Implement calculated-expression extension

catalog/src/main/assets/calculated_expression_questionnaire.json

@@ -0,0 +1,36 @@
+{
+  "resourceType": "Questionnaire",
+  "item": [
+    {
+      "linkId": "a-birthdate",
+      "text": "Birth Date",
+      "type": "date",
+      "extension": [
+        {
+          "url": "http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-calculatedExpression",
+          "valueExpression": {
+            "language": "text/fhirpath",
+            "expression": "%resource.repeat(item).where(linkId='a-age-years' and answer.empty().not()).select(today() - answer.value)"
+          }
+        }
+      ]
+    },
+    {
+      "linkId": "a-age-years",
+      "text": "Age years",
+      "type": "quantity",
+      "initial": [{
+        "valueQuantity": {
+          "unit": "years",
+          "system": "http://unitsofmeasure.org",
+          "code": "years"
+        }
+      }]
+    },
+    {
+      "linkId": "a-age-acknowledge",
+      "text": "Input age to automatically calculate birthdate until birthdate is updated manually",
+      "type": "display"
+    }
+  ]
+}

catalog/src/main/java/com/google/android/fhir/catalog/BehaviorListViewModel.kt

@@ -33,7 +33,11 @@ class BehaviorListViewModel(application: Application) : AndroidViewModel(applica
     val questionnaireFileName: String,
     val workFlow: WorkflowType = WorkflowType.DEFAULT
   ) {
-    CALCULATIONS(R.drawable.ic_calculations_behavior, R.string.behavior_name_calculation, ""),
-    SKIP_LOGIC(R.drawable.ic_skiplogic_behavior, R.string.behavior_name_skip_logic, "")
+    SKIP_LOGIC(R.drawable.ic_skiplogic_behavior, R.string.behavior_name_skip_logic, ""),
+    CALCULATED_EXPRESSION(
+      R.drawable.ic_calculations_behavior,
+      R.string.behavior_name_calculated_expression,
+      "calculated_expression_questionnaire.json"
+    ),
   }
 }

catalog/src/main/res/values/strings.xml

@@ -35,8 +35,10 @@
   <string name="layout_name_paginated">Paginated</string>
   <string name="layout_name_review">Review</string>
   <string name="layout_name_read_only">Read only</string>
-  <string name="behavior_name_calculation">Calculation</string>
   <string name="behavior_name_skip_logic">Skip logic</string>
+  <string
+        name="behavior_name_calculated_expression"
+    >Calculated Expression</string>
   <string name="toolbar_text">Structured data capture \n Catalog</string>
   <string
         name="questionnaire_response_title"

datacapture/src/androidTest/java/com/google/android/fhir/datacapture/views/QuestionnaireItemEditTextQuantityViewHolderFactoryEspressoTest.kt

