controllets/draggable-element-controllet/draggable-element-controllet.html

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@license
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    Copyright (c) 2015 Dipartimento di Informatica - Università di Salerno - Italy

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* Developed by :
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<link rel="import" href="../../bower_components/polymer/polymer.html">
<link rel="import" href="../../bower_components/paper-styles/color.html">
<link rel="import" href="../../bower_components/paper-material/paper-material.html">
<link rel="import" href="../../bower_components/paper-fab/paper-fab.html">

<!--
`draggable-element-controllet` is a controllet that represents a draggable element. It can be a target or source. When it's a suorce is possible to drag the content in to a
 container( a draggable-element-controllet with target feature active). When it's a target it manage the drag-and event to get the the text and id value of the source content.
 During the dragging phase all the target border will be emphasize to facilitate the drop phase.

Example:

    SOURCE

    <draggable-element-controllet
       identifier="MyId"
       label="MyLablel">
    </draggable-element-controllet>

    TARGET

    <draggable-element-controllet
       is-target="true"
       heading="MyHeading"
       description="MyDescription"
       number="MyIndex">
    </draggable-element-controllet>


@element draggable-element-controllet
@status beta
@homepage
@group controllets
-->


<dom-module id="draggable-element-controllet">
    <template>

        <style is="custom-style">

            :host{
                font-size: 0.84em;
            }

            .drag-content-target{
                margin-bottom: 6em;
                width: 13.5em;
                font-weight: bolder;
            }

            .drag-content-source{
                height: 1.5em;
                width: 12.5em;
            }

            .draggable-card-source{
                position: relative;
                float: left;
                margin : 0.625em;
                height: 1.5em;
                width: 13.5em;
                border-width : 0.0625em;
                background-color: #e8e8e8;;
                padding: 1em;
                overflow: hidden;
            }

            .draggable-card-target{
                position: relative;
                float: left;
                margin : 0.625em;
                height: 1.5em;
                width: 13.5em;
                border-width : 0.0625em;
                background-color: #2196f3;;
                color: #ffffff;
                padding: 1em;
                overflow: hidden;
            }

            .avatar {
                display: inline-block;
                position: relative;
                float: left;
                height: 2em;
                width: 2em;
                border-radius: 50%;
                background: var(--paper-blue-500);
                color: white;
                line-height: 2em;
                font-size: 0.9375em;
                text-align: center;
            }

            .heading{
                /*width: 12.5em;*/
            }

            .big {
                display: inline-block;
                position: relative;
                float: left;
                font-size: 1em;
                padding: 0.5em 0.25em 0.5em;
                color: var(--google-grey-500);
            }

            .medium {
                font-size: 0.8125em;
                padding-bottom: 0px;
                display: inline-block;
                /*width: 12.5em;*/
            }

            .unselectable {
                -webkit-touch-callout: none;
                -webkit-user-select: none;
                -khtml-user-select: none;
                -moz-user-select: none;
                -ms-user-select: none;
                user-select: none;
            }

            #delete{
                position: relative;
                top: 24px;
                left: 200px;
                width: 24px;
                height: 24px;
                z-index: 1;
                --iron-icon-height: 18px;
                --iron-icon-width: 18px;
                --paper-fab-background:#cccccc;
            }

        </style>

        <template is="dom-if" if="{{isTarget}}">
            <div class="drag-content-target" draggable="false">
                <div class="card-content">
                    <div class="heading">
                        <div class="avatar">{{number}}</div>
                        <div class="big">{{heading}}</div><br>
                    </div>
                    <div class="medium">{{description}}</div>
                </div>
                <paper-fab id="delete" mini icon="clear" on-click="_handleDeleteClick"></paper-fab>
                <paper-material elevation="2" id="target_dragged_identifier" class='draggable-card-target dd-content-target unselectable'>{{label}}</paper-material>
            </div>
        </template>

        <template is="dom-if" if="{{!isTarget}}">
            <div id="source" class="drag-content-source" draggable="true" ondragstart="event.dataTransfer.setData('text/plain', 'This text may be dragged')" on-track="_handleTrack" on-drag="_handleOnDrag" on-dragstart="_handleStartDrag" on-dragenter="_handleEnterDrag">
                <paper-material elevation="2" id="{{identifier}}" class='draggable-card-source unselectable'>{{label}}</paper-material>
            </div>
        </template>

