Refactor broadcast page

src/main/resources/static/js/broadcast/layers.js

@@ -0,0 +1,44 @@
+import { isVisualAsset } from "./assetKinds.js";
+
+export function ensureLayerPosition(state, assetId, placement = "keep") {
+    const asset = state.assets.get(assetId);
+    if (asset && !isVisualAsset(asset)) {
+        return;
+    }
+    const existingIndex = state.layerOrder.indexOf(assetId);
+    if (existingIndex !== -1 && placement === "keep") {
+        return;
+    }
+    if (existingIndex !== -1) {
+        state.layerOrder.splice(existingIndex, 1);
+    }
+    if (placement === "append") {
+        state.layerOrder.push(assetId);
+    } else {
+        state.layerOrder.unshift(assetId);
+    }
+    state.layerOrder = state.layerOrder.filter((id) => state.assets.has(id));
+}
+
+export function getLayerOrder(state) {
+    state.layerOrder = state.layerOrder.filter((id) => {
+        const asset = state.assets.get(id);
+        return asset && isVisualAsset(asset);
+    });
+    state.assets.forEach((asset, id) => {
+        if (!isVisualAsset(asset)) {
+            return;
+        }
+        if (!state.layerOrder.includes(id)) {
+            state.layerOrder.unshift(id);
+        }
+    });
+    return state.layerOrder;
+}
+
+export function getRenderOrder(state) {
+    return [...getLayerOrder(state)]
+        .reverse()
+        .map((id) => state.assets.get(id))
+        .filter(Boolean);
+}