feat: add support for the Web Share Target API (#1100)

Co-authored-by: userquin <userquin@gmail.com>

components/publish/PublishWidget.vue

@@ -1,7 +1,6 @@
 <script setup lang="ts">
 import { EditorContent } from '@tiptap/vue-3'
 import type { mastodon } from 'masto'
-import type { Ref } from 'vue'
 import type { Draft } from '~/types'
 
 const {
@@ -90,6 +89,19 @@ async function publish() {
     emit('published', status)
 }
 
+useWebShareTarget(async ({ data: { data, action } }: any) => {
+  if (action !== 'compose-with-shared-data')
+    return
+
+  editor.value?.commands.focus('end')
+
+  if (data.text !== undefined)
+    editor.value?.commands.insertContent(data.text)
+
+  if (data.files !== undefined)
+    await uploadAttachments(data.files)
+})
+
 defineExpose({
   focusEditor: () => {
     editor.value?.commands?.focus?.()

composables/web-share-target.ts

@@ -0,0 +1,24 @@
+export function useWebShareTarget(listener?: (message: MessageEvent) => void) {
+  if (process.server)
+    return
+
+  onBeforeMount(() => {
+    // PWA must be installed to use share target
+    if (useNuxtApp().$pwa.isInstalled && 'serviceWorker' in navigator) {
+      if (listener)
+        navigator.serviceWorker.addEventListener('message', listener)
+
+      navigator.serviceWorker.getRegistration()
+        .then((registration) => {
+          if (registration && registration.active) {
+            // we need to signal the service worker that we are ready to receive data
+            registration.active.postMessage({ action: 'ready-to-receive' })
+          }
+        })
+        .catch(err => console.error('Could not get registration', err))
+
+      if (listener)
+        onBeforeUnmount(() => navigator.serviceWorker.removeEventListener('message', listener))
+    }
+  })
+}

locales/en-GB.json

@@ -282,6 +282,11 @@
       "label": "Logged in users"
     }
   },
+  "share-target": {
+    "description": "Elk can be configured so that you can share content from other applications, simply install Elk on your device or computer and sign in.",
+    "hint": "In order to share content with Elk, Elk must be installed and you must be signed in.",
+    "title": "Share with Elk"
+  },
   "state": {
     "attachments_exceed_server_limit": "The number of attachments exceeded the limit per post.",
     "attachments_limit_error": "Limit per post exceeded",

locales/en-US.json

@@ -359,6 +359,11 @@
       "label": "Wellness"
     }
   },
+  "share-target": {
+    "description": "Elk can be configured so that you can share content from other applications, simply install Elk on your device or computer and sign in.",
+    "hint": "In order to share content with Elk, Elk must be installed and you must be signed in.",
+    "title": "Share with Elk"
+  },
   "state": {
     "attachments_exceed_server_limit": "The number of attachments exceeded the limit per post.",
     "attachments_limit_error": "Limit per post exceeded",

locales/es-ES.json

@@ -356,6 +356,11 @@
       "label": "Bienestar"
     }
   },
+  "share-target": {
+    "description": "Elk puede ser configurado para que pueda compartir contenido desde otras aplicaciones, simplemente tiene que instalar Elk en su dispositivo u ordenador e iniciar sesión.",
+    "hint": "Para poder compartir contenido con Elk, debes instalar Elk e iniciar sesión.",
+    "title": "Compartir con Elk"
+  },
   "state": {
     "attachments_exceed_server_limit": "Número máximo de archivos adjuntos por publicación excedido.",
     "attachments_limit_error": "Límite por publicación excedido",

middleware/auth.ts

@@ -5,8 +5,12 @@ export default defineNuxtRouteMiddleware((to) => {
     return
 
   onMastoInit(() => {
-    if (!currentUser.value)
-      return navigateTo(`/${currentServer.value}/public/local`)
+    if (!currentUser.value) {
+      if (to.path === '/home' && to.query['share-target'] !== undefined)
+        return navigateTo('/share-target')
+      else
+        return navigateTo(`/${currentServer.value}/public/local`)
+    }
     if (to.path === '/')
       return navigateTo('/home')
   })

modules/pwa/i18n.ts

@@ -5,12 +5,30 @@ import { getEnv } from '../../config/env'
 import { i18n } from '../../config/i18n'
 import type { LocaleObject } from '#i18n'
 
