Extract and unit test MultipleTapToUnlock

libraries/ui-utils/build.gradle.kts

@@ -15,5 +15,7 @@ android {
     dependencies {
         testImplementation(libs.test.junit)
         testImplementation(libs.test.truth)
+        testImplementation(libs.coroutines.test)
+        testImplementation(libs.test.truth)
     }
 }

libraries/ui-utils/src/main/kotlin/io/element/android/libraries/ui/utils/MultipleTapToUnlock.kt

@@ -0,0 +1,42 @@
+/*
+ * Copyright 2025 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.ui.utils
+
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.delay
+import kotlinx.coroutines.launch
+import kotlin.time.Duration.Companion.seconds
+
+/**
+ * Returns true if the user has tapped [numberOfTapToUnlock] times in a short amount of time.
+ * The counter is reset after 2 seconds of inactivity.
+ *
+ * @param numberOfTapToUnlock The number of taps required to unlock.
+ */
+class MultipleTapToUnlock(
+    private val numberOfTapToUnlock: Int = 7,
+) {
+    private var counter = numberOfTapToUnlock
+    private var currentJob: Job? = null
+
+    fun unlock(scope: CoroutineScope): Boolean {
+        counter--
+        currentJob?.cancel()
+        return if (counter > 0) {
+            currentJob = scope.launch {
+                delay(2.seconds)
+                // Reset counter if user is not fast enough
+                counter = numberOfTapToUnlock
+            }
+            false
+        } else {
+            true
+        }
+    }
+}

libraries/ui-utils/src/test/kotlin/io/element/android/libraries/ui/utils/MultipleTapToUnlockTest.kt

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2025 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+@file:OptIn(ExperimentalCoroutinesApi::class)
+
+package io.element.android.libraries.ui.utils
+
+import com.google.common.truth.Truth.assertThat
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.test.advanceTimeBy
+import kotlinx.coroutines.test.runTest
+import org.junit.Test
+import kotlin.time.Duration.Companion.seconds
+
+class MultipleTapToUnlockTest {
+    @Test
+    fun `test multiple tap should unlock`() = runTest {
+        val sut = MultipleTapToUnlock(3)
+        assertThat(sut.unlock(backgroundScope)).isFalse()
+        assertThat(sut.unlock(backgroundScope)).isFalse()
+        assertThat(sut.unlock(backgroundScope)).isTrue()
+        assertThat(sut.unlock(backgroundScope)).isTrue()
+        // All next call returns true
+        advanceTimeBy(3.seconds)
+        assertThat(sut.unlock(backgroundScope)).isTrue()
+    }
+    @Test
+    fun `test waiting should reset counter`() = runTest {
+        val sut = MultipleTapToUnlock(3)
+        assertThat(sut.unlock(backgroundScope)).isFalse()
+        assertThat(sut.unlock(backgroundScope)).isFalse()
+        advanceTimeBy(3.seconds)
+        assertThat(sut.unlock(backgroundScope)).isFalse()
+        assertThat(sut.unlock(backgroundScope)).isFalse()
+        assertThat(sut.unlock(backgroundScope)).isTrue()
+    }
+}