@@ -0,0 +1,124 @@
+/*
+ * Copyright 2022 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.android.fhir.datacapture.views
+
+import android.view.View
+import android.widget.FrameLayout
+import android.widget.TextView
+import androidx.test.espresso.Espresso.onView
+import androidx.test.espresso.action.ViewActions.click
+import androidx.test.espresso.action.ViewActions.typeText
+import androidx.test.espresso.matcher.ViewMatchers.withId
+import androidx.test.ext.junit.rules.ActivityScenarioRule
+import androidx.test.platform.app.InstrumentationRegistry
+import com.google.android.fhir.datacapture.R
+import com.google.android.fhir.datacapture.TestActivity
+import com.google.android.fhir.datacapture.validation.NotValidated
+import com.google.common.truth.Truth.assertThat
+import java.math.BigDecimal
+import org.hl7.fhir.r4.model.Quantity
+import org.hl7.fhir.r4.model.Questionnaire
+import org.hl7.fhir.r4.model.QuestionnaireResponse
+import org.junit.Before
+import org.junit.Rule
+import org.junit.Test
+
+class QuestionnaireItemEditTextQuantityViewHolderFactoryEspressoTest {
+  @Rule
+  @JvmField
+  var activityScenarioRule: ActivityScenarioRule<TestActivity> =
+    ActivityScenarioRule(TestActivity::class.java)
+
+  private lateinit var parent: FrameLayout
+  private lateinit var viewHolder: QuestionnaireItemViewHolder
+
+  @Before
+  fun setup() {
+    activityScenarioRule.scenario.onActivity { activity -> parent = FrameLayout(activity) }
+    viewHolder = QuestionnaireItemEditTextQuantityViewHolderFactory.create(parent)
+    setTestLayout(viewHolder.itemView)
+  }
+
+  @Test
+  fun getValue_WithInitial_shouldReturn_Quantity_With_UnitAndSystem() {
+    val questionnaireItemViewItem =
+      QuestionnaireItemViewItem(
+        Questionnaire.QuestionnaireItemComponent().apply {
+          required = true
+          addInitial(
+            Questionnaire.QuestionnaireItemInitialComponent(
+              Quantity().apply {
+                code = "months"
+                system = "http://unitofmeasure.com"
+              }
+            )
+          )
+        },
+        QuestionnaireResponse.QuestionnaireResponseItemComponent(),
+        validationResult = NotValidated,
+        answersChangedCallback = { _, _, _ -> },
+      )
+    runOnUI { viewHolder.bind(questionnaireItemViewItem) }
+
+    onView(withId(R.id.text_input_edit_text)).perform(click())
+    onView(withId(R.id.text_input_edit_text)).perform(typeText("22"))
+    assertThat(
+        viewHolder.itemView.findViewById<TextView>(R.id.text_input_edit_text).text.toString()
+      )
+      .isEqualTo("22")
+
+    val responseValue = questionnaireItemViewItem.answers.first().valueQuantity
+    assertThat(responseValue.code).isEqualTo("months")
+    assertThat(responseValue.system).isEqualTo("http://unitofmeasure.com")
+    assertThat(responseValue.value).isEqualTo(BigDecimal(22))
+  }
+
+  @Test
+  fun getValue_WithoutInitial_shouldReturn_Quantity_Without_UnitAndSystem() {
+    val questionnaireItemViewItem =
+      QuestionnaireItemViewItem(
+        Questionnaire.QuestionnaireItemComponent().apply { required = true },
+        QuestionnaireResponse.QuestionnaireResponseItemComponent(),
+        validationResult = NotValidated,
+        answersChangedCallback = { _, _, _ -> },
+      )
+    runOnUI { viewHolder.bind(questionnaireItemViewItem) }
+
+    onView(withId(R.id.text_input_edit_text)).perform(click())
+    onView(withId(R.id.text_input_edit_text)).perform(typeText("22"))
+    assertThat(
+        viewHolder.itemView.findViewById<TextView>(R.id.text_input_edit_text).text.toString()
+      )
+      .isEqualTo("22")
+
+    val responseValue = questionnaireItemViewItem.answers.first().valueQuantity
+    assertThat(responseValue.code).isNull()
+    assertThat(responseValue.system).isNull()
+    assertThat(responseValue.value).isEqualTo(BigDecimal(22))
+  }
+
+  /** Method to run code snippet on UI/main thread */
+  private fun runOnUI(action: () -> Unit) {
+    activityScenarioRule.scenario.onActivity { action() }
+  }
+
+  /** Method to set content view for test activity */
+  private fun setTestLayout(view: View) {
+    activityScenarioRule.scenario.onActivity { activity -> activity.setContentView(view) }
+    InstrumentationRegistry.getInstrumentation().waitForIdleSync()
+  }
+}

datacapture/src/main/java/com/google/android/fhir/datacapture/MoreQuestionnaireItemComponents.kt

@@ -56,6 +56,9 @@ internal const val EXTENSION_ITEM_CONTROL_SYSTEM = "http://hl7.org/fhir/question
 internal const val EXTENSION_HIDDEN_URL =
   "http://hl7.org/fhir/StructureDefinition/questionnaire-hidden"
 
+internal const val EXTENSION_CALCULATED_EXPRESSION_URL =
+  "http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-calculatedExpression"
+
 internal const val EXTENSION_ENTRY_FORMAT_URL =
   "http://hl7.org/fhir/StructureDefinition/entryFormat"
 
@@ -69,6 +72,9 @@ internal const val EXTENSION_ENABLE_WHEN_EXPRESSION_URL: String =
 
 internal const val EXTENSION_VARIABLE_URL = "http://hl7.org/fhir/StructureDefinition/variable"
 
+internal const val EXTENSION_CQF_CALCULATED_VALUE_URL: String =
+  "http://hl7.org/fhir/StructureDefinition/cqf-calculatedValue"
+
 internal val Questionnaire.QuestionnaireItemComponent.variableExpressions: List<Expression>
   get() =
     this.extension.filter { it.url == EXTENSION_VARIABLE_URL }.map { it.castToExpression(it.value) }
@@ -87,8 +93,29 @@ internal fun Questionnaire.QuestionnaireItemComponent.findVariableExpression(
   return variableExpressions.find { it.name == variableName }
 }
 
-internal const val CQF_CALCULATED_EXPRESSION_URL: String =
-  "http://hl7.org/fhir/StructureDefinition/cqf-calculatedValue"
+/** Returns Calculated expression, or null */
+internal val Questionnaire.QuestionnaireItemComponent.calculatedExpression: Expression?
+  get() =
+    this.getExtensionByUrl(EXTENSION_CALCULATED_EXPRESSION_URL)?.let {
+      it.castToExpression(it.value)
+    }
+
+/** Returns list of extensions whose value is of type [Expression] */
+internal val Questionnaire.QuestionnaireItemComponent.expressionBasedExtensions
+  get() = this.extension.filter { it.value is Expression }
+
+/**
+ * Check if given [item] has calculable expression based extension and is referencing current item
+ */
+internal fun Questionnaire.QuestionnaireItemComponent.isReferencedBy(
+  item: Questionnaire.QuestionnaireItemComponent
+) =
+  item.expressionBasedExtensions.any {
+    it.castToExpression(it.value)
+      .expression
+      .replace(" ", "")
+      .contains(Regex(".*linkId='${this.linkId}'.*"))
+  }
 
