node/tools/eslint/lib/token-store/backward-token-cursor.js

/**
 * @fileoverview Define the cursor which iterates tokens only in reverse.
 * @author Toru Nagashima
 */
"use strict";

//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------

const Cursor = require("./cursor");
const utils = require("./utils");

//------------------------------------------------------------------------------
// Exports
//------------------------------------------------------------------------------

/**
 * The cursor which iterates tokens only in reverse.
 */
module.exports = class BackwardTokenCursor extends Cursor {

    /**
     * Initializes this cursor.
     * @param {Token[]} tokens - The array of tokens.
     * @param {Comment[]} comments - The array of comments.
     * @param {Object} indexMap - The map from locations to indices in `tokens`.
     * @param {number} startLoc - The start location of the iteration range.
     * @param {number} endLoc - The end location of the iteration range.
     */
    constructor(tokens, comments, indexMap, startLoc, endLoc) {
        super();
        this.tokens = tokens;
        this.index = utils.getLastIndex(tokens, indexMap, endLoc);
        this.indexEnd = utils.getFirstIndex(tokens, indexMap, startLoc);
    }

    /** @inheritdoc */
    moveNext() {
        if (this.index >= this.indexEnd) {
            this.current = this.tokens[this.index];
            this.index -= 1;
            return true;
        }
        return false;
    }

    //
    // Shorthand for performance.
    //

    /** @inheritdoc */
    getOneToken() {
        return (this.index >= this.indexEnd) ? this.tokens[this.index] : null;
    }
};