Introducing Upload Strategies (#2171)

* refactoring for upload request generator

* spotless application

* spotless application

* added UploadRequestGeneratorFactory

* Spotless applications

* review comments

* Upload Strategy

* Adding factories

* patch generator mode in same class as patch generator

* making local fetch mode not internal

* addressed review comments

* using bundle request

engine/src/main/java/com/google/android/fhir/sync/upload/UploadStrategy.kt

@@ -0,0 +1,93 @@
+/*
+ * Copyright 2023 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.sync.upload
+
+import com.google.android.fhir.sync.upload.patch.PatchGeneratorMode
+import com.google.android.fhir.sync.upload.request.UploadRequestGeneratorMode
+import org.hl7.fhir.r4.model.Bundle
+import org.hl7.fhir.r4.model.codesystems.HttpVerb
+
+/**
+ * Strategy to define how to upload the [LocalChange]s to the FHIR server.
+ *
+ * Each strategy comprises of deciding appropriate modes for [LocalChangeFetcher],
+ * [PatchGeneratorMode], [UploadRequestGeneratorMode]. The strategies mentioned here are exhaustive
+ * as the different modes for the components mentioned above can only be used together in some
+ * specific ways.
+ */
+sealed class UploadStrategy
+private constructor(
+  internal val localChangesFetchMode: LocalChangesFetchMode,
+  internal val patchGeneratorMode: PatchGeneratorMode,
+  internal val requestGeneratorMode: UploadRequestGeneratorMode,
+) {
+  object SingleChangePut :
+    UploadStrategy(
+      LocalChangesFetchMode.EarliestChange,
+      PatchGeneratorMode.PerChange,
+      UploadRequestGeneratorMode.UrlRequest(HttpVerb.PUT, HttpVerb.PATCH),
+    )
+
+  object SingleChangePost :
+    UploadStrategy(
+      LocalChangesFetchMode.EarliestChange,
+      PatchGeneratorMode.PerChange,
+      UploadRequestGeneratorMode.UrlRequest(HttpVerb.POST, HttpVerb.PATCH),
+    )
+
+  object SingleResourcePut :
+    UploadStrategy(
+      LocalChangesFetchMode.PerResource,
+      PatchGeneratorMode.PerResource,
+      UploadRequestGeneratorMode.UrlRequest(HttpVerb.PUT, HttpVerb.PATCH),
+    )
+
+  object SingleResourcePost :
+    UploadStrategy(
+      LocalChangesFetchMode.PerResource,
+      PatchGeneratorMode.PerResource,
+      UploadRequestGeneratorMode.UrlRequest(HttpVerb.POST, HttpVerb.PATCH),
+    )
+
+  object AllChangesBundlePut :
+    UploadStrategy(
+      LocalChangesFetchMode.AllChanges,
+      PatchGeneratorMode.PerChange,
+      UploadRequestGeneratorMode.BundleRequest(Bundle.HTTPVerb.PUT, Bundle.HTTPVerb.PATCH),
+    )
+
+  object AllChangesBundlePost :
+    UploadStrategy(
+      LocalChangesFetchMode.AllChanges,
+      PatchGeneratorMode.PerChange,
+      UploadRequestGeneratorMode.BundleRequest(Bundle.HTTPVerb.POST, Bundle.HTTPVerb.PATCH),
+    )
+
+  object AllChangesSquashedBundlePut :
+    UploadStrategy(
+      LocalChangesFetchMode.AllChanges,
+      PatchGeneratorMode.PerResource,
+      UploadRequestGeneratorMode.BundleRequest(Bundle.HTTPVerb.PUT, Bundle.HTTPVerb.PATCH),
+    )
+
+  object AllChangesSquashedBundlePost :
+    UploadStrategy(
+      LocalChangesFetchMode.AllChanges,
+      PatchGeneratorMode.PerResource,
+      UploadRequestGeneratorMode.BundleRequest(Bundle.HTTPVerb.POST, Bundle.HTTPVerb.PATCH),
+    )
+}

engine/src/main/java/com/google/android/fhir/sync/upload/patch/PatchGenerator.kt

@@ -35,3 +35,22 @@ internal interface PatchGenerator {
    */
   fun generate(localChanges: List<LocalChange>): List<Patch>
 }
+
+internal object PatchGeneratorFactory {
+  fun byMode(
+    mode: PatchGeneratorMode,
+  ): PatchGenerator =
+    when (mode) {
+      is PatchGeneratorMode.PerChange -> PerChangePatchGenerator
+      is PatchGeneratorMode.PerResource -> PerResourcePatchGenerator
+    }
+}
+
+/**
+ * Mode to decide the type of [PatchGenerator] that needs to be used to upload the [LocalChange]s
+ */
+internal sealed class PatchGeneratorMode {
+  object PerResource : PatchGeneratorMode()
+
+  object PerChange : PatchGeneratorMode()
+}