background - introduce ObservableStore

1 files changed, 50 insertions, 0 deletions

diff --git a/app/scripts/lib/observable/host.js b/app/scripts/lib/observable/host.js
new file mode 100644
index 000000000..69f674be8
--- /dev/null
+++ b/app/scripts/lib/observable/host.js
@@ -0,0 +1,50 @@
+const Dnode = require('dnode')
+const ObservableStore = require('./index')
+const endOfStream = require('end-of-stream')
+
+//
+// HostStore
+//
+// plays host to many RemoteStores and sends its state over a stream
+//
+
+class HostStore extends ObservableStore {
+
+  constructor (initState, opts) {
+    super(initState)
+    this.opts = opts || {}
+  }
+
+  createStream () {
+    const self = this
+    // setup remotely exposed api
+    let remoteApi = {}
+    if (!self.opts.readOnly) {
+      remoteApi.put = (newState) => self.put(newState)
+    }
+    // listen for connection to remote
+    const dnode = Dnode(remoteApi)
+    dnode.on('remote', (remote) => {
+      // setup update subscription lifecycle
+      const updateHandler = (state) => remote.put(state)
+      self._onConnect(updateHandler)
+      endOfStream(dnode, () => self._onDisconnect(updateHandler))
+    })
+    return dnode
+  }
+
+  _onConnect (updateHandler) {
+    // subscribe to updates
+    this.subscribe(updateHandler)
+    // send state immediately
+    updateHandler(this.get())
+  }
+
+  _onDisconnect (updateHandler) {
+    // unsubscribe to updates
+    this.unsubscribe(updateHandler)
+  }
+
+}
+
+module.exports = HostStore