From 0330e84394522ccb60a195124949eb6b21898f6d Mon Sep 17 00:00:00 2001
From: Pavel Tereschenko <me@stupidcat.wtf>
Date: Wed, 2 Dec 2020 19:01:42 +0000
Subject: [PATCH] feat: add intersection contract

---
 __tests__/contracts/intersection.js | 53 ++++++++++++++++
 src/contracts/index.js              |  1 +
 src/contracts/intersection.js       | 94 +++++++++++++++++++++++++++++
 src/index.d.ts                      | 60 ++++++++++++++++++
 4 files changed, 208 insertions(+)
 create mode 100644 __tests__/contracts/intersection.js
 create mode 100644 src/contracts/intersection.js

diff --git a/__tests__/contracts/intersection.js b/__tests__/contracts/intersection.js
new file mode 100644
index 0000000..9214b2a
--- /dev/null
+++ b/__tests__/contracts/intersection.js
@@ -0,0 +1,53 @@
+/* @flow */
+
+import { intersection } from '../../src/contracts/intersection';
+import { ValidationError } from '../../src/ValidationError';
+
+const createError = (...types: $ReadOnlyArray<string>) => (
+  name: string,
+  value: mixed,
+) => new ValidationError(name, value, types);
+
+describe('intersection', () => {
+  describe('Creates new Contract for one or more other contracts or validation functions', () => {
+    it('Return ValidationError if at least one Contract returns ValidationError', () => {
+      const validate1 = jest.fn().mockReturnValue({ a: 1, b: 2 });
+      const validate2 = jest.fn().mockReturnValue({ a: 1, b: 2 });
+      const validate3 = jest.fn(createError('type3'));
+
+      const result = intersection(
+        validate1,
+        validate2,
+        validate3,
+      )('valueName', { a: 1, b: 2 });
+
+      expect(result).toBeInstanceOf(ValidationError);
+      expect(result.expectedTypes).toEqual(['Intersection']);
+      expect(result.nested).toEqual([
+        new ValidationError('valueName', { a: 1, b: 2 }, 'type3'),
+      ]);
+
+      expect(validate1).lastCalledWith('valueName', { a: 1, b: 2 });
+      expect(validate2).lastCalledWith('valueName', { a: 1, b: 2 });
+      expect(validate3).lastCalledWith('valueName', { a: 1, b: 2 });
+    });
+
+    it('Return value in other cases', () => {
+      const validate1 = jest.fn().mockReturnValue({ a: 1, b: 2 });
+      const validate2 = jest.fn().mockReturnValue({ a: 1, b: 2 });
+      const validate3 = jest.fn().mockReturnValue({ a: 1, b: 2 });
+
+      expect(
+        intersection(
+          validate1,
+          validate2,
+          validate3,
+        )('valueName', { a: 1, b: 2 }),
+      ).toEqual({ a: 1, b: 2 });
+
+      expect(validate1).lastCalledWith('valueName', { a: 1, b: 2 });
+      expect(validate2).lastCalledWith('valueName', { a: 1, b: 2 });
+      expect(validate3).lastCalledWith('valueName', { a: 1, b: 2 });
+    });
+  });
+});
diff --git a/src/contracts/index.js b/src/contracts/index.js
index 7545ab1..9776075 100644
--- a/src/contracts/index.js
+++ b/src/contracts/index.js
@@ -2,6 +2,7 @@
 
