feat(graphql): add ModelTypeMap for GraphQL object type materialization

Author: FionaBronwen

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

@@ -1,2 +1,3 @@
 export { TypeMap, type TSPContext, type TypeKey } from "../type-maps.js";
 export { EnumTypeMap } from "./enum.js";
+export { ModelTypeMap } from "./model.js";

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

@@ -0,0 +1,55 @@
+import type { Model } from "@typespec/compiler";
+import {
+  GraphQLObjectType,
+  GraphQLString,
+  type GraphQLFieldConfigMap,
+  type GraphQLOutputType,
+} from "graphql";
+import { TypeMap, type TSPContext, type TypeKey } from "../type-maps.js";
+
+/**
+ * TypeMap for converting TypeSpec Models to GraphQL ObjectTypes.
+ *
+ * Handles registration of TSP models and lazy materialization into
+ * GraphQLObjectType instances.
+ */
+export class ModelTypeMap extends TypeMap<Model, GraphQLObjectType> {
+  /**
+   * Derives the type key from the context.
+   * Uses graphqlName override if provided, otherwise uses the model's name.
+   */
+  protected getNameFromContext(context: TSPContext<Model>): TypeKey {
+    return (context.graphqlName ?? context.type.name) as TypeKey;
+  }
+
+  /**
+   * Materializes a TypeSpec Model into a GraphQL ObjectType.
+   */
+  protected materialize(context: TSPContext<Model>): GraphQLObjectType {
+    const tspModel = context.type;
+    const name = context.graphqlName ?? tspModel.name;
+
+    const fields: GraphQLFieldConfigMap<unknown, unknown> = {};
+
+    for (const [propName, prop] of tspModel.properties) {
+      fields[propName] = {
+        type: this.mapPropertyType(prop.type),
+        // TODO: Add description from doc comments
+      };
+    }
+
+    return new GraphQLObjectType({
+      name,
+      fields,
+    });
+  }
+
+  /**
+   * Map a TypeSpec property type to a GraphQL output type.
+   * TODO: Implement full type mapping with references to other registered types.
+   */
+  private mapPropertyType(_type: unknown): GraphQLOutputType {
+    // Placeholder - will need to resolve references to other types
+    return GraphQLString;
+  }
+}