From c071ac117444122ce7a49b173ffe59114563d6d9 Mon Sep 17 00:00:00 2001
From: Nolan Lawson <nolan@nolanlawson.com>
Date: Sat, 30 Nov 2019 17:43:31 -0800
Subject: [PATCH] refactor: refactor focus management (#1662)

---
 src/routes/_components/FocusRestoration.html  |  99 ++++++++++++++
 src/routes/_components/list/listStore.js      |   3 +-
 src/routes/_components/timeline/Timeline.html | 122 ++++--------------
 src/routes/_static/pages.js                   |   1 +
 tests/spec/010-focus.js                       |  18 +++
 5 files changed, 148 insertions(+), 95 deletions(-)
 create mode 100644 src/routes/_components/FocusRestoration.html
 create mode 100644 src/routes/_static/pages.js

diff --git a/src/routes/_components/FocusRestoration.html b/src/routes/_components/FocusRestoration.html
new file mode 100644
index 00000000..05420a21
--- /dev/null
+++ b/src/routes/_components/FocusRestoration.html
@@ -0,0 +1,99 @@
+<div
+  on:focusin="saveFocus(event)"
+  on:focusout="clearFocus()"
+>
+  <slot></slot>
+</div>
+<script>
+  import { PAGE_HISTORY_SIZE } from '../_static/pages'
+  import { QuickLRU } from '../_thirdparty/quick-lru/quick-lru'
+  import { doubleRAF } from '../_utils/doubleRAF'
+
+  const cache = new QuickLRU({ maxSize: PAGE_HISTORY_SIZE })
+
+  if (process.browser) {
+    window.__focusRestorationCache = cache
+  }
+
+  export default {
+    oncreate () {
+      this.setupPushState()
+      this.restoreFocus()
+      if (process.env.NODE_ENV !== 'production') {
+        if (!this.get().realm) {
+          throw new Error('FocusRestoration needs a realm')
+        }
+      }
+    },
+    ondestroy () {
+      this.teardownPushState()
+    },
+    methods: {
+      setupPushState () {
+        this.onPushState = this.onPushState.bind(this)
+        this.setInCache({ ignoreBlurEvents: false })
+        window.addEventListener('pushState', this.onPushState)
+      },
+      teardownPushState () {
+        window.removeEventListener('pushState', this.onPushState)
+      },
+      setInCache (obj) {
+        const { realm } = this.get()
+        if (!cache.has(realm)) {
+          cache.set(realm, {})
+        }
+        Object.assign(cache.get(realm), obj)
+      },
+      deleteInCache (key) {
+        const { realm } = this.get()
+        if (cache.has(realm)) {
+          delete cache.get(realm)[key]
+        }
+      },
+      getInCache () {
+        const { realm } = this.get()
+        return cache.get(realm) || {}
+      },
+      onPushState () {
+        this.setInCache({ ignoreBlurEvents: true })
+      },
+      restoreFocus () {
+        const { realm } = this.get()
+        const { elementId } = this.getInCache()
+        if (!elementId) {
+          return
+        }
+        console.log('restoreFocus', realm, elementId)
+        doubleRAF(() => {
+          const element = document.getElementById(elementId)
+          if (element) {
+            try {
+              element.focus({ preventScroll: true })
+            } catch (err) {
+              console.warn('failed to focus', elementId, err)
+            }
+          }
+        })
+      },
+      clearFocus () {
+        const { realm } = this.get()
+        const { ignoreBlurEvents } = this.getInCache()
+        if (!ignoreBlurEvents) {
+          console.log('clearFocus', realm)
+          this.deleteInCache('elementId')
+        }
+      },
+      saveFocus (e) {
+        const { realm } = this.get()
+        const element = e.target
+        if (element) {
+          const elementId = element.getAttribute('id')
+          if (elementId) {
+            console.log('saveFocus', realm, elementId)
+            this.setInCache({ elementId })
+          }
+        }
+      }
+    }
+  }
+</script>
diff --git a/src/routes/_components/list/listStore.js b/src/routes/_components/list/listStore.js
index 0668c8de..92ae5701 100644
--- a/src/routes/_components/list/listStore.js
+++ b/src/routes/_components/list/listStore.js
@@ -1,8 +1,9 @@
 import { RealmStore } from '../../_utils/RealmStore'
+import { PAGE_HISTORY_SIZE } from '../../_static/pages'
 
