cursors.js
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/**
* @fileoverview Define 2 token factories; forward and backward.
* @author Toru Nagashima
*/
"use strict";
//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------
const BackwardTokenCommentCursor = require("./backward-token-comment-cursor");
const BackwardTokenCursor = require("./backward-token-cursor");
const FilterCursor = require("./filter-cursor");
const ForwardTokenCommentCursor = require("./forward-token-comment-cursor");
const ForwardTokenCursor = require("./forward-token-cursor");
const LimitCursor = require("./limit-cursor");
const SkipCursor = require("./skip-cursor");
//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------
/**
* The cursor factory.
* @private
*/
class CursorFactory {
/**
* Initializes this cursor.
* @param {Function} TokenCursor - The class of the cursor which iterates tokens only.
* @param {Function} TokenCommentCursor - The class of the cursor which iterates the mix of tokens and comments.
*/
constructor(TokenCursor, TokenCommentCursor) {
this.TokenCursor = TokenCursor;
this.TokenCommentCursor = TokenCommentCursor;
}
/**
* Creates a base cursor instance that can be decorated by createCursor.
*
* @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.
* @param {boolean} includeComments - The flag to iterate comments as well.
* @returns {Cursor} The created base cursor.
*/
createBaseCursor(tokens, comments, indexMap, startLoc, endLoc, includeComments) {
const Cursor = includeComments ? this.TokenCommentCursor : this.TokenCursor;
return new Cursor(tokens, comments, indexMap, startLoc, endLoc);
}
/**
* Creates a cursor that iterates tokens with normalized options.
*
* @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.
* @param {boolean} includeComments - The flag to iterate comments as well.
* @param {Function|null} filter - The predicate function to choose tokens.
* @param {number} skip - The count of tokens the cursor skips.
* @param {number} count - The maximum count of tokens the cursor iterates. Zero is no iteration for backward compatibility.
* @returns {Cursor} The created cursor.
*/
createCursor(tokens, comments, indexMap, startLoc, endLoc, includeComments, filter, skip, count) {
let cursor = this.createBaseCursor(tokens, comments, indexMap, startLoc, endLoc, includeComments);
if (filter) {
cursor = new FilterCursor(cursor, filter);
}
if (skip >= 1) {
cursor = new SkipCursor(cursor, skip);
}
if (count >= 0) {
cursor = new LimitCursor(cursor, count);
}
return cursor;
}
}
//------------------------------------------------------------------------------
// Exports
//------------------------------------------------------------------------------
exports.forward = new CursorFactory(ForwardTokenCursor, ForwardTokenCommentCursor);
exports.backward = new CursorFactory(BackwardTokenCursor, BackwardTokenCommentCursor);