Make API compatibility decisions

zipline-kotlin-plugin/src/main/kotlin/app/cash/zipline/api/compatibility/ApiCompatibilityDecision.kt

@@ -0,0 +1,99 @@
+/*
+ * Copyright (C) 2023 Cash App
+ *
+ * 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 app.cash.zipline.api.compatibility
+
+import app.cash.zipline.api.fir.FirZiplineApi
+import app.cash.zipline.api.toml.TomlZiplineApi
+import app.cash.zipline.api.toml.TomlZiplineFunction
+import app.cash.zipline.api.toml.TomlZiplineService
+
+sealed interface ApiCompatibilityDecision
+
+class ActualApiHasProblems(
+  val messages: List<String>,
+) : ApiCompatibilityDecision
+
+class ExpectedApiRequiresUpdates(
+  val updatedApi: TomlZiplineApi,
+) : ApiCompatibilityDecision
+
+object ExpectedApiIsUpToDate : ApiCompatibilityDecision
+
+/** Compare the expected and actual API and decide what to do about it. */
+fun makeApiCompatibilityDecision(
+  expectedApi: TomlZiplineApi,
+  actualApi: FirZiplineApi,
+): ApiCompatibilityDecision {
+  val problemMessages = mutableListOf<String>()
+  var hasChanges = false
+
+  val actualServices = actualApi.services.associateBy { it.name }
+  if (actualServices.size != expectedApi.services.size) hasChanges = true
+
+  for (expectedService in expectedApi.services) {
+    val serviceName = expectedService.name
+    val actualService = actualServices[serviceName]
+
+    if (actualService == null) {
+      problemMessages +=
+        """
+        |Expected service not found:
+        |  $serviceName
+        """.trimMargin()
+      continue
+    }
+
+    val actualFunctions = actualService.functions.associateBy { it.id }
+    if (actualFunctions.size != expectedService.functions.size) hasChanges = true
+
+    for (expectedFunction in expectedService.functions) {
+      val functionId = expectedFunction.id
+      val actualFunction = actualFunctions[functionId]
+      if (actualFunction == null) {
+        val comment = expectedFunction.leadingComment
+        problemMessages += buildString {
+          append("Expected function $functionId of $serviceName not found")
+          if (comment.isNotEmpty()) {
+            append(":\n  ")
+            append(comment.replace("\n", "\n  "))
+          }
+        }
+      }
+    }
+  }
+
+  return when {
+    problemMessages.isNotEmpty() -> ActualApiHasProblems(problemMessages)
+    hasChanges -> ExpectedApiRequiresUpdates(actualApi.toToml())
+    else -> ExpectedApiIsUpToDate
+  }
+}
+
+private fun FirZiplineApi.toToml(): TomlZiplineApi {
+  return TomlZiplineApi(
+    services.map { service ->
+      TomlZiplineService(
+        name = service.name,
+        functions = service.functions.map { function ->
+          TomlZiplineFunction(
+            leadingComment = function.signature,
+            id = function.id,
+          )
+        },
+      )
+    },
+  )
+}