Render bmi when height and weight changes

app/src/main/java/org/simple/clinic/patientattribute/entry/BMIEntryUi.kt

@@ -4,4 +4,6 @@ interface BMIEntryUi {
   fun closeSheet()
   fun changeFocusToHeight()
   fun changeFocusToWeight()
+  fun showBMI(bmi: String)
+  fun hideBMI()
 }

app/src/main/java/org/simple/clinic/patientattribute/entry/BMIEntryUiRenderer.kt

@@ -0,0 +1,22 @@
+package org.simple.clinic.patientattribute.entry
+
+import org.simple.clinic.mobius.ViewRenderer
+import org.simple.clinic.patientattribute.BMIReading
+
+class BMIEntryUiRenderer(
+    val ui: BMIEntryUi
+) : ViewRenderer<BMIEntryModel> {
+
+  override fun render(model: BMIEntryModel) {
+    if (model.height.isNotEmpty() && model.weight.isNotEmpty()) {
+      val bmi = BMIReading(
+          height = model.height,
+          weight = model.weight
+      ).calculateBMI()
+
+      ui.showBMI(bmi.toString())
+    } else {
+      ui.hideBMI()
+    }
+  }
+}

app/src/test/java/org/simple/clinic/patientattribute/entry/BMIEntryUiRendererTest.kt

@@ -0,0 +1,42 @@
+package org.simple.clinic.patientattribute.entry
+
+import org.junit.Test
+import org.mockito.kotlin.mock
+import org.mockito.kotlin.verify
+import org.mockito.kotlin.verifyNoMoreInteractions
+import org.simple.clinic.patientattribute.BMIReading
+import java.util.UUID
+
+class BMIEntryUiRendererTest {
+  private val ui = mock<BMIEntryUi>()
+  private val uiRenderer = BMIEntryUiRenderer(ui)
+  private val patientUuid = UUID.fromString("d6dd1708-9061-4c6c-b5c7-47b132198862")
+  private val defaultModel = BMIEntryModel
+      .default(patientUuid)
+
+  @Test
+  fun `when the sheet is show for a new entry, then hide bmi`() {
+    // when
+    uiRenderer.render(defaultModel)
+
+    // then
+    verify(ui).hideBMI()
+    verifyNoMoreInteractions(ui)
+  }
+
+  @Test
+  fun `when the height and weight are entered, then show bmi`() {
+    //given
+    val height = "177"
+    val weight = "68"
+    val reading = BMIReading(height, weight)
+    val bmi = reading.calculateBMI().toString()
+
+    // when
+    uiRenderer.render(defaultModel.heightChanged(height).weightChanged(weight))
+
+    // then
+    verify(ui).showBMI(bmi)
+    verifyNoMoreInteractions(ui)
+  }
+}