Merge pull request #13 from mvarnagiris/memory_cache

Memory cache

src/main/kotlin/com/mvcoding/mvp/DataSource.kt

@@ -0,0 +1,5 @@
+package com.mvcoding.mvp
+
+interface DataSource<DATA> {
+    fun data(): O<DATA>
+}

src/main/kotlin/com/mvcoding/mvp/data/FunctionDataSource.kt

@@ -0,0 +1,10 @@
+package com.mvcoding.mvp.data
+
+import com.mvcoding.mvp.DataSource
+import com.mvcoding.mvp.O
+
+class FunctionDataSource<DATA>(private val dataSource: () -> O<DATA>) : DataSource<DATA> {
+    override fun data(): O<DATA> = dataSource()
+}
+
+fun <DATA> (() -> O<DATA>).dataSource() = FunctionDataSource(this)

src/main/kotlin/com/mvcoding/mvp/data/MemoryDataSource.kt

@@ -0,0 +1,15 @@
+package com.mvcoding.mvp.data
+
+import com.mvcoding.mvp.DataSource
+import com.mvcoding.mvp.O
+
+class MemoryDataSource<DATA>(dataSource: DataSource<DATA>) : DataSource<DATA> {
+    constructor(dataSource: () -> O<DATA>) : this(dataSource.dataSource())
+
+    private val observable by lazy { dataSource.data().replay(1).autoConnect() }
+
+    override fun data(): O<DATA> = observable
+}
+
+fun <DATA> DataSource<DATA>.memoryDataSource() = MemoryDataSource(this)
+fun <DATA> (() -> O<DATA>).memoryDataSource() = MemoryDataSource(this)

src/test/kotlin/com/mvcoding/mvp/data/MemoryDataSourceTest.kt

@@ -0,0 +1,72 @@
+package com.mvcoding.mvp.data
+
+import com.jakewharton.rxrelay2.PublishRelay
+import com.mvcoding.mvp.DataSource
+import com.nhaarman.mockitokotlin2.mock
+import com.nhaarman.mockitokotlin2.times
+import com.nhaarman.mockitokotlin2.verify
+import com.nhaarman.mockitokotlin2.whenever
+import io.reactivex.observers.TestObserver
+import org.junit.Test
+
+class MemoryDataSourceTest {
+
+    @Test
+    fun `upstream DataSource is called only once and cached data is returned to other observers`() {
+        testUpstreamDataSourceIsCalledOnlyOnceAndCachedDataIsReturnedToOtherObservers(1) { it.memoryDataSource() }
+    }
+
+    @Test
+    fun `returns data to late observers when initial observers are disposed before data is delivered`() {
+        testReturnsDataToLateObserversWhenInitialObserversAreDisposedBeforeDataIsDelivered(1) { it.memoryDataSource() }
+    }
+}
+
+fun <DATA> testMemoryDataSource(data: DATA, createDataSource: (DataSource<DATA>) -> DataSource<DATA>) {
+    testUpstreamDataSourceIsCalledOnlyOnceAndCachedDataIsReturnedToOtherObservers(data, createDataSource)
+    testReturnsDataToLateObserversWhenInitialObserversAreDisposedBeforeDataIsDelivered(data, createDataSource)
+}
+
+private fun <DATA> testUpstreamDataSourceIsCalledOnlyOnceAndCachedDataIsReturnedToOtherObservers(
+        data: DATA,
+        createDataSource: (DataSource<DATA>) -> DataSource<DATA>) {
+
+    val initialObserver1 = TestObserver.create<DATA>()
+    val initialObserver2 = TestObserver.create<DATA>()
+    val otherObserver = TestObserver.create<DATA>()
+    val relay = PublishRelay.create<DATA>()
+    val upstreamDataSource = mock<DataSource<DATA>>()
+    val dataSource = createDataSource(upstreamDataSource)
+    whenever(upstreamDataSource.data()).thenReturn(relay)
+
+    dataSource.data().subscribe(initialObserver1)
+    dataSource.data().subscribe(initialObserver2)
+    relay.accept(data)
+    dataSource.data().subscribe(otherObserver)
+
+    initialObserver1.assertValue(data)
+    initialObserver2.assertValue(data)
+    otherObserver.assertValue(data)
+    verify(upstreamDataSource, times(1)).data()
+}
+
+private fun <DATA> testReturnsDataToLateObserversWhenInitialObserversAreDisposedBeforeDataIsDelivered(
+        data: DATA,
+        createDataSource: (DataSource<DATA>) -> DataSource<DATA>) {
+
+    val initialObserver = TestObserver.create<DATA>()
+    val otherObserver = TestObserver.create<DATA>()
+    val relay = PublishRelay.create<DATA>()
+    val upstreamDataSource = mock<DataSource<DATA>>()
+    val dataSource = createDataSource(upstreamDataSource)
+    whenever(upstreamDataSource.data()).thenReturn(relay)
+
+    dataSource.data().subscribe(initialObserver)
+    initialObserver.dispose()
+    relay.accept(data)
+    dataSource.data().subscribe(otherObserver)
+
+    initialObserver.assertNoValues()
+    otherObserver.assertValue(data)
+    verify(upstreamDataSource, times(1)).data()
+}