Implement the waiter matcher generator

codegen-client/src/main/kotlin/software/amazon/smithy/rust/codegen/client/smithy/ClientRustModule.kt

@@ -102,6 +102,8 @@ object ClientRustModule {
         /** crate::types::error */
         val Error = RustModule.public("error", parent = self)
     }
+
+    val waiters = RustModule.pubCrate("waiters")
 }
 
 class ClientModuleDocProvider(

codegen-client/src/main/kotlin/software/amazon/smithy/rust/codegen/client/smithy/generators/waiters/RustWaiterMatcherGenerator.kt

@@ -0,0 +1,190 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package software.amazon.smithy.rust.codegen.client.smithy.generators.waiters
+
+import software.amazon.smithy.codegen.core.CodegenException
+import software.amazon.smithy.codegen.core.Symbol
+import software.amazon.smithy.jmespath.JmespathExpression
+import software.amazon.smithy.model.node.Node
+import software.amazon.smithy.model.shapes.Shape
+import software.amazon.smithy.rust.codegen.client.smithy.ClientCodegenContext
+import software.amazon.smithy.rust.codegen.client.smithy.ClientRustModule
+import software.amazon.smithy.rust.codegen.core.rustlang.RustModule
+import software.amazon.smithy.rust.codegen.core.rustlang.RustType
+import software.amazon.smithy.rust.codegen.core.rustlang.RustWriter
+import software.amazon.smithy.rust.codegen.core.rustlang.replaceLifetimes
+import software.amazon.smithy.rust.codegen.core.rustlang.rust
+import software.amazon.smithy.rust.codegen.core.rustlang.rustBlockTemplate
+import software.amazon.smithy.rust.codegen.core.rustlang.rustTemplate
+import software.amazon.smithy.rust.codegen.core.rustlang.writable
+import software.amazon.smithy.rust.codegen.core.smithy.RuntimeType
+import software.amazon.smithy.rust.codegen.core.smithy.RuntimeType.Companion.preludeScope
+import software.amazon.smithy.rust.codegen.core.util.dq
+import software.amazon.smithy.rust.codegen.core.util.toSnakeCase
+import software.amazon.smithy.waiters.Matcher
+import software.amazon.smithy.waiters.Matcher.ErrorTypeMember
+import software.amazon.smithy.waiters.Matcher.InputOutputMember
+import software.amazon.smithy.waiters.Matcher.OutputMember
+import software.amazon.smithy.waiters.Matcher.SuccessMember
+import software.amazon.smithy.waiters.PathComparator
+import java.security.MessageDigest
+
+private typealias Scope = Array<Pair<String, Any>>
+
+/**
+ * Generates the Rust code for the Smithy waiter "matcher union".
+ * See https://smithy.io/1.0/spec/waiters.html#matcher-union
+ */
+class RustWaiterMatcherGenerator(
+    private val codegenContext: ClientCodegenContext,
+    private val operationName: String,
+    private val inputShape: Shape,
+    private val outputShape: Shape,
+) {
+    private val runtimeConfig = codegenContext.runtimeConfig
+    private val module = RustModule.pubCrate("matchers", ClientRustModule.waiters)
+    private val inputSymbol = codegenContext.symbolProvider.toSymbol(inputShape)
+    private val outputSymbol = codegenContext.symbolProvider.toSymbol(outputShape)
+
+    fun generate(
+        errorSymbol: Symbol,
+        matcher: Matcher<*>,
+    ): RuntimeType {
+        val fnName = fnName(operationName, matcher)
+        val scope =
+            arrayOf(
+                *preludeScope,
+                "Input" to inputSymbol,
+                "Output" to outputSymbol,
+                "Error" to errorSymbol,
+                "ProvideErrorMetadata" to RuntimeType.provideErrorMetadataTrait(runtimeConfig),
+            )
+        return RuntimeType.forInlineFun(fnName, module) {
+            rustBlockTemplate("pub(crate) fn $fnName(_input: &#{Input}, _result: &#{Result}<#{Output}, #{Error}>) -> bool", *scope) {
+                when (matcher) {
+                    is OutputMember -> generateOutputMember(outputShape, matcher, scope)
+                    is InputOutputMember -> generateInputOutputMember(matcher, scope)
+                    is SuccessMember -> generateSuccessMember(matcher)
+                    is ErrorTypeMember -> generateErrorTypeMember(matcher, scope)
+                    else -> throw CodegenException("Unknown waiter matcher type: $matcher")
+                }
+            }
+        }
+    }
+
+    private fun RustWriter.generateOutputMember(
+        outputShape: Shape,
+        matcher: OutputMember,
