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define([
'../res/ruleImageTemplate.html',
'EventEmitter',
'zepto'
], function (
ruleImageTemplate,
EventEmitter,
$
) {
/**
* Manages the Sortable List interface for reordering rules by drag and drop
* @param {Element} container The DOM element that contains this Summary Widget's view
* @param {string[]} ruleOrder An array of rule IDs representing the current rule order
* @param {Object} rulesById An object mapping rule IDs to rule configurations
*/
function WidgetDnD(container, ruleOrder, rulesById) {
this.container = container;
this.ruleOrder = ruleOrder;
this.rulesById = rulesById;
this.imageContainer = $(ruleImageTemplate);
this.image = $('.t-drag-rule-image', this.imageContainer);
this.draggingId = '';
this.draggingRulePrevious = '';
this.eventEmitter = new EventEmitter();
this.supportedCallbacks = ['drop'];
this.drag = this.drag.bind(this);
this.drop = this.drop.bind(this);
$(this.container).on('mousemove', this.drag);
$(document).on('mouseup', this.drop);
$(this.container).before(this.imageContainer);
$(this.imageContainer).hide();
}
/**
* Remove event listeners registered to elements external to the widget
*/
WidgetDnD.prototype.destroy = function () {
$(this.container).off('mousemove', this.drag);
$(document).off('mouseup', this.drop);
};
/**
* Register a callback with this WidgetDnD: supported callback is drop
* @param {string} event The key for the event to listen to
* @param {function} callback The function that this rule will envoke on this event
* @param {Object} context A reference to a scope to use as the context for
* context for the callback function
*/
WidgetDnD.prototype.on = function (event, callback, context) {
if (this.supportedCallbacks.includes(event)) {
this.eventEmitter.on(event, callback, context || this);
}
};
/**
* Sets the image for the dragged element to the given DOM element
* @param {Element} image The HTML element to set as the drap image
*/
WidgetDnD.prototype.setDragImage = function (image) {
this.image.html(image);
};
/**
* Calculate where this rule has been dragged relative to the other rules
* @param {Event} event The mousemove or mouseup event that triggered this
event handler
* @return {string} The ID of the rule whose drag indicator should be displayed
*/
WidgetDnD.prototype.getDropLocation = function (event) {
const ruleOrder = this.ruleOrder;
const rulesById = this.rulesById;
const draggingId = this.draggingId;
let offset;
let y;
let height;
const dropY = event.pageY;
let target = '';
ruleOrder.forEach(function (ruleId, index) {
offset = rulesById[ruleId].getDOM().offset();
y = offset.top;
height = offset.height;
if (index === 0) {
if (dropY < y + 7 * height / 3) {
target = ruleId;
}
} else if (index === ruleOrder.length - 1 && ruleId !== draggingId) {
if (y + height / 3 < dropY) {
target = ruleId;
}
} else {
if (y + height / 3 < dropY && dropY < y + 7 * height / 3) {
target = ruleId;
}
}
});
return target;
};
/**
* Called by a {Rule} instance that initiates a drag gesture
* @param {string} ruleId The identifier of the rule which is being dragged
*/
WidgetDnD.prototype.dragStart = function (ruleId) {
const ruleOrder = this.ruleOrder;
this.draggingId = ruleId;
this.draggingRulePrevious = ruleOrder[ruleOrder.indexOf(ruleId) - 1];
this.rulesById[this.draggingRulePrevious].showDragIndicator();
this.imageContainer.show();
this.imageContainer.offset({
top: event.pageY - this.image.height() / 2,
left: event.pageX - $('.t-grippy', this.image).width()
});
};
/**
* An event handler for a mousemove event, once a rule has begun a drag gesture
* @param {Event} event The mousemove event that triggered this callback
*/
WidgetDnD.prototype.drag = function (event) {
let dragTarget;
if (this.draggingId && this.draggingId !== '') {
event.preventDefault();
dragTarget = this.getDropLocation(event);
this.imageContainer.offset({
top: event.pageY - this.image.height() / 2,
left: event.pageX - $('.t-grippy', this.image).width()
});
if (this.rulesById[dragTarget]) {
this.rulesById[dragTarget].showDragIndicator();
} else {
this.rulesById[this.draggingRulePrevious].showDragIndicator();
}
}
};
/**
* Handles the mouseup event that corresponds to the user dropping the rule
* in its final location. Invokes any registered drop callbacks with the dragged
* rule's ID and the ID of the target rule that the dragged rule should be
* inserted after
* @param {Event} event The mouseup event that triggered this callback
*/
WidgetDnD.prototype.drop = function (event) {
let dropTarget = this.getDropLocation(event);
const draggingId = this.draggingId;
if (this.draggingId && this.draggingId !== '') {
if (!this.rulesById[dropTarget]) {
dropTarget = this.draggingId;
}
this.eventEmitter.emit('drop', {
draggingId: draggingId,
dropTarget: dropTarget
});
this.draggingId = '';
this.draggingRulePrevious = '';
this.imageContainer.hide();
}
};
return WidgetDnD;
});
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