Integrate Element Call with widget API (#1581)

* Integrate Element Call with widget API.

- Add `appconfig` module and extract constants that can be overridden in forks there.
- Add an Element Call feature flag, disabled by default.
- Refactor the whole `ElementCallActivity`, move most logic out of it.
- Integrate with the Rust Widget Driver API (note the Rust SDK version used in this PR lacks some needed changes to make the calls actually work).
- Handle calls differently based on `CallType`.
- Add UI to create/join a call.

---------

Co-authored-by: ElementBot <benoitm+elementbot@element.io>

libraries/matrix/api/build.gradle.kts

@@ -34,6 +34,7 @@ anvil {
 }
 
 dependencies {
+    implementation(projects.appconfig)
     implementation(projects.libraries.di)
     implementation(libs.dagger)
     implementation(projects.libraries.core)

libraries/matrix/api/src/main/kotlin/io/element/android/libraries/matrix/api/permalink/MatrixToConverter.kt

@@ -17,7 +17,7 @@
 package io.element.android.libraries.matrix.api.permalink
 
 import android.net.Uri
-import io.element.android.libraries.matrix.api.config.MatrixConfiguration
+import io.element.android.appconfig.MatrixConfiguration
 
 /**
  * Mapping of an input URI to a matrix.to compliant URI.

libraries/matrix/api/src/main/kotlin/io/element/android/libraries/matrix/api/permalink/PermalinkBuilder.kt

@@ -16,7 +16,7 @@
 
 package io.element.android.libraries.matrix.api.permalink
 
-import io.element.android.libraries.matrix.api.config.MatrixConfiguration
+import io.element.android.appconfig.MatrixConfiguration
 import io.element.android.libraries.matrix.api.core.MatrixPatterns
 import io.element.android.libraries.matrix.api.core.RoomId
 import io.element.android.libraries.matrix.api.core.UserId

libraries/matrix/api/src/main/kotlin/io/element/android/libraries/matrix/api/room/MatrixRoom.kt

@@ -30,6 +30,8 @@ import io.element.android.libraries.matrix.api.media.VideoInfo
 import io.element.android.libraries.matrix.api.poll.PollKind
 import io.element.android.libraries.matrix.api.room.location.AssetType
 import io.element.android.libraries.matrix.api.timeline.MatrixTimeline
+import io.element.android.libraries.matrix.api.widget.MatrixWidgetDriver
+import io.element.android.libraries.matrix.api.widget.MatrixWidgetSettings
 import kotlinx.coroutines.flow.StateFlow
 import java.io.Closeable
 import java.io.File
@@ -192,5 +194,27 @@ interface MatrixRoom : Closeable {
         progressCallback: ProgressCallback?
     ): Result<MediaUploadHandler>
 
+    /**
+     * Generates a Widget url to display in a [android.webkit.WebView] given the provided parameters.
+     * @param widgetSettings The widget settings to use.
+     * @param clientId The client id to use. It should be unique per app install.
+     * @param languageTag The language tag to use. If null, the default language will be used.
+     * @param theme The theme to use. If null, the default theme will be used.
+     * @return The resulting url, or a failure.
+     */
+    suspend fun generateWidgetWebViewUrl(
+        widgetSettings: MatrixWidgetSettings,
+        clientId: String,
+        languageTag: String? = null,
+        theme: String? = null,
+    ): Result<String>
+
+    /**
+     * Get a [MatrixWidgetDriver] for the provided [widgetSettings].
+     * @param widgetSettings The widget settings to use.
+     * @return The resulting [MatrixWidgetDriver], or a failure.
+     */
+    fun getWidgetDriver(widgetSettings: MatrixWidgetSettings): Result<MatrixWidgetDriver>
+
     override fun close() = destroy()
 }

libraries/matrix/api/src/main/kotlin/io/element/android/libraries/matrix/api/widget/CallWidgetSettingsProvider.kt

@@ -14,9 +14,13 @@
  * limitations under the License.
  */
 
-package io.element.android.libraries.matrix.api.config
+package io.element.android.libraries.matrix.api.widget
 
