@baleada/listenable-gestures/lib/handler-getters/pan.js

A collection of gesture recognizers that are compatible with Baleada Logic's Listenable class.

import { emit, toEmitted, storeStartMetadata, storeMoveMetadata, isDefined } from '../util';
/*
 * pan is defined as a single touch that:
 * - starts at given point
 * - travels a distance greater than 0px (or a minimum distance of your choice)
 * - does not cancel or end
 */

var defaultOptions = {
  minDistance: 0 // TODO: research appropriate/accessible minDistance

};
export default function pan() {
  var options = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : {};
  var onStart = options.onStart,
      onMove = options.onMove,
      onCancel = options.onCancel,
      onEnd = options.onEnd,
      minDistance = isDefined(options.minDistance) ? options.minDistance : defaultOptions.minDistance;

  function touchstart(handlerApi) {
    var event = handlerApi.event,
        setMetadata = handlerApi.setMetadata;
    setMetadata({
      path: 'touchTotal',
      value: event.touches.length
    });
    storeStartMetadata(event, handlerApi, 'touch');
    emit(onStart, toEmitted(handlerApi));
  }

  function touchmove(handlerApi) {
    var event = handlerApi.event,
        getMetadata = handlerApi.getMetadata,
        denied = handlerApi.denied;

    if (getMetadata().touchTotal === 1) {
      storeMoveMetadata(event, handlerApi, 'touch');
      recognize(handlerApi);
    } else {
      denied();
    }

    emit(onMove, toEmitted(handlerApi));
  }

  function recognize(_ref) {
    var getMetadata = _ref.getMetadata,
        recognized = _ref.recognized;

    if (getMetadata().distance.fromStart >= minDistance) {
      recognized();
    }
  }

  function touchcancel(handlerApi) {
    var denied = handlerApi.denied;
    denied();
    emit(onCancel, toEmitted(handlerApi));
  }

  function touchend(handlerApi) {
    var denied = handlerApi.denied;
    denied();
    emit(onEnd, toEmitted(handlerApi));
  }

  return {
    touchstart: touchstart,
    touchmove: touchmove,
    touchcancel: touchcancel,
    touchend: touchend
  };
}