1 files changed, 107 insertions, 0 deletions
diff --git a/sdnr/wt-odlux/odlux/framework/src/flux/middleware.ts b/sdnr/wt-odlux/odlux/framework/src/flux/middleware.ts
new file mode 100644
index 000000000..de6505c4f
--- /dev/null
+++ b/sdnr/wt-odlux/odlux/framework/src/flux/middleware.ts
@@ -0,0 +1,107 @@
+/**
+ * ============LICENSE_START========================================================================
+ * ONAP : ccsdk feature sdnr wt odlux
+ * =================================================================================================
+ * Copyright (C) 2019 highstreet technologies GmbH Intellectual Property. All rights reserved.
+ * =================================================================================================
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
+ * in compliance with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License
+ * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+ * or implied. See the License for the specific language governing permissions and limitations under
+ * the License.
+ * ============LICENSE_END==========================================================================
+ */
+import { Action, IActionHandler } from './action';
+import { Store, Dispatch, Enhancer } from './store';
+
+export interface MiddlewareArg<T> {
+  dispatch: Dispatch;
+  getState: () => T;
+}
+
+export interface Middleware<T> {
+  (obj: MiddlewareArg<T>): Function;
+}
+
+class InitialisationAction extends Action { };
+const initialisationAction = new InitialisationAction();
+
+export type ActionHandlerMapObject<S extends { [key: string]: any }, A extends Action = Action> = {
+  [K in keyof S]: IActionHandler<S[K], A>
+}
+
+export const combineActionHandler = <TState extends { [key: string]: any }, TAction extends Action = Action>(actionHandlers: ActionHandlerMapObject<TState, TAction>) : IActionHandler<TState, TAction> => {
+  const finalActionHandlers = {} as { [key: string]: any }; // https://github.com/microsoft/TypeScript/issues/31808
+  Object.keys(actionHandlers).forEach(actionHandlerKey => {
+    const handler = actionHandlers[actionHandlerKey];
+    if (typeof handler === 'function') {
+      finalActionHandlers[actionHandlerKey] = handler;
+    }
+  });
+
+  // ensure initialisation
+  Object.keys(finalActionHandlers).forEach(key => {
+    const actionHandler = finalActionHandlers[key];
+    const initialState = actionHandler(undefined, initialisationAction);
+    if (typeof initialState === 'undefined') {
+      const errorMessage = `Action handler ${ key } returned undefiend during initialization.`;
+      throw new Error(errorMessage);
+    }
+  });
+
+  return function combination<TAction extends Action>(state: TState = ({} as TState), action: TAction) {
+    let hasChanged = false;
+    const nextState = {} as { [key: string]: any }; // https://github.com/microsoft/TypeScript/issues/31808
+    Object.keys(finalActionHandlers).forEach(key => {
+      const actionHandler = finalActionHandlers[key];
+      const previousState = state[key];
+      const nextStateKey = actionHandler(previousState, action);
+      if (typeof nextStateKey === 'undefined') {
+        const errorMessage = `Given ${ action.constructor } and action handler ${ key } returned undefiend.`;
+        throw new Error(errorMessage);
+      }
+      nextState[key] = nextStateKey;
+      hasChanged = hasChanged || nextStateKey !== previousState;
+    });
+    return (hasChanged ? nextState : state) as TState;
+  };
+};
+
+export const chainMiddleware = <TStoreState>(...middlewares: Middleware<TStoreState>[]): Enhancer<TStoreState> => {
+  return (store: Store<TStoreState>) => {
+    const middlewareAPI = {
+      getState() { return store.state },
+      dispatch: <TAction extends Action>(action: TAction) => store.dispatch(action) // we want to use the combinded dispatch
+      // we should NOT use the flux dispatcher here, since the action would affect ALL stores
+    };
+    const chain = middlewares.map(middleware => middleware(middlewareAPI));
+    return compose(...chain)(store.dispatch) as Dispatch;
+  }
+};
+
+/**
+ * Composes single-argument functions from right to left. The rightmost
+ * function can take multiple arguments as it provides the signature for
+ * the resulting composite function.
+ *
+ * @param {...Function} funcs The functions to compose.
+ * @returns {Function} A function obtained by composing the argument functions
+ * from right to left. For example, compose(f, g, h) is identical to doing
+ * (...args) => f(g(h(...args))).
+ */
+const compose = (...funcs: Function[]) => {
+  if (funcs.length === 0) {
+    return (arg: any) => arg
+  }
+
+  if (funcs.length === 1) {
+    return funcs[0]
+  }
+
+  return funcs.reduce((a, b) => (...args: any[]) => a(b(...args)));
+};
+