Add FhirEngine interface method 'withTransaction'

engine/src/main/java/com/google/android/fhir/FhirEngine.kt

@@ -202,6 +202,12 @@ interface FhirEngine {
    *   back and no record is purged.
    */
   suspend fun purge(type: ResourceType, ids: Set<String>, forcePurge: Boolean = false)
+
+  /**
+   * Adds support for performing actions on `FhirEngine` as a single atomic transaction where the
+   * entire set of changes succeed or fail as a single entity
+   */
+  suspend fun withTransaction(block: suspend FhirEngine.() -> Unit)
 }
 
 /**

engine/src/main/java/com/google/android/fhir/impl/FhirEngineImpl.kt

@@ -97,6 +97,10 @@ internal class FhirEngineImpl(private val database: Database, private val contex
     }
   }
 
+  override suspend fun withTransaction(block: suspend FhirEngine.() -> Unit) {
+    database.withTransaction { block.invoke(this@FhirEngineImpl) }
+  }
+
   private suspend fun saveResolvedResourcesToDatabase(resolved: List<Resource>?) {
     resolved?.let {
       database.deleteUpdates(it)

engine/src/main/java/com/google/android/fhir/testing/Utilities.kt

@@ -176,6 +176,8 @@ internal object TestFhirEngineImpl : FhirEngine {
     download().collect()
   }
 
+  override suspend fun withTransaction(block: suspend FhirEngine.() -> Unit) {}
+
   override suspend fun count(search: Search): Long {
     return 0
   }

engine/src/test/java/com/google/android/fhir/impl/FhirEngineImplTest.kt

@@ -47,13 +47,18 @@ import kotlinx.coroutines.runBlocking
 import kotlinx.coroutines.test.runTest
 import org.hl7.fhir.exceptions.FHIRException
 import org.hl7.fhir.r4.model.Address
+import org.hl7.fhir.r4.model.Appointment
 import org.hl7.fhir.r4.model.CanonicalType
 import org.hl7.fhir.r4.model.Coding
 import org.hl7.fhir.r4.model.DateTimeType
+import org.hl7.fhir.r4.model.Encounter
 import org.hl7.fhir.r4.model.Enumerations
 import org.hl7.fhir.r4.model.HumanName
 import org.hl7.fhir.r4.model.Meta
+import org.hl7.fhir.r4.model.Observation
 import org.hl7.fhir.r4.model.Patient
+import org.hl7.fhir.r4.model.Practitioner
+import org.hl7.fhir.r4.model.Reference
 import org.hl7.fhir.r4.model.ResourceType
 import org.junit.Assert.assertThrows
 import org.junit.Before
@@ -783,6 +788,132 @@ class FhirEngineImplTest {
     assertThat(services.database.getLocalChangesCount()).isEqualTo(0)
   }
 
