feat(tile): complete RadioTile

Closes #34

- Add Tile to list of supported components
- Make RadioTile composable as a "child" component

src/components/Tile/RadioTile.svelte

@@ -1,5 +1,4 @@
 <script>
-  // TODO: compose as "children" components
   let className = undefined;
   export { className as class };
   export let checked = false;
@@ -11,25 +10,15 @@
   export let light = false;
   export let style = undefined;
 
-  import { createEventDispatcher } from 'svelte';
+  import { getContext } from 'svelte';
   import CheckmarkFilled16 from 'carbon-icons-svelte/lib/CheckmarkFilled16';
   import { cx } from '../../lib';
 
-  const dispatch = createEventDispatcher();
+  const { addTile, updateSelected, selected } = getContext('TileGroup');
 
-  function handleChange(event) {
-    dispatch('change', event);
-  }
-
-  function handleKeyDown(event) {
-    if (event.key === ' ' || event.key === 'Enter') {
-      event.preventDefault();
-      handleChange(event);
-    }
-
-    dispatch('keydown', event);
-  }
+  addTile({ id, value, checked });
 
+  $: checked = value === $selected.value;
   $: _class = cx(
     '--tile',
     '--tile--selectable',
@@ -43,7 +32,9 @@
   type="radio"
   class={cx('--tile-input')}
   on:change
-  on:change={handleChange}
+  on:change={() => {
+    updateSelected({ id, value });
+  }}
   {id}
   {name}
   {value}
@@ -56,7 +47,12 @@
   on:mouseenter
   on:mouseleave
   on:keydown
-  on:keydown={handleKeyDown}
+  on:keydown={event => {
+    if (event.key === ' ' || event.key === 'Enter') {
+      event.preventDefault();
+      updateSelected({ id, value });
+    }
+  }}
   {tabindex}
   {style}>
   <span class={cx('--tile__checkmark')}>

src/components/Tile/Tile.Story.svelte

@@ -17,7 +17,7 @@
     { value: 'selected', id: 'tile-3', labelText: 'Selectable Tile' }
   ];
 
-  let selected = radioTiles[1].value;
+  let defaultSelected = radioTiles[1];
 </script>
 
 <Layout>
@@ -33,19 +33,9 @@
         <SelectableTile {...$$props} id="tile-3" name="tiles">Multi-select Tile</SelectableTile>
       </div>
     {:else if story === 'selectable'}
-      <TileGroup legend="Selectable Tile Group">
+      <TileGroup legend="Selectable Tile Group" bind:defaultSelected>
         {#each radioTiles as { value, id, labelText }, i (id)}
-          <RadioTile
-            {...$$props}
-            checked={selected === value}
-            on:change={() => {
-              selected = value;
-            }}
-            {value}
-            {id}
-            {labelText}>
-            Selectable Tile
-          </RadioTile>
+          <RadioTile {...$$props} {value} {id} {labelText}>Selectable Tile</RadioTile>
         {/each}
       </TileGroup>
     {:else if story === 'expandable'}

src/components/Tile/TileGroup.svelte

@@ -1,12 +1,50 @@
 <script>
   let className = undefined;
   export { className as class };
+  export let defaultSelected = { value: undefined };
   export let disabled = false;
   export let legend = '';
   export let style = undefined;
 
+  import { createEventDispatcher, setContext } from 'svelte';
+  import { writable } from 'svelte/store';
   import { cx } from '../../lib';
 
+  const dispatch = createEventDispatcher();
+  let tiles = [];
+  let selected = writable(defaultSelected);
+
+  setContext('TileGroup', {
+    selected,
+    addTile: tile => {
+      tiles = [...tiles, tile];
+    },
+    updateSelected: tile => {
+      selected.set(tile);
+    }
+  });
+
+  $: {
+    const checkedTiles = tiles.filter(tile => tile.checked);
+
+    if (checkedTiles.length > 1) {
+      console.warn('Multiple RadioTiles cannot be checked.');
+
+      if (defaultSelected.value) {
+        console.warn('Using `defaultSelected`:', defaultSelected);
+      } else {
+        console.warn('Using `RadioTile`:', checkedTiles[0]);
+        selected.set(checkedTiles[0]);
+      }
+    } else if (checkedTiles.length === 1) {
+      selected.set(checkedTiles[0]);
+      tiles = [];
+    }
+
+    defaultSelected = $selected;
+    dispatch('select', $selected);
+  }
+
   const _class = cx('--tile-group', className);
 </script>