/**
 * AKSRT Input Expand
 *
 * Lightweight input field enhancements:
 * - Textarea auto-resize on input
 * - Character counter with limit display
 * - Validation feedback (min/max length, required)
 *
 * No external dependencies — pure vanilla JS.
 *
 * Usage:
 *   <textarea data-aksrt-autoresize></textarea>
 *   <input data-aksrt-counter data-aksrt-maxlength="200">
 *   <input data-aksrt-validate data-aksrt-minlength="3" required>
 *
 * @package AKSRT
 */

(function () {
  'use strict';

  var STYLE_ID = 'aksrt-input-expand-style';

  function injectStyle() {
    if (document.getElementById(STYLE_ID)) return;
    var style = document.createElement('style');
    style.id = STYLE_ID;
    style.textContent =
      '.aksrt-counter{display:block;text-align:right;font-size:12px;color:#8a909c;margin-top:4px;transition:color 0.2s;}' +
      '.aksrt-counter.is-over{color:#e74c3c;}' +
      '.aksrt-counter.is-warn{color:#f39c12;}' +
      '.aksrt-validate-msg{display:block;font-size:12px;margin-top:4px;color:#e74c3c;opacity:0;max-height:0;overflow:hidden;transition:all 0.2s;}' +
      '.aksrt-validate-msg.is-visible{opacity:1;max-height:30px;}' +
      'textarea[data-aksrt-autoresize]{overflow:hidden;resize:none;}';
    document.head.appendChild(style);
  }

  // ── Auto-resize Textarea ──

  function queryAll(root, selector) {
    var nodes = Array.prototype.slice.call(root.querySelectorAll(selector));
    if (root.nodeType === 1 && root.matches(selector)) nodes.unshift(root);
    return nodes;
  }

  function initAutoResize(root) {
    var textareas = queryAll(root, 'textarea[data-aksrt-autoresize]');
    textareas.forEach(function (ta) {
      if (ta.dataset.aksrtAutoresizeBound === '1') return;
      ta.dataset.aksrtAutoresizeBound = '1';
      function resize() {
        ta.style.height = 'auto';
        ta.style.height = ta.scrollHeight + 'px';
      }
      ta.addEventListener('input', resize);
      // Initial resize
      resize();
    });
  }

  // ── Character Counter ──

  function initCounters(root) {
    var fields = queryAll(root, '[data-aksrt-counter]');
    fields.forEach(function (field) {
      if (field.dataset.aksrtCounterBound === '1') return;
      field.dataset.aksrtCounterBound = '1';
      var max = parseInt(field.getAttribute('data-aksrt-maxlength') || field.getAttribute('maxlength') || '0', 10);
      var counter = document.createElement('span');
      counter.className = 'aksrt-counter';
      field.parentNode.insertBefore(counter, field.nextSibling);

      function update() {
        var len = (field.value || '').length;
        if (max > 0) {
          counter.textContent = len + ' / ' + max;
          counter.classList.toggle('is-over', len > max);
          counter.classList.toggle('is-warn', len > max * 0.9 && len <= max);
        } else {
          counter.textContent = len + ' 字';
          counter.classList.remove('is-over', 'is-warn');
        }
      }

      field.addEventListener('input', update);
      update();
    });
  }

  // ── Validation Feedback ──

  function initValidation(root) {
    var fields = queryAll(root, '[data-aksrt-validate]');
    fields.forEach(function (field) {
      if (field.dataset.aksrtValidateBound === '1') return;
      field.dataset.aksrtValidateBound = '1';
      var minLen = parseInt(field.getAttribute('data-aksrt-minlength') || field.getAttribute('minlength') || '0', 10);
      var maxLen = parseInt(field.getAttribute('data-aksrt-maxlength') || field.getAttribute('maxlength') || '0', 10);
      var required = field.hasAttribute('required');

      var msg = document.createElement('span');
      msg.className = 'aksrt-validate-msg';
      field.parentNode.insertBefore(msg, field.nextSibling);

      function validate() {
        var val = (field.value || '').trim();
        var error = '';

        if (required && val === '') {
          error = '此项为必填';
        } else if (minLen > 0 && val.length > 0 && val.length < minLen) {
          error = '至少需要 ' + minLen + ' 个字符';
        } else if (maxLen > 0 && val.length > maxLen) {
          error = '不能超过 ' + maxLen + ' 个字符';
        }

        msg.textContent = error;
        msg.classList.toggle('is-visible', error !== '');
        field.classList.toggle('is-invalid', error !== '');
        field.classList.toggle('is-valid', error === '' && val !== '');
      }

      field.addEventListener('input', validate);
      field.addEventListener('blur', validate);
    });
  }

  // ── Main Init ──

  function init(root) {
    root = root || document;
    injectStyle();
    initAutoResize(root);
    initCounters(root);
    initValidation(root);
  }

  window.AksrtFrontend.register('aksrt-input-expand', init);
})();