Constraint support (local and error case only)

catalog/src/main/assets/behavior_questionnaire_constraint.json

@@ -0,0 +1,86 @@
+{
+  "resourceType": "Questionnaire",
+  "item": [
+    {
+      "linkId": "1",
+      "text": "Password",
+      "type": "string",
+      "item": [
+        {
+          "extension": [
+            {
+              "url": "http://hl7.org/fhir/StructureDefinition/questionnaire-displayCategory",
+              "valueCodeableConcept": {
+                "coding": [
+                  {
+                    "system": "http://hl7.org/fhir/questionnaire-display-category",
+                    "code": "instructions"
+                  }
+                ]
+              }
+            }
+          ],
+          "linkId": "1.1",
+          "text": "Fill the password first",
+          "type": "display"
+        }
+      ]
+    },
+    {
+      "extension": [
+        {
+          "url": "http://hl7.org/fhir/StructureDefinition/questionnaire-constraint",
+          "extension": [
+            {
+              "url": "key",
+              "valueId": "constraint-1"
+            },
+            {
+              "url": "requirements",
+              "valueString": "Confirm password field must have the same value as password field"
+            },
+            {
+              "url": "severity",
+              "valueCode": "error"
+            },
+            {
+              "url": "expression",
+              "valueString": "%context.answer.value = %resource.descendants().where(linkId='1').answer.value"
+            },
+            {
+              "url": "human",
+              "valueString": "Password does not match"
+            },
+            {
+              "url": "location",
+              "valueString": "1"
+            }
+          ]
+        }
+      ],
+      "linkId": "2",
+      "text": "Confirm password",
+      "type": "string",
+      "item": [
+        {
+          "extension": [
+            {
+              "url": "http://hl7.org/fhir/StructureDefinition/questionnaire-displayCategory",
+              "valueCodeableConcept": {
+                "coding": [
+                  {
+                    "system": "http://hl7.org/fhir/questionnaire-display-category",
+                    "code": "instructions"
+                  }
+                ]
+              }
+            }
+          ],
+          "linkId": "2.1",
+          "text": "Show error message if confirm password does not match with password",
+          "type": "display"
+        }
+      ]
+    }
+  ]
+}

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

@@ -63,6 +63,11 @@ class BehaviorListViewModel(application: Application) : AndroidViewModel(applica
       R.string.behavior_name_dynamic_question_text,
       "behavior_dynamic_question_text.json",
     ),
+    QUESTIONNAIRE_CONSTRAINT(
+      R.drawable.ic_rule,
+      R.string.behavior_name_questionnaire_constraint,
+      "behavior_questionnaire_constraint.json",
+    ),
   }
 
   fun isBehavior(context: Context, title: String) =

catalog/src/main/res/drawable/ic_rule.xml

@@ -0,0 +1,12 @@
+<vector
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="48dp"
+    android:height="48dp"
+    android:viewportWidth="960"
+    android:viewportHeight="960"
+>
+  <path
+        android:fillColor="#1A73E8"
+        android:pathData="M576,800L534,758L645,647L534,536L576,494L687,605L798,494L840,536L729,647L840,758L798,800L687,689L576,800ZM659,426L517,284L559,242L659,341L838,162L880,205L659,426ZM80,670L80,610L440,610L440,670L80,670ZM80,350L80,290L440,290L440,350L80,350Z"
+    />
+</vector>

catalog/src/main/res/layout/behavior_list_fragment.xml

@@ -11,6 +11,7 @@
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:layout_marginHorizontal="@dimen/component_horizontal_margin"
+        android:layout_marginBottom="@dimen/bottom_navigation_view_height"
     />
 
 </FrameLayout>

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

@@ -52,6 +52,9 @@
     <string
         name="behavior_name_dynamic_question_text"
     >Dynamic question text</string>
+    <string
+        name="behavior_name_questionnaire_constraint"
+    >Questionnaire constraint</string>
     <string name="component_name_initial_value">Initial Value</string>
     <string
         name="behavior_name_calculated_expression_info"

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

@@ -386,6 +386,9 @@ internal class QuestionnaireViewModel(application: Application, state: SavedStat
       externalValueSetResolver,
     )
 
+  private val questionnaireResponseItemValidator: QuestionnaireResponseItemValidator =
+    QuestionnaireResponseItemValidator(expressionEvaluator)
+
   /**
    * Adds empty [QuestionnaireResponseItemComponent]s to `responseItems` so that each
    * [QuestionnaireItemComponent] in `questionnaireItems` has at least one corresponding
@@ -729,17 +732,11 @@ internal class QuestionnaireViewModel(application: Application, state: SavedStat
           forceValidation ||
           isInReviewModeFlow.value
       ) {
-        QuestionnaireResponseItemValidator.validate(
+        questionnaireResponseItemValidator.validate(
           questionnaireItem,
-          questionnaireResponseItem.answer,
+          questionnaireResponseItem,
           [email protected](),
-        ) {
-          expressionEvaluator.evaluateExpressionValue(
-            questionnaireItem,
-            questionnaireResponseItem,
-            it,
-          )
-        }
+        )
       } else {
         NotValidated
       }

