Issue #10335: Add TargetTab helper for observing specific tabs.

components/browser/state/build.gradle

@@ -12,6 +12,8 @@ android {
     defaultConfig {
         minSdkVersion config.minSdkVersion
         targetSdkVersion config.targetSdkVersion
+
+        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
     }
 
     buildTypes {
@@ -21,6 +23,15 @@ android {
         }
     }
 
+    buildFeatures {
+        compose true
+    }
+
+    composeOptions {
+        kotlinCompilerVersion = Versions.kotlin
+        kotlinCompilerExtensionVersion = Versions.compose_version
+    }
+
     packagingOptions {
         exclude 'META-INF/proguard/androidx-annotations.pro'
     }
@@ -38,6 +49,7 @@ dependencies {
     api project(':concept-fetch')
 
     implementation Dependencies.androidx_browser
+    implementation Dependencies.androidx_compose_ui
     implementation Dependencies.kotlin_coroutines
     implementation Dependencies.kotlin_stdlib
 
@@ -47,6 +59,10 @@ dependencies {
     testImplementation Dependencies.testing_junit
     testImplementation Dependencies.testing_mockito
     testImplementation Dependencies.testing_robolectric
+
+    androidTestImplementation Dependencies.androidx_test_junit
+    androidTestImplementation Dependencies.androidx_compose_ui_test_manifest
+    androidTestImplementation Dependencies.androidx_compose_ui_test
 }
 
 apply from: '../../../publish.gradle'

components/browser/state/src/androidTest/java/mozilla/components/browser/state/helper/OnDeviceTargetTabTest.kt

@@ -0,0 +1,179 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package mozilla.components.browser.state.helper
+
+import androidx.compose.ui.test.junit4.createComposeRule
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import kotlinx.coroutines.runBlocking
+import mozilla.components.browser.state.action.BrowserAction
+import mozilla.components.browser.state.action.CustomTabListAction
+import mozilla.components.browser.state.action.TabListAction
+import mozilla.components.browser.state.state.BrowserState
+import mozilla.components.browser.state.state.createCustomTab
+import mozilla.components.browser.state.state.createTab
+import mozilla.components.browser.state.store.BrowserStore
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNull
+import org.junit.Rule
+import org.junit.Test
+import org.junit.runner.RunWith
+
+/**
+ * On-device tests for [TargetTab].
+ */
+@RunWith(AndroidJUnit4::class)
+class OnDeviceTargetTabTest {
+    @get:Rule
+    val rule = createComposeRule()
+
+    @Test
+    fun observingSelectedTab() {
+        val store = BrowserStore()
+
+        val target = TargetTab.Selected
+        var observedTabId: String? = null
+
+        rule.setContent {
+            val state = target.observeAsStateFrom(
+                store = store,
+                observe = { tab -> tab?.id }
+            )
+            observedTabId = state.value?.id
+        }
+
+        assertNull(observedTabId)
+
+        store.dispatchBlockingOnIdle(
+            TabListAction.AddTabAction(createTab("https://www.mozilla.org", id = "mozilla"))
+        )
+
+        rule.runOnIdle {
+            assertEquals("mozilla", observedTabId)
+        }
+
+        store.dispatchBlockingOnIdle(
+            TabListAction.AddTabAction(createTab("https://example.org", id = "example"))
+        )
+
+        rule.runOnIdle {
+            assertEquals("mozilla", observedTabId)
+        }
+
+        store.dispatchBlockingOnIdle(
+            TabListAction.SelectTabAction("example")
+        )
+
+        rule.runOnIdle {
+            assertEquals("example", observedTabId)
+        }
+
+        store.dispatchBlockingOnIdle(
+            TabListAction.RemoveTabAction("example")
+        )
+
+        rule.runOnIdle {
+            assertEquals("mozilla", observedTabId)
+        }
+
+        store.dispatchBlockingOnIdle(TabListAction.RemoveAllTabsAction)
+
+        rule.runOnIdle {
+            assertNull(observedTabId)
+        }
+    }
+
+    @Test
+    fun observingPinnedTab() {
+        val store = BrowserStore(
+            initialState = BrowserState(
+                tabs = listOf(
+                    createTab("https://www.mozilla.org", id = "mozilla"),
+                    createTab("https://www.example.org", id = "example")
+                ),
+                selectedTabId = "mozilla"
+            )
+        )
+
+        val target = TargetTab.Pinned("mozilla")
+        var observedTabId: String? = null
+
+        rule.setContent {
+            val state = target.observeAsStateFrom(
+                store = store,
+                observe = { tab -> tab?.id }
+            )
+            observedTabId = state.value?.id
+        }
+
+        assertEquals("mozilla", observedTabId)
+
+        store.dispatchBlockingOnIdle(TabListAction.SelectTabAction("example"))
+
+        rule.runOnIdle {
+            assertEquals("mozilla", observedTabId)
+        }
+
+        store.dispatchBlockingOnIdle(TabListAction.RemoveTabAction("mozilla"))
+
+        rule.runOnIdle {
+            assertNull(observedTabId)
+        }
+    }
+
+    @Test
+    fun observingCustomTab() {
+        val store = BrowserStore(
+            initialState = BrowserState(
+                tabs = listOf(
+                    createTab("https://www.mozilla.org", id = "mozilla"),
+                    createTab("https://www.example.org", id = "example")
+                ),
+                customTabs = listOf(
+                    createCustomTab("https://www.reddit.com/r/firefox/", id = "reddit")
+                ),
+                selectedTabId = "mozilla"
+            )
+        )
+
+        val target = TargetTab.Custom("reddit")
+
+        var observedTabId: String? = null
+
+        rule.setContent {
+            val state = target.observeAsStateFrom(
+                store = store,
+                observe = { tab -> tab?.id }
+            )
+            observedTabId = state.value?.id
+        }
+
+        assertEquals("reddit", observedTabId)
+
+        store.dispatchBlockingOnIdle(TabListAction.SelectTabAction("example"))
+
+        rule.runOnIdle {
+            assertEquals("reddit", observedTabId)
+        }
+
+        store.dispatchBlockingOnIdle(TabListAction.RemoveTabAction("mozilla"))
+
+        rule.runOnIdle {
+            assertEquals("reddit", observedTabId)
+        }
+
+        store.dispatchBlockingOnIdle(CustomTabListAction.RemoveCustomTabAction("reddit"))
+
+        rule.runOnIdle {
+            assertNull(observedTabId)
+        }
+    }
+
+    private fun BrowserStore.dispatchBlockingOnIdle(action: BrowserAction) {
+        rule.runOnIdle {
+            val job = dispatch(action)
+            runBlocking { job.join() }
+        }
+    }
+}

