var scanner = (function() {
  var _callback = null;
  var _allow_raw = true;
  var _allowed_types = null;
  var _camera = null;
  var _modal = null;
  var _buffer = '';
  var _last_key_ts = 0;
  var _max_key_gap = 0;
  var _HW_THRESHOLD = 50;

  function _on_paste(e) {
    if (!_callback) return;
    var el = document.activeElement;
    if (el && el.tagName === 'TEXTAREA') return;
    var text = ((e.originalEvent || e).clipboardData || window.clipboardData).getData('text');
    if (!text) return;
    text = text.trim();
    if (text.length < 3) return;
    e.preventDefault();
    _resolve(text);
  }

  function _on_keydown(e) {
    var now = Date.now();
    var gap = now - _last_key_ts;

    if (gap > 500) {
      _buffer = '';
      _max_key_gap = 0;
    } else if (_buffer.length > 0) {
      _max_key_gap = Math.max(_max_key_gap, gap);
    }
    _last_key_ts = now;

    if (e.key === 'Enter' && _buffer.length >= 3) {
      var barcode = _buffer;
      var is_scanner_input = _max_key_gap <= _HW_THRESHOLD;
      _buffer = '';
      _max_key_gap = 0;
      if (is_scanner_input) {
        e.preventDefault();
        _remove_typed_barcode(barcode);
        _resolve(barcode);
      }
      return;
    }

    if (e.key.length === 1) {
      _buffer += e.key;
    }
  }

  function _remove_typed_barcode(barcode) {
    var el = document.activeElement;
    if (!el || !('value' in el)) return;
    if (el.tagName !== 'INPUT' && el.tagName !== 'TEXTAREA') return;

    var value = String(el.value || '');
    if (!value.endsWith(barcode)) return;
    el.value = value.slice(0, value.length - barcode.length);
    $(el).trigger('input');
  }

  function _resolve(barcode) {
    if (!barcode || !_callback) return;

    $.ajax({
      url: server_url + 'ics/api/engine/barcode_lookup.php',
      type: 'POST',
      dataType: 'json',
      data: { json: JSON.stringify({ barcode: barcode, action: 'read' }) },
      headers: { 'X-CSRF-TOKEN': $('meta[name="csrf-token"]').attr('content') },
      success: function(res) {
        if (res && res.success) {
          if ((!_allow_raw && res.type === 'raw') || (_allowed_types && _allowed_types.indexOf(res.type) === -1)) {
            _show_error('This page only accepts generated barcode labels.');
            return;
          }
          _callback(res.sku || '', res.product_name || '', res.uom || '', res);
          return;
        }
        _show_error('Barcode not found: ' + barcode);
      },
      error: function(xhr) {
        var msg = xhr.responseJSON && xhr.responseJSON.message ? xhr.responseJSON.message : 'Scanner error. Please try again.';
        _show_error(msg === 'Barcode not found.' ? 'Barcode not found: ' + barcode : msg);
      }
    });
  }

  function _build_modal() {
    if (_modal) return;
    $('body').append(`
      <div class="modal fade" id="scanner_modal" tabindex="-1" aria-hidden="true">
        <div class="modal-dialog modal-dialog-centered">
          <div class="modal-content">
            <div class="modal-header">
              <h5 class="modal-title"><i class="ti ti-scan me-2"></i>Scan Barcode</h5>
              <button type="button" class="btn-close" data-bs-dismiss="modal"></button>
            </div>
            <div class="modal-body">
              <div id="scanner_qr_reader"></div>
              <div id="scanner_error" class="alert alert-danger mt-3 d-none"></div>
            </div>
          </div>
        </div>
      </div>`);
    _modal = new bootstrap.Modal(document.getElementById('scanner_modal'));
    document.getElementById('scanner_modal').addEventListener('hidden.bs.modal', _stop_camera);
  }

  function _start_camera() {
    if (_camera) return;
    if (typeof Html5Qrcode === 'undefined') {
      _show_error('Camera scanner library is not available.');
      return;
    }
    _camera = new Html5Qrcode('scanner_qr_reader');
    _camera.start(
      { facingMode: 'environment' },
      { fps: 10, qrbox: { width: 250, height: 120 } },
      function(decodedText) {
        _modal.hide();
        _resolve(decodedText);
      },
      function() {}
    ).catch(function(err) {
      _show_error('Camera error: ' + err);
    });
  }

  function _stop_camera() {
    if (!_camera) return;
    _camera.stop().catch(function() {}).finally(function() {
      _camera = null;
    });
  }

  function _show_error(msg) {
    var $err = $('#scanner_error');
    if ($err.length) {
      $err.text(msg).removeClass('d-none');
      setTimeout(function() { $err.addClass('d-none'); }, 3000);
      return;
    }
    if (typeof bootbox !== 'undefined') bootbox.alert(msg);
  }

  return {
    init: function(options) {
      options = options || {};
      _callback = options.onScan || null;
      _allow_raw = options.allowRaw !== false;
      _allowed_types = Array.isArray(options.allowedTypes) ? options.allowedTypes : null;
      document.removeEventListener('keydown', _on_keydown);
      document.removeEventListener('paste', _on_paste);
      document.addEventListener('keydown', _on_keydown);
      document.addEventListener('paste', _on_paste);
      _build_modal();
    },
    open_camera: function() {
      if (!_modal) _build_modal();
      _modal.show();
      setTimeout(_start_camera, 400);
    },
    destroy: function() {
      document.removeEventListener('keydown', _on_keydown);
      document.removeEventListener('paste', _on_paste);
      _stop_camera();
    }
  };
})();