-object MatrixConfiguration {
-    const val matrixToPermalinkBaseUrl: String = "https://matrix.to/#/"
-    val clientPermalinkBaseUrl: String? = null
+import java.util.UUID
+
+interface CallWidgetSettingsProvider {
+    fun provide(
+        baseUrl: String,
+        widgetId: String = UUID.randomUUID().toString()
+    ): MatrixWidgetSettings
 }

libraries/matrix/api/src/main/kotlin/io/element/android/libraries/matrix/api/widget/MatrixWidgetDriver.kt

@@ -0,0 +1,27 @@
+/*
+ * Copyright (c) 2023 New Vector Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.element.android.libraries.matrix.api.widget
+
+import kotlinx.coroutines.flow.Flow
+
+interface MatrixWidgetDriver : AutoCloseable {
+    val id: String
+    val incomingMessages: Flow<String>
+
+    suspend fun run()
+    suspend fun send(message: String)
+}

libraries/matrix/api/src/main/kotlin/io/element/android/libraries/matrix/api/widget/MatrixWidgetSettings.kt

@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) 2023 New Vector Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.element.android.libraries.matrix.api.widget
+
+import android.os.Parcelable
+import kotlinx.parcelize.Parcelize
+
+@Parcelize
+class MatrixWidgetSettings(
+    val id: String,
+    val initAfterContentLoad: Boolean,
+    val rawUrl: String,
+) : Parcelable {
+    companion object
+}

libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/room/RustMatrixRoom.kt

@@ -40,6 +40,8 @@ import io.element.android.libraries.matrix.api.room.location.AssetType
 import io.element.android.libraries.matrix.api.room.roomMembers
 import io.element.android.libraries.matrix.api.room.roomNotificationSettings
 import io.element.android.libraries.matrix.api.timeline.MatrixTimeline
+import io.element.android.libraries.matrix.api.widget.MatrixWidgetDriver
+import io.element.android.libraries.matrix.api.widget.MatrixWidgetSettings
 import io.element.android.libraries.matrix.impl.core.toProgressWatcher
 import io.element.android.libraries.matrix.impl.media.MediaUploadHandlerImpl
 import io.element.android.libraries.matrix.impl.media.map
@@ -48,6 +50,8 @@ import io.element.android.libraries.matrix.impl.poll.toInner
 import io.element.android.libraries.matrix.impl.room.location.toInner
 import io.element.android.libraries.matrix.impl.timeline.RustMatrixTimeline
 import io.element.android.libraries.matrix.impl.util.destroyAll
+import io.element.android.libraries.matrix.impl.widget.RustWidgetDriver
+import io.element.android.libraries.matrix.impl.widget.generateWidgetWebViewUrl
 import io.element.android.libraries.sessionstorage.api.SessionData
 import io.element.android.services.toolbox.api.systemclock.SystemClock
 import kotlinx.coroutines.CancellationException
@@ -65,6 +69,8 @@ import org.matrix.rustcomponents.sdk.RoomListItem
 import org.matrix.rustcomponents.sdk.RoomMember
 import org.matrix.rustcomponents.sdk.RoomMessageEventContentWithoutRelation
 import org.matrix.rustcomponents.sdk.SendAttachmentJoinHandle
+import org.matrix.rustcomponents.sdk.WidgetPermissions
+import org.matrix.rustcomponents.sdk.WidgetPermissionsProvider
 import org.matrix.rustcomponents.sdk.messageEventContentFromHtml
 import org.matrix.rustcomponents.sdk.messageEventContentFromMarkdown
 import timber.log.Timber
@@ -478,6 +484,27 @@ class RustMatrixRoom(
         )
     }
 
+    override suspend fun generateWidgetWebViewUrl(
+        widgetSettings: MatrixWidgetSettings,
+        clientId: String,
+        languageTag: String?,
+        theme: String?,
+    ) = runCatching {
+        widgetSettings.generateWidgetWebViewUrl(innerRoom, clientId, languageTag, theme)
+    }
+
+    override fun getWidgetDriver(widgetSettings: MatrixWidgetSettings): Result<MatrixWidgetDriver> = runCatching {
+        RustWidgetDriver(
+            widgetSettings = widgetSettings,
+            room = innerRoom,
+            widgetPermissionsProvider = object : WidgetPermissionsProvider {
+                override fun acquirePermissions(permissions: WidgetPermissions): WidgetPermissions {
+                    return permissions
+                }
+           },
+        )
+    }
+
     private suspend fun sendAttachment(files: List<File>, handle: () -> SendAttachmentJoinHandle): Result<MediaUploadHandler> {
         return runCatching {
             MediaUploadHandlerImpl(files, handle())

libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/widget/DefaultCallWidgetSettingsProvider.kt

