From 55d38a1a858f362a8bc3738c277b15dff4c4c09c Mon Sep 17 00:00:00 2001
From: "Homa Wong (unional)" <homawong@gmail.com>
Date: Wed, 10 Apr 2019 23:41:07 -0700
Subject: [PATCH] feat: add set()

---
 README.md                 |  1 +
 src/createContext.spec.ts | 16 ++++++++++++++++
 src/createContext.ts      |  8 ++++++--
 3 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/README.md b/README.md
index 4b4d723..6e4eec6 100644
--- a/README.md
+++ b/README.md
@@ -63,6 +63,7 @@ async function someOtherFunc(
 
 - `createContext(context)`: Create a new async context object. The input can be an object (sync) or a `Promise` returning function (async).
 - `Context.merge(context)`: Merge new context input to create a new async context object.
+- `Context.set(context)`: Set context to a new value. This is used when `createContext()` is made by the producer while `set()` is called by consumer.
 
 [circleci-image]: https://circleci.com/gh/unional/async-fp/tree/master.svg?style=shield
 [circleci-url]: https://circleci.com/gh/unional/async-fp/tree/master
diff --git a/src/createContext.spec.ts b/src/createContext.spec.ts
index eaf0b66..90f214c 100644
--- a/src/createContext.spec.ts
+++ b/src/createContext.spec.ts
@@ -28,3 +28,19 @@ test('sync context merge', async () => {
 
   expect(await actual.get()).toEqual({ a: 1, b: 'b' })
 })
+
+test('async context set', async () => {
+  const ctx = createContext<{ a: number }>()
+
+  ctx.set(async () => ({ a: 1 }))
+
+  expect(await ctx.get()).toEqual({ a: 1 })
+})
+
+test('sync context set', async () => {
+  const ctx = createContext<{ a: number }>()
+
+  ctx.set({ a: 1 })
+
+  expect(await ctx.get()).toEqual({ a: 1 })
+})
diff --git a/src/createContext.ts b/src/createContext.ts
index ac64db6..481d5f8 100644
--- a/src/createContext.ts
+++ b/src/createContext.ts
@@ -1,14 +1,18 @@
 export type Context<T> = {
   get(): Promise<T>,
+  set(context: T | (() => Promise<T>)): void
   merge<R>(context: R | (() => Promise<R>)): Context<T & R>
 }
 
-export function createContext<T extends Record<string | symbol, any>>(context: (() => Promise<T>) | T): Context<T> {
-  const ready = typeof context === 'function' ? (context as any)() : Promise.resolve(context)
+export function createContext<T extends Record<string | symbol, any>>(context?: (() => Promise<T>) | T): Context<T> {
+  let ready = typeof context === 'function' ? (context as any)() : Promise.resolve(context)
   return {
     get() {
       return ready
     },
+    set(context: (() => Promise<T>) | T) {
+      ready = typeof context === 'function' ? (context as any)() : Promise.resolve(context)
+    },
     merge(context) {
       return createContext(async () => {
         const r = typeof context === 'function' ? await (context as any)() : context