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120 lines
3.7 KiB
120 lines
3.7 KiB
import { CursorPos } from "app/client/components/Cursor";
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import { getStorage } from "app/client/lib/localStorageObs";
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import { IDocPage } from "app/common/gristUrls";
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import { Disposable } from "grainjs";
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import { GristDoc } from "app/client/components/GristDoc";
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/**
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* Enriched cursor position with a view id
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*/
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export type ViewCursorPos = CursorPos & { viewId: number }
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/**
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* Component for GristDoc that allows it to keep track of the latest cursor position.
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* In case, when a document is reloaded abnormally, the latest cursor
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* position should be restored from a local storage.
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*/
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export class CursorMonitor extends Disposable {
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// abstraction to work with local storage
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private _store: StorageWrapper;
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// document id that this monitor is attached
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private _docId: string;
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// flag that tells if the position was already restored
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// we track document's view change event, so we only want
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// to react to that event once
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private _restored = false;
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constructor(
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doc: GristDoc,
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store?: Storage) {
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super();
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this._store = new StorageWrapper(store);
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this._docId = doc.docId();
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/**
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* When document loads last cursor position should be restored from local storage.
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*/
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this._whenDocumentLoadsRestorePosition(doc);
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/**
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* When a cursor position changes, its value is stored in a local storage.
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*/
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this._whenCursorHasChangedStoreInMemory(doc);
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}
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private _whenCursorHasChangedStoreInMemory(doc: GristDoc) {
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// whenever current position changes, store it in the memory
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this.autoDispose(doc.cursorPosition.addListener(pos => {
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// if current position is not restored yet, don't change it
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if (!this._restored) { return; }
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if (pos) { this._storePosition(pos); }
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}));
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}
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private _whenDocumentLoadsRestorePosition(doc: GristDoc) {
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// on view shown
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this.autoDispose(doc.currentView.addListener(async view => {
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// if the position was restored for this document do nothing
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if (this._restored) { return; }
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// set that we already restored the position, as some view is shown to the user
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this._restored = true;
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// if view wasn't rendered (page is displaying history or code view) do nothing
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if (!view) { return; }
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const viewId = doc.activeViewId.get();
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const position = this._restoreLastPosition(viewId);
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if (position) {
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await doc.recursiveMoveToCursorPos(position, true);
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}
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}));
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}
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private _storePosition(pos: ViewCursorPos) {
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this._store.update(this._docId, pos);
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}
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private _restoreLastPosition(view: IDocPage) {
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const lastPosition = this._store.read(this._docId);
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this._store.clear(this._docId);
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if (lastPosition && lastPosition.position.viewId == view) {
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return lastPosition.position;
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}
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return null;
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}
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}
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// Internal implementations for working with local storage
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class StorageWrapper {
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constructor(private _storage = getStorage()) {
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}
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public update(docId: string, position: ViewCursorPos): void {
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try {
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const storage = this._storage;
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const data = { docId, position, timestamp: Date.now() };
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storage.setItem(this._key(docId), JSON.stringify(data));
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} catch (e) {
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console.error("Can't store latest position in storage. Detail error " + e.message);
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}
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}
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public clear(docId: string,): void {
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const storage = this._storage;
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storage.removeItem(this._key(docId));
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}
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public read(docId: string): { docId: string; position: ViewCursorPos; } | undefined {
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const storage = this._storage;
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const result = storage.getItem(this._key(docId));
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if (!result) { return undefined; }
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return JSON.parse(result);
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}
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protected _key(docId: string) {
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return `grist-last-position-${docId}`;
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}
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}
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