-export type LocalizedWebManifest = Record<string, Partial<ManifestOptions>>
+// We have to extend the ManifestOptions interface from 'vite-plugin-pwa'
+// as that interface doesn't define the share_target field of Web App Manifests.
+interface ExtendedManifestOptions extends ManifestOptions {
+  share_target: {
+    action: string
+    method: string
+    enctype: string
+    params: {
+      text: string
+      url: string
+      files: [{
+        name: string
+        accept: string[]
+      }]
+    }
+  }
+}
+
+export type LocalizedWebManifest = Record<string, Partial<ExtendedManifestOptions>>
 
 export const pwaLocales = i18n.locales as LocaleObject[]
 
-type WebManifestEntry = Pick<ManifestOptions, 'name' | 'short_name' | 'description'>
-type RequiredWebManifestEntry = Required<WebManifestEntry & Pick<ManifestOptions, 'dir' | 'lang'>>
+type WebManifestEntry = Pick<ExtendedManifestOptions, 'name' | 'short_name' | 'description'>
+type RequiredWebManifestEntry = Required<WebManifestEntry & Pick<ExtendedManifestOptions, 'dir' | 'lang'>>
 
 export const createI18n = async (): Promise<LocalizedWebManifest> => {
   const { env } = await getEnv()
@@ -73,6 +91,21 @@ export const createI18n = async (): Promise<LocalizedWebManifest> => {
           type: 'image/png',
         },
       ],
+      share_target: {
+        action: '/web-share-target',
+        method: 'POST',
+        enctype: 'multipart/form-data',
+        params: {
+          text: 'text',
+          url: 'text',
+          files: [
+            {
+              name: 'files',
+              accept: ['image/*', 'video/*'],
+            },
+          ],
+        },
+      },
     }
     acc[`${lang}-dark`] = {
       scope: '/',
@@ -98,6 +131,21 @@ export const createI18n = async (): Promise<LocalizedWebManifest> => {
           type: 'image/png',
         },
       ],
+      share_target: {
+        action: '/web-share-target',
+        method: 'POST',
+        enctype: 'multipart/form-data',
+        params: {
+          text: 'text',
+          url: 'text',
+          files: [
+            {
+              name: 'files',
+              accept: ['image/*', 'video/*'],
+            },
+          ],
+        },
+      },
     }
 
     return acc

pages/share-target.vue

@@ -0,0 +1,38 @@
+<script setup>
+definePageMeta({
+  middleware: () => {
+    if (!useRuntimeConfig().public.pwaEnabled)
+      return navigateTo('/')
+  },
+})
+
+useWebShareTarget()
+
+const pwaIsInstalled = process.server ? false : useNuxtApp().$pwa.isInstalled
+</script>
+
+<template>
+  <MainContent>
+    <template #title>
+      <NuxtLink to="/share-target" flex items-center gap-2>
+        <div i-ri:share-line />
+        <span>{{ $t('share-target.title') }}</span>
+      </NuxtLink>
+    </template>
+    <slot>
+      <div flex="~ col" px5 py2 gap-y-4>
+        <div
+          v-if="!pwaIsInstalled || !currentUser"
+          role="alert"
+          gap-1
+          p-2
+          text-red-600 dark:text-red-400
+          border="~ base rounded red-600 dark:red-400"
+        >
+          {{ $t('share-target.hint') }}
+        </div>
+        <div>{{ $t('share-target.description') }}</div>
+      </div>
+    </slot>
+  </MainContent>
+</template>

plugins/pwa.client.ts

@@ -5,6 +5,12 @@ export default defineNuxtPlugin(() => {
   const registrationError = ref(false)
   const swActivated = ref(false)
 
