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website/src/lib/all-hidden.ts

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+import { readable } from 'svelte/store';
+import { engine, FileStateCollectionObserver, type FileState, type Selection } from '$lib/engine';
+import { isSelectionHidden } from '$lib/selection-helpers';
+
+/**
+ * Whether all the selected elements are hidden. It follows the selection and, through the
+ * observer of the files, the state of every file (hiding, editing).
+ */
+export const allHidden = readable(false, (set) => {
+    let selection: Selection = { type: 'empty' };
+    const states = new Map<string, FileState>();
+    const unsubscribes = new Map<string, () => void>();
+
+    const update = () => set(isSelectionHidden(selection, states));
+
+    const unsubscribeSelection = engine.selection.subscribe(($selection) => {
+        selection = $selection;
+        update();
+    });
+    const observer = new FileStateCollectionObserver(
+        (files) => {
+            files.forEach((store, fileId) => {
+                unsubscribes.set(
+                    fileId,
+                    store.subscribe(($file) => {
+                        states.set(fileId, $file);
+                        update();
+                    })
+                );
+            });
+        },
+        (fileId) => {
+            unsubscribes.get(fileId)?.();
+            unsubscribes.delete(fileId);
+            states.delete(fileId);
+            update();
+        },
+        () => {
+            unsubscribes.forEach((unsubscribe) => unsubscribe());
+            unsubscribes.clear();
+            states.clear();
+        }
+    );
+
+    return () => {
+        unsubscribeSelection();
+        observer.destroy();
+    };
+});