/src/actions/drop.js

const actions        = require('./base');
const utils          = require('../utils');
const scope          = require('../scope');
/** @lends module:interact */
const interact       = require('../interact');
const InteractEvent  = require('../InteractEvent');
/** @lends Interactable */
const Interactable   = require('../Interactable');
const Interaction    = require('../Interaction');
const defaultOptions = require('../defaultOptions');

const drop = {
  defaults: {
    enabled: false,
    accept : null,
    overlap: 'pointer',
  },
};

let dynamicDrop = false;

Interaction.signals.on('action-start', function ({ interaction, event }) {
  if (interaction.prepared.name !== 'drag') { return; }

  // reset active dropzones
  interaction.activeDrops.dropzones = [];
  interaction.activeDrops.elements  = [];
  interaction.activeDrops.rects     = [];

  interaction.dropEvents = null;

  if (!interaction.dynamicDrop) {
    setActiveDrops(interaction, interaction.element);
  }

  const dragEvent = interaction.prevEvent;
  const dropEvents = getDropEvents(interaction, event, dragEvent);

  if (dropEvents.activate) {
    fireActiveDrops(interaction, dropEvents.activate);
  }
});

InteractEvent.signals.on('new', function ({ interaction, iEvent, event }) {
  if (iEvent.type !== 'dragmove' && iEvent.type !== 'dragend') { return; }

  const draggableElement = interaction.element;
  const dragEvent = iEvent;
  const dropResult = getDrop(dragEvent, event, draggableElement);

  interaction.dropTarget  = dropResult.dropzone;
  interaction.dropElement = dropResult.element;

  interaction.dropEvents = getDropEvents(interaction, event, dragEvent);
});

Interaction.signals.on('action-move', function ({ interaction }) {
  if (interaction.prepared.name !== 'drag') { return; }

  fireDropEvents(interaction, interaction.dropEvents);
});

Interaction.signals.on('action-end', function ({ interaction }) {
  if (interaction.prepared.name === 'drag') {
    fireDropEvents(interaction, interaction.dropEvents);
  }
});

Interaction.signals.on('stop-drag', function ({ interaction }) {
  interaction.activeDrops.dropzones =
    interaction.activeDrops.elements =
    interaction.activeDrops.rects =
    interaction.dropEvents = null;
});

function collectDrops (interaction, element) {
  const drops = [];
  const elements = [];

  element = element || interaction.element;

  // collect all dropzones and their elements which qualify for a drop
  for (const current of scope.interactables) {
    if (!current.options.drop.enabled) { continue; }

    const accept = current.options.drop.accept;

    // test the draggable element against the dropzone's accept setting
    if ((utils.is.element(accept) && accept !== element)
        || (utils.is.string(accept)
        && !utils.matchesSelector(element, accept))) {

      continue;
    }

    // query for new elements if necessary
    const dropElements = utils.is.string(current.target)
      ? current._context.querySelectorAll(current.target)
      : [current.target];

    for (const currentElement of dropElements) {
      if (currentElement !== element) {
        drops.push(current);
        elements.push(currentElement);
      }
    }
  }

  return {
    elements,
    dropzones: drops,
  };
}

function fireActiveDrops (interaction, event) {
  let prevElement;

  // loop through all active dropzones and trigger event
  for (let i = 0; i < interaction.activeDrops.dropzones.length; i++) {
    const current = interaction.activeDrops.dropzones[i];
    const currentElement = interaction.activeDrops.elements [i];

    // prevent trigger of duplicate events on same element
    if (currentElement !== prevElement) {
      // set current element as event target
      event.target = currentElement;
      current.fire(event);
    }
    prevElement = currentElement;
  }
}

