Implement internal spanner stream exchanges method

src/main/kotlin/org/wfanet/measurement/kingdom/deploy/gcloud/spanner/SpannerExchangesService.kt

@@ -15,6 +15,8 @@
 package org.wfanet.measurement.kingdom.deploy.gcloud.spanner
 
 import io.grpc.Status
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.singleOrNull
 import org.wfanet.measurement.common.grpc.failGrpc
 import org.wfanet.measurement.common.identity.IdGenerator
@@ -26,8 +28,10 @@ import org.wfanet.measurement.internal.kingdom.CreateExchangeRequest
 import org.wfanet.measurement.internal.kingdom.Exchange
 import org.wfanet.measurement.internal.kingdom.ExchangesGrpcKt.ExchangesCoroutineImplBase
 import org.wfanet.measurement.internal.kingdom.GetExchangeRequest
+import org.wfanet.measurement.internal.kingdom.StreamExchangesRequest
 import org.wfanet.measurement.kingdom.deploy.gcloud.spanner.common.PROVIDER_PARAM
 import org.wfanet.measurement.kingdom.deploy.gcloud.spanner.common.providerFilter
+import org.wfanet.measurement.kingdom.deploy.gcloud.spanner.queries.StreamExchanges
 import org.wfanet.measurement.kingdom.deploy.gcloud.spanner.readers.ExchangeReader
 import org.wfanet.measurement.kingdom.deploy.gcloud.spanner.writers.CreateExchange
 
@@ -60,4 +64,10 @@ class SpannerExchangesService(
       ?.exchange
       ?: failGrpc(Status.NOT_FOUND) { "Exchange not found" }
   }
+
+  override fun streamExchanges(request: StreamExchangesRequest): Flow<Exchange> {
+    return StreamExchanges(request.filter, request.limit).execute(client.singleUse()).map {
+      it.exchange
+    }
+  }
 }

src/main/kotlin/org/wfanet/measurement/kingdom/deploy/gcloud/spanner/queries/StreamExchanges.kt

@@ -0,0 +1,59 @@
+/*
+ * Copyright 2023 The Cross-Media Measurement Authors
+ *
+ * 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 org.wfanet.measurement.kingdom.deploy.gcloud.spanner.queries
+
+import com.google.cloud.spanner.Statement
+import org.wfanet.measurement.gcloud.common.toCloudDate
+import org.wfanet.measurement.gcloud.spanner.appendClause
+import org.wfanet.measurement.gcloud.spanner.bind
+import org.wfanet.measurement.internal.kingdom.StreamExchangesRequest
+import org.wfanet.measurement.kingdom.deploy.gcloud.spanner.readers.ExchangeReader
+
+class StreamExchanges(requestFilter: StreamExchangesRequest.Filter, limit: Int = 0) :
+  SimpleSpannerQuery<ExchangeReader.Result>() {
+
+  override val reader =
+    ExchangeReader().fillStatementBuilder {
+      appendWhereClause(requestFilter)
+      appendClause("ORDER BY Exchanges.Date ASC")
+      if (limit > 0) {
+        appendClause("LIMIT @${Params.LIMIT}")
+        bind(Params.LIMIT to limit.toLong())
+      }
+    }
+
+  private fun Statement.Builder.appendWhereClause(filter: StreamExchangesRequest.Filter) {
+    val conjuncts = mutableListOf<String>()
+
+    if (filter.hasDateBefore()) {
+      conjuncts.add("Exchanges.Date < @${Params.EXCHANGED_BEFORE}")
+      bind(Params.EXCHANGED_BEFORE to filter.dateBefore.toCloudDate())
+    }
+
+    if (conjuncts.isEmpty()) {
+      return
+    }
+
+    appendClause("WHERE ")
+    append(conjuncts.joinToString(" AND "))
+  }
+
+  private object Params {
+    const val LIMIT = "limit"
+    const val EXCHANGED_BEFORE = "exchangedBefore"
+  }
+}

src/main/kotlin/org/wfanet/measurement/kingdom/service/internal/testing/ExchangesServiceTest.kt

