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/**
* @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.");
}
};
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