From bf4f86104ab0438cb07fa61182009564c00d21e0 Mon Sep 17 00:00:00 2001
From: Matt Styles <matt@personalurban.com>
Date: Thu, 23 Mar 2017 06:33:39 +0000
Subject: [PATCH] add patch

---
 examples/patch/index.js                 | 52 ++++++++++++++++++++++
 packages/raid-addons/spec/patch.test.js | 57 +++++++++++++++++++++++++
 packages/raid-addons/src/index.js       |  1 +
 packages/raid-addons/src/patch.js       | 24 +++++++++++
 4 files changed, 134 insertions(+)
 create mode 100644 examples/patch/index.js
 create mode 100644 packages/raid-addons/spec/patch.test.js
 create mode 100644 packages/raid-addons/src/patch.js

diff --git a/examples/patch/index.js b/examples/patch/index.js
new file mode 100644
index 0000000..8c1e6b9
--- /dev/null
+++ b/examples/patch/index.js
@@ -0,0 +1,52 @@
+
+import {render} from 'inferno-dom'
+
+import {Signal} from 'raid/src'
+import patch from 'raid-addons/src/patch'
+
+import element from '../_common/element'
+import Button from '../_common/actionButton'
+import {View, Main, Code} from '../_common/layout'
+
+const signal = new Signal({
+  patched: {
+    foo: 'bar'
+  }
+})
+
+const actions = {
+  'foo': 'bar'
+}
+
+const dispatch = type => payload => signal.emit({type, payload})
+
+const update = (state, event) => {
+  const {foo} = state
+  return {
+    ...state,
+    foo: foo === 'bar' ? 'quux' : 'bar'
+  }
+}
+
+const App = ({state}) => {
+  return (
+    <View>
+      <Main>
+        <Button onClick={dispatch(actions.foo)}>Click me</Button>
+      </Main>
+      <Code>
+        <pre>{JSON.stringify(state, null, '  ')}</pre>
+      </Code>
+    </View>
+  )
+}
+
+// signal.register(patch('patched', update))
+signal.register(patch('patched')(update))
+
+signal.observe(state => {
+  render(
+    <App state={state} />,
+    element
+  )
+})
diff --git a/packages/raid-addons/spec/patch.test.js b/packages/raid-addons/spec/patch.test.js
new file mode 100644
index 0000000..a9c7e2f
--- /dev/null
+++ b/packages/raid-addons/spec/patch.test.js
@@ -0,0 +1,57 @@
+
+import {namespace} from './utils'
+
+import {patch} from '../src'
+
+const test = namespace(__filename)
+
+const createState = (key, value) => ({
+  foo: 'bar',
+  [key]: value
+})
+
+test('Should return a function to be used as an update', t => {
+  t.plan(3)
+
+  const single = patch('key')
+  const double = patch('key', () => {})
+  const addFn = single(() => {})
+
+  t.equal(typeof single, 'function', 'Single argument returns a function')
+  t.equal(typeof double, 'function', 'Two arguments returns a function')
+  t.equal(typeof addFn, 'function', 'Using fixed arity returns a function')
+})
+
+test('Should throw if a key is not supplied', t => {
+  t.plan(1)
+
+  t.throws(patch, 'Key must be supplied')
+})
+
+test('Should pass through the specified keys value as state', t => {
+  t.plan(1)
+
+  const key = 'bar'
+  const value = {
+    baz: 'quux'
+  }
+  const state = createState(key, value)
+  const update = patch(key, state => {
+    t.deepEqual(state, value, 'Passes the key through')
+  })
+
+  update(state)
+})
+
+test('Should apply the update to correct key', t => {
+  t.plan(2)
+
+  const state = createState('bar', {baz: 'quux'})
+  const expected = createState('bar', {baz: 'fred'})
+  const update = state => ({baz: 'fred'})
+  const patched = patch('bar', update)
+  const fixedArity = patch('bar')(update)
+
+  t.deepEqual(patched(state), expected, 'Changes applied correctly')
+  t.deepEqual(fixedArity(state), expected, 'Changes applied correctly')
+})
diff --git a/packages/raid-addons/src/index.js b/packages/raid-addons/src/index.js
index cb12590..b1ca689 100644
--- a/packages/raid-addons/src/index.js
+++ b/packages/raid-addons/src/index.js
@@ -7,6 +7,7 @@ export {default as hook} from './hook'
 export {default as safe} from './safe'
 export {default as squash} from './squash'
 export {default as sin} from './sin'
+export {default as patch} from './patch'
 
 // var addons = {
 //   adaptor,
diff --git a/packages/raid-addons/src/patch.js b/packages/raid-addons/src/patch.js
new file mode 100644
index 0000000..824d50e
--- /dev/null
+++ b/packages/raid-addons/src/patch.js
@@ -0,0 +1,24 @@
+
+// Provides selected key to update and applies back to state
+const select = (key, update) => (state, event) => ({
+  ...state,
+  [key]: update(state[key], event)
+})
+
+// Returns a function accepting an update
+const createPatch = key => update => select(key, update)
+
+// Allow fixed arity for easier composition
+const patch = (key, update) => {
+  if (!key) {
+    throw new Error('[raid:patch] key must be supplied')
+  }
+
+  if (!update || typeof update !== 'function') {
+    return createPatch(key)
+  }
+
+  return select(key, update)
+}
+
+export default patch