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

@@ -44,6 +44,7 @@ import org.hl7.fhir.r4.model.DecimalType
 import org.hl7.fhir.r4.model.Expression
 import org.hl7.fhir.r4.model.IntegerType
 import org.hl7.fhir.r4.model.Questionnaire
+import org.hl7.fhir.r4.model.Questionnaire.QuestionnaireItemComponent
 import org.hl7.fhir.r4.model.QuestionnaireResponse
 import org.hl7.fhir.r4.model.Reference
 import org.hl7.fhir.r4.model.Resource
@@ -113,6 +114,27 @@ internal const val EXTENSION_MAX_SIZE = "http://hl7.org/fhir/StructureDefinition
 
 internal const val EXTENSION_MIME_TYPE = "http://hl7.org/fhir/StructureDefinition/mimeType"
 
+/**
+ * Extension for questionnaire and its items, representing a rule that must be satisfied before
+ * [QuestionnaireResponse] can be considered valid.
+ *
+ * See https://hl7.org/fhir/extensions/StructureDefinition-questionnaire-constraint.html.
+ */
+internal const val EXTENSION_QUESTIONNAIRE_CONSTRAINT_URL =
+  "http://hl7.org/fhir/StructureDefinition/questionnaire-constraint"
+
+internal const val EXTENSION_QUESTIONNAIRE_CONSTRAINT_KEY = "key"
+
+internal const val EXTENSION_QUESTIONNAIRE_CONSTRAINT_REQUIREMENTS = "requirements"
+
+internal const val EXTENSION_QUESTIONNAIRE_CONSTRAINT_SEVERITY = "severity"
+
+internal const val EXTENSION_QUESTIONNAIRE_CONSTRAINT_EXPRESSION = "expression"
+
+internal const val EXTENSION_QUESTIONNAIRE_CONSTRAINT_HUMAN = "human"
+
+internal const val EXTENSION_QUESTIONNAIRE_CONSTRAINT_LOCATION = "location"
+
 /**
  * Extension for questionnaire items of integer and decimal types including a single unit to be
  * displayed.
@@ -775,6 +797,14 @@ internal fun Questionnaire.QuestionnaireItemComponent.extractAnswerOptions(
   }.map { Questionnaire.QuestionnaireItemAnswerOptionComponent(it) }
 }
 
+/** See http://hl7.org/fhir/constraint-severity */
+enum class ConstraintSeverityTypes(
+  val code: String,
+) {
+  ERROR("error"),
+  WARNING("warning"),
+}
+
 // ********************************************************************************************** //
 //                                                                                                //
 // Utilities: zip with questionnaire response item list, nested items, create response items,     //

datacapture/src/main/java/com/google/android/fhir/datacapture/validation/AnswerConstraintValidator.kt

@@ -23,10 +23,10 @@ import org.hl7.fhir.r4.model.QuestionnaireResponse
 import org.hl7.fhir.r4.model.Type
 
 /**
- * Validates [QuestionnaireResponse.QuestionnaireResponseItemComponent] against a particular
+ * Validates [QuestionnaireResponse.QuestionnaireResponseItemAnswerComponent] against a particular
  * constraint.
  */
-internal interface AnswerConstraintValidator {
+internal interface AnswerConstraintValidator : ConstraintValidator {
   /**
    * Validates whether the [answer] satisfies any constraints of the [questionnaireItem] according
    * to the [Structured Data Capture Implementation Guide]
@@ -42,11 +42,5 @@ internal interface AnswerConstraintValidator {
     answer: QuestionnaireResponse.QuestionnaireResponseItemAnswerComponent,
     context: Context,
     expressionEvaluator: suspend (Expression) -> Type?,
-  ): Result
-
-  /**
-   * The validation result containing whether the answer is valid and any error message if it is not
-   * valid.
-   */
-  data class Result(val isValid: Boolean, val errorMessage: String?)
+  ): ConstraintValidator.Result
 }

datacapture/src/main/java/com/google/android/fhir/datacapture/validation/AnswerExtensionConstraintValidator.kt

