Add a duration formatter.

libraries/dateformatter/api/build.gradle.kts

@@ -11,4 +11,9 @@ plugins {
 
 android {
     namespace = "io.element.android.libraries.dateformatter.api"
+
+    dependencies {
+        testImplementation(libs.test.junit)
+        testImplementation(libs.test.truth)
+    }
 }

libraries/dateformatter/api/src/main/kotlin/io/element/android/libraries/dateformatter/api/DurationFormatter.kt

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2024 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ * Please see LICENSE in the repository root for full details.
+ */
+
+package io.element.android.libraries.dateformatter.api
+
+import java.util.Locale
+
+/**
+ * Convert milliseconds to human readable duration.
+ * Hours in 1 digit or more.
+ * Minutes in 2 digits when hours are available.
+ * Seconds always on 2 digits.
+ * Example:
+ * - when the duration is longer than 1 hour:
+ * - "10:23:34"
+ * - "1:23:34"
+ * - "1:03:04"
+ * - when the duration is shorter:
+ * - "4:56"
+ * - "14:06"
+ * - Less than one minute:
+ * - "0:00"
+ * - "0:01"
+ * - "0:59"
+ */
+fun Long.toHumanReadableDuration(): String {
+    val inSeconds = this / 1_000
+    val hours = inSeconds / 3_600
+    val minutes = (inSeconds % 3_600) / 60
+    val seconds = inSeconds % 60
+    return if (hours > 0) {
+        String.format(Locale.US, "%d:%02d:%02d", hours, minutes, seconds)
+    } else {
+        String.format(Locale.US, "%d:%02d", minutes, seconds)
+    }
+}

libraries/dateformatter/api/src/test/kotlin/io/element/android/libraries/dateformatter/api/DurationFormatterTest.kt

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2024 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ * Please see LICENSE in the repository root for full details.
+ */
+
+package io.element.android.libraries.dateformatter.api
+
+import com.google.common.truth.Truth.assertThat
+import org.junit.Test
+
+class DurationFormatterTest {
+    @Test
+    fun `format seconds only`() {
+        assertThat(buildDuration().toHumanReadableDuration()).isEqualTo("0:00")
+        assertThat(buildDuration(seconds = 1).toHumanReadableDuration()).isEqualTo("0:01")
+        assertThat(buildDuration(seconds = 59).toHumanReadableDuration()).isEqualTo("0:59")
+    }
+
+    @Test
+    fun `format minutes and seconds`() {
+        assertThat(buildDuration(minutes = 1).toHumanReadableDuration()).isEqualTo("1:00")
+        assertThat(buildDuration(minutes = 1, seconds = 30).toHumanReadableDuration()).isEqualTo("1:30")
+        assertThat(buildDuration(minutes = 59, seconds = 59).toHumanReadableDuration()).isEqualTo("59:59")
+    }
+
+    @Test
+    fun `format hours, minutes and seconds`() {
+        assertThat(buildDuration(hours = 1).toHumanReadableDuration()).isEqualTo("1:00:00")
+        assertThat(buildDuration(hours = 1, minutes = 1, seconds = 1).toHumanReadableDuration()).isEqualTo("1:01:01")
+        assertThat(buildDuration(hours = 24, minutes = 59, seconds = 59).toHumanReadableDuration()).isEqualTo("24:59:59")
+        assertThat(buildDuration(hours = 25, minutes = 0, seconds = 0).toHumanReadableDuration()).isEqualTo("25:00:00")
+    }
+
+    private fun buildDuration(
+        hours: Int = 0,
+        minutes: Int = 0,
+        seconds: Int = 0
+    ): Long {
+        return (hours * 60 * 60 + minutes * 60 + seconds) * 1000L
+    }
+}