| /** |
| * @fileoverview Define the abstract class about cursors which iterate tokens. |
| * @author Toru Nagashima |
| */ |
| "use strict"; |
| |
| //------------------------------------------------------------------------------ |
| // Exports |
| //------------------------------------------------------------------------------ |
| |
| /** |
| * The abstract class about cursors which iterate tokens. |
| * |
| * This class has 2 abstract methods. |
| * |
| * - `current: Token | Comment | null` ... The current token. |
| * - `moveNext(): boolean` ... Moves this cursor to the next token. If the next token didn't exist, it returns `false`. |
| * |
| * This is similar to ES2015 Iterators. |
| * However, Iterators were slow (at 2017-01), so I created this class as similar to C# IEnumerable. |
| * |
| * There are the following known sub classes. |
| * |
| * - ForwardTokenCursor .......... The cursor which iterates tokens only. |
| * - BackwardTokenCursor ......... The cursor which iterates tokens only in reverse. |
| * - ForwardTokenCommentCursor ... The cursor which iterates tokens and comments. |
| * - BackwardTokenCommentCursor .. The cursor which iterates tokens and comments in reverse. |
| * - DecorativeCursor |
| * - FilterCursor ............ The cursor which ignores the specified tokens. |
| * - SkipCursor .............. The cursor which ignores the first few tokens. |
| * - LimitCursor ............. The cursor which limits the count of tokens. |
| * |
| */ |
| module.exports = class Cursor { |
| |
| /** |
| * Initializes this cursor. |
| */ |
| constructor() { |
| this.current = null; |
| } |
| |
| /** |
| * Gets the first token. |
| * This consumes this cursor. |
| * @returns {Token|Comment} The first token or null. |
| */ |
| getOneToken() { |
| return this.moveNext() ? this.current : null; |
| } |
| |
| /** |
| * Gets the first tokens. |
| * This consumes this cursor. |
| * @returns {(Token|Comment)[]} All tokens. |
| */ |
| getAllTokens() { |
| const tokens = []; |
| |
| while (this.moveNext()) { |
| tokens.push(this.current); |
| } |
| |
| return tokens; |
| } |
| |
| /** |
| * Moves this cursor to the next token. |
| * @returns {boolean} `true` if the next token exists. |
| * @abstract |
| */ |
| /* istanbul ignore next */ |
| moveNext() { // eslint-disable-line class-methods-use-this |
| throw new Error("Not implemented."); |
| } |
| }; |