add context

Author: yisar

Diff for: compat/README.md

@@ -0,0 +1,4 @@
+# fre/compat
+
+> Something that can be implemanted in userland.
+

Diff for: compat/context.ts

@@ -0,0 +1,40 @@
+import {
+    useReducer,
+    useLayout,
+    useRef,
+  } from 'fre'
+  
+  export const createContext = defaultValue => {
+    const context = {
+      value: defaultValue,
+      subs: new Set(),
+      Provider: function Provider({ value, children }) {
+        useLayout(() => {
+          context.subs.forEach((fn:Function) => fn(value))
+          context.value = value
+        })
+        return children
+      }
+    }
+    return context
+  }
+  
+  export const useContext = (context, selector) => {
+    const subs = context.subs
+    const [, forceUpdate] = useReducer(c => c + 1, 0)
+    const selected = selector ? selector(context.value) : context.value
+    const ref = useRef(null)
+    useLayout(() => {
+      ref.current = selected
+    })
+    useLayout(() => {
+      const fn = nextValue => {
+        if (ref.current === selector(nextValue)) return
+        forceUpdate()
+      }
+      subs.add(fn)
+      return () => subs.delete(fn)
+    }, [subs])
+    return selected
+  }
+  

Diff for: compat/index.ts

@@ -1,3 +1,4 @@
-import { lazy, Suspense } from './Suspense'
+import { lazy, Suspense } from './suspense'
+import { createContext, useContext } from './context'
 
-export { lazy, Suspense }
+export { lazy, Suspense, createContext, useContext }

Diff for: tsconfig.json

@@ -11,5 +11,5 @@
       "sourceMap": false
     },
     "exclude": ["node_modules", "dist"],
-    "include": ["src", "compat/Suspense.ts"]
+    "include": ["src", "compat/suspense.ts"]
   }