Add copyPath (#31)

* Add copyPath

* 💅

API.md

@@ -17,6 +17,7 @@
 | [`combineWithP`](#combinewithp) | `(c -> b -> d) (a -> Promise b) -> Promise c -> Promise d` |
 | [`convergeP`](#convergep) | `(b -> c -> Promise d) -> [(a -> Promise b), (a -> Promise c)] -> a -> Promise d` |
 | [`copyProp`](#copyprop) | `String -> String -> { k: v } -> { k: v }` |
+| [`copyPath`](#copypath) | `[String] -> [String] -> { k: v } -> { k: v }` |
 | [`evolveP`](#evolvep) | `{ k: (v -> Promise v) } -> { k: v } -> Promise { k: v }` |
 | [`juxtP`](#juxtp) | `[a... -> Promise b] -> a... -> Promise [b]` |
 | [`mapP`](#mapp) | `Functor f => (a -> Promise b) -> f a -> Promise f b` |
@@ -302,6 +303,24 @@ const getCourse = convergeP(assoc('course'), [ fetchByCourseId, identity ])
 const addCourseLesson = composeP(addLesson, getCourse)
 ```
 
+### copyPath
+
+`@articulate/funky/lib/copyPath`
+
+```haskell
+copyPath :: [String] -> [String] -> { k: v } -> { k: v }
+```
+
+Quickly copy one path on an object to another path.
+
+```js
+copyPath(
+  ['user', 'id'],
+  ['payload', 'userId'],
+  { user: { id: 'abc' }, payload: { name: 'Bob' } }
+) //=> { user { id: 'abc' }, payload: { name: 'Bob', userId: 'abc' } }
+```
+
 ### copyProp
 
 `@articulate/funky/lib/copyProp`

index.js

@@ -12,6 +12,7 @@ exports.combineP     = require('./lib/combineP')
 exports.combineWith  = require('./lib/combineWith')
 exports.combineWithP = require('./lib/combineWithP')
 exports.convergeP    = require('./lib/convergeP')
+exports.copyPath     = require('./lib/copyPath')
 exports.copyProp     = require('./lib/copyProp')
 exports.evolveP      = require('./lib/evolveP')
 exports.juxtP        = require('./lib/juxtP')

src/copyPath.js

@@ -0,0 +1,9 @@
+const assocPath = require('ramda/src/assocPath')
+const curry = require('ramda/src/curry')
+const path = require('ramda/src/path')
+
+// copyPath :: [String] -> [String] -> { k: v } -> { k: v }
+const copyPath = (fromPath, toPath, obj) =>
+  assocPath(toPath, path(fromPath, obj), obj)
+
+module.exports = curry(copyPath)

test/copyPath.js

@@ -0,0 +1,13 @@
+const { expect } = require('chai')
+
+const { copyPath } = require('..')
+
+describe('copyPath', () => {
+  it('copies one path on an object to another path', () =>
+    expect(
+      copyPath(['foo', 'baz'], ['meta', 'bar'], {
+        foo: { baz: 'hey' },
+        meta: { secret: 'sec' }
+      })
+    ).to.eql({ foo: { baz: 'hey' }, meta: { secret: 'sec', bar: 'hey' } }))
+})