@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) 2023 New Vector Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.element.android.libraries.matrix.impl.widget
+
+import com.squareup.anvil.annotations.ContributesBinding
+import io.element.android.libraries.di.AppScope
+import io.element.android.libraries.matrix.api.widget.CallWidgetSettingsProvider
+import io.element.android.libraries.matrix.api.widget.MatrixWidgetSettings
+import org.matrix.rustcomponents.sdk.VirtualElementCallWidgetOptions
+import org.matrix.rustcomponents.sdk.newVirtualElementCallWidget
+import javax.inject.Inject
+
+@ContributesBinding(AppScope::class)
+class DefaultCallWidgetSettingsProvider @Inject constructor() : CallWidgetSettingsProvider {
+    override fun provide(baseUrl: String, widgetId: String): MatrixWidgetSettings {
+        val options = VirtualElementCallWidgetOptions(
+            elementCallUrl = baseUrl,
+            widgetId = widgetId,
+            parentUrl = null,
+            hideHeader = null,
+            preload = null,
+            fontScale = null,
+            appPrompt = false,
+            skipLobby = true,
+            confineToRoom = true,
+            fonts = null,
+            analyticsId = null
+        )
+        val rustWidgetSettings = newVirtualElementCallWidget(options)
+        return MatrixWidgetSettings.fromRustWidgetSettings(rustWidgetSettings)
+    }
+}

libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/widget/MatrixWidgetSettings.kt

@@ -0,0 +1,50 @@
+/*
+ * Copyright (c) 2023 New Vector Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.element.android.libraries.matrix.impl.widget
+
+import io.element.android.libraries.matrix.api.widget.MatrixWidgetSettings
+import org.matrix.rustcomponents.sdk.ClientProperties
+import org.matrix.rustcomponents.sdk.Room
+import org.matrix.rustcomponents.sdk.WidgetSettings
+import org.matrix.rustcomponents.sdk.generateWebviewUrl
+
+fun MatrixWidgetSettings.toRustWidgetSettings() = WidgetSettings(
+    id = this.id,
+    initAfterContentLoad = this.initAfterContentLoad,
+    rawUrl = this.rawUrl,
+)
+
+fun MatrixWidgetSettings.Companion.fromRustWidgetSettings(widgetSettings: WidgetSettings) = MatrixWidgetSettings(
+    id = widgetSettings.id,
+    initAfterContentLoad = widgetSettings.initAfterContentLoad,
+    rawUrl = widgetSettings.rawUrl,
+)
+
+suspend fun MatrixWidgetSettings.generateWidgetWebViewUrl(
+    room: Room,
+    clientId: String,
+    languageTag: String? = null,
+    theme: String? = null
+) = generateWebviewUrl(
+    widgetSettings = this.toRustWidgetSettings(),
+    room = room,
+    props = ClientProperties(
+        clientId = clientId,
+        languageTag = languageTag,
+        theme = theme,
+    )
+)

libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/widget/RustWidgetDriver.kt