 class ListStore extends RealmStore {
   constructor (state) {
-    super(state, /* maxSize */ 10)
+    super(state, /* maxSize */ PAGE_HISTORY_SIZE)
   }
 }
 
diff --git a/src/routes/_components/timeline/Timeline.html b/src/routes/_components/timeline/Timeline.html
index e5ee25b8..417b93e9 100644
--- a/src/routes/_components/timeline/Timeline.html
+++ b/src/routes/_components/timeline/Timeline.html
@@ -1,29 +1,27 @@
 <h1 class="sr-only">{label}</h1>
-<div class="timeline"
-     role="feed"
-     on:focusin="saveFocus(event)"
-     on:focusout="clearFocus()"
->
-  {#if components}
-    <svelte:component this={components.listComponent}
-                component={components.listItemComponent}
-                realm="{$currentInstance + '/' + timeline}"
-                {makeProps}
-                items={itemIds}
-                showFooter={true}
-                footerComponent={LoadingFooter}
-                showHeader={$showHeader}
-                headerComponent={MoreHeaderVirtualWrapper}
-                {headerProps}
-                {scrollToItem}
-                on:scrollToBottom="onScrollToBottom()"
-                on:scrollToTop="onScrollToTop()"
-                on:scrollTopChanged="onScrollTopChanged(event)"
-                on:initialized="initialize()"
-                on:noNeedToScroll="onNoNeedToScroll()"
-    />
-  {/if}
-</div>
+<FocusRestoration realm={focusRealm}>
+  <div class="timeline" role="feed">
+    {#if components}
+      <svelte:component this={components.listComponent}
+                  component={components.listItemComponent}
+                  realm="{$currentInstance + '/' + timeline}"
+                  {makeProps}
+                  items={itemIds}
+                  showFooter={true}
+                  footerComponent={LoadingFooter}
+                  showHeader={$showHeader}
+                  headerComponent={MoreHeaderVirtualWrapper}
+                  {headerProps}
+                  {scrollToItem}
+                  on:scrollToBottom="onScrollToBottom()"
+                  on:scrollToTop="onScrollToTop()"
+                  on:scrollTopChanged="onScrollTopChanged(event)"
+                  on:initialized="initialize()"
+                  on:noNeedToScroll="onNoNeedToScroll()"
+      />
+    {/if}
+  </div>
+</FocusRestoration>
 <Shortcut scope="global" key="." on:pressed="showMoreAndScrollToTop()" />
 <ScrollListShortcuts />
 <script>
@@ -52,20 +50,15 @@
   import { observe } from 'svelte-extras'
   import { createMakeProps } from '../../_actions/createMakeProps'
   import { showMoreAndScrollToTop } from '../../_actions/showMoreAndScrollToTop'
+  import FocusRestoration from '../FocusRestoration.html'
 
