feat(experimental): create an RPC GraphQL (#1660)

* refactor(experimental): init rpc-graphql package

* refactor(experimental): create an RPC GraphQL

packages/rpc-graphql/src/context.ts

@@ -0,0 +1,10 @@
+import { SolanaRpcMethods } from '@solana/rpc-core';
+import { Rpc } from '@solana/rpc-transport/dist/types/json-rpc-types';
+
+export interface RpcGraphQLContext {
+    rpc: Rpc<SolanaRpcMethods>;
+}
+
+export function createSolanaGraphQLContext(rpc: Rpc<SolanaRpcMethods>): RpcGraphQLContext {
+    return { rpc };
+}

packages/rpc-graphql/src/index.ts

@@ -0,0 +1 @@
+export * from './rpc';

packages/rpc-graphql/src/rpc.ts

@@ -0,0 +1,39 @@
+import { SolanaRpcMethods } from '@solana/rpc-core';
+import { Rpc } from '@solana/rpc-transport/dist/types/json-rpc-types';
+import { graphql, GraphQLObjectType, GraphQLSchema, Source } from 'graphql';
+
+import { createSolanaGraphQLContext, RpcGraphQLContext } from './context';
+
+export interface RpcGraphQL {
+    context: RpcGraphQLContext;
+    query(
+        source: string | Source,
+        variableValues?: { readonly [variable: string]: unknown }
+    ): ReturnType<typeof graphql>;
+    schema: GraphQLSchema;
+}
+
+export function createRpcGraphQL(rpc: Rpc<SolanaRpcMethods>): RpcGraphQL {
+    const context = createSolanaGraphQLContext(rpc);
+    const schema = new GraphQLSchema({
+        query: new GraphQLObjectType({
+            fields: {
+                /** Root queries */
+            },
+            name: 'RootQuery',
+        }),
+        types: [],
+    });
+    return {
+        context,
+        async query(source: string | Source, variableValues?: { readonly [variable: string]: unknown }) {
+            return graphql({
+                contextValue: this.context,
+                schema: this.schema,
+                source,
+                variableValues,
+            });
+        },
+        schema,
+    };
+}