carta-md/dist/internal/history.js

A lightweight, fully customizable, Markdown editor

import { mergeDefaultInterface } from './utils';
const defaultHistoryOptions = {
    minInterval: 300,
    maxSize: 1_000_000
};
/**
 * Input undo/redo functionality.
 */
export class TextAreaHistory {
    states = [];
    currentIndex = -1; // Only <= 0 numbers
    options;
    constructor(options) {
        this.options = mergeDefaultInterface(options, defaultHistoryOptions);
    }
    /**
     * Rollback to the previous state.
     * @returns The previous state, if any.
     */
    undo() {
        if (-this.currentIndex > this.states.length)
            return; // Cannot go back
        const prev = this.states.at(this.currentIndex - 1);
        if (!prev)
            return undefined;
        this.currentIndex--;
        return prev;
    }
    /**
     * Move forward one state.
     * @returns The successive value, if any.
     */
    redo() {
        if (this.currentIndex >= -1)
            return; // Cannot go forward
        const next = this.states.at(this.currentIndex + 1);
        if (!next)
            return undefined;
        this.currentIndex++;
        return next;
    }
    /**
     * Get current stored history in bytes.
     */
    getSize = () => this.states.reduce((acc, curr) => acc + curr.value.length * 2, 0);
    /**
     * Save a value into history.
     * @param value The value to save.
     * @param cursor Cursor position.
     */
    saveState(value, cursor) {
        const latest = this.states.at(-1);
        if (latest?.value === value)
            return;
        if (this.currentIndex < -1) {
            // Remove history
            this.states = this.states.slice(0, this.currentIndex + 1);
        }
        this.currentIndex = -1;
        if (latest && Date.now() - latest.timestamp.getTime() <= (this.options.minInterval ?? 300)) {
            this.states.pop();
        }
        let size = this.getSize();
        this.states.push({
            timestamp: new Date(),
            cursor,
            value
        });
        // every char is 2 bytes
        size += value.length * 2;
        while (size > (this.options.maxSize ?? 1_000_000)) {
            const removed = this.states.shift();
            if (!removed)
                break; // This should never happen
            size -= removed.value.length * 2;
        }
    }
}