feat: exponential backoff policy for webview reload

app/src/main/AndroidManifest.xml

@@ -0,0 +1,3 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
+</manifest>

app/src/main/java/cz/c3c/webviewkiosk/BackoffPolicy.kt

@@ -0,0 +1,19 @@
+package cz.c3c.webviewkiosk
+
+class BackoffPolicy(
+    private val initialDelayMs: Long,
+    private val maxDelayMs: Long,
+    private val factor: Double = 2.0,
+) {
+    private var nextMs = initialDelayMs
+
+    fun nextDelayMs(): Long {
+        val current = nextMs
+        nextMs = (nextMs * factor).toLong().coerceAtMost(maxDelayMs)
+        return current
+    }
+
+    fun reset() {
+        nextMs = initialDelayMs
+    }
+}

app/src/test/java/cz/c3c/webviewkiosk/BackoffPolicyTest.kt

@@ -0,0 +1,39 @@
+package cz.c3c.webviewkiosk
+
+import org.junit.Assert.assertEquals
+import org.junit.Test
+
+class BackoffPolicyTest {
+
+    @Test
+    fun firstDelayIsInitial() {
+        val b = BackoffPolicy(initialDelayMs = 2_000, maxDelayMs = 60_000)
+        assertEquals(2_000, b.nextDelayMs())
+    }
+
+    @Test
+    fun delayDoublesOnEachCall() {
+        val b = BackoffPolicy(initialDelayMs = 2_000, maxDelayMs = 60_000)
+        b.nextDelayMs()
+        assertEquals(4_000, b.nextDelayMs())
+        assertEquals(8_000, b.nextDelayMs())
+    }
+
+    @Test
+    fun delayCapsAtMax() {
+        val b = BackoffPolicy(initialDelayMs = 2_000, maxDelayMs = 5_000)
+        b.nextDelayMs() // 2000
+        b.nextDelayMs() // 4000
+        assertEquals(5_000, b.nextDelayMs())
+        assertEquals(5_000, b.nextDelayMs())
+    }
+
+    @Test
+    fun resetReturnsToInitial() {
+        val b = BackoffPolicy(initialDelayMs = 2_000, maxDelayMs = 60_000)
+        b.nextDelayMs()
+        b.nextDelayMs()
+        b.reset()
+        assertEquals(2_000, b.nextDelayMs())
+    }
+}