@@ -16,7 +16,9 @@ package org.wfanet.measurement.kingdom.service.internal.testing
 
 import com.google.common.truth.extensions.proto.ProtoTruth.assertThat
 import com.google.protobuf.ByteString
+import com.google.type.date
 import kotlin.test.assertFails
+import kotlinx.coroutines.flow.toList
 import kotlinx.coroutines.runBlocking
 import org.junit.Before
 import org.junit.Rule
@@ -37,6 +39,10 @@ import org.wfanet.measurement.internal.kingdom.GetExchangeRequest
 import org.wfanet.measurement.internal.kingdom.ModelProvider
 import org.wfanet.measurement.internal.kingdom.RecurringExchange
 import org.wfanet.measurement.internal.kingdom.RecurringExchangesGrpcKt.RecurringExchangesCoroutineImplBase
+import org.wfanet.measurement.internal.kingdom.StreamExchangesRequestKt.filter
+import org.wfanet.measurement.internal.kingdom.copy
+import org.wfanet.measurement.internal.kingdom.createExchangeRequest
+import org.wfanet.measurement.internal.kingdom.streamExchangesRequest
 import org.wfanet.measurement.kingdom.deploy.common.testing.DuchyIdSetter
 import org.wfanet.measurement.kingdom.service.internal.testing.Population.Companion.DUCHIES
 
@@ -205,6 +211,95 @@ abstract class ExchangesServiceTest {
     assertFails { getExchange() }
   }
 
+  @Test
+  fun `streamExchange returns all exchanges`(): Unit = runBlocking {
+    val createRequest1 = createExchangeRequest { exchange = EXCHANGE }
+    val createRequest2 = createExchangeRequest {
+      exchange =
+        EXCHANGE.copy {
+          date = date {
+            year = 2021
+            month = 1
+            day = 1
+          }
+        }
+    }
+
+    val exchange1 = createExchange(createRequest1)
+    val exchange2 = createExchange(createRequest2)
+
+    val response = exchanges.streamExchanges(streamExchangesRequest {}).toList()
+
+    assertThat(response).hasSize(2)
+    assertThat(response).containsExactly(exchange1, exchange2)
+  }
+
+  @Test
+  fun `streamExchange respects filter before date`(): Unit = runBlocking {
+    val oldExchangeRequest = createExchangeRequest {
+      exchange =
+        EXCHANGE.copy {
+          date = date {
+            year = 2021
+            month = 1
+            day = 1
+          }
+        }
+    }
+    val newExchangeRequest = createExchangeRequest {
+      exchange =
+        EXCHANGE.copy {
+          date = date {
+            year = 2023
+            month = 1
+            day = 1
+          }
+        }
+    }
+
+    val oldExchange = createExchange(oldExchangeRequest)
+    createExchange(newExchangeRequest)
+
+    val response =
+      exchanges
+        .streamExchanges(
+          streamExchangesRequest {
+            filter = filter {
+              dateBefore = date {
+                year = 2022
+                month = 1
+                day = 1
+              }
+            }
+          }
+        )
+        .toList()
+
+    assertThat(response).containsExactly(oldExchange)
+  }
+
+  @Test
+  fun `streamExchange respects limit`(): Unit = runBlocking {
+    val createRequest1 = createExchangeRequest { exchange = EXCHANGE }
+    val createRequest2 = createExchangeRequest {
+      exchange =
+        EXCHANGE.copy {
+          date = date {
+            year = 2021
+            month = 1
+            day = 1
+          }
+        }
+    }
+
+    createExchange(createRequest1)
+    createExchange(createRequest2)
+
+    val response = exchanges.streamExchanges(streamExchangesRequest { limit = 1 }).toList()
+
+    assertThat(response).hasSize(1)
+  }
+
   private fun createExchange(request: CreateExchangeRequest): Exchange {
     return runBlocking { exchanges.createExchange(request) }
   }