 // Item control code, or null
 internal val Questionnaire.QuestionnaireItemComponent.itemControl: ItemControlTypes?
@@ -297,7 +324,12 @@ val Questionnaire.QuestionnaireItemComponent.enableWhenExpression: Expression?
  */
 private fun Questionnaire.QuestionnaireItemComponent.createQuestionnaireResponseItemAnswers():
   MutableList<QuestionnaireResponse.QuestionnaireResponseItemAnswerComponent>? {
-  if (initial.isEmpty()) {
+  // https://build.fhir.org/ig/HL7/sdc/behavior.html#initial
+  // quantity given as initial without value is for unit reference purpose only. Answer conversion
+  // not needed
+  if (initial.isEmpty() ||
+      (initialFirstRep.hasValueQuantity() && initialFirstRep.valueQuantity.value == null)
+  ) {
     return null
   }
 
@@ -336,6 +368,15 @@ fun QuestionnaireResponse.QuestionnaireResponseItemComponent.addNestedItemsToAns
   }
 }
 
+/**
+ * Flatten a nested list of [QuestionnaireResponse.QuestionnaireResponseItemAnswerComponent]
+ * recursively and returns a flat list of all items into list embedded at any level
+ */
+fun List<Questionnaire.QuestionnaireItemComponent>.flattened():
+  List<Questionnaire.QuestionnaireItemComponent> {
+  return this + this.flatMap { it.item.flattened() }
+}
+
 /**
  * Creates a list of [QuestionnaireResponse.QuestionnaireResponseItemComponent]s from the nested
  * items in the [Questionnaire.QuestionnaireItemComponent].

datacapture/src/main/java/com/google/android/fhir/datacapture/QuestionnaireViewModel.kt

@@ -26,6 +26,8 @@ import ca.uhn.fhir.context.FhirContext
 import ca.uhn.fhir.context.FhirVersionEnum
 import ca.uhn.fhir.parser.IParser
 import com.google.android.fhir.datacapture.enablement.EnablementEvaluator
+import com.google.android.fhir.datacapture.fhirpath.ExpressionEvaluator.detectExpressionCyclicDependency
+import com.google.android.fhir.datacapture.fhirpath.ExpressionEvaluator.evaluateCalculatedExpressions
 import com.google.android.fhir.datacapture.validation.NotValidated
 import com.google.android.fhir.datacapture.validation.QuestionnaireResponseItemValidator
 import com.google.android.fhir.datacapture.validation.QuestionnaireResponseValidator.checkQuestionnaireResponse
@@ -268,8 +270,10 @@ internal class QuestionnaireViewModel(application: Application, state: SavedStat
     if (questionnaireItem.hasNestedItemsWithinAnswers) {
       questionnaireResponseItem.addNestedItemsToAnswer(questionnaireItem)
     }
-
     modifiedQuestionnaireResponseItemSet.add(questionnaireResponseItem)
+
+    runCalculations(questionnaireItem)
+
     modificationCount.update { it + 1 }
   }
 
@@ -366,8 +370,41 @@ internal class QuestionnaireViewModel(application: Application, state: SavedStat
             currentPageIndex = getInitialPageIndex(),
             reviewMode = enableReviewPage
           )
+            .also { detectExpressionCyclicDependency(questionnaire.item) }
+            .also { questionnaire.item.flattened().forEach { runCalculations(it) } }
       )
 
+  fun runCalculations(updatedQuestionnaireItem: Questionnaire.QuestionnaireItemComponent) {
+    evaluateCalculatedExpressions(
+      updatedQuestionnaireItem,
+      questionnaire,
+      questionnaireResponse,
+      modifiedQuestionnaireResponseItemSet,
+      questionnaireItemParentMap
+    )
+      .forEach { updatedCalculable ->
+        val updatedCalculableResponse =
+          questionnaireResponseItemPreOrderList.find { it.linkId == updatedCalculable.first.linkId }
+
+        val evaluatedAnswer = updatedCalculable.second
+        val currentAnswer = updatedCalculableResponse?.answer?.map { it.value } ?: emptyList()
+
+        // update and notify only if new answer has changed to prevent any event loop
+        if (evaluatedAnswer.size != currentAnswer.size ||
+            evaluatedAnswer.zip(currentAnswer).any { (v1, v2) -> v1.equalsDeep(v2).not() }
+        ) {
+          updatedCalculableResponse?.let {
+            it.answer =
+              evaluatedAnswer.map {
+                QuestionnaireResponse.QuestionnaireResponseItemAnswerComponent().apply {
+                  value = it
+                }
+              }
+          }
+        }
+      }
+  }
+
   @PublishedApi
   internal suspend fun resolveAnswerValueSet(
     uri: String