feat(component): add Slider

Closes #26

src/components/Slider/Slider.Skeleton.svelte

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+<script>
+  let className = undefined;
+  export { className as class };
+  export let hideLabel = false;
+  export let style = undefined;
+
+  import { cx } from '../../lib';
+</script>
+
+<div on:click on:mouseover on:mouseenter on:mouseleave class={cx('--form-item', className)} {style}>
+  {#if !hideLabel}
+    <span class={cx('--label', '--skeleton')} />
+  {/if}
+  <div class={cx('--slider-container', '--skeleton')}>
+    <span class={cx('--slider__range-label')} />
+    <div class={cx('--slider')}>
+      <div class={cx('--slider__track')} />
+      <div class={cx('--slider__filled-track')} />
+      <div class={cx('--slider__thumb')} />
+    </div>
+    <span class={cx('--slider__range-label')} />
+  </div>
+</div>

src/components/Slider/Slider.Story.svelte

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+<script>
+  export let story = undefined;
+
+  import Layout from '../../internal/ui/Layout.svelte';
+  import Slider from './Slider.svelte';
+  import SliderSkeleton from './Slider.Skeleton.svelte';
+
+  let value = 50;
+</script>
+
+<Layout>
+  {#if story === 'skeleton'}
+    <SliderSkeleton {...$$props} />
+  {:else}
+    <Slider
+      {...$$props}
+      id="slider"
+      bind:value
+      on:change={({ detail }) => {
+        console.log('on:change', detail);
+      }} />
+  {/if}
+</Layout>

src/components/Slider/Slider.stories.js

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+import { withKnobs, text, boolean, number } from '@storybook/addon-knobs';
+import Component from './Slider.Story.svelte';
+
+export default { title: 'Slider', decorators: [withKnobs] };
+
+export const Default = () => ({
+  Component,
+  props: {
+    name: text('Form item name (name)', ''),
+    inputType: text('The form element type (inputType)', 'number'),
+    ariaLabelInput: text(
+      'The ARIA label for the <input> (ariaLabelInput)',
+      'Label for slider value'
+    ),
+    disabled: boolean('Disabled (disabled)', false),
+    light: boolean('Light variant (light)', false),
+    hideTextInput: boolean('Without text input (hideTextInput)', false),
+    min: number('The minimum value (min)', 0),
+    max: number('The maximum value (max)', 100),
+    step: number('The step (step)', 1),
+    stepMuliplier: number('The step factor for Shift+arrow keys (stepMuliplier)', 4),
+    labelText: text('Label text (labelText)', 'Slider Label'),
+    minLabel: text('Label for minimum value (minLabel)', ''),
+    maxLabel: text('Label for maximum value (maxLabel)', ''),
+    hideLabel: boolean('Hide label (hideLabel)', false)
+  }
+});
+
+export const Skeleton = () => ({
+  Component,
+  props: {
+    story: 'skeleton',
+    hideLabel: boolean('Hide label (hideLabel)', false)
+  }
+});

src/components/Slider/Slider.svelte

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+<script>
+  let className = undefined;
+  export { className as class };
+  export let hideTextInput = false;
+  export let id = Math.random();
+  export let value = '';
+  export let min = 0;
+  export let max = 100;
+  export let minLabel = '';
+  export let maxLabel = '';
+  export let labelText = '';
+  export let formatLabel = (value, label) => {
+    return typeof label === 'function' ? label(value) : `${value}${label}`;
+  };
+  export let step = 1;
+  export let stepMultiplier = 4;
+  export let disabled = false;
+  export let name = '';
+  export let inputType = 'number';
+  export let invalid = false;
+  export let required = false;
+  export let light = false;
+  export let style = undefined;
+
+  import { createEventDispatcher, afterUpdate, tick } from 'svelte';
+  import { cx } from '../../lib';
+
+  const dispatch = createEventDispatcher();
+
+  let dragging = false;
+  let holding = false;
+  let elementRef = undefined;
+  let trackRef = undefined;
+
+  function startDragging() {
+    dragging = true;
+  }
+
+  function startHolding() {
+    holding = true;
+  }
+
+  function stopHolding() {
+    holding = false;
+  }
+
+  function calcValue(event) {
+    const offsetX = event.touches ? event.touches[0].clientX : event.clientX;
+    const { left, width } = trackRef.getBoundingClientRect();
+    let nextValue = min + Math.round(((max - min) * ((offsetX - left) / width)) / step) * step;
+
+    if (nextValue <= min) {
+      nextValue = min;
+    } else if (nextValue >= max) {
+      nextValue = max;
+    }
+
+    value = nextValue;
+  }
+
+  afterUpdate(() => {
+    if (!holding) {
+      dispatch('change', value);
+    }
+  });
+
+  $: range = max - min;
+  $: left = ((value - min) / range) * 100;
+  $: {
+    if (value <= min) {
+      value = min;
+    } else if (value >= max) {
+      value = max;
+    }
+
+    if (dragging) {
+      calcValue(event);
+      dragging = false;
+    }
+  }
+</script>
+
+<div on:click on:mouseover on:mouseenter on:mouseleave class={cx('--form-item', className)} {style}>
+  <label for={id} class={cx('--label', disabled && '--label--disabled')}>{labelText}</label>
+  <div class={cx('--slider-container')}>
+    <span class={cx('--slider__range-label')}>{formatLabel(min, minLabel)}</span>
+    <div
+      bind:this={elementRef}
+      role="presentation"
+      tabindex="-1"
+      class={cx('--slider', disabled && '--slider--disabled')}
+      on:click={startDragging}
+      on:mousemove={() => {
+        if (holding) {
+          startDragging();
+        }
+      }}
+      on:touchmove={() => {
+        if (holding) {
+          startDragging();
+        }
+      }}
+      on:mouseup={stopHolding}
+      on:touchup={stopHolding}
+      on:touchend={stopHolding}
+      on:touchcancel={stopHolding}>
+      <div
+        role="slider"
+        tabindex="0"
+        class={cx('--slider__thumb')}
+        style={`left: ${left}%`}
+        aria-valuemax={max}
+        aria-valuemin={min}
+        aria-valuenow={value}
+        on:mousedown={startHolding}
+        on:touchstart={startHolding}
+        on:keydown={({ shiftKey, key }) => {
+          const keys = { ArrowDown: -1, ArrowLeft: -1, ArrowRight: 1, ArrowUp: 1 };
+          if (keys[key]) {
+            value += step * (shiftKey ? range / step / stepMultiplier : 1) * keys[key];
+          }
+        }}
+        {id} />
+      <div bind:this={trackRef} class={cx('--slider__track')} />
+      <div
+        class={cx('--slider__filled-track')}
+        style={`transform: translate(0, -50%) scaleX(${left / 100})`} />
+      <input
+        type="hidden"
+        class={cx('--slider__input')}
+        {name}
+        {value}
+        {required}
+        {min}
+        {max}
+        {step} />
+    </div>
+    <span class={cx('--slider__range-label')}>{formatLabel(max, maxLabel)}</span>
+    {#if !hideTextInput}
+      <input
+        type={inputType}
+        id={`input-${id}`}
+        aria-label={$$props['aria-label'] || 'Slider number input'}
+        class={cx('--text-input', '--slider-text-input', light && '--text-input--light', invalid && '--text-input--invalid')}
+        on:change={({ target }) => {
+          value = Number(target.value);
+        }}
+        {disabled}
+        {value} />
+    {/if}
+  </div>
+</div>

src/components/Slider/index.js

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+import Slider from './Slider.svelte';
+
+export default Slider;
+export { default as SliderSkeleton } from './Slider.Skeleton.svelte';