Merge pull request #3975 from MetaMask/i3947-composableStore

Add ComposableObservableStore for subscription management

1 files changed, 49 insertions, 0 deletions

diff --git a/app/scripts/lib/ComposableObservableStore.js b/app/scripts/lib/ComposableObservableStore.js
new file mode 100644
index 000000000..d5ee708a1
--- /dev/null
+++ b/app/scripts/lib/ComposableObservableStore.js
@@ -0,0 +1,49 @@
+const ObservableStore = require('obs-store')
+
+/**
+ * An ObservableStore that can composes a flat
+ * structure of child stores based on configuration
+ */
+class ComposableObservableStore extends ObservableStore {
+  /**
+   * Create a new store
+   *
+   * @param {Object} [initState] - The initial store state
+   * @param {Object} [config] - Map of internal state keys to child stores
+   */
+  constructor (initState, config) {
+    super(initState)
+    this.updateStructure(config)
+  }
+
+  /**
+   * Composes a new internal store subscription structure
+   *
+   * @param {Object} [config] - Map of internal state keys to child stores
+   */
+  updateStructure (config) {
+    this.config = config
+    this.removeAllListeners()
+    for (const key in config) {
+      config[key].subscribe((state) => {
+        this.updateState({ [key]: state })
+      })
+    }
+  }
+
+  /**
+   * Merges all child store state into a single object rather than
+   * returning an object keyed by child store class name
+   *
+   * @returns {Object} - Object containing merged child store state
+   */
+  getFlatState () {
+    let flatState = {}
+    for (const key in this.config) {
+      flatState = { ...flatState, ...this.config[key].getState() }
+    }
+    return flatState
+  }
+}
+
+module.exports = ComposableObservableStore