@@ -0,0 +1,78 @@
+/*
+ * Copyright (c) 2023 New Vector Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.element.android.libraries.matrix.impl.widget
+
+import io.element.android.libraries.matrix.api.widget.MatrixWidgetDriver
+import io.element.android.libraries.matrix.api.widget.MatrixWidgetSettings
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.flow.MutableSharedFlow
+import kotlinx.coroutines.isActive
+import kotlinx.coroutines.launch
+import org.matrix.rustcomponents.sdk.Room
+import org.matrix.rustcomponents.sdk.WidgetPermissionsProvider
+import org.matrix.rustcomponents.sdk.makeWidgetDriver
+import java.util.concurrent.atomic.AtomicBoolean
+import kotlin.coroutines.coroutineContext
+
+class RustWidgetDriver(
+    widgetSettings: MatrixWidgetSettings,
+    private val room: Room,
+    private val widgetPermissionsProvider: WidgetPermissionsProvider,
+): MatrixWidgetDriver {
+
+    override val incomingMessages = MutableSharedFlow<String>()
+
+    private val driverAndHandle = makeWidgetDriver(widgetSettings.toRustWidgetSettings())
+    private var receiveMessageJob: Job? = null
+
+    private var isRunning = AtomicBoolean(false)
+
+    override val id: String = widgetSettings.id
+
+    override suspend fun run() {
+        // Don't run the driver if it's already running
+        if (!isRunning.compareAndSet(false, true)) {
+            return
+        }
+
+        val coroutineScope = CoroutineScope(coroutineContext)
+        coroutineScope.launch {
+            // This call will suspend the coroutine while the driver is running, so it needs to be launched separately
+            driverAndHandle.driver.run(room, widgetPermissionsProvider)
+        }
+        receiveMessageJob = coroutineScope.launch(Dispatchers.IO) {
+            try {
+                while (isActive) {
+                    driverAndHandle.handle.recv()?.let { incomingMessages.emit(it) }
+                }
+            } finally {
+                driverAndHandle.handle.close()
+            }
+        }
+    }
+
+    override suspend fun send(message: String) {
+        driverAndHandle.handle.send(message)
+    }
+
+    override fun close() {
+        receiveMessageJob?.cancel()
+        driverAndHandle.driver.close()
+    }
+}

libraries/matrix/test/src/main/kotlin/io/element/android/libraries/matrix/test/FakeMatrixClient.kt

@@ -208,8 +208,12 @@ class FakeMatrixClient(
         findDmResult = result
     }
 
-    fun givenGetRoomResult(roomId: RoomId, result: MatrixRoom) {
-        getRoomResults[roomId] = result
+    fun givenGetRoomResult(roomId: RoomId, result: MatrixRoom?) {
+        if (result == null) {
+            getRoomResults.remove(roomId)
+        } else {
+            getRoomResults[roomId] = result
+        }
     }
 
     fun givenSearchUsersResult(searchTerm: String, result: Result<MatrixSearchUserResults>) {

libraries/matrix/test/src/main/kotlin/io/element/android/libraries/matrix/test/FakeMatrixClientProvider.kt

@@ -0,0 +1,27 @@
+/*
+ * Copyright (c) 2023 New Vector Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.element.android.libraries.matrix.test
+
+import io.element.android.libraries.matrix.api.MatrixClient
+import io.element.android.libraries.matrix.api.MatrixClientProvider
+import io.element.android.libraries.matrix.api.core.SessionId
+
+class FakeMatrixClientProvider(
+    private val getClient: (SessionId) -> Result<MatrixClient> = { Result.success(FakeMatrixClient()) }
+) : MatrixClientProvider {
+    override suspend fun getOrRestore(sessionId: SessionId): Result<MatrixClient> = getClient(sessionId)
+}

libraries/matrix/test/src/main/kotlin/io/element/android/libraries/matrix/test/room/FakeMatrixRoom.kt

@@ -36,11 +36,14 @@ import io.element.android.libraries.matrix.api.room.MessageEventType
 import io.element.android.libraries.matrix.api.room.StateEventType
 import io.element.android.libraries.matrix.api.room.location.AssetType
 import io.element.android.libraries.matrix.api.timeline.MatrixTimeline
+import io.element.android.libraries.matrix.api.widget.MatrixWidgetDriver
+import io.element.android.libraries.matrix.api.widget.MatrixWidgetSettings
 import io.element.android.libraries.matrix.test.A_ROOM_ID
 import io.element.android.libraries.matrix.test.A_SESSION_ID
 import io.element.android.libraries.matrix.test.media.FakeMediaUploadHandler
 import io.element.android.libraries.matrix.test.notificationsettings.FakeNotificationSettingsService
 import io.element.android.libraries.matrix.test.timeline.FakeMatrixTimeline
+import io.element.android.libraries.matrix.test.widget.FakeWidgetDriver
 import io.element.android.tests.testutils.simulateLongTask
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.MutableStateFlow
@@ -92,6 +95,8 @@ class FakeMatrixRoom(
     private var sendPollResponseResult = Result.success(Unit)
     private var endPollResult = Result.success(Unit)
     private var progressCallbackValues = emptyList<Pair<Long, Long>>()
+    private var generateWidgetWebViewUrlResult = Result.success("https://call.element.io")
+    private var getWidgetDriverResult: Result<MatrixWidgetDriver> = Result.success(FakeWidgetDriver())
     val editMessageCalls = mutableListOf<Pair<String, String?>>()
 