 export * from './array';
 export * from './boolean';
+export * from './intersection';
 export * from './literal';
 export * from './null';
 export * from './number';
diff --git a/src/contracts/intersection.js b/src/contracts/intersection.js
new file mode 100644
index 0000000..c51bd4d
--- /dev/null
+++ b/src/contracts/intersection.js
@@ -0,0 +1,94 @@
+/* @flow */
+
+import { ValidationError } from '../ValidationError';
+import * as contract from '../Contract';
+
+export class IntersectionError extends ValidationError {
+  constructor(
+    valueName: string,
+    value: mixed,
+    errors: $ReadOnlyArray<ValidationError>,
+  ) {
+    super(valueName, value, 'Intersection', errors);
+    this.name = 'IntersectionError';
+  }
+}
+
+declare export function intersection<A>(
+  a: (name: string, value: mixed) => ValidationError | A,
+): contract.Contract<A>;
+
+declare export function intersection<A, B>(
+  a: (name: string, value: mixed) => ValidationError | A,
+  b: (name: string, value: mixed) => ValidationError | B,
+): contract.Contract<A & B>;
+
+declare export function intersection<A, B, C>(
+  a: (name: string, value: mixed) => ValidationError | A,
+  b: (name: string, value: mixed) => ValidationError | B,
+  c: (name: string, value: mixed) => ValidationError | C,
+): contract.Contract<A & B & C>;
+
+declare export function intersection<A, B, C, D>(
+  a: (name: string, value: mixed) => ValidationError | A,
+  b: (name: string, value: mixed) => ValidationError | B,
+  c: (name: string, value: mixed) => ValidationError | C,
+  d: (name: string, value: mixed) => ValidationError | D,
+): contract.Contract<A & B & C & D>;
+
+declare export function intersection<A, B, C, D, E>(
+  a: (name: string, value: mixed) => ValidationError | A,
+  b: (name: string, value: mixed) => ValidationError | B,
+  c: (name: string, value: mixed) => ValidationError | C,
+  d: (name: string, value: mixed) => ValidationError | D,
+  e: (name: string, value: mixed) => ValidationError | E,
+): contract.Contract<A & B & C & D & E>;
+
+declare export function intersection<A, B, C, D, E, F>(
+  a: (name: string, value: mixed) => ValidationError | A,
+  b: (name: string, value: mixed) => ValidationError | B,
+  c: (name: string, value: mixed) => ValidationError | C,
+  d: (name: string, value: mixed) => ValidationError | D,
+  e: (name: string, value: mixed) => ValidationError | E,
+  f: (name: string, value: mixed) => ValidationError | F,
+): contract.Contract<A & B & C & D & E & F>;
+
+declare export function intersection<A, B, C, D, E, F, G>(
+  a: (name: string, value: mixed) => ValidationError | A,
+  b: (name: string, value: mixed) => ValidationError | B,
+  c: (name: string, value: mixed) => ValidationError | C,
+  d: (name: string, value: mixed) => ValidationError | D,
+  e: (name: string, value: mixed) => ValidationError | E,
+  f: (name: string, value: mixed) => ValidationError | F,
+  g: (name: string, value: mixed) => ValidationError | G,
+): contract.Contract<A & B & C & D & E & F & G>;
+
+declare export function intersection<A, B, C, D, E, F, G, H>(
+  a: (name: string, value: mixed) => ValidationError | A,
+  b: (name: string, value: mixed) => ValidationError | B,
+  c: (name: string, value: mixed) => ValidationError | C,
+  d: (name: string, value: mixed) => ValidationError | D,
+  e: (name: string, value: mixed) => ValidationError | E,
+  f: (name: string, value: mixed) => ValidationError | F,
+  g: (name: string, value: mixed) => ValidationError | G,
+  h: (name: string, value: mixed) => ValidationError | H,
+): contract.Contract<A & B & C & D & E & F & G & H>;
+
+export function intersection<T>(
+  ...rules: $ReadOnlyArray<(name: string, value: mixed) => ValidationError | T>
+): contract.Contract<T> {
+  const validators = rules;
+
+  const intersectionContract = (name, value: any): ValidationError | T => {
+    const errors = validators
+      .map(validate => validate(name, value))
+      .reduce((scope, error) => {
+        if (error instanceof ValidationError) scope.push(error);
+        return scope;
+      }, []);
+
+    return errors.length ? new IntersectionError(name, value, errors) : value;
+  };
+
+  return contract.of(intersectionContract);
+}
diff --git a/src/index.d.ts b/src/index.d.ts
index c4fe965..dcb6418 100644
--- a/src/index.d.ts
+++ b/src/index.d.ts
@@ -112,6 +112,66 @@ export declare var str: typeof string;
 export declare var isStr: typeof string;
 export declare var passStr: typeof string;
 
+export declare function intersection<A>(
+  a: Validator<A>,
+): Contract<A>;
+
+ export declare function intersection<A, B>(
+  a: Validator<A>,
+  b: Validator<B>,
+): Contract<A & B>;
+
+ export declare function intersection<A, B, C>(
+  a: Validator<A>,
+  b: Validator<B>,
+  c: Validator<C>,
+): Contract<A & B & C>;
+
+ export declare function intersection<A, B, C, D>(
+  a: Validator<A>,
+  b: Validator<B>,
+  c: Validator<C>,
+  d: Validator<D>,
+): Contract<A & B & C & D>;
+
+ export declare function intersection<A, B, C, D, E>(
+  a: Validator<A>,
+  b: Validator<B>,
+  c: Validator<C>,
+  d: Validator<D>,
+  e: Validator<E>,
+): Contract<A & B & C & D & E>;
+
+export declare function intersection<A, B, C, D, E, F>(
+  a: Validator<A>,
+  b: Validator<B>,
+  c: Validator<C>,
+  d: Validator<D>,
+  e: Validator<E>,
+  f: Validator<F>,
+): Contract<A & B & C & D & E & F>;
+
+ export declare function intersection<A, B, C, D, E, F, G>(
+  a: Validator<A>,
+  b: Validator<B>,
+  c: Validator<C>,
+  d: Validator<D>,
+  e: Validator<E>,
+  f: Validator<F>,
+  g: Validator<G>,
+): Contract<A & B & C & D & E & F & G>;
+
+ export declare function intersection<A, B, C, D, E, F, G, H>(
+  a: Validator<A>,
+  b: Validator<B>,
+  c: Validator<C>,
+  d: Validator<D>,
+  e: Validator<E>,
+  f: Validator<F>,
+  g: Validator<G>,
+  h: Validator<H>,
+): Contract<A & B & C & D & E & F & G & H>;
+
 export declare function union<T extends Array<Validator<any> | string | number | boolean>>(
   ...rules: T
 ): Contract<