1 files changed, 73 insertions, 0 deletions
diff --git a/web/src/js/backends/websocket.js b/web/src/js/backends/websocket.js
new file mode 100644
index 00000000..44b260c9
--- /dev/null
+++ b/web/src/js/backends/websocket.js
@@ -0,0 +1,73 @@
+/**
+ *  The WebSocket backend is responsible for updating our knowledge of flows and events
+ *  from the REST API and live updates delivered via a WebSocket connection.
+ *  An alternative backend may use the REST API only to host static instances.
+ */
+import { fetchApi } from "../utils"
+
+const CMD_RESET = 'reset'
+
+export default class WebsocketBackend {
+    constructor(store) {
+        this.activeFetches = {}
+        this.store = store
+        this.connect()
+    }
+
+    connect() {
+        this.socket = new WebSocket(location.origin.replace('http', 'ws') + '/updates')
+        this.socket.addEventListener('open', () => this.onOpen())
+        this.socket.addEventListener('close', () => this.onClose())
+        this.socket.addEventListener('message', msg => this.onMessage(JSON.parse(msg.data)))
+        this.socket.addEventListener('error', error => this.onError(error))
+    }
+
+    onOpen() {
+        this.fetchData("settings")
+        this.fetchData("flows")
+        this.fetchData("events")
+    }
+
+    fetchData(resource) {
+        let queue = []
+        this.activeFetches[resource] = queue
+        fetchApi(`/${resource}`)
+            .then(res => res.json())
+            .then(json => {
+                // Make sure that we are not superseded yet by the server sending a RESET.
+                if (this.activeFetches[resource] === queue)
+                    this.receive(resource, json)
+            })
+    }
+
+    onMessage(msg) {
+
+        if (msg.cmd === CMD_RESET) {
+            return this.fetchData(msg.resource)
+        }
+        if (msg.resource in this.activeFetches) {
+            this.activeFetches[msg.resource].push(msg)
+        } else {
+            let type = `${msg.resource}_${msg.cmd}`.toUpperCase()
+            this.store.dispatch({ type, ...msg })
+        }
+    }
+
+    receive(resource, data) {
+        let type = `${resource}_RECEIVE`.toUpperCase()
+        this.store.dispatch({ type, cmd: "receive", resource, data })
+        let queue = this.activeFetches[resource]
+        delete this.activeFetches[resource]
+        queue.forEach(msg => this.onMessage(msg))
+    }
+
+    onClose() {
+        // FIXME
+        console.error("onClose", arguments)
+    }
+
+    onError() {
+        // FIXME
+        console.error("onError", arguments)
+    }
+}