+  @Test
+  fun `withTransaction saves all changes successfully in order`() = runTest {
+    val patient01ID = "patient-01"
+    val patient01 =
+      Patient().apply {
+        id = patient01ID
+        gender = Enumerations.AdministrativeGender.FEMALE
+      }
+    val patient01AppointmentID = "appointment-01"
+    val patient01Appointment =
+      Appointment().apply {
+        id = patient01AppointmentID
+        status = Appointment.AppointmentStatus.BOOKED
+        addParticipant(
+          Appointment.AppointmentParticipantComponent().apply {
+            actor = Reference("${patient01.resourceType}/$patient01ID")
+          },
+        )
+      }
+    fhirEngine.create(patient01, patient01Appointment)
+
+    // Fulfill appointment with related Encounter/Observation
+    val patient01AppointmentEncounterID = "enc-01"
+    val patient01AppointmentEncounter =
+      Encounter().apply {
+        id = patient01AppointmentEncounterID
+        subject = Reference("${patient01.resourceType}/$patient01ID")
+        addAppointment(Reference("${patient01Appointment.resourceType}/$patient01AppointmentID"))
+      }
+    val patient01AppointmentEncounterObservationID = "obs-01"
+    val patient01AppointmentEncounterObservation =
+      Observation().apply {
+        id = patient01AppointmentEncounterObservationID
+        encounter =
+          Reference(
+            "${patient01AppointmentEncounter.resourceType}/$patient01AppointmentEncounterID",
+          )
+      }
+    val updatedAppointment =
+      patient01Appointment.copy().apply { status = Appointment.AppointmentStatus.FULFILLED }
+
+    fhirEngine.withTransaction {
+      this.create(patient01AppointmentEncounter, patient01AppointmentEncounterObservation)
+      this.update(updatedAppointment)
+    }
+
+    assertThat(
+        fhirEngine.get<Encounter>(patient01AppointmentEncounterID).appointmentFirstRep.reference,
+      )
+      .isEqualTo("Appointment/$patient01AppointmentID")
+    assertThat(
+        fhirEngine.get<Observation>(patient01AppointmentEncounterObservationID).encounter.reference,
+      )
+      .isEqualTo("Encounter/$patient01AppointmentEncounterID")
+    assertThat(fhirEngine.get<Appointment>(patient01AppointmentID).status)
+      .isEqualTo(Appointment.AppointmentStatus.FULFILLED)
+  }
+
+  @Test
+  fun `withTransaction reverts all changes when an error occurs`() = runTest {
+    val patient01ID = "patient-01"
+    val patient01 =
+      Patient().apply {
+        id = patient01ID
+        gender = Enumerations.AdministrativeGender.FEMALE
+      }
+    val patient01AppointmentID = "appointment-01"
+    val patient01Appointment =
+      Appointment().apply {
+        id = patient01AppointmentID
+        status = Appointment.AppointmentStatus.BOOKED
+        addParticipant(
+          Appointment.AppointmentParticipantComponent().apply {
+            actor = Reference("${patient01.resourceType}/$patient01ID")
+          },
+        )
+      }
+    fhirEngine.create(patient01, patient01Appointment)
+
+    // Fulfill appointment with related Encounter/Observation
+    val patient01AppointmentEncounterID = "enc-01"
+    val patient01AppointmentEncounter =
+      Encounter().apply {
+        id = patient01AppointmentEncounterID
+        subject = Reference("${patient01.resourceType}/$patient01ID")
+        addAppointment(Reference("${patient01Appointment.resourceType}/$patient01AppointmentID"))
+      }
+    val patient01AppointmentEncounterObservationID = "obs-01"
+    val patient01AppointmentEncounterObservation =
+      Observation().apply {
+        id = patient01AppointmentEncounterObservationID
+        encounter =
+          Reference(
+            "${patient01AppointmentEncounter.resourceType}/$patient01AppointmentEncounterID",
+          )
+      }
+
+    try {
+      fhirEngine.withTransaction {
+        this.create(patient01AppointmentEncounter, patient01AppointmentEncounterObservation)
+        // Get non-existent practitioner to force ResourceNotFoundException
+        val nonExistentPractitioner =
+          this.get(ResourceType.Practitioner, "non_existent_practitioner_id") as Practitioner
+        val updatedAppointment =
+          patient01Appointment.copy().apply {
+            status = Appointment.AppointmentStatus.FULFILLED
+            addParticipant(
+              Appointment.AppointmentParticipantComponent().apply {
+                actor = Reference("Practitioner/${nonExistentPractitioner.logicalId}")
+              },
+            )
+          }
+        this.update(updatedAppointment)
+      }
+    } catch (_: ResourceNotFoundException) {}
+
+    assertThrows(ResourceNotFoundException::class.java) {
+      runBlocking { fhirEngine.get<Encounter>(patient01AppointmentEncounterID) }
+    }
+    assertThrows(ResourceNotFoundException::class.java) {
+      runBlocking { fhirEngine.get<Observation>(patient01AppointmentEncounterObservationID) }
+    }
+    assertThat(fhirEngine.get<Appointment>(patient01AppointmentID).status)
+      .isEqualTo(Appointment.AppointmentStatus.BOOKED)
+  }
+
   companion object {
     private const val TEST_PATIENT_1_ID = "test_patient_1"
     private var TEST_PATIENT_1 =