// Collect a new set of possible drops and save them in activeDrops.
// setActiveDrops should always be called when a drag has just started or a
// drag event happens while dynamicDrop is true
function setActiveDrops (interaction, dragElement) {
  // get dropzones and their elements that could receive the draggable
  const possibleDrops = collectDrops(interaction, dragElement, true);

  interaction.activeDrops.dropzones = possibleDrops.dropzones;
  interaction.activeDrops.elements  = possibleDrops.elements;
  interaction.activeDrops.rects     = [];

  for (let i = 0; i < interaction.activeDrops.dropzones.length; i++) {
    interaction.activeDrops.rects[i] =
      interaction.activeDrops.dropzones[i].getRect(interaction.activeDrops.elements[i]);
  }
}

function getDrop (dragEvent, event, dragElement) {
  const interaction = dragEvent.interaction;
  const validDrops = [];

  if (dynamicDrop) {
    setActiveDrops(interaction, dragElement);
  }

  // collect all dropzones and their elements which qualify for a drop
  for (let j = 0; j < interaction.activeDrops.dropzones.length; j++) {
    const current        = interaction.activeDrops.dropzones[j];
    const currentElement = interaction.activeDrops.elements [j];
    const rect           = interaction.activeDrops.rects    [j];

    validDrops.push(current.dropCheck(dragEvent, event, interaction.target, dragElement, currentElement, rect)
      ? currentElement
      : null);
  }

  // get the most appropriate dropzone based on DOM depth and order
  const dropIndex = utils.indexOfDeepestElement(validDrops);

  return {
    dropzone: interaction.activeDrops.dropzones[dropIndex] || null,
    element : interaction.activeDrops.elements [dropIndex] || null,
  };
}

function getDropEvents (interaction, pointerEvent, dragEvent) {
  const dropEvents = {
    enter     : null,
    leave     : null,
    activate  : null,
    deactivate: null,
    move      : null,
    drop      : null,
  };

  const tmpl = {
    dragEvent,
    interaction,
    target       : interaction.dropElement,
    dropzone     : interaction.dropTarget,
    relatedTarget: dragEvent.target,
    draggable    : dragEvent.interactable,
    timeStamp    : dragEvent.timeStamp,
  };

  if (interaction.dropElement !== interaction.prevDropElement) {
    // if there was a prevDropTarget, create a dragleave event
    if (interaction.prevDropTarget) {
      dropEvents.leave = utils.extend({ type: 'dragleave' }, tmpl);

      dragEvent.dragLeave    = dropEvents.leave.target   = interaction.prevDropElement;
      dragEvent.prevDropzone = dropEvents.leave.dropzone = interaction.prevDropTarget;
    }
    // if the dropTarget is not null, create a dragenter event
    if (interaction.dropTarget) {
      dropEvents.enter = {
        dragEvent,
        interaction,
        target       : interaction.dropElement,
        dropzone     : interaction.dropTarget,
        relatedTarget: dragEvent.target,
        draggable    : dragEvent.interactable,
        timeStamp    : dragEvent.timeStamp,
        type         : 'dragenter',
      };

      dragEvent.dragEnter = interaction.dropElement;
      dragEvent.dropzone = interaction.dropTarget;
    }
  }

  if (dragEvent.type === 'dragend' && interaction.dropTarget) {
    dropEvents.drop = utils.extend({ type: 'drop' }, tmpl);

    dragEvent.dropzone = interaction.dropTarget;
    dragEvent.relatedTarget = interaction.dropElement;
  }
  if (dragEvent.type === 'dragstart') {
    dropEvents.activate = utils.extend({ type: 'dropactivate' }, tmpl);

    dropEvents.activate.target   = null;
    dropEvents.activate.dropzone = null;
  }
  if (dragEvent.type === 'dragend') {
    dropEvents.deactivate = utils.extend({ type: 'dropdeactivate' }, tmpl);

    dropEvents.deactivate.target   = null;
    dropEvents.deactivate.dropzone = null;
  }
  if (dragEvent.type === 'dragmove' && interaction.dropTarget) {
    dropEvents.move = utils.extend({
      dragmove     : dragEvent,
      type         : 'dropmove',
    }, tmpl);

