From c1d21350a88670521e97c9494ea680c6148165da Mon Sep 17 00:00:00 2001
From: Jerko Steiner <jerko.steiner@gmail.com>
Date: Sat, 19 Jan 2019 17:30:15 +0100
Subject: [PATCH] Add PromiseMiddleware

---
 packages/client/jest.config.js                | 16 ++++
 packages/client/jest.setup.js                 |  0
 .../src/middleware/PromiseMiddleware.test.ts  | 76 +++++++++++++++++++
 .../src/middleware/PromiseMiddleware.ts       | 45 +++++++++++
 packages/client/tsconfig.json                 |  2 +-
 packages/tsconfig.common.json                 |  1 -
 6 files changed, 138 insertions(+), 2 deletions(-)
 create mode 100644 packages/client/jest.config.js
 create mode 100644 packages/client/jest.setup.js
 create mode 100644 packages/client/src/middleware/PromiseMiddleware.test.ts
 create mode 100644 packages/client/src/middleware/PromiseMiddleware.ts

diff --git a/packages/client/jest.config.js b/packages/client/jest.config.js
new file mode 100644
index 0000000..737dab0
--- /dev/null
+++ b/packages/client/jest.config.js
@@ -0,0 +1,16 @@
+module.exports = {
+  roots: [
+    '<rootDir>/src'
+  ],
+  transform: {
+    '^.+\\.tsx?$': 'ts-jest'
+  },
+  testRegex: '(/__tests__/.*|\\.(test|spec))\\.tsx?$',
+  moduleFileExtensions: [
+    'ts',
+    'tsx',
+    'js',
+    'jsx'
+  ],
+  setupFiles: ['<rootDir>/jest.setup.js']
+}
diff --git a/packages/client/jest.setup.js b/packages/client/jest.setup.js
new file mode 100644
index 0000000..e69de29
diff --git a/packages/client/src/middleware/PromiseMiddleware.test.ts b/packages/client/src/middleware/PromiseMiddleware.test.ts
new file mode 100644
index 0000000..e94fe4f
--- /dev/null
+++ b/packages/client/src/middleware/PromiseMiddleware.test.ts
@@ -0,0 +1,76 @@
+import {createStore, applyMiddleware, Store} from 'redux'
+import {PromiseMiddleware} from './PromiseMiddleware'
+
+describe('PromiseMiddleware', () => {
+
+  async function getError(promise: Promise<any>): Promise<Error> {
+    let error: Error
+    try {
+      await promise
+    } catch (err) {
+      error = err
+    }
+    expect(error!).toBeTruthy()
+    return error!
+  }
+
+  describe('constructor', () => {
+    it('throws an error when action types are the same', () => {
+      expect(() => new PromiseMiddleware('a', 'a', 'a')).toThrowError()
+      expect(new PromiseMiddleware('a', 'b', 'c')).toBeTruthy()
+    })
+  })
+
+  let store!: Store
+  beforeEach(() => {
+    const middleware = new PromiseMiddleware()
+    store = createStore((state: any[] = [], action) => {
+      state.push(action)
+      return state
+    }, applyMiddleware(middleware.handle))
+  })
+
+  it('does nothing when payload is not a promise', () => {
+    const action = {type: 'test'}
+    store.dispatch(action)
+    expect(store.getState().slice(1)).toEqual([action])
+  })
+
+  it('dispatches pending and fulfilled action', async () => {
+    const value = 123
+    const type = 'TEST'
+    const action = {
+      payload: Promise.resolve(value),
+      type,
+    }
+    const result = store.dispatch(action)
+    expect(result).toBe(action)
+    await result.payload
+    expect(store.getState().slice(1)).toEqual([{
+      type: `${type}_PENDING`,
+    }, {
+      payload: value,
+      type,
+    }])
+  })
+
+  it('dispatches pending and rejected action on error', async () => {
+    const error = new Error('test')
+    const type = 'TEST'
+    const action = {
+      payload: Promise.reject(error),
+      type,
+    }
+    const result = store.dispatch(action)
+    expect(result).toBe(action)
+    const err = await getError(result.payload)
+    expect(err).toBe(error)
+    expect(store.getState().slice(1)).toEqual([{
+      type: `${type}_PENDING`,
+    }, {
+      error,
+      type: `${type}_REJECTED`,
+    }])
+  })
+
+})
diff --git a/packages/client/src/middleware/PromiseMiddleware.ts b/packages/client/src/middleware/PromiseMiddleware.ts
new file mode 100644
index 0000000..aab2d35
--- /dev/null
+++ b/packages/client/src/middleware/PromiseMiddleware.ts
@@ -0,0 +1,45 @@
+import assert from 'assert'
+import {AnyAction, Middleware} from 'redux'
+
+function isPromise(value: any): value is Promise<any> {
+  return value && typeof value === 'object' &&
+    typeof (value as any).then === 'function'
+}
+
+export class PromiseMiddleware {
+  constructor(
+    readonly pendingExtension = '_PENDING',
+    readonly fulfilledExtension = '',
+    readonly rejectedExtension = '_REJECTED',
+  ) {
+    assert(
+      this.pendingExtension !== this.fulfilledExtension &&
+      this.fulfilledExtension !== this.rejectedExtension &&
+      this.pendingExtension !== this.rejectedExtension,
+      'Pending, fulfilled and rejected extensions must be unique')
+  }
+  handle: Middleware = store => next => (action: AnyAction) => {
+    const {payload, type} = action
+    if (!isPromise(payload)) {
+      next(action)
+      return
+    }
+    store.dispatch({type: type + this.pendingExtension})
+
+    payload
+    .then(result => {
+      store.dispatch({
+        payload: result,
+        type,
+      })
+    })
+    .catch(err => {
+      store.dispatch({
+        error: err,
+        type: type + this.rejectedExtension,
+      })
+    })
+
+    return action
+  }
+}
diff --git a/packages/client/tsconfig.json b/packages/client/tsconfig.json
index 56fff90..caad41d 100644
--- a/packages/client/tsconfig.json
+++ b/packages/client/tsconfig.json
@@ -1,5 +1,5 @@
 {
-  "extends": "../tsconfig.common.json"
+  "extends": "../tsconfig.common.json",
   "compilerOptions": {
     "outDir": "lib",
     "rootDir": "src"
diff --git a/packages/tsconfig.common.json b/packages/tsconfig.common.json
index a003e86..9997d22 100644
--- a/packages/tsconfig.common.json
+++ b/packages/tsconfig.common.json
@@ -1,6 +1,5 @@
 {
   "compilerOptions": {
-    // following settings required for referenced projects
     "composite": true,
     "declaration": true,
     "declarationMap": true,