Editor refactor: extract state

web/open_pages.ts

@@ -0,0 +1,53 @@
+import { EditorSelection, EditorView } from "./deps.ts";
+
+class PageState {
+  constructor(
+    readonly scrollTop: number,
+    readonly selection: EditorSelection,
+  ) {}
+}
+
+export class OpenPages {
+  openPages = new Map<string, PageState>();
+
+  constructor(private editorView: EditorView) {}
+
+  restoreState(pageName: string): boolean {
+    const pageState = this.openPages.get(pageName);
+    const editorView = this.editorView;
+    if (pageState) {
+      // Restore state
+      editorView.scrollDOM.scrollTop = pageState!.scrollTop;
+      try {
+        editorView.dispatch({
+          selection: pageState.selection,
+          scrollIntoView: true,
+        });
+      } catch {
+        // This is fine, just go to the top
+        editorView.dispatch({
+          selection: { anchor: 0 },
+          scrollIntoView: true,
+        });
+      }
+    } else {
+      editorView.scrollDOM.scrollTop = 0;
+      editorView.dispatch({
+        selection: { anchor: 0 },
+        scrollIntoView: true,
+      });
+    }
+    editorView.focus();
+    return !!pageState;
+  }
+
+  saveState(currentPage: string) {
+    this.openPages.set(
+      currentPage,
+      new PageState(
+        this.editorView!.scrollDOM.scrollTop,
+        this.editorView!.state.selection,
+      ),
+    );
+  }
+}