populate initial with initialExpression result collection (#2751)

* populate initial with initialExpression result collection

* handle invariant rules for initialExpression

* convert evaluatedExpressionResult to questionnaireItem.type

* updated answerOptions in test to match initialExpressions' result

* added rule url in check message for initial value on group or display items.

* added test for invariant rule que-8 & codings without system match in initialExpression

* - refactored populateInitialValue
Handles repeats logic for answerOption

* - integrated tests for populateInitialValues

* - (spotless fix) ResourceMapperTest.kt

* - (feedback) added test & refactored code to use variables.

* - (refactor) updated multiline comment

Author: parthfloyd

datacapture/src/main/java/com/google/android/fhir/datacapture/mapping/ResourceMapper.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2022-2024 Google LLC
+ * Copyright 2022-2025 Google LLC
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,6 +19,7 @@ package com.google.android.fhir.datacapture.mapping
 import com.google.android.fhir.datacapture.extensions.createQuestionnaireResponseItem
 import com.google.android.fhir.datacapture.extensions.filterByCodeInNameExtension
 import com.google.android.fhir.datacapture.extensions.initialExpression
+import com.google.android.fhir.datacapture.extensions.initialSelected
 import com.google.android.fhir.datacapture.extensions.logicalId
 import com.google.android.fhir.datacapture.extensions.questionnaireLaunchContexts
 import com.google.android.fhir.datacapture.extensions.targetStructureMap
@@ -248,22 +249,59 @@ object ResourceMapper {
       "QuestionnaireItem item is not allowed to have both initial.value and initial expression. See rule at http://build.fhir.org/ig/HL7/sdc/expressions.html#initialExpression."
     }
 
+    // Initial values can't be specified for groups or display items
+    check(
+      !(questionnaireItem.type == Questionnaire.QuestionnaireItemType.GROUP ||
+        questionnaireItem.type == Questionnaire.QuestionnaireItemType.DISPLAY) ||
+        (questionnaireItem.initial.isEmpty() && questionnaireItem.initialExpression == null),
+    ) {
+      "QuestionnaireItem item is not allowed to have initial value or initial expression for groups or display items. See rule at http://build.fhir.org/ig/HL7/sdc/expressions.html#initialExpression."
+    }
+
     questionnaireItem.initialExpression
       ?.let {
         evaluateToBase(
-            questionnaireResponse = null,
-            questionnaireResponseItem = null,
-            expression = it.expression,
-            contextMap = launchContexts,
-          )
-          .firstOrNull()
+          questionnaireResponse = null,
+          questionnaireResponseItem = null,
+          expression = it.expression,
+          contextMap = launchContexts,
+        )
       }
       ?.let {
-        // Set initial value for the questionnaire item. Questionnaire items should not have both
-        // initial value and initial expression.
-        val value = it.asExpectedType(questionnaireItem.type)
-        questionnaireItem.initial =
-          mutableListOf(Questionnaire.QuestionnaireItemInitialComponent().setValue(value))
+        // Set initial value for the questionnaire item.
+        if (it.isEmpty()) return@let
+
+        // If questionnaireItem.repeats is false only first value is selected from initialExpression
+        // result set
+        val evaluatedExpressionResult =
+          if (questionnaireItem.repeats) {
+            it.map { it.asExpectedType(questionnaireItem.type) }
+          } else {
+            listOf(it.first().asExpectedType(questionnaireItem.type))
+          }
+
+        /**
+         * For answer options, the initialSelected extension is used to highlight initial values.
+         *
+         * Note: If the initial expression evaluates to five values (1, 2, 3, 4, 5) but only three
+         * answer options (1, 2, 3) exist, then 4 and 5 will be ignored. These values are not added
+         * as additional options, nor would it make sense to do so. This behavior ensures the answer
+         * options remain consistent with the defined set.
+         */
+        if (questionnaireItem.answerOption.isNotEmpty()) {
+          questionnaireItem.answerOption.forEach { answerOption ->
+            answerOption.initialSelected =
+              evaluatedExpressionResult.any { answerOption.value.equalsDeep(it) }
+          }
+        } else {
+          questionnaireItem.initial =
+            evaluatedExpressionResult.map {
+              Questionnaire.QuestionnaireItemInitialComponent()
+                .setValue(
+                  it,
+                )
+            }
+        }
       }
 
     populateInitialValues(questionnaireItem.item, launchContexts)