    </template>

    <script>

        Polymer({

            is: 'draggable-element-controllet',

            /**
             * Fired when the user drags a suorce in to a target element.
             *
             * @event draggable-element-controllet_content-dragged
             */

            targets : null,

            properties: {
                /**
                 * It's a boolean flag to give to the controllet the role of target.
                 *
                 * @attribute isTarget
                 * @type Boolean
                 * @default false
                 */
                isTarget : {
                    type : Boolean,
                    value: false
                },
                /**
                 * It's a string value the represent the current number of target. It will be use in the label section.
                 *
                 * @attribute number
                 * @type Strig
                 * @default '0'
                 */
                number: {
                    type: String,
                    value : "1"
                },
                /**
                 * It's the name of the target field
                 *
                 * @attribute heading
                 * @type Strig
                 * @default 'Heading'
                 */
                heading : {
                    type : String,
                    value : "Heading"
                },
                /**
                 * It's the description of the target field
                 *
                 * @attribute description
                 * @type Strig
                 * @default 'Description'
                 */
                description: {
                    type: String,
                    value: "Description"
                },
                /**
                 * It's the value of the source field
                 *
                 * @attribute label
                 * @type Strig
                 * @default 'Label'
                 */
                label : {
                    type : String,
                    value : undefined
                },
                /**
                 * It's the identifier associated to the source field element
                 *
                 * @attribute identifier
                 * @type Strig
                 * @default ''
                 */
                identifier : {
                    type : String,
                    value : ""
                },

                value : {
                    type : String,
                    value : ""
                }

            },

            ready : function(){
            },

            _handleStartDrag : function(e){
                /*var target = EventUtil.getCurrentTarget(e);
                target.style.cursor = 'move';*/
                return true;
            },

            _handleEnterDrag : function(e){
                /*var target = e.target;
                if(target.draggable == false && (target.className.indexOf("dd-content-target") != -1)){

                    target.parentNode.parentNode.value = e.srcElement.id;
                    target.innerHTML = e.srcElement.innerText;

                    this.fire('draggable-element-controllet_content-dragged', {target: target, source: e.srcElement});
                }

                for (var i = 0; i < this.targets.length; i++) {
                    this.targets[i].children[0].children[1].className = "draggable-card dd-content-target unselectable style-scope draggable-element-controllet";
                }*/
                return false;
            },
            /**
             * Callback associated to event on-drag for the source element. When the user is dragging a source element all the target border will be emphasized.
             *
             * @method _handleOnDrag
             *
             * @param {Event} e
             */
            _handleOnDrag : function(e){
                this.targets = document.querySelectorAll('draggable-element-controllet[is-target=true]');
                for (var i = 0; i < this.targets.length; i++) {
                    this.targets[i].children[0].children[2].elevation = "5";
                }

            },
            /**
             * Callback associated to event on-trak for the source element. When the user stops dragging a source element the relative target is recognized and an event will be
             * fired to broadcast to all listeners the information about the current dragging operation.
             *
             * @method _handleTrack
             *
             * @param {Event} e
             */
            _handleTrack : function(e) {

                switch(e.detail.state) {
                    case 'start':
                        break;
                    case 'track':
                        break;
                    case 'end':

                        var target = e.detail.hover();

                        if(target.draggable == false && (target.className.indexOf("dd-content-target") != -1)){

                            target.parentNode.parentNode.value = e.target.id;
                            target.innerHTML = e.target.innerHTML;

                            this.fire('draggable-element-controllet_content-dragged', {target: target, source: e.target});
                        }

                        for (var i = 0; i < this.targets.length; i++) {
                            this.targets[i].children[0].children[2].elevation = "2";
                        }

                        break;
                }
            },
            /**
             * Manage the delete operation of the content.
             *
             * @param e
             * @private
             */
            _handleDeleteClick: function(e){
                this.value = "";
                e.currentTarget.nextElementSibling.innerHTML = "";

                this.fire('draggable-element-controllet_content-dragged', {target: e.target, source: e.target});
            }
        });

    </script>

</dom-module>