    dragEvent.dropzone = interaction.dropTarget;
  }

  return dropEvents;
}

function fireDropEvents (interaction, dropEvents) {
  if (dropEvents.leave) { interaction.prevDropTarget.fire(dropEvents.leave); }
  if (dropEvents.move ) {     interaction.dropTarget.fire(dropEvents.move ); }
  if (dropEvents.enter) {     interaction.dropTarget.fire(dropEvents.enter); }
  if (dropEvents.drop ) {     interaction.dropTarget.fire(dropEvents.drop ); }
  if (dropEvents.deactivate) {
    fireActiveDrops(interaction, dropEvents.deactivate);
  }

  interaction.prevDropTarget  = interaction.dropTarget;
  interaction.prevDropElement = interaction.dropElement;
}

/**
 * ```js
 * interact(target)
 * .dropChecker(function(dragEvent,         // related dragmove or dragend event
 *                       event,             // TouchEvent/PointerEvent/MouseEvent
 *                       dropped,           // bool result of the default checker
 *                       dropzone,          // dropzone Interactable
 *                       dropElement,       // dropzone elemnt
 *                       draggable,         // draggable Interactable
 *                       draggableElement) {// draggable element
 *
 *   return dropped && event.target.hasAttribute('allow-drop');
 * }
 * ```
 *
 * ```js
 * interact('.drop').dropzone({
 *   accept: '.can-drop' || document.getElementById('single-drop'),
 *   overlap: 'pointer' || 'center' || zeroToOne
 * }
 * ```
 *
 * Returns or sets whether draggables can be dropped onto this target to
 * trigger drop events
 *
 * Dropzones can receive the following events:
 *  - `dropactivate` and `dropdeactivate` when an acceptable drag starts and ends
 *  - `dragenter` and `dragleave` when a draggable enters and leaves the dropzone
 *  - `dragmove` when a draggable that has entered the dropzone is moved
 *  - `drop` when a draggable is dropped into this dropzone
 *
 * Use the `accept` option to allow only elements that match the given CSS
 * selector or element. The value can be:
 *
 *  - **an Element** - only that element can be dropped into this dropzone.
 *  - **a string**, - the element being dragged must match it as a CSS selector.
 *  - **`null`** - accept options is cleared - it accepts any element.
 *
 * Use the `overlap` option to set how drops are checked for. The allowed
 * values are:
 *
 *   - `'pointer'`, the pointer must be over the dropzone (default)
 *   - `'center'`, the draggable element's center must be over the dropzone
 *   - a number from 0-1 which is the `(intersection area) / (draggable area)`.
 *   e.g. `0.5` for drop to happen when half of the area of the draggable is
 *   over the dropzone
 *
 * Use the `checker` option to specify a function to check if a dragged element
 * is over this Interactable.
 *
 * @param {boolean | object | null} [options] The new options to be set.
 * @return {boolean | Interactable} The current setting or this Interactable
 */
Interactable.prototype.dropzone = function (options) {
  if (utils.is.object(options)) {
    this.options.drop.enabled = options.enabled === false? false: true;

    if (utils.is.function(options.ondrop)          ) { this.events.ondrop           = options.ondrop          ; }
    if (utils.is.function(options.ondropactivate)  ) { this.events.ondropactivate   = options.ondropactivate  ; }
    if (utils.is.function(options.ondropdeactivate)) { this.events.ondropdeactivate = options.ondropdeactivate; }
    if (utils.is.function(options.ondragenter)     ) { this.events.ondragenter      = options.ondragenter     ; }
    if (utils.is.function(options.ondragleave)     ) { this.events.ondragleave      = options.ondragleave     ; }
    if (utils.is.function(options.ondropmove)      ) { this.events.ondropmove       = options.ondropmove      ; }

    if (/^(pointer|center)$/.test(options.overlap)) {
      this.options.drop.overlap = options.overlap;
    }
    else if (utils.is.number(options.overlap)) {
      this.options.drop.overlap = Math.max(Math.min(1, options.overlap), 0);
    }
    if ('accept' in options) {
      this.options.drop.accept = options.accept;
    }
    if ('checker' in options) {
      this.options.drop.checker = options.checker;
    }


    return this;
  }

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

    if (!options) {
      this.ondragenter = this.ondragleave = this.ondrop
        = this.ondropactivate = this.ondropdeactivate = null;
    }

    return this;
  }

  return this.options.drop;
};

