(val) ? '' : '❌ IPv4 형식이 아닙니다.');
  }

  _setError(text){ if (this.errorEl) this.errorEl.textContent = text || ''; }
}

/* ipData(JSON) 읽기: (이미 페이지에 있다면) */
function parseEmbeddedJson(id){
  const el=document.getElementById(id); if(!el) return [];
  let txt=el.textContent||'';
  txt = txt
    .replace(/\/\*[\s\S]*?\*\//g,'')
    .replace(/(^|[^:])\/\/.*$/mg,'$1')
    .replace(/,\s*([}\]])/g,'$1');
  try { const data=JSON.parse(txt); return Array.isArray(data)?data:[]; }
  catch(e){ console.error('ipData parse error',e); return []; }
}

/* 초기화 */
document.addEventListener('DOMContentLoaded', () => {
  // ipData <script>에 서버가 넣어준 배열 사용 (API 호출 없음)
  const ips = parseEmbeddedJson('ipData');

  const ac = new IpAutoComplete('#ipInput', '#ipPanel', ips, {
    validateIPv4: true,
    enforceListOnly: false,
    previewOnFocus: true,
    previewCount: 30,
    resultLimit: 2000   // 너무 많으면 1000~2000 정도로 제한 추천
  });
});