<template>

        <svg ref="svg" v-bind:width="thumbnailWidth" v-bind:height="thumbnailHeight">

            <image xmlns:xlink="http://www.w3.org/1999/xlink"

                x="0" y="0"

                v-bind:width="thumbnailWidth" v-bind:height="thumbnailHeight"

                v-bind:xlink:href="image"></image>

            <rect ref="handler"

                class="move-handler"

                v-bind:x="x" v-bind:y="y"

                v-bind:width="width" v-bind:height="height"

                style="fill: black; opacity: 0.4"></rect>

        </svg>

    </div>

</template>

<script>

    import Snap from 'snapsvg'

    export default {

        props: [

            'image',

            'viewport',

            'viewBox',

            'imageWidth',

            'imageHeight',

        ],

        data() {

            return {

                thumbnailWidth: 0,

                thumbnailHeight: 0,

                loaded: false

            }

        },

        computed: {

            x: function() {

                return this.viewBox[0] * this.getRatioX();

            },

            y: function() {

                return this.viewBox[1] * this.getRatioY();

            },

            width: function() {

                return this.viewBox[2] * this.getRatioX();

            },

            height: function() {

                return this.viewBox[3] * this.getRatioY();

            }

        },

        methods: {

            reset: function() {

                var handler = new Snap(this.$refs.handler);

                handler.node.removeAttribute('transform');

            },

            getRatioX: function() {

                if (this.imageWidth === 0) { return 0; }

                return this.thumbnailWidth / this.imageWidth;

            },

            getRatioY: function() {

                if (this.imageHeight === 0) { return 0; }

                return this.thumbnailHeight / this.imageHeight;

            }

        },

        mounted() {

            var svg = new Snap(this.$refs.svg);

            var handler = new Snap(this.$refs.handler);

            var img = new Image();

            img.onload = (e) => {

                var self = this;

                svg.attr({

                    viewBox: [0, 0, img.width, img.height]

                });

                Object.assign(this, {

                    thumbnailWidth: img.width,

                    thumbnailHeight: img.height,

                    loaded: true

                });

                var events = {

                    onMove: function (dx, dy, x, y) {

                        var snapInvMatrix = this.transform().diffMatrix.invert();

                        snapInvMatrix.e = snapInvMatrix.f = 0;

                        var tdx = snapInvMatrix.x(dx, dy);

                        var tdy = snapInvMatrix.y(dx, dy);

                        var transformValue = this.data('origTransform') + (this.data('origTransform') ? "T" : "t") + [tdx, tdy];

                        this.transform(transformValue);

                        self.$emit('change', {

                            x: this.getBBox().x * (self.imageWidth / self.thumbnailWidth),

                            y: this.getBBox().y * (self.imageHeight / self.thumbnailHeight),

                        });

                    },

                    onStart: function () {

                        this.data('origTransform', this.transform().local);

                        self.$emit('dragstart');

                    },

                    onEnd: function () {

                        self.$emit('dragend');

                    }

                }

                handler.drag(events.onMove, events.onStart, events.onEnd);

            }

            img.src = this.image;

        }

    }

</script>

<style scoped>

.move-handler {

    cursor: -moz-grab;

    cursor: -webkit-grab;

    cursor: grab;

}

</style>