Refactor state database to make namespace fetching available as a static method.

packages/coreutils/src/statedb.ts

@@ -189,7 +189,7 @@ class StateDB implements IStateDB {
    *
    * @param namespace - The namespace to retrieve.
    *
-   * @returns A promise that bears a collection data payloads for a namespace.
+   * @returns A promise that bears a collection of payloads for a namespace.
    *
    * #### Notes
    * Namespaces are entirely conventional entities. The `id` values of stored
@@ -202,32 +202,10 @@ class StateDB implements IStateDB {
    */
   fetchNamespace(namespace: string): Promise<IStateItem[]> {
     return this._ready.then(() => {
-      const { localStorage } = window;
       const prefix = `${this._window}:${this.namespace}:${namespace}:`;
-      let items: IStateItem[] = [];
-      let i = localStorage.length;
-
-      while (i) {
-        let key = localStorage.key(--i);
-
-        if (key && key.indexOf(prefix) === 0) {
-          let value = localStorage.getItem(key);
-
-          try {
-            let envelope = JSON.parse(value) as Private.Envelope;
-
-            items.push({
-              id: key.replace(`${this._window}:${this.namespace}:`, ''),
-              value: envelope ? envelope.v : undefined
-            });
-          } catch (error) {
-            console.warn(error);
-            localStorage.removeItem(key);
-          }
-        }
-      }
+      const replace = `${this._window}:${this.namespace}:`;
 
-      return items;
+      return StateDB.fetchNamespace(prefix, key => key.replace(replace, ''));
     });
   }
 
@@ -275,31 +253,13 @@ class StateDB implements IStateDB {
    */
   toJSON(): Promise<ReadonlyJSONObject> {
     return this._ready.then(() => {
-      const { localStorage } = window;
       const prefix = `${this._window}:${this.namespace}:`;
-      const contents: Partial<ReadonlyJSONObject> =  { };
-      let i = localStorage.length;
-
-      while (i) {
-        let key = localStorage.key(--i);
-
-        if (key && key.indexOf(prefix) === 0) {
-          let value = localStorage.getItem(key);
-
-          try {
-            let envelope = JSON.parse(value) as Private.Envelope;
-
-            if (envelope) {
-              contents[key.replace(prefix, '')] = envelope.v;
-            }
-          } catch (error) {
-            console.warn(error);
-            localStorage.removeItem(key);
-          }
-        }
-      }
 
-      return contents;
+      return StateDB.fetchNamespace(prefix, key => key.replace(prefix, ''))
+        .reduce((acc, val) => {
+          acc[val.id] = val.value;
+          return acc;
+        }, { } as Partial<ReadonlyJSONObject>);
     });
   }
 
@@ -462,6 +422,49 @@ namespace StateDB {
      */
     windowName?: string;
   }
+
+  /**
+   * Retrieve all the saved bundles for a given namespace in local storage.
+   *
+   * @param prefix - The namespace to retrieve.
+   *
+   * @param mask - Optional mask function to transform each key retrieved.
+   *
+   * @returns A collection of data payloads for a given prefix.
+   *
+   * #### Notes
+   * If there are any errors in retrieving the data, they will be logged to the
+   * console in order to optimistically return any extant data without failing.
+   */
+  export
+  function fetchNamespace(namespace: string, mask: (key: string) => string = key => key): IStateItem[] {
+    const { localStorage } = window;
+
+    let items: IStateItem[] = [];
+    let i = localStorage.length;
+
+    while (i) {
+      let key = localStorage.key(--i);
+
+      if (key && key.indexOf(namespace) === 0) {
+        let value = localStorage.getItem(key);
+
+        try {
+          let envelope = JSON.parse(value) as Private.Envelope;
+
+          items.push({
+            id: mask(key),
+            value: envelope ? envelope.v : undefined
+          });
+        } catch (error) {
+          console.warn(error);
+          localStorage.removeItem(key);
+        }
+      }
+    }
+
+    return items;
+  }
 }