feat: add Result functor

src/Result/Result.ts

@@ -0,0 +1,66 @@
+export interface Result<F, S> {
+  failure<T>(fn: (value: F) => T): Result<T, S>;
+
+  success<T>(fn: (value: S) => T): Result<F, T>;
+
+  isFailure(): boolean;
+
+  isSuccess(): boolean;
+
+  value(): F | S;
+}
+
+export class Failure<F, S> implements Result<F, S> {
+  private constructor(private val: F) {}
+
+  static create<F, S>(value: F): Result<F, S> {
+    return new Failure<F, S>(value);
+  }
+
+  failure<T>(fn: (value: F) => T): Result<T, S> {
+    return new Failure<T, S>(fn(this.val));
+  }
+
+  success<T>(fn: (value: S) => T): Result<F, T> {
+    return this as unknown as Result<F, ReturnType<typeof fn>>;
+  }
+
+  isFailure(): boolean {
+    return true;
+  }
+
+  isSuccess(): boolean {
+    return false;
+  }
+  value(): F | S {
+    return this.val;
+  }
+}
+
+export class Success<F, S> implements Result<F, S> {
+  private constructor(private val: S) {}
+
+  static create<F, S>(value: S): Result<F, S> {
+    return new Success<F, S>(value);
+  }
+
+  failure<T>(fn: (value: F) => T): Result<T, S> {
+    return this as unknown as Result<ReturnType<typeof fn>, S>;
+  }
+
+  success<T>(fn: (value: S) => T): Result<F, T> {
+    return new Success(fn(this.val));
+  }
+
+  isFailure(): boolean {
+    return false;
+  }
+
+  isSuccess(): boolean {
+    return true;
+  }
+
+  value(): F | S {
+    return this.val;
+  }
+}