     var sendMediaCount = 0
@@ -368,6 +373,15 @@ class FakeMatrixRoom(
         progressCallback: ProgressCallback?
     ): Result<MediaUploadHandler> = fakeSendMedia(progressCallback)
 
+    override suspend fun generateWidgetWebViewUrl(
+        widgetSettings: MatrixWidgetSettings,
+        clientId: String,
+        languageTag: String?,
+        theme: String?,
+    ): Result<String> = generateWidgetWebViewUrlResult
+
+    override fun getWidgetDriver(widgetSettings: MatrixWidgetSettings): Result<MatrixWidgetDriver> = getWidgetDriverResult
+
     fun givenLeaveRoomError(throwable: Throwable?) {
         this.leaveRoomError = throwable
     }
@@ -475,6 +489,14 @@ class FakeMatrixRoom(
     fun givenProgressCallbackValues(values: List<Pair<Long, Long>>) {
         progressCallbackValues = values
     }
+
+    fun givenGenerateWidgetWebViewUrlResult(result: Result<String>) {
+        generateWidgetWebViewUrlResult = result
+    }
+
+    fun givenGetWidgetDriverResult(result: Result<MatrixWidgetDriver>) {
+        getWidgetDriverResult = result
+    }
 }
 
 data class SendLocationInvocation(

libraries/matrix/test/src/main/kotlin/io/element/android/libraries/matrix/test/widget/FakeCallWidgetSettingsProvider.kt

@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) 2023 New Vector Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.element.android.libraries.matrix.test.widget
+
+import io.element.android.libraries.matrix.api.widget.CallWidgetSettingsProvider
+import io.element.android.libraries.matrix.api.widget.MatrixWidgetSettings
+
+class FakeCallWidgetSettingsProvider(
+    private val provideFn: (String, String) -> MatrixWidgetSettings = { _, _ -> MatrixWidgetSettings("id", true, "url") }
+) : CallWidgetSettingsProvider {
+
+    val providedBaseUrls = mutableListOf<String>()
+
+    override fun provide(baseUrl: String, widgetId: String): MatrixWidgetSettings {
+        providedBaseUrls += baseUrl
+        return provideFn(baseUrl, widgetId)
+    }
+}

libraries/matrix/test/src/main/kotlin/io/element/android/libraries/matrix/test/widget/FakeWidgetDriver.kt

@@ -0,0 +1,52 @@
+/*
+ * Copyright (c) 2023 New Vector Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.element.android.libraries.matrix.test.widget
+
+import io.element.android.libraries.matrix.api.widget.MatrixWidgetDriver
+import kotlinx.coroutines.flow.MutableSharedFlow
+import java.util.UUID
+
+class FakeWidgetDriver(
+    override val id: String = UUID.randomUUID().toString(),
+) : MatrixWidgetDriver {
+
+    private val _sentMessages = mutableListOf<String>()
+    val sentMessages: List<String> = _sentMessages
+
+    var runCalledCount = 0
+        private set
+    var closeCalledCount = 0
+        private set
+
+    override val incomingMessages = MutableSharedFlow<String>(extraBufferCapacity = 1)
+
+    override suspend fun run() {
+        runCalledCount++
+    }
+
+    override suspend fun send(message: String) {
+        _sentMessages.add(message)
+    }
+
+    override fun close() {
+        closeCalledCount++
+    }
+
+    fun givenIncomingMessage(message: String) {
+        incomingMessages.tryEmit(message)
+    }
+}