@@ -50,7 +50,7 @@ internal open class AnswerExtensionConstraintValidator(
     answer: QuestionnaireResponse.QuestionnaireResponseItemAnswerComponent,
     context: Context,
     expressionEvaluator: suspend (Expression) -> Type?,
-  ): AnswerConstraintValidator.Result {
+  ): ConstraintValidator.Result {
     if (questionnaireItem.hasExtension(url)) {
       val extension = questionnaireItem.getExtensionByUrl(url)
       val extensionValue =
@@ -61,12 +61,12 @@ internal open class AnswerExtensionConstraintValidator(
       if (
         extensionValue.hasValue() && answer.value.hasValue() && predicate(extensionValue, answer)
       ) {
-        return AnswerConstraintValidator.Result(
+        return ConstraintValidator.Result(
           false,
           messageGenerator(extensionValue, context),
         )
       }
     }
-    return AnswerConstraintValidator.Result(true, null)
+    return ConstraintValidator.Result(true, null)
   }
 }

datacapture/src/main/java/com/google/android/fhir/datacapture/validation/ConstraintItemExtensionValidator.kt

@@ -0,0 +1,87 @@
+/*
+ * Copyright 2022-2024 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.validation
+
+import android.content.Context
+import com.google.android.fhir.datacapture.extensions.ConstraintSeverityTypes
+import com.google.android.fhir.datacapture.extensions.EXTENSION_QUESTIONNAIRE_CONSTRAINT_EXPRESSION
+import com.google.android.fhir.datacapture.extensions.EXTENSION_QUESTIONNAIRE_CONSTRAINT_HUMAN
+import com.google.android.fhir.datacapture.extensions.EXTENSION_QUESTIONNAIRE_CONSTRAINT_SEVERITY
+import com.google.android.fhir.datacapture.extensions.EXTENSION_QUESTIONNAIRE_CONSTRAINT_URL
+import com.google.android.fhir.datacapture.extensions.asStringValue
+import com.google.android.fhir.datacapture.fhirpath.ExpressionEvaluator
+import com.google.android.fhir.datacapture.fhirpath.convertToBoolean
+import org.hl7.fhir.r4.model.CodeType
+import org.hl7.fhir.r4.model.Expression
+import org.hl7.fhir.r4.model.Questionnaire.QuestionnaireItemComponent
+import org.hl7.fhir.r4.model.QuestionnaireResponse.QuestionnaireResponseItemComponent
+
+/**
+ * TODO: Add constraint support for global case, create a separate validator,
+ *   https://github.com/google/android-fhir/issues/2479
+ */
+internal class ConstraintItemExtensionValidator(
+  private val expressionEvaluator: ExpressionEvaluator,
+) : QuestionnaireResponseItemConstraintValidator {
+  override suspend fun validate(
+    questionnaireItem: QuestionnaireItemComponent,
+    questionnaireResponseItem: QuestionnaireResponseItemComponent,
+    context: Context,
+  ): List<ConstraintValidator.Result> {
+    return questionnaireItem.extension
+      .filter { extension ->
+        /**
+         * TODO: Add constraint support for warning case, update the [ConstraintValidator.Result]
+         *   data class to also include warning state,
+         *   https://github.com/google/android-fhir/issues/2480
+         */
+        extension.url == EXTENSION_QUESTIONNAIRE_CONSTRAINT_URL &&
+          (extension.getExtensionByUrl(EXTENSION_QUESTIONNAIRE_CONSTRAINT_SEVERITY).value
+              as CodeType)
+            .valueAsString == ConstraintSeverityTypes.ERROR.code
+      }
+      .map { extension ->
+        val expression =
+          Expression().apply {
+            language = "text/fhirpath"
+            expression =
+              extension
+                .getExtensionByUrl(EXTENSION_QUESTIONNAIRE_CONSTRAINT_EXPRESSION)
+                .value
+                .asStringValue()
+          }
+        val isValid =
+          expressionEvaluator
+            .evaluateExpression(
+              questionnaireItem,
+              questionnaireResponseItem,
+              expression,
+            )
+            .let { convertToBoolean(it) }
+        if (isValid) {
+          ConstraintValidator.Result(true, null)
+        } else {
+          val errorMessage =
+            extension
+              .getExtensionByUrl(EXTENSION_QUESTIONNAIRE_CONSTRAINT_HUMAN)
+              .value
+              .asStringValue()
+          ConstraintValidator.Result(false, errorMessage)
+        }
+      }
+  }
+}

datacapture/src/main/java/com/google/android/fhir/datacapture/validation/ConstraintValidator.kt

@@ -0,0 +1,27 @@
+/*
+ * Copyright 2022-2024 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.validation
+
+/** Validator base interface. */
+internal interface ConstraintValidator {
+
+  /**
+   * The validation result containing whether the response item is valid and any error message if it
+   * is not valid.
+   */
+  data class Result(val isValid: Boolean, val errorMessage: String?)
+}