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eb39fafa DC |
1 | /** |
2 | * @fileoverview Define the abstract class about cursors which iterate tokens. | |
3 | * @author Toru Nagashima | |
4 | */ | |
5 | "use strict"; | |
6 | ||
7 | //------------------------------------------------------------------------------ | |
8 | // Exports | |
9 | //------------------------------------------------------------------------------ | |
10 | ||
11 | /** | |
12 | * The abstract class about cursors which iterate tokens. | |
13 | * | |
14 | * This class has 2 abstract methods. | |
15 | * | |
16 | * - `current: Token | Comment | null` ... The current token. | |
17 | * - `moveNext(): boolean` ... Moves this cursor to the next token. If the next token didn't exist, it returns `false`. | |
18 | * | |
19 | * This is similar to ES2015 Iterators. | |
20 | * However, Iterators were slow (at 2017-01), so I created this class as similar to C# IEnumerable. | |
21 | * | |
22 | * There are the following known sub classes. | |
23 | * | |
24 | * - ForwardTokenCursor .......... The cursor which iterates tokens only. | |
25 | * - BackwardTokenCursor ......... The cursor which iterates tokens only in reverse. | |
26 | * - ForwardTokenCommentCursor ... The cursor which iterates tokens and comments. | |
27 | * - BackwardTokenCommentCursor .. The cursor which iterates tokens and comments in reverse. | |
28 | * - DecorativeCursor | |
29 | * - FilterCursor ............ The cursor which ignores the specified tokens. | |
30 | * - SkipCursor .............. The cursor which ignores the first few tokens. | |
31 | * - LimitCursor ............. The cursor which limits the count of tokens. | |
32 | * | |
33 | */ | |
34 | module.exports = class Cursor { | |
35 | ||
36 | /** | |
37 | * Initializes this cursor. | |
38 | */ | |
39 | constructor() { | |
40 | this.current = null; | |
41 | } | |
42 | ||
43 | /** | |
44 | * Gets the first token. | |
45 | * This consumes this cursor. | |
46 | * @returns {Token|Comment} The first token or null. | |
47 | */ | |
48 | getOneToken() { | |
49 | return this.moveNext() ? this.current : null; | |
50 | } | |
51 | ||
52 | /** | |
53 | * Gets the first tokens. | |
54 | * This consumes this cursor. | |
55 | * @returns {(Token|Comment)[]} All tokens. | |
56 | */ | |
57 | getAllTokens() { | |
58 | const tokens = []; | |
59 | ||
60 | while (this.moveNext()) { | |
61 | tokens.push(this.current); | |
62 | } | |
63 | ||
64 | return tokens; | |
65 | } | |
66 | ||
67 | /** | |
68 | * Moves this cursor to the next token. | |
69 | * @returns {boolean} `true` if the next token exists. | |
70 | * @abstract | |
71 | */ | |
72 | /* istanbul ignore next */ | |
609c276f | 73 | moveNext() { // eslint-disable-line class-methods-use-this -- Unused |
eb39fafa DC |
74 | throw new Error("Not implemented."); |
75 | } | |
76 | }; |