   export default {
     oncreate () {
       console.log('timeline oncreate()')
-      this.setupFocus()
       setupTimeline()
-      this.restoreFocus()
       this.setupStreaming()
       this.setupAsyncComponents()
     },
-    ondestroy () {
-      console.log('ondestroy')
-      this.teardownFocus()
-    },
     data: () => ({
       LoadingFooter,
       MoreHeaderVirtualWrapper,
@@ -133,7 +126,8 @@
           count: itemIdsToAdd ? itemIdsToAdd.length : 0,
           onClick: showMoreItemsForCurrentTimeline
         }
-      }
+      },
+      focusRealm: ({ $currentInstance, timeline }) => `${$currentInstance}-${timeline}`
     },
     store: () => store,
     methods: {
@@ -216,16 +210,6 @@
           scheduleIdleTask(handleItemIdsToAdd)
         })
       },
-      setupFocus () {
-        this.onPushState = this.onPushState.bind(this)
-        this.store.setForCurrentTimeline({
-          ignoreBlurEvents: false
-        })
-        window.addEventListener('pushState', this.onPushState)
-      },
-      teardownFocus () {
-        window.removeEventListener('pushState', this.onPushState)
-      },
       setupAsyncComponents () {
         this.observe('componentsPromise', async componentsPromise => {
           if (componentsPromise) {
@@ -236,57 +220,6 @@
           }
         })
       },
-      onPushState () {
-        this.store.setForCurrentTimeline({ ignoreBlurEvents: true })
-      },
-      saveFocus (e) {
-        try {
-          const { currentInstance } = this.store.get()
-          const { timeline } = this.get()
-          let lastFocusedElementId
-          const activeElement = e.target
-          if (activeElement) {
-            lastFocusedElementId = activeElement.getAttribute('id')
-          }
-          console.log('saving focus to ', lastFocusedElementId)
-          this.store.setForTimeline(currentInstance, timeline, {
-            lastFocusedElementId: lastFocusedElementId
-          })
-        } catch (err) {
-          console.error('unable to save focus', err)
-        }
-      },
-      clearFocus () {
-        try {
-          const { ignoreBlurEvents } = this.store.get()
-          if (ignoreBlurEvents) {
-            return
-          }
-          console.log('clearing focus')
-          const { currentInstance } = this.store.get()
-          const { timeline } = this.get()
-          this.store.setForTimeline(currentInstance, timeline, {
-            lastFocusedElementId: null
-          })
-        } catch (err) {
-          console.error('unable to clear focus', err)
-        }
-      },
-      restoreFocus () {
-        const { lastFocusedElementId } = this.store.get()
-        if (!lastFocusedElementId) {
-          return
-        }
-        console.log('restoreFocus', lastFocusedElementId)
-        requestAnimationFrame(() => {
-          requestAnimationFrame(() => {
-            const element = document.getElementById(lastFocusedElementId)
-            if (element) {
-              element.focus({ preventScroll: true })
-            }
-          })
-        })
-      },
       onNoNeedToScroll () {
         // If the timeline doesn't need to scroll, then we can safely "preinitialize,"
         // i.e. render anything above the fold of the timeline. This avoids the affect
@@ -298,7 +231,8 @@
     },
     components: {
       ScrollListShortcuts,
-      Shortcut
+      Shortcut,
+      FocusRestoration
     }
   }
 </script>
diff --git a/src/routes/_static/pages.js b/src/routes/_static/pages.js
new file mode 100644
index 00000000..39f20eb9
--- /dev/null
+++ b/src/routes/_static/pages.js
@@ -0,0 +1 @@
+export const PAGE_HISTORY_SIZE = 10
diff --git a/tests/spec/010-focus.js b/tests/spec/010-focus.js
index 1ef042c6..4b3b3436 100644
--- a/tests/spec/010-focus.js
+++ b/tests/spec/010-focus.js
@@ -137,3 +137,21 @@ test('clicking sensitive button returns focus to sensitive button', async t => {
     .click(getNthStatusSensitiveMediaButton(sensitiveKittenIdx + 1))
     .expect(getActiveElementAriaLabel()).eql('Show sensitive media')
 })
+
+test('preserves focus two levels deep', async t => {
+  await loginAsFoobar(t)
+  await t
+    .hover(getNthStatus(1))
+    .click($('.status-author-name').withText(('admin')))
+    .expect(getUrl()).contains('/accounts/1')
+    .click(getNthStatus(1))
+    .expect(getUrl()).contains('status')
+  await goBack()
+  await t
+    .expect(getUrl()).contains('/accounts/1')
+    .expect(getActiveElementClassList()).contains('status-article')
+  await goBack()
+  await t
+    .expect(getUrl()).eql('http://localhost:4002/')
+    .expect(getActiveElementClassList()).contains('status-author-name')
+})