+        scope: Scope,
+    ) {
+        val pathExpression = JmespathExpression.parse(matcher.value.path)
+        val pathTraversal =
+            RustJmespathShapeTraversalGenerator(codegenContext).generate(
+                pathExpression,
+                listOf(TraversalBinding.Global("_output", outputShape)),
+            )
+
+        generatePathTraversalMatcher(pathTraversal, matcher.value.expected, matcher.value.comparator, scope)
+    }
+
+    private fun RustWriter.generateInputOutputMember(
+        matcher: InputOutputMember,
+        scope: Scope,
+    ) {
+        val pathExpression = JmespathExpression.parse(matcher.value.path)
+        val pathTraversal =
+            RustJmespathShapeTraversalGenerator(codegenContext).generate(
+                pathExpression,
+                listOf(
+                    TraversalBinding.Named("input", "_input", inputShape),
+                    TraversalBinding.Named("output", "_output", outputShape),
+                ),
+            )
+
+        generatePathTraversalMatcher(pathTraversal, matcher.value.expected, matcher.value.comparator, scope)
+    }
+
+    private fun RustWriter.generatePathTraversalMatcher(
+        pathTraversal: GeneratedExpression,
+        expected: String,
+        comparatorKind: PathComparator,
+        scope: Scope,
+    ) {
+        val comparator =
+            writable {
+                rust(
+                    when (comparatorKind) {
+                        PathComparator.ALL_STRING_EQUALS -> "value.iter().all(|s| s == ${expected.dq()})"
+                        PathComparator.ANY_STRING_EQUALS -> "value.iter().any(|s| s == ${expected.dq()})"
+                        PathComparator.STRING_EQUALS -> "value == ${expected.dq()}"
+                        PathComparator.BOOLEAN_EQUALS ->
+                            when (pathTraversal.outputType is RustType.Reference) {
+                                true -> "*value == $expected"
+                                else -> "value == $expected"
+                            }
+                        else -> throw CodegenException("Unknown path matcher comparator: $comparatorKind")
+                    },
+                )
+            }
+
+        rustTemplate(
+            """
+            fn path_traversal<'a>(_input: &'a #{Input}, _output: &'a #{Output}) -> #{Option}<#{TraversalOutput}> {
+                #{traversal}
+                #{Some}(${pathTraversal.identifier})
+            }
+            _result.as_ref()
+                .ok()
+                .and_then(|output| path_traversal(_input, output))
+                .map(|value| #{comparator})
+                .unwrap_or_default()
+            """,
+            *scope,
+            "traversal" to pathTraversal.output,
+            "TraversalOutput" to pathTraversal.outputType.replaceLifetimes("a"),
+            "comparator" to comparator,
+        )
+    }
+
+    private fun RustWriter.generateSuccessMember(matcher: SuccessMember) {
+        rust(
+            if (matcher.value) {
+                "_result.is_ok()"
+            } else {
+                "_result.is_err()"
+            },
+        )
+    }
+
+    private fun RustWriter.generateErrorTypeMember(
+        matcher: ErrorTypeMember,
+        scope: Scope,
+    ) {
+        rustTemplate(
+            """
+            if let #{Err}(err) = _result {
+                if let #{Some}(code) = #{ProvideErrorMetadata}::code(err) {
+                    return code == ${matcher.value.dq()};
+                }
+            }
+            false
+            """,
+            *scope,
+        )
+    }
+
+    private fun fnName(
+        operationName: String,
+        matcher: Matcher<*>,
+    ): String {
+        // Smithy models don't give us anything useful to name these functions with, so just
+        // SHA-256 hash the matcher JSON and truncate it to a reasonable length. This will have
+        // a nice side-effect of de-duplicating identical matchers within a given operation.
+        val jsonValue = Node.printJson(matcher.toNode())
+        val bytes = MessageDigest.getInstance("SHA-256").digest(jsonValue.toByteArray())
+        val hex = bytes.map { byte -> String.format("%02x", byte) }.joinToString("")
+        return "match_${operationName.toSnakeCase()}_${hex.substring(0..16)}"
+    }
+}