Solve

server/api/decorator/test2.ts

@@ -0,0 +1,72 @@
+import { InvalidConversion } from "./base";
+
+export interface Converter<Out, In extends object = Record<string, never>> {
+    (inCtx: In): Out;
+}
+
+type Empty = Record<string, never>;
+
+interface Login {
+    userID: number;
+}
+interface GameLogin {
+    userID: number;
+    generalID: number;
+}
+interface UserLevel {
+    userID: number;
+    userLevel: number;
+}
+
+export function ParseUserLevel<Q extends Login = Login>(): Converter<Q & UserLevel, Q> {
+    return (inCtx: Q): Q & UserLevel => {
+        return {
+            userLevel: 123,
+            ...inCtx,
+        };
+    }
+}
+
+export function ReqLogin<Q extends object = Empty>(): Converter<Q & Login, Q> {
+    return (inCtx: Q): Q & Login => {
+        return {
+            userID: 999,
+            ...inCtx,
+        };
+    }
+}
+
+export function ReqGameLogin<Q extends Login = Login>(): Converter<Q & GameLogin, Q> {
+    return (inCtx: Q): Q & GameLogin => {
+        return {
+            generalID: inCtx.userID * 4,
+            ...inCtx,
+        };
+    }
+}
+
+const x = [
+    ReqLogin(),
+    ParseUserLevel(),
+] as const;
+
+const y = [
+    ReqLogin,
+    ParseUserLevel,
+    ReqGameLogin,
+] as const;
+
+type Split<A> = A extends (q: infer Q) => infer R ? [Q, R] : never;
+
+type Compose<B, A> = B extends A ? B : never;
+type Compose2<B, A extends object, D, C extends object> = D & B extends A & C ? B extends C ? Converter<D, A> : never : never;
+type Chain<T> =
+    T extends readonly [() => Converter<infer B, infer A>] ? Converter<B & A, A> :
+    T extends readonly [() => Converter<infer B, infer A>, () => Converter<infer D, infer C>] ? Compose2<B, A, D, C> :
+    T extends readonly [() => Converter<infer B, infer A>, () => Converter<infer D, infer C>, ... infer R] ? Chain<[() => Compose2<B, A, D, C>, ...R]> :
+    never;
+
+
+type Solve<T> = T extends Converter<infer B, infer A> ? Empty extends A ? B : never : never;
+
+type Z = Solve<Chain<typeof y>>;