Interactable.prototype.dropCheck = function (dragEvent, event, draggable, draggableElement, dropElement, rect) {
  let dropped = false;

  // if the dropzone has no rect (eg. display: none)
  // call the custom dropChecker or just return false
  if (!(rect = rect || this.getRect(dropElement))) {
    return (this.options.drop.checker
      ? this.options.drop.checker(dragEvent, event, dropped, this, dropElement, draggable, draggableElement)
      : false);
  }

  const dropOverlap = this.options.drop.overlap;

  if (dropOverlap === 'pointer') {
    const origin = utils.getOriginXY(draggable, draggableElement, 'drag');
    const page = utils.getPageXY(dragEvent);

    page.x += origin.x;
    page.y += origin.y;

    const horizontal = (page.x > rect.left) && (page.x < rect.right);
    const vertical   = (page.y > rect.top ) && (page.y < rect.bottom);

    dropped = horizontal && vertical;
  }

  const dragRect = draggable.getRect(draggableElement);

  if (dragRect && dropOverlap === 'center') {
    const cx = dragRect.left + dragRect.width  / 2;
    const cy = dragRect.top  + dragRect.height / 2;

    dropped = cx >= rect.left && cx <= rect.right && cy >= rect.top && cy <= rect.bottom;
  }

  if (dragRect && utils.is.number(dropOverlap)) {
    const overlapArea  = (Math.max(0, Math.min(rect.right , dragRect.right ) - Math.max(rect.left, dragRect.left))
                          * Math.max(0, Math.min(rect.bottom, dragRect.bottom) - Math.max(rect.top , dragRect.top )));

    const overlapRatio = overlapArea / (dragRect.width * dragRect.height);

    dropped = overlapRatio >= dropOverlap;
  }

  if (this.options.drop.checker) {
    dropped = this.options.drop.checker(dragEvent, event, dropped, this, dropElement, draggable, draggableElement);
  }

  return dropped;
};

Interactable.signals.on('unset', function ({ interactable }) {
  interactable.dropzone(false);
});

Interactable.settingsMethods.push('dropChecker');

Interaction.signals.on('new', function (interaction) {
  interaction.dropTarget      = null; // the dropzone a drag target might be dropped into
  interaction.dropElement     = null; // the element at the time of checking
  interaction.prevDropTarget  = null; // the dropzone that was recently dragged away from
  interaction.prevDropElement = null; // the element at the time of checking
  interaction.dropEvents      = null; // the dropEvents related to the current drag event

  interaction.activeDrops = {
    dropzones: [],      // the dropzones that are mentioned below
    elements : [],      // elements of dropzones that accept the target draggable
    rects    : [],      // the rects of the elements mentioned above
  };

});

Interaction.signals.on('stop', function ({ interaction }) {
  interaction.dropTarget = interaction.dropElement =
    interaction.prevDropTarget = interaction.prevDropElement = null;
});

/**
 * Returns or sets whether the dimensions of dropzone elements are calculated
 * on every dragmove or only on dragstart for the default dropChecker
 *
 * @param {boolean} [newValue] True to check on each move. False to check only
 * before start
 * @return {boolean | interact} The current setting or interact
 */
interact.dynamicDrop = function (newValue) {
  if (utils.is.bool(newValue)) {
    //if (dragging && dynamicDrop !== newValue && !newValue) {
      //calcRects(dropzones);
    //}

    dynamicDrop = newValue;

    return interact;
  }
  return dynamicDrop;
};

utils.merge(Interactable.eventTypes, [
  'dragenter',
  'dragleave',
  'dropactivate',
  'dropdeactivate',
  'dropmove',
  'drop',
]);
actions.methodDict.drop = 'dropzone';

defaultOptions.drop = drop.defaults;

module.exports = drop;