🚧 Props nav

packages/immutadot/src/nav2/finalNav.js

@@ -1,10 +1,14 @@
 const update = updater => value => updater(value)
 
+const get = () => value => value
+
+const unset = () => undefined
+
 export const finalNav = operation => {
   switch (operation) {
   case 'update': return update
-  case 'get': return null
-  case 'unset': return null
+  case 'get': return get
+  case 'unset': return unset
   }
   throw TypeError(`Unknown navigator operation ${operation}`)
 }

packages/immutadot/src/nav2/nav.js

@@ -1,9 +1,11 @@
 import { finalNav } from './finalNav'
 import { propNav } from './propNav'
+import { propsNav } from './propsNav'
 
 const toNav = ([type, params]) => {
   switch (type) {
   case 'prop': return propNav(params)
+  case 'props': return propsNav(params)
   }
   throw TypeError(`Unknown navigator type ${type}`)
 }

packages/immutadot/src/nav2/nav.spec.js

@@ -18,4 +18,12 @@ describe('nav.nav', () => {
       return output
     },
   ))
+
+  it('should get a nested prop', () => {
+    const input = {
+      nested: { prop: 'foo' },
+      other: { prop: 'baz' },
+    }
+    expect(nav([['prop', 'nested'], ['prop', 'prop']])('get')()(input)).toEqual('foo')
+  })
 })

packages/immutadot/src/nav2/objectNav.js

@@ -1,3 +1,9 @@
 import { isNil } from 'util/lang'
 
-export const copy = value => isNil(value) ? {} : { ...value }
+export const onCopy = (cb, force = false) => value => {
+  const nil = isNil(value)
+  if (nil && !force) return value
+  const newValue = nil ? {} : { ...value }
+  cb(newValue, value)
+  return newValue
+}

packages/immutadot/src/nav2/propNav.js

@@ -1,20 +1,35 @@
-import { copy } from './objectNav'
 import { isNil } from 'util/lang'
+import { onCopy } from './objectNav'
 
 const update = (key, next) => updater => {
   const nextUpdater = next(updater)
-  return value => {
-    const newValue = copy(value)
+  return onCopy((newValue, value) => {
     newValue[key] = nextUpdater(isNil(value) ? undefined : value[key])
-    return newValue
+  })
+}
+
+const get = (key, next) => () => {
+  const nextGetter = next()
+  return value => nextGetter(isNil(value) ? undefined : value[key])
+}
+
+const unset = (key, next) => () => {
+  const nextUnsetter = next()
+  if (nextUnsetter) {
+    return onCopy((newValue, value) => {
+      newValue[key] = nextUnsetter(isNil(value) ? undefined : value[key])
+    })
   }
+  return onCopy(newValue => {
+    delete newValue[key]
+  })
 }
 
 export const propNav = key => next => operation => {
   switch (operation) {
   case 'update': return update(key, next(operation))
-  case 'get': return null
-  case 'unset': return null
+  case 'get': return get(key, next(operation))
+  case 'unset': return unset(key, next(operation))
   }
   throw TypeError(`Unknown navigator operation ${operation}`)
 }