<template>
    <div :class="containerClass" @click="onBarClick">
        <span class="p-slider-range" :style="rangeStyle"></span>
        <span
            v-if="!range"
            class="p-slider-handle"
            :style="handleStyle"
            @touchstart="onDragStart($event)"
            @touchmove="onDrag($event)"
            @touchend="onDragEnd($event)"
            @mousedown="onMouseDown($event)"
            @keydown="onKeyDown($event)"
            :tabindex="tabindex"
            role="slider"
            :aria-valuemin="min"
            :aria-valuenow="modelValue"
            :aria-valuemax="max"
            :aria-labelledby="ariaLabelledby"
            :aria-label="ariaLabel"
            :aria-orientation="orientation"
        ></span>
        <span
            v-if="range"
            class="p-slider-handle"
            :style="rangeStartHandleStyle"
            @touchstart="onDragStart($event, 0)"
            @touchmove="onDrag($event)"
            @touchend="onDragEnd($event)"
            @mousedown="onMouseDown($event, 0)"
            @keydown="onKeyDown($event, 0)"
            :tabindex="tabindex"
            role="slider"
            :aria-valuemin="min"
            :aria-valuenow="modelValue ? modelValue[0] : null"
            :aria-valuemax="max"
            :aria-labelledby="ariaLabelledby"
            :aria-label="ariaLabel"
            :aria-orientation="orientation"
        ></span>
        <span
            v-if="range"
            class="p-slider-handle"
            :style="rangeEndHandleStyle"
            @touchstart="onDragStart($event, 1)"
            @touchmove="onDrag($event)"
            @touchend="onDragEnd($event)"
            @mousedown="onMouseDown($event, 1)"
            @keydown="onKeyDown($event, 1)"
            :tabindex="tabindex"
            role="slider"
            :aria-valuemin="min"
            :aria-valuenow="modelValue ? modelValue[1] : null"
            :aria-valuemax="max"
            :aria-labelledby="ariaLabelledby"
            :aria-label="ariaLabel"
            :aria-orientation="orientation"
        ></span>
    </div>
</template>

<script>
import { DomHandler } from 'primevue/utils';

export default {
    name: 'Slider',
    emits: ['update:modelValue', 'change', 'slideend'],
    props: {
        modelValue: [Number, Array],
        min: {
            type: Number,
            default: 0
        },
        max: {
            type: Number,
            default: 100
        },
        orientation: {
            type: String,
            default: 'horizontal'
        },
        step: {
            type: Number,
            default: null
        },
        range: {
            type: Boolean,
            default: false
        },
        disabled: {
            type: Boolean,
            default: false
        },
        tabindex: {
            type: Number,
            default: 0
        },
        'aria-labelledby': {
            type: String,
            default: null
        },
        'aria-label': {
            type: String,
            default: null
        }
    },
    dragging: false,
    handleIndex: null,
    initX: null,
    initY: null,
    barWidth: null,
    barHeight: null,
    dragListener: null,
    dragEndListener: null,
    beforeUnmount() {
        this.unbindDragListeners();
    },
    methods: {
        updateDomData() {
            let rect = this.$el.getBoundingClientRect();

            this.initX = rect.left + DomHandler.getWindowScrollLeft();
            this.initY = rect.top + DomHandler.getWindowScrollTop();
            this.barWidth = this.$el.offsetWidth;
            this.barHeight = this.$el.offsetHeight;
        },
        setValue(event) {
            let handleValue;
            let pageX = event.touches ? event.touches[0].pageX : event.pageX;
            let pageY = event.touches ? event.touches[0].pageY : event.pageY;

            if (this.orientation === 'horizontal') handleValue = ((pageX - this.initX) * 100) / this.barWidth;
            else handleValue = ((this.initY + this.barHeight - pageY) * 100) / this.barHeight;
            let newValue = (this.max - this.min) * (handleValue / 100) + this.min;

            if (this.step) {
                const oldValue = this.range ? this.modelValue[this.handleIndex] : this.modelValue;
                const diff = newValue - oldValue;

