eslint/lib/source-code/token-store/cursors.js

   1 /**
   2  * @fileoverview Define 2 token factories; forward and backward.
   3  * @author Toru Nagashima
   4  */
   5 "use strict";
   6
   7 //------------------------------------------------------------------------------
   8 // Requirements
   9 //------------------------------------------------------------------------------
  10
  11 const BackwardTokenCommentCursor = require("./backward-token-comment-cursor");
  12 const BackwardTokenCursor = require("./backward-token-cursor");
  13 const FilterCursor = require("./filter-cursor");
  14 const ForwardTokenCommentCursor = require("./forward-token-comment-cursor");
  15 const ForwardTokenCursor = require("./forward-token-cursor");
  16 const LimitCursor = require("./limit-cursor");
  17 const SkipCursor = require("./skip-cursor");
  18
  19 //------------------------------------------------------------------------------
  20 // Helpers
  21 //------------------------------------------------------------------------------
  22
  23 /**
  24  * The cursor factory.
  25  * @private
  26  */
  27 class CursorFactory {
  28
  29     /**
  30      * Initializes this cursor.
  31      * @param {Function} TokenCursor The class of the cursor which iterates tokens only.
  32      * @param {Function} TokenCommentCursor The class of the cursor which iterates the mix of tokens and comments.
  33      */
  34     constructor(TokenCursor, TokenCommentCursor) {
  35         this.TokenCursor = TokenCursor;
  36         this.TokenCommentCursor = TokenCommentCursor;
  37     }
  38
  39     /**
  40      * Creates a base cursor instance that can be decorated by createCursor.
  41      * @param {Token[]} tokens The array of tokens.
  42      * @param {Comment[]} comments The array of comments.
  43      * @param {Object} indexMap The map from locations to indices in `tokens`.
  44      * @param {number} startLoc The start location of the iteration range.
  45      * @param {number} endLoc The end location of the iteration range.
  46      * @param {boolean} includeComments The flag to iterate comments as well.
  47      * @returns {Cursor} The created base cursor.
  48      */
  49     createBaseCursor(tokens, comments, indexMap, startLoc, endLoc, includeComments) {
  50         const Cursor = includeComments ? this.TokenCommentCursor : this.TokenCursor;
  51
  52         return new Cursor(tokens, comments, indexMap, startLoc, endLoc);
  53     }
  54
  55     /**
  56      * Creates a cursor that iterates tokens with normalized options.
  57      * @param {Token[]} tokens The array of tokens.
  58      * @param {Comment[]} comments The array of comments.
  59      * @param {Object} indexMap The map from locations to indices in `tokens`.
  60      * @param {number} startLoc The start location of the iteration range.
  61      * @param {number} endLoc The end location of the iteration range.
  62      * @param {boolean} includeComments The flag to iterate comments as well.
  63      * @param {Function|null} filter The predicate function to choose tokens.
  64      * @param {number} skip The count of tokens the cursor skips.
  65      * @param {number} count The maximum count of tokens the cursor iterates. Zero is no iteration for backward compatibility.
  66      * @returns {Cursor} The created cursor.
  67      */
  68     createCursor(tokens, comments, indexMap, startLoc, endLoc, includeComments, filter, skip, count) {
  69         let cursor = this.createBaseCursor(tokens, comments, indexMap, startLoc, endLoc, includeComments);
  70
  71         if (filter) {
  72             cursor = new FilterCursor(cursor, filter);
  73         }
  74         if (skip >= 1) {
  75             cursor = new SkipCursor(cursor, skip);
  76         }
  77         if (count >= 0) {
  78             cursor = new LimitCursor(cursor, count);
  79         }
  80
  81         return cursor;
  82     }
  83 }
  84
  85 //------------------------------------------------------------------------------
  86 // Exports
  87 //------------------------------------------------------------------------------
  88
  89 exports.forward = new CursorFactory(ForwardTokenCursor, ForwardTokenCommentCursor);
  90 exports.backward = new CursorFactory(BackwardTokenCursor, BackwardTokenCommentCursor);