feat(graphql): add EnumTypeMap for GraphQL enum materialization

Author: FionaBronwen

packages/graphql/src/type-maps.ts

@@ -15,7 +15,7 @@ export interface TSPContext<T extends Type> {
 /**
  * Nominal type for keys in the TypeMap
  */
-type TypeKey = string & { __typeKey: any };
+export type TypeKey = string & { __typeKey: any };
 
 /**
  * Base TypeMap for all GraphQL type mappings

packages/graphql/src/type-maps/enum.ts

@@ -0,0 +1,37 @@
+import type { Enum } from "@typespec/compiler";
+import { GraphQLEnumType } from "graphql";
+import { TypeMap, type TSPContext, type TypeKey } from "../type-maps.js";
+
+/**
+ * TypeMap for converting TypeSpec Enums to GraphQL EnumTypes.
+ *
+ * Handles registration of TSP enums and lazy materialization into
+ * GraphQLEnumType instances.
+ */
+export class EnumTypeMap extends TypeMap<Enum, GraphQLEnumType> {
+  /**
+   * Derives the type key from the context.
+   * Uses graphqlName override if provided, otherwise uses the enum's name.
+   */
+  protected getNameFromContext(context: TSPContext<Enum>): TypeKey {
+    return (context.graphqlName ?? context.type.name) as TypeKey;
+  }
+
+  /**
+   * Materializes a TypeSpec Enum into a GraphQL EnumType.
+   */
+  protected materialize(context: TSPContext<Enum>): GraphQLEnumType {
+    const tspEnum = context.type;
+    const name = context.graphqlName ?? tspEnum.name;
+
+    return new GraphQLEnumType({
+      name,
+      values: Object.fromEntries(
+        Array.from(tspEnum.members.values()).map((member) => [
+          member.name,
+          { value: member.value ?? member.name },
+        ]),
+      ),
+    });
+  }
+}

packages/graphql/src/type-maps/index.ts

@@ -0,0 +1,2 @@
+export { TypeMap, type TSPContext, type TypeKey } from "../type-maps.js";
+export { EnumTypeMap } from "./enum.js";