implementation of server synchronization

src/app/core/cache/server-sync-buffer.reducer.ts

@@ -0,0 +1,92 @@
+import { RestRequestMethod } from '../data/request.models';
+import { hasNoValue, hasValue } from '../../shared/empty.util';
+import {
+  AddToSSBAction,
+  EmptySSBAction,
+  ServerSyncBufferAction,
+  ServerSyncBufferActionTypes
+} from './server-sync-buffer.actions';
+
+/**
+ * An entry in the ServerSyncBufferState
+ * href: unique href of an ObjectCacheEntry
+ * method: RestRequestMethod type
+ */
+export class ServerSyncBufferEntry {
+  href: string;
+  method: RestRequestMethod;
+}
+
+/**
+ * The ServerSyncBuffer State
+ *
+ * Consists list of ServerSyncBufferState
+ */
+export interface ServerSyncBufferState {
+  buffer: ServerSyncBufferEntry[];
+}
+
+// Object.create(null) ensures the object has no default js properties (e.g. `__proto__`)
+const initialState: ServerSyncBufferState = { buffer: [] };
+
+/**
+ * The ServerSyncBuffer Reducer
+ *
+ * @param state
+ *    the current state
+ * @param action
+ *    the action to perform on the state
+ * @return ServerSyncBufferState
+ *    the new state
+ */
+export function serverSyncBufferReducer(state = initialState, action: ServerSyncBufferAction): ServerSyncBufferState {
+  switch (action.type) {
+
+    case ServerSyncBufferActionTypes.ADD: {
+      return addToServerSyncQueue(state, action as AddToSSBAction)
+    }
+
+    case ServerSyncBufferActionTypes.EMPTY: {
+      return emptyServerSyncQueue(state, action as EmptySSBAction);
+    }
+    default: {
+      return state;
+    }
+  }
+}
+
+/**
+ * Add a new entry to the buffer with a specified method
+ *
+ * @param state
+ *    the current state
+ * @param action
+ *    an AddToSSBAction
+ * @return ServerSyncBufferState
+ *    the new state, with a new entry added to the buffer
+ */
+function addToServerSyncQueue(state: ServerSyncBufferState, action: AddToSSBAction): ServerSyncBufferState {
+  const actionEntry = action.payload as ServerSyncBufferEntry;
+  if (hasNoValue(state.buffer.find((entry) => entry.href === actionEntry.href && entry.method === actionEntry.method))) {
+    return Object.assign({}, state, { buffer: state.buffer.concat(actionEntry) });
+  }
+}
+
+/**
+ * Remove all ServerSyncBuffers entry from the buffer with a specified method
+ * If no method is specified, empty the whole buffer
+ *
+ * @param state
+ *    the current state
+ * @param action
+ *    an AddToSSBAction
+ * @return ServerSyncBufferState
+ *    the new state, with a new entry added to the buffer
+ */
+function emptyServerSyncQueue(state: ServerSyncBufferState, action: EmptySSBAction): ServerSyncBufferState {
+    let newBuffer = [];
+    if (hasValue(action.payload)) {
+      newBuffer = state.buffer.filter((entry) => entry.method !== action.payload);
+    }
+    return Object.assign({}, state, { buffer: newBuffer });
+}