From d5fb12f338554b6f42982da223adb396cd3d78d2 Mon Sep 17 00:00:00 2001
From: Tim Kendall <timkendall18@gmail.com>
Date: Sun, 12 Sep 2021 19:31:25 -0700
Subject: [PATCH] Implement Selector and selector APIs

---
 src/Query.ts                   | 46 ++++++++++++++++++
 src/Selector.ts                | 61 ++++++++++++++++++++++++
 src/__tests__/Selector.test.ts | 86 ++++++++++++++++++++++++++++++++++
 starwars.example.ts            |  6 +--
 4 files changed, 195 insertions(+), 4 deletions(-)
 create mode 100644 src/Query.ts
 create mode 100644 src/Selector.ts
 create mode 100644 src/__tests__/Selector.test.ts

diff --git a/src/Query.ts b/src/Query.ts
new file mode 100644
index 0000000..b4a80dd
--- /dev/null
+++ b/src/Query.ts
@@ -0,0 +1,46 @@
+import { ISelector } from "./Selector";
+
+// export const operation = <S extends ISelector<any>>(
+//   type: "query" | "mutation" | "subscription",
+//   selector: S
+// ) => <T extends Array<Selection>>(
+//   name: string,
+//   select: (t: S) => T
+// ): Operation<SelectionSet<T>> =>
+//   new Operation(name, type, new SelectionSet(select(selector)));
+
+// ```
+// // or new Query({ ... })
+// const operation = query({
+//   name: 'Example',
+//   variables: {
+//     id: t.string,
+//   },
+//   selection: (t, v) => [
+//     t.user({ id: v.id }, t => [
+//       t.id,
+//       t.name,
+//       t.friends(t => [
+//         t.id,
+//         t.firstName,
+//       ])
+//     ])
+//   ]
+//   extensions: []
+// })
+// ```
+
+export interface QueryConfig<TQuery> {
+  name?: string;
+  variables?: Record<string, unknown /* @todo */>;
+  selection: ISelector<TQuery>;
+  // extensions?: Array<Extension>
+}
+
+export class Query<Q> {
+  // ast?: DocumentNode or OperationDefinitionNode
+
+  constructor(config: QueryConfig<Q>) {}
+
+  // toString()
+}
diff --git a/src/Selector.ts b/src/Selector.ts
new file mode 100644
index 0000000..3e6dc53
--- /dev/null
+++ b/src/Selector.ts
@@ -0,0 +1,61 @@
+import {
+  Field,
+  SelectionSet,
+  Selection,
+  Argument,
+  Primitive,
+} from "./Operation";
+
+export type ISelector<T> = {
+  // @todo use Paramaters<T> to support variables
+  [F in keyof T]: T[F] extends Primitive
+    ? (variables?: Record<string, any>) => Field<F extends string ? F : never>
+    : <S extends Array<Selection>>(
+        arg0?: ((selector: ISelector<T[F]>) => S) | Record<string, any> | never,
+        arg1?: ((selector: ISelector<T[F]>) => S) | never
+      ) => Field<F extends string ? F : never, never, SelectionSet<S>>;
+};
+
+export class Selector<T> {
+  constructor(public readonly select: (t: ISelector<T>) => Array<Selection>) {}
+
+  toSelectionSet() {
+    return new SelectionSet(this.select(selector()));
+  }
+}
+
+export const selector = <T>(): ISelector<T> =>
+  new Proxy(Object.create(null), {
+    get(target, field) /*: FieldFn*/ {
+      return function fieldFn(...args: any[]) {
+        if (args.length === 0) {
+          return new Field<any, any, any>(field);
+        } else if (typeof args[0] === "function") {
+          return new Field<any, any, any>(
+            field,
+            undefined,
+            new SelectionSet(args[0](selector()))
+          );
+        } else if (typeof args[0] === "object") {
+          if (typeof args[1] === "function") {
+            return new Field<any, any, any>(
+              field,
+              Object.entries(args[0]).map(
+                ([name, value]) => new Argument(name, value)
+              ),
+              new SelectionSet(args[1](selector()))
+            );
+          } else {
+            return new Field<any, any, any>(
+              field,
+              Object.entries(args[0]).map(
+                ([name, value]) => new Argument(name, value)
+              )
+            );
+          }
+        }
+
+        throw new Error(`Unable to derive field function from arguments.`);
+      };
+    },
+  });
diff --git a/src/__tests__/Selector.test.ts b/src/__tests__/Selector.test.ts
new file mode 100644
index 0000000..884322a
--- /dev/null
+++ b/src/__tests__/Selector.test.ts
@@ -0,0 +1,86 @@
+import { print } from "graphql";
+
+import { selector, Selector } from "../Selector";
+import { SelectionSet } from "../Operation";
+import { Result } from "../Result";
+
+describe("Selector", () => {
+  describe("type-saftey", () => {
+    it("supports selecting against an interface", () => {
+      interface Query {
+        foo: string;
+        bar: number;
+        baz: {
+          id: string;
+        };
+      }
+
+      const { foo, bar, baz } = selector<Query>();
+
+      const selection = [foo(), bar(), baz((t) => [t.id()])];
+      type ExampleResult = Result<Query, SelectionSet<typeof selection>>;
+
+      const query = print(new SelectionSet(selection).ast);
+
+      expect(query).toMatchInlineSnapshot(`
+        "{
+          foo
+          bar
+          baz {
+            id
+          }
+        }"
+      `);
+    });
+  });
+
+  describe("class API", () => {
+    it("supports arbitrarily deep seletions", () => {
+      const selector = new Selector<any>((t) => [
+        t.user({ id: "foo" }, (t) => [t.id()]),
+      ]);
+
+      const query = print(selector.toSelectionSet().ast);
+
+      expect(query).toMatchInlineSnapshot(`
+        "{
+          user(id: \\"foo\\") {
+            id
+          }
+        }"
+      `);
+    });
+  });
+
+  describe("function API", () => {
+    it("supports arbitrarily deep selections", () => {
+      const { authors, user } = selector<any>();
+
+      const selection = [
+        authors((t) => [t.name(), t.address((t) => [t.country()])]),
+
+        user({ id: "foo" }, (t) => [t.foo((t) => [t.bar((t) => [t.baz()])])]),
+      ];
+
+      const query = print(new SelectionSet(selection).ast);
+
+      expect(query).toMatchInlineSnapshot(`
+        "{
+          authors {
+            name
+            address {
+              country
+            }
+          }
+          user(id: \\"foo\\") {
+            foo {
+              bar {
+                baz
+              }
+            }
+          }
+        }"
+      `);
+    });
+  });
+});
diff --git a/starwars.example.ts b/starwars.example.ts
index a694803..123d175 100644
--- a/starwars.example.ts
+++ b/starwars.example.ts
@@ -1,7 +1,7 @@
 import { Executor } from "./src";
 import { Starwars } from "./starwars.api";
 (async () => {
-  const starwars = new Starwars(new Executor(""));
+  const starwars = new Starwars(new Executor({ uri: "" }));
 
   const character = await starwars.query.character({ id: "frf" }, (t) => [
     t.__typename(),
@@ -11,9 +11,7 @@ import { Starwars } from "./starwars.api";
       t.friends((t) => [t.id()]),
     ]),
 
-    // t.on('Droid', t => [
-    //   t.primaryFunction(),
-    // ])
+    t.on("Droid", (t) => [t.primaryFunction()]),
   ]);
 
   character.data.character.__typename;