                if (diff < 0) newValue = oldValue + Math.ceil(newValue / this.step - oldValue / this.step) * this.step;
                else if (diff > 0) newValue = oldValue + Math.floor(newValue / this.step - oldValue / this.step) * this.step;
            } else {
                newValue = Math.floor(newValue);
            }

            this.updateModel(event, newValue);
        },
        updateModel(event, value) {
            let newValue = parseFloat(value.toFixed(10));
            let modelValue;

            if (this.range) {
                modelValue = this.modelValue ? [...this.modelValue] : [];

                if (this.handleIndex == 0) {
                    if (newValue < this.min) newValue = this.min;
                    else if (newValue >= this.max) newValue = this.max;

                    if (newValue > modelValue[1]) {
                        modelValue[1] = newValue;

                        this.handleIndex = 1;
                    } else {
                        modelValue[0] = newValue;
                    }
                } else {
                    if (newValue > this.max) newValue = this.max;
                    else if (newValue <= this.min) newValue = this.min;

                    if (newValue < modelValue[0]) {
                        modelValue[0] = newValue;

                        this.handleIndex = 0;
                    } else {
                        modelValue[1] = newValue;
                    }
                }
            } else {
                if (newValue < this.min) newValue = this.min;
                else if (newValue > this.max) newValue = this.max;

                modelValue = newValue;
            }

            this.$emit('update:modelValue', modelValue);
            this.$emit('change', modelValue);
        },
        onDragStart(event, index) {
            if (this.disabled) {
                return;
            }

            DomHandler.addClass(this.$el, 'p-slider-sliding');
            this.dragging = true;
            this.updateDomData();

            if (this.range && this.modelValue[0] === this.max) {
                this.handleIndex = 0;
            } else {
                this.handleIndex = index;
            }

            event.preventDefault();
        },
        onDrag(event) {
            if (this.dragging) {
                this.setValue(event);
                event.preventDefault();
            }
        },
        onDragEnd(event) {
            if (this.dragging) {
                this.dragging = false;
                DomHandler.removeClass(this.$el, 'p-slider-sliding');
                this.$emit('slideend', { originalEvent: event, value: this.modelValue });
            }
        },
        onBarClick(event) {
            if (this.disabled) {
                return;
            }

            if (!DomHandler.hasClass(event.target, 'p-slider-handle')) {
                this.updateDomData();
                this.setValue(event);
            }
        },
        onMouseDown(event, index) {
            this.bindDragListeners();
            this.onDragStart(event, index);
        },
        onKeyDown(event, index) {
            this.handleIndex = index;

            switch (event.code) {
                case 'ArrowDown':
                case 'ArrowLeft':
                    this.decrementValue(event, index);
                    event.preventDefault();
                    break;

                case 'ArrowUp':
                case 'ArrowRight':
                    this.incrementValue(event, index);
                    event.preventDefault();
                    break;

                case 'PageDown':
                    this.decrementValue(event, index, true);
                    event.preventDefault();
                    break;

                case 'PageUp':
                    this.incrementValue(event, index, true);
                    event.preventDefault();
                    break;

                case 'Home':
                    this.updateModel(event, this.min);
                    event.preventDefault();
                    break;

                case 'End':
                    this.updateModel(event, this.max);
                    event.preventDefault();
                    break;

                default:
                    break;
            }
        },
        decrementValue(event, index, pageKey = false) {
            let newValue;

            if (this.range) {
                if (this.step) newValue = this.modelValue[index] - this.step;
                else newValue = this.modelValue[index] - 1;
            } else {
                if (this.step) newValue = this.modelValue - this.step;
                else if (!this.step && pageKey) newValue = this.modelValue - 10;
                else newValue = this.modelValue - 1;
            }

            this.updateModel(event, newValue);
            event.preventDefault();
        },
        incrementValue(event, index, pageKey = false) {
            let newValue;

