Convert ViewModel to kotlin (#233)

Fixes #232

BrickKit/app/build.gradle

@@ -30,6 +30,7 @@ android {
     lintOptions {
         warningsAsErrors true
         abortOnError true
+        disable "GradleDependency"
     }
 }
 

BrickKit/bricks/src/androidTest/java/com/wayfair/brickkit/brick/ViewModelBrickTest.kt

@@ -230,7 +230,13 @@ class ViewModelBrickTest {
             .build()
 
         val countDownLatch = CountDownLatch(1)
-        viewModel.addUpdateListener { countDownLatch.countDown() }
+        viewModel.addUpdateListener(
+            object : ViewModel.ViewModelUpdateListener {
+                override fun onChange() {
+                    countDownLatch.countDown()
+                }
+            }
+        )
 
         assertFalse(viewModelBrick.isHidden)
 

BrickKit/bricks/src/androidTest/java/com/wayfair/brickkit/brick/ViewModelTest.kt

@@ -0,0 +1,46 @@
+package com.wayfair.brickkit.brick
+
+import com.nhaarman.mockitokotlin2.mock
+import com.nhaarman.mockitokotlin2.verify
+import com.nhaarman.mockitokotlin2.whenever
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertTrue
+import org.junit.Before
+import org.junit.Test
+
+class ViewModelTest {
+    private val dataModel: DataModel = mock()
+    private lateinit var viewModel: ViewModel<DataModel>
+
+    @Before
+    fun setup() {
+        viewModel = object : ViewModel<DataModel>(dataModel) { }
+
+        verify(dataModel).addUpdateListener(viewModel)
+    }
+
+    @Test
+    fun testNotifyChange() {
+        val updateListener = mock<ViewModel.ViewModelUpdateListener>()
+
+        viewModel.addUpdateListener(updateListener)
+
+        viewModel.notifyChange()
+
+        verify(updateListener).onChange()
+    }
+
+    @Test
+    fun testIsDataModelReady_dataModelReady() {
+        whenever(dataModel.isReady).thenReturn(true)
+
+        assertTrue(viewModel.isDataModelReady)
+    }
+
+    @Test
+    fun testIsDataModelReady_dataModelNotReady() {
+        whenever(dataModel.isReady).thenReturn(false)
+
+        assertFalse(viewModel.isDataModelReady)
+    }
+}

BrickKit/bricks/src/main/java/com/wayfair/brickkit/brick/ViewModel.kt

@@ -0,0 +1,52 @@
+package com.wayfair.brickkit.brick
+
+import androidx.databinding.BaseObservable
+import com.wayfair.brickkit.brick.DataModel.DataModelUpdateListener
+import java.io.Serializable
+
+/**
+ * The object used to bind information in a [ViewModelBrick].
+ */
+abstract class ViewModel<DM : DataModel> protected constructor(
+    open val dataModel: DM
+) : BaseObservable(), DataModelUpdateListener, Serializable {
+
+    @Transient
+    private var updateListeners = mutableSetOf<ViewModelUpdateListener>()
+
+    init {
+        dataModel.addUpdateListener(this)
+    }
+
+    /**
+     * Add an [ViewModelUpdateListener] to the list of items watching for changes.
+     *
+     * @param updateListener the object that is watching
+     */
+    open fun addUpdateListener(updateListener: ViewModelUpdateListener) {
+        updateListeners.add(updateListener)
+    }
+
+    override fun notifyChange() {
+        super.notifyChange()
+        updateListeners.forEach { updateListener -> updateListener.onChange() }
+    }
+
+    /**
+     * Determines if the [DataModel] is ready, meaning the ViewModel is ready.
+     *
+     * @return if the data model is ready, IE fully populated
+     */
+    open val isDataModelReady: Boolean
+        get() = dataModel.isReady
+
+    /**
+     * Interface for listening to changes.
+     */
+    interface ViewModelUpdateListener {
+        /**
+         * Called when notify change is called.
+         */
+        fun onChange()
+    }
+}