+  // https://thomashunter.name/posts/2021-12-11-detecting-if-pwa-twa-is-installed
+  const ua = navigator.userAgent
+  const ios = ua.match(/iPhone|iPad|iPod/)
+  const standalone = window.matchMedia('(display-mode: standalone)').matches
+  const isInstalled = !!(standalone || (ios && !ua.match(/Safari/)))
+
   const registerPeriodicSync = (swUrl: string, r: ServiceWorkerRegistration) => {
     setInterval(async () => {
       if (!online.value)
@@ -54,6 +60,7 @@ export default defineNuxtPlugin(() => {
   return {
     provide: {
       pwa: reactive({
+        isInstalled,
         swActivated,
         registrationError,
         needRefresh,

service-worker/share-target.ts

@@ -0,0 +1,64 @@
+/// <reference lib="WebWorker" />
+declare const self: ServiceWorkerGlobalScope
+
+const clientResolves: { [key: string]: Function } = {}
+
+self.addEventListener('message', (event) => {
+  if (event.data.action !== 'ready-to-receive')
+    return
+
+  const id: string | undefined = (event.source as any)?.id ?? undefined
+
+  if (id && clientResolves[id] !== undefined)
+    clientResolves[id]()
+})
+
+export const onShareTarget = (event: FetchEvent) => {
+  if (!event.request.url.endsWith('/web-share-target') || event.request.method !== 'POST')
+    return
+
+  event.waitUntil(handleSharedTarget(event))
+}
+
+async function handleSharedTarget(event: FetchEvent) {
+  event.respondWith(Response.redirect('/home?share-target=true'))
+  await waitForClientToGetReady(event.resultingClientId)
+
+  const [client, formData] = await getClientAndFormData(event)
+  if (client === undefined)
+    return
+
+  await sendShareTargetMessage(client, formData)
+}
+
+async function sendShareTargetMessage(client: Client, data: FormData) {
+  const sharedData: { text?: string; files?: File[] } = {}
+
+  const text = data.get('text')
+  if (text !== null)
+    sharedData.text = text.toString()
+
+  const files: File[] = []
+  for (const [name, file] of data.entries()) {
+    if (name === 'files' && file instanceof File)
+      files.push(file)
+  }
+
+  if (files.length !== 0)
+    sharedData.files = files
+
+  client.postMessage({ data: sharedData, action: 'compose-with-shared-data' })
+}
+
+function waitForClientToGetReady(clientId: string) {
+  return new Promise<void>((resolve) => {
+    clientResolves[clientId] = resolve
+  })
+}
+
+function getClientAndFormData(event: FetchEvent): Promise<[client: Client | undefined, formData: FormData]> {
+  return Promise.all([
+    self.clients.get(event.resultingClientId),
+    event.request.formData(),
+  ])
+}

service-worker/sw.ts

@@ -7,6 +7,7 @@ import { StaleWhileRevalidate } from 'workbox-strategies'
 import { ExpirationPlugin } from 'workbox-expiration'
 
 import { onNotificationClick, onPush } from './web-push-notifications'
+import { onShareTarget } from './share-target'
 
 declare const self: ServiceWorkerGlobalScope
 
@@ -32,7 +33,7 @@ if (import.meta.env.DEV)
 // deny api and server page calls
 let denylist: undefined | RegExp[]
 if (import.meta.env.PROD)
-  denylist = [/^\/api\//, /^\/login\//, /^\/oauth\//, /^\/signin\//]
+  denylist = [/^\/api\//, /^\/login\//, /^\/oauth\//, /^\/signin\//, /^\/web-share-target\//]
 
 // only cache pages and external assets on local build + start or in production
 if (import.meta.env.PROD) {
@@ -90,3 +91,4 @@ registerRoute(new NavigationRoute(
 
 self.addEventListener('push', onPush)
 self.addEventListener('notificationclick', onNotificationClick)
+self.addEventListener('fetch', onShareTarget)