Added withDeepLink extension function

decompose/src/androidMain/kotlin/com/arkivanov/decompose/DeeplinkUtils.kt

@@ -0,0 +1,83 @@
+package com.arkivanov.decompose
+
+import android.app.Activity
+import android.app.TaskStackBuilder
+import android.content.Intent
+import android.net.Uri
+import android.os.Bundle
+import androidx.activity.ComponentActivity
+import androidx.core.os.bundleOf
+
+/**
+ * Extracts a deep link URL from this [Activity] [Intent], calls [block]
+ * function with the extracted deep link URL (if any) and returns the result.
+ *
+ * It is strongly recommended to always use the `standard` (default)
+ * `launchMode` for the [Activity] when handling deep links. This function takes
+ * care of restarting the [Activity] task if needed, in which case the returned
+ * value is `null`.
+ *
+ * Example of creating a root component with deep link support.
+ *
+ * ```kotlin
+ * class MainActivity : AppCompatActivity() {
+ *     override fun onCreate(savedInstanceState: Bundle?) {
+ *         super.onCreate(savedInstanceState)
+ *
+ *         val root =
+ *             withDeepLink { uri ->
+ *                 val itemId = uri?.extractItemId() // Parse the deep link
+ *                 DefaultRootComponent(
+ *                     componentContext = defaultComponentContext(discardSavedState = itemId != null),
+ *                     itemId = itemId,
+ *                 )
+ *             } ?: return
+ *
+ *         // Display the root component as usual
+ *     }
+ *
+ *     private fun Uri.extractItemId(): String? =
+ *         TODO("Extract item id from the deep link")
+ * }
+ * ```
+ */
+@ExperimentalDecomposeApi
+fun <T : Any> ComponentActivity.withDeepLink(block: (deepLink: Uri?) -> T): T? {
+    if (restartIfNeeded()) {
+        return null
+    }
+
+    val savedState: Bundle? = savedStateRegistry.consumeRestoredStateForKey(key = KEY_SAVED_DEEP_LINK_STATE)
+    val lastDeepLink = savedState?.getParcelable(KEY_LAST_DEEP_LINK) as Uri?
+    val deepLink = intent.data
+
+    savedStateRegistry.registerSavedStateProvider(key = KEY_SAVED_DEEP_LINK_STATE) {
+        bundleOf(KEY_LAST_DEEP_LINK to deepLink)
+    }
+
+    return block(deepLink.takeUnless { it == lastDeepLink })
+}
+
+// Derived from https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:navigation/navigation-runtime/src/main/java/androidx/navigation/NavController.kt;l=1487-1504?q=Intent.flags&ss=androidx%2Fplatform%2Fframeworks%2Fsupport:navigation%2F
+private fun Activity.restartIfNeeded(): Boolean {
+    if ((intent.flags and Intent.FLAG_ACTIVITY_NEW_TASK == 0) || (intent.flags and Intent.FLAG_ACTIVITY_CLEAR_TASK != 0)) {
+        return false
+    }
+
+    // Someone called us with NEW_TASK, but we don't know what state our whole
+    // task stack is in, so we need to manually restart the whole stack to
+    // ensure we're in a predictably good state.
+
+    intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK)
+    TaskStackBuilder.create(this).addNextIntentWithParentStack(intent).startActivities()
+    finish()
+    // Disable second animation in case where the Activity is created twice.
+    @Suppress("DEPRECATION")
+    overridePendingTransition(0, 0)
+
+    return true
+}
+
+private const val KEY_SAVED_DEEP_LINK_STATE = "SAVED_DEEP_LINK_STATE"
+private const val KEY_LAST_DEEP_LINK = "LAST_DEEP_LINK"
+