components/browser/state/src/main/java/mozilla/components/browser/state/helper/TargetTab.kt

@@ -0,0 +1,84 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package mozilla.components.browser.state.helper
+
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.State
+import androidx.lifecycle.Lifecycle
+import androidx.lifecycle.LifecycleOwner
+import mozilla.components.browser.state.selector.findCustomTab
+import mozilla.components.browser.state.selector.findTab
+import mozilla.components.browser.state.selector.selectedTab
+import mozilla.components.browser.state.state.BrowserState
+import mozilla.components.browser.state.state.SessionState
+import mozilla.components.browser.state.store.BrowserStore
+import mozilla.components.lib.state.Store
+import mozilla.components.lib.state.ext.observeAsState
+
+/**
+ * Helper for allowing a component consumer to specify which tab a component should target (e.g.
+ * the selected tab, a specific pinned tab or a custom tab). Additional helper methods make it
+ * easier to lookup the current state of the tab or observe changes.
+ */
+sealed class TargetTab {
+    /**
+     * Looks up this target in the given [BrowserStore] and returns the matching [SessionState] if
+     * available. Otherwise returns `null`.
+     */
+    fun lookupIn(store: BrowserStore): SessionState? = lookupIn(store.state)
+
+    /**
+     * Looks up this target in the given [BrowserState] and returns the matching [SessionState] if
+     * available. Otherwise returns `null`.
+     */
+    abstract fun lookupIn(state: BrowserState): SessionState?
+
+    /**
+     * Observes this target and represents the mapped state (using [map]) via [State].
+     *
+     * Everytime the [Store] state changes and the result of the [observe] function changes for this
+     * state, the returned [State] will be updated causing recomposition of every [State.value] usage.
+     *
+     * The [Store] observer will automatically be removed when this composable disposes or the current
+     * [LifecycleOwner] moves to the [Lifecycle.State.DESTROYED] state.
+     */
+    @Composable
+    fun <R> observeAsStateFrom(
+        store: BrowserStore,
+        observe: (SessionState?) -> R
+    ): State<SessionState?> {
+        return store.observeAsState(
+            map = { state -> lookupIn(state) },
+            observe = { state -> observe(lookupIn(state)) }
+        )
+    }
+
+    /**
+     * Targets the selected tab.
+     */
+    object Selected : TargetTab() {
+        override fun lookupIn(state: BrowserState): SessionState? {
+            return state.selectedTab
+        }
+    }
+
+    /**
+     * Targets a specific tab by its [tabId].
+     */
+    class Pinned(val tabId: String) : TargetTab() {
+        override fun lookupIn(state: BrowserState): SessionState? {
+            return state.findTab(tabId)
+        }
+    }
+
+    /**
+     * Targets a specific custom tab by its [customTabId].
+     */
+    class Custom(val customTabId: String) : TargetTab() {
+        override fun lookupIn(state: BrowserState): SessionState? {
+            return state.findCustomTab(customTabId)
+        }
+    }
+}