@jbrowse/core/esm/util/TimeTraveller.js

JBrowse 2 core libraries used by plugins

import { applySnapshot, getEnv, getSnapshot, onSnapshot, resolvePath, types, } from '@jbrowse/mobx-state-tree';
const MAX_HISTORY_LENGTH = 20;
const TimeTraveller = types
    .model('TimeTraveller', {
    undoIdx: -1,
    targetPath: '',
})
    .volatile(() => ({
    history: [],
    notTrackingUndo: false,
}))
    .views(self => ({
    get canUndo() {
        return self.undoIdx > 0 && !self.notTrackingUndo;
    },
    get canRedo() {
        return self.undoIdx < self.history.length - 1 && !self.notTrackingUndo;
    },
}))
    .actions(self => {
    let targetStore;
    let snapshotDisposer;
    let skipNextUndoState = false;
    let debounceTimer;
    let pendingSnapshot;
    return {
        stopTrackingUndo() {
            self.notTrackingUndo = true;
        },
        resumeTrackingUndo() {
            self.notTrackingUndo = false;
        },
        addUndoState(snapshot) {
            if (self.notTrackingUndo) {
                return;
            }
            if (skipNextUndoState) {
                skipNextUndoState = false;
                return;
            }
            self.history.splice(self.undoIdx + 1);
            self.history.push(snapshot);
            if (self.history.length > MAX_HISTORY_LENGTH) {
                self.history.shift();
            }
            self.undoIdx = self.history.length - 1;
        },
        beforeDestroy() {
            snapshotDisposer();
            if (debounceTimer) {
                clearTimeout(debounceTimer);
            }
        },
        initialize() {
            targetStore = self.targetPath
                ? resolvePath(self, self.targetPath)
                : getEnv(self).targetStore;
            if (!targetStore) {
                throw new Error('Failed to find target store for TimeTraveller. Please provide `targetPath` property, or a `targetStore` in the environment');
            }
            snapshotDisposer = onSnapshot(targetStore, snapshot => {
                if (self.notTrackingUndo || skipNextUndoState) {
                    return;
                }
                pendingSnapshot = snapshot;
                if (debounceTimer) {
                    clearTimeout(debounceTimer);
                }
                debounceTimer = setTimeout(() => {
                    debounceTimer = undefined;
                    this.addUndoState(pendingSnapshot);
                }, 300);
            });
            if (self.history.length === 0) {
                this.addUndoState(getSnapshot(targetStore));
            }
        },
        undo() {
            self.undoIdx--;
            skipNextUndoState = true;
            if (targetStore) {
                applySnapshot(targetStore, self.history[self.undoIdx]);
            }
        },
        redo() {
            self.undoIdx++;
            skipNextUndoState = true;
            if (targetStore) {
                applySnapshot(targetStore, self.history[self.undoIdx]);
            }
        },
    };
});
export default TimeTraveller;