            if (this.range) {
                if (this.step) newValue = this.modelValue[index] + this.step;
                else newValue = this.modelValue[index] + 1;
            } else {
                if (this.step) newValue = this.modelValue + this.step;
                else if (!this.step && pageKey) newValue = this.modelValue + 10;
                else newValue = this.modelValue + 1;
            }

            this.updateModel(event, newValue);
            event.preventDefault();
        },
        bindDragListeners() {
            if (!this.dragListener) {
                this.dragListener = this.onDrag.bind(this);
                document.addEventListener('mousemove', this.dragListener);
            }

            if (!this.dragEndListener) {
                this.dragEndListener = this.onDragEnd.bind(this);
                document.addEventListener('mouseup', this.dragEndListener);
            }
        },
        unbindDragListeners() {
            if (this.dragListener) {
                document.removeEventListener('mousemove', this.dragListener);
                this.dragListener = null;
            }

            if (this.dragEndListener) {
                document.removeEventListener('mouseup', this.dragEndListener);
                this.dragEndListener = null;
            }
        }
    },
    computed: {
        containerClass() {
            return [
                'p-slider p-component',
                {
                    'p-disabled': this.disabled,
                    'p-slider-horizontal': this.orientation === 'horizontal',
                    'p-slider-vertical': this.orientation === 'vertical'
                }
            ];
        },
        horizontal() {
            return this.orientation === 'horizontal';
        },
        vertical() {
            return this.orientation === 'vertical';
        },
        rangeStyle() {
            if (this.range) {
                const rangeSliderWidth = this.rangeEndPosition > this.rangeStartPosition ? this.rangeEndPosition - this.rangeStartPosition : this.rangeStartPosition - this.rangeEndPosition;
                const rangeSliderPosition = this.rangeEndPosition > this.rangeStartPosition ? this.rangeStartPosition : this.rangeEndPosition;

                if (this.horizontal) return { left: rangeSliderPosition + '%', width: rangeSliderWidth + '%' };
                else return { bottom: rangeSliderPosition + '%', height: rangeSliderWidth + '%' };
            } else {
                if (this.horizontal) return { width: this.handlePosition + '%' };
                else return { height: this.handlePosition + '%' };
            }
        },
        handleStyle() {
            if (this.horizontal) return { left: this.handlePosition + '%' };
            else return { bottom: this.handlePosition + '%' };
        },
        handlePosition() {
            if (this.modelValue < this.min) return 0;
            else if (this.modelValue > this.max) return 100;
            else return ((this.modelValue - this.min) * 100) / (this.max - this.min);
        },
        rangeStartPosition() {
            if (this.modelValue && this.modelValue[0]) return ((this.modelValue[0] < this.min ? 0 : this.modelValue[0] - this.min) * 100) / (this.max - this.min);
            else return 0;
        },
        rangeEndPosition() {
            if (this.modelValue && this.modelValue.length === 2) return ((this.modelValue[1] > this.max ? 100 : this.modelValue[1] - this.min) * 100) / (this.max - this.min);
            else return 100;
        },
        rangeStartHandleStyle() {
            if (this.horizontal) return { left: this.rangeStartPosition + '%' };
            else return { bottom: this.rangeStartPosition + '%' };
        },
        rangeEndHandleStyle() {
            if (this.horizontal) return { left: this.rangeEndPosition + '%' };
            else return { bottom: this.rangeEndPosition + '%' };
        }
    }
};
</script>

<style>
.p-slider {
    position: relative;
}

.p-slider .p-slider-handle {
    position: absolute;
    cursor: grab;
    touch-action: none;
    display: block;
}

.p-slider-range {
    position: absolute;
    display: block;
}

.p-slider-horizontal .p-slider-range {
    top: 0;
    left: 0;
    height: 100%;
}

.p-slider-horizontal .p-slider-handle {
    top: 50%;
}

.p-slider-vertical {
    height: 100px;
}

.p-slider-vertical .p-slider-handle {
    left: 50%;
}

.p-slider-vertical .p-slider-range {
    bottom: 0;
    left: 0;
    width: 100%;
}
</style>
