[web] add connection indicator

1 files changed, 44 insertions, 0 deletions

diff --git a/web/src/js/ducks/connection.js b/web/src/js/ducks/connection.js
new file mode 100644
index 00000000..ffa2c309
--- /dev/null
+++ b/web/src/js/ducks/connection.js
@@ -0,0 +1,44 @@
+export const ConnectionState = {
+    INIT: Symbol("init"),
+    FETCHING: Symbol("fetching"), // WebSocket is established, but still startFetching resources.
+    ESTABLISHED: Symbol("established"),
+    ERROR: Symbol("error"),
+    OFFLINE: Symbol("offline"), // indicates that there is no live (websocket) backend.
+}
+
+const defaultState = {
+    state: ConnectionState.INIT,
+    message: null,
+}
+
+export default function reducer(state = defaultState, action) {
+    switch (action.type) {
+
+        case ConnectionState.ESTABLISHED:
+        case ConnectionState.FETCHING:
+        case ConnectionState.ERROR:
+        case ConnectionState.OFFLINE:
+            return {
+                state: action.type,
+                message: action.message
+            }
+
+        default:
+            return state
+    }
+}
+
+export function startFetching() {
+    return { type: ConnectionState.FETCHING }
+}
+
+export function connectionEstablished() {
+    return { type: ConnectionState.ESTABLISHED }
+}
+
+export function connectionError(message) {
+    return { type: ConnectionState.ERROR, message }
+}
+export function setOffline() {
+    return { type: ConnectionState.OFFLINE }
+}