TransactionBundleGenerator.kt

/*
 * 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:https://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.LocalChange
import com.google.android.fhir.LocalChange.Type
import com.google.android.fhir.db.impl.dao.LocalChangeToken
import org.hl7.fhir.r4.model.Bundle

typealias ResourceBundleAndAssociatedLocalChangeTokens = Pair<Bundle, List<LocalChangeToken>>

/**
 * Generates pairs of Transaction [Bundle] and [LocalChangeToken]s associated with the resources
 * present in the transaction bundle.
 */
internal open class TransactionBundleGenerator(
  val getBundleEntryComponentGeneratorForLocalChangeType:
    (type: Type) -> HttpVerbBasedBundleEntryComponentGenerator
) {

  fun generate(
    localChanges: List<List<LocalChange>>
  ): List<ResourceBundleAndAssociatedLocalChangeTokens> {
    return localChanges.filter { it.isNotEmpty() }.map { generateBundle(it) }
  }

  private fun generateBundle(
    localChanges: List<LocalChange>
  ): ResourceBundleAndAssociatedLocalChangeTokens {
    return Bundle().apply {
      type = Bundle.BundleType.TRANSACTION
      localChanges.forEach {
        this.addEntry(getBundleEntryComponentGeneratorForLocalChangeType(it.type).getEntry(it))
      }
    } to localChanges.map { it.token }
  }

  companion object Factory {

    fun getDefault(useETagForUpload: Boolean = true) =
      PutForCreateAndPatchForUpdateBasedTransactionGenerator(useETagForUpload)

    /**
     * Returns a [TransactionBundleGenerator] based on the provided [Bundle.HTTPVerb]s for creating
     * and updating resources. The function may throw an [IllegalArgumentException] if the provided
     * [Bundle.HTTPVerb]s are not supported.
     */
    fun getGenerator(
      httpVerbToUseForCreate: Bundle.HTTPVerb,
      httpVerbToUseForUpdate: Bundle.HTTPVerb,
      useETagForUpload: Boolean,
    ): TransactionBundleGenerator {

      return if (httpVerbToUseForCreate == Bundle.HTTPVerb.PUT &&
          httpVerbToUseForUpdate == Bundle.HTTPVerb.PATCH
      ) {
        PutForCreateAndPatchForUpdateBasedTransactionGenerator(useETagForUpload)
      } else {
        throw IllegalArgumentException(
          "Engine currently supports creation using [PUT] and updates using [PATCH]"
        )
      }
    }
  }
}

internal class PutForCreateAndPatchForUpdateBasedTransactionGenerator(useETagForUpload: Boolean) :
  TransactionBundleGenerator({ type ->
    when (type) {
      Type.INSERT -> HttpPutForCreateEntryComponentGenerator(useETagForUpload)
      Type.UPDATE -> HttpPatchForUpdateEntryComponentGenerator(useETagForUpload)
      Type.DELETE -> HttpDeleteEntryComponentGenerator(useETagForUpload)
    }
  })