Handle stale sync state in client UI

src/web/state/harborReducer.js

@@ -0,0 +1,92 @@
+export const initialHarborState = {
+  snapshot: null,
+  pendingServerId: '',
+  transport: {
+    bootStatus: 'loading',
+    lastSuccessfulSyncAt: null,
+    consecutiveFailures: 0,
+    stale: false,
+    error: null,
+  },
+};
+
+export const STALE_FAILURE_THRESHOLD = 3;
+
+export function compatibleSnapshot(snapshot) {
+  return snapshot?.apiVersion === 1 &&
+    Number.isSafeInteger(snapshot.revision) &&
+    typeof snapshot.selection?.desiredServerId === 'string' &&
+    Array.isArray(snapshot.servers);
+}
+
+export function classifySyncError(error) {
+  const status = Number(error?.status) || 0;
+  if (error?.code === 'INCOMPATIBLE_API' || status === 404) return 'incompatible-api';
+  if (error?.name === 'TypeError' || status >= 500) return 'control-unreachable';
+  return 'fatal';
+}
+
+function reconcilePendingServer(pendingServerId, snapshot) {
+  if (!pendingServerId || snapshot.selection.desiredServerId === pendingServerId) return '';
+  return snapshot.servers.some((server) => server.id === pendingServerId)
+    ? pendingServerId
+    : '';
+}
+
+export function harborReducer(current, action) {
+  if (action.type === 'select-server') {
+    return action.serverId === current.pendingServerId
+      ? current
+      : { ...current, pendingServerId: action.serverId };
+  }
+
+  if (action.type === 'clear-pending-server') {
+    return current.pendingServerId ? { ...current, pendingServerId: '' } : current;
+  }
+
+  if (action.type === 'retry-sync') {
+    return current.snapshot ? current : {
+      ...current,
+      transport: { ...current.transport, bootStatus: 'loading', error: null },
+    };
+  }
+
+  if (action.type === 'sync-failed') {
+    const consecutiveFailures = current.transport.consecutiveFailures + 1;
+    const bootStatus = classifySyncError(action.error);
+    return {
+      ...current,
+      transport: {
+        ...current.transport,
+        bootStatus: current.snapshot ? 'ready' : bootStatus,
+        consecutiveFailures,
+        stale: Boolean(current.snapshot) && (
+          bootStatus === 'incompatible-api' || consecutiveFailures >= STALE_FAILURE_THRESHOLD
+        ),
+        error: {
+          kind: bootStatus,
+          message: action.error?.message || 'Неизвестная ошибка',
+        },
+      },
+    };
+  }
+
+  if (action.type !== 'sync-succeeded') return current;
+
+  const snapshot = action.snapshot;
+  const newer = !current.snapshot || snapshot.revision > current.snapshot.revision;
+
+  return {
+    snapshot: newer ? snapshot : current.snapshot,
+    pendingServerId: newer
+      ? reconcilePendingServer(current.pendingServerId, snapshot)
+      : current.pendingServerId,
+    transport: {
+      bootStatus: 'ready',
+      lastSuccessfulSyncAt: action.receivedAt,
+      consecutiveFailures: 0,
+      stale: false,
+      error: null,
+    },
+  };
+}