/src/actions/drag.js

const is  = require('../utils/is');
const arr = require('../utils/arr');

function init (scope) {
  const {
    actions,
    InteractEvent,
    Interactable,
    Interaction,
    defaults,
  } = scope;

  Interaction.signals.on('before-action-move', beforeMove);
  Interaction.signals.on('action-resume', beforeMove);

  // dragmove
  InteractEvent.signals.on('new', newInteractEvent);

  Interactable.prototype.draggable = module.exports.draggable;

  actions.drag = module.exports;
  actions.names.push('drag');
  arr.merge(Interactable.eventTypes, [
    'dragstart',
    'dragmove',
    'draginertiastart',
    'draginertiaresume',
    'dragend',
  ]);
  actions.methodDict.drag = 'draggable';

  defaults.drag = module.exports.defaults;
}

function beforeMove ({ interaction }) {
  if (interaction.prepared.name !== 'drag') { return; }

  const axis = interaction.prepared.axis;

  if (axis === 'x') {
    interaction.curCoords.page.y   = interaction.startCoords.page.y;
    interaction.curCoords.client.y = interaction.startCoords.client.y;

    interaction.pointerDelta.page.speed   = Math.abs(interaction.pointerDelta.page.vx);
    interaction.pointerDelta.client.speed = Math.abs(interaction.pointerDelta.client.vx);
    interaction.pointerDelta.client.vy = 0;
    interaction.pointerDelta.page.vy   = 0;
  }
  else if (axis === 'y') {
    interaction.curCoords.page.x   = interaction.startCoords.page.x;
    interaction.curCoords.client.x = interaction.startCoords.client.x;

    interaction.pointerDelta.page.speed   = Math.abs(interaction.pointerDelta.page.vy);
    interaction.pointerDelta.client.speed = Math.abs(interaction.pointerDelta.client.vy);
    interaction.pointerDelta.client.vx = 0;
    interaction.pointerDelta.page.vx   = 0;
  }
}

function newInteractEvent ({ iEvent, interaction }) {
  if (iEvent.type !== 'dragmove') { return; }

  const axis = interaction.prepared.axis;

  if (axis === 'x') {
    iEvent.pageY   = interaction.startCoords.page.y;
    iEvent.clientY = interaction.startCoords.client.y;
    iEvent.dy = 0;
  }
  else if (axis === 'y') {
    iEvent.pageX   = interaction.startCoords.page.x;
    iEvent.clientX = interaction.startCoords.client.x;
    iEvent.dx = 0;
  }
}

/**
 * ```js
 * interact(element).draggable({
 *     onstart: function (event) {},
 *     onmove : function (event) {},
 *     onend  : function (event) {},
 *
 *     // the axis in which the first movement must be
 *     // for the drag sequence to start
 *     // 'xy' by default - any direction
 *     startAxis: 'x' || 'y' || 'xy',
 *
 *     // 'xy' by default - don't restrict to one axis (move in any direction)
 *     // 'x' or 'y' to restrict movement to either axis
 *     // 'start' to restrict movement to the axis the drag started in
 *     lockAxis: 'x' || 'y' || 'xy' || 'start',
 *
 *     // max number of drags that can happen concurrently
 *     // with elements of this Interactable. Infinity by default
 *     max: Infinity,
 *
 *     // max number of drags that can target the same element+Interactable
 *     // 1 by default
 *     maxPerElement: 2
 * });
 *
 * var isDraggable = interact('element').draggable(); // true
 * ```
 *
 * Get or set whether drag actions can be performed on the target
 *
 * @alias Interactable.prototype.draggable
 *
 * @param {boolean | object} [options] true/false or An object with event
 * listeners to be fired on drag events (object makes the Interactable
 * draggable)
 * @return {boolean | Interactable} boolean indicating if this can be the
 * target of drag events, or this Interctable
 */
function draggable (options) {
  if (is.object(options)) {
    this.options.drag.enabled = options.enabled === false? false: true;
    this.setPerAction('drag', options);
    this.setOnEvents('drag', options);

    if (/^(xy|x|y|start)$/.test(options.lockAxis)) {
      this.options.drag.lockAxis = options.lockAxis;
    }
    if (/^(xy|x|y)$/.test(options.startAxis)) {
      this.options.drag.startAxis = options.startAxis;
    }

    return this;
  }

  if (is.bool(options)) {
    this.options.drag.enabled = options;

    if (!options) {
      this.ondragstart = this.ondragstart = this.ondragend = null;
    }

    return this;
  }

  return this.options.drag;
}

module.exports = {
  init,
  draggable,
  beforeMove,
  newInteractEvent,
  defaults: {
    startAxis : 'xy',
    lockAxis  : 'xy',
  },

  checker (pointer, event, interactable) {
    const dragOptions = interactable.options.drag;

    return dragOptions.enabled
      ? {
        name: 'drag',
        axis: (dragOptions.lockAxis === 'start'
          ? dragOptions.startAxis
          : dragOptions.lockAxis),
      }
      : null;
  },

  getCursor () {
    return 'move';
  },
};