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Filename : index.js
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/**
 * @fileoverview Object to handle access and retrieval of tokens.
 * @author Brandon Mills
 */
"use strict";

//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------

const assert = require("assert");
const { isCommentToken } = require("eslint-utils");
const cursors = require("./cursors");
const ForwardTokenCursor = require("./forward-token-cursor");
const PaddedTokenCursor = require("./padded-token-cursor");
const utils = require("./utils");

//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------

const TOKENS = Symbol("tokens");
const COMMENTS = Symbol("comments");
const INDEX_MAP = Symbol("indexMap");

/**
 * Creates the map from locations to indices in `tokens`.
 *
 * The first/last location of tokens is mapped to the index of the token.
 * The first/last location of comments is mapped to the index of the next token of each comment.
 *
 * @param {Token[]} tokens - The array of tokens.
 * @param {Comment[]} comments - The array of comments.
 * @returns {Object} The map from locations to indices in `tokens`.
 * @private
 */
function createIndexMap(tokens, comments) {
    const map = Object.create(null);
    let tokenIndex = 0;
    let commentIndex = 0;
    let nextStart = 0;
    let range = null;

    while (tokenIndex < tokens.length || commentIndex < comments.length) {
        nextStart = (commentIndex < comments.length) ? comments[commentIndex].range[0] : Number.MAX_SAFE_INTEGER;
        while (tokenIndex < tokens.length && (range = tokens[tokenIndex].range)[0] < nextStart) {
            map[range[0]] = tokenIndex;
            map[range[1] - 1] = tokenIndex;
            tokenIndex += 1;
        }

        nextStart = (tokenIndex < tokens.length) ? tokens[tokenIndex].range[0] : Number.MAX_SAFE_INTEGER;
        while (commentIndex < comments.length && (range = comments[commentIndex].range)[0] < nextStart) {
            map[range[0]] = tokenIndex;
            map[range[1] - 1] = tokenIndex;
            commentIndex += 1;
        }
    }

    return map;
}

/**
 * Creates the cursor iterates tokens with options.
 *
 * @param {CursorFactory} factory - The cursor factory to initialize cursor.
 * @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 {number|Function|Object} [opts=0] - The option object. If this is a number then it's `opts.skip`. If this is a function then it's `opts.filter`.
 * @param {boolean} [opts.includeComments=false] - The flag to iterate comments as well.
 * @param {Function|null} [opts.filter=null] - The predicate function to choose tokens.
 * @param {number} [opts.skip=0] - The count of tokens the cursor skips.
 * @returns {Cursor} The created cursor.
 * @private
 */
function createCursorWithSkip(factory, tokens, comments, indexMap, startLoc, endLoc, opts) {
    let includeComments = false;
    let skip = 0;
    let filter = null;

    if (typeof opts === "number") {
        skip = opts | 0;
    } else if (typeof opts === "function") {
        filter = opts;
    } else if (opts) {
        includeComments = !!opts.includeComments;
        skip = opts.skip | 0;
        filter = opts.filter || null;
    }
    assert(skip >= 0, "options.skip should be zero or a positive integer.");
    assert(!filter || typeof filter === "function", "options.filter should be a function.");

    return factory.createCursor(tokens, comments, indexMap, startLoc, endLoc, includeComments, filter, skip, -1);
}

/**
 * Creates the cursor iterates tokens with options.
 *
 * @param {CursorFactory} factory - The cursor factory to initialize cursor.
 * @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 {number|Function|Object} [opts=0] - The option object. If this is a number then it's `opts.count`. If this is a function then it's `opts.filter`.
 * @param {boolean} [opts.includeComments] - The flag to iterate comments as well.
 * @param {Function|null} [opts.filter=null] - The predicate function to choose tokens.
 * @param {number} [opts.count=0] - The maximum count of tokens the cursor iterates. Zero is no iteration for backward compatibility.
 * @returns {Cursor} The created cursor.
 * @private
 */
function createCursorWithCount(factory, tokens, comments, indexMap, startLoc, endLoc, opts) {
    let includeComments = false;
    let count = 0;
    let countExists = false;
    let filter = null;

    if (typeof opts === "number") {
        count = opts | 0;
        countExists = true;
    } else if (typeof opts === "function") {
        filter = opts;
    } else if (opts) {
        includeComments = !!opts.includeComments;
        count = opts.count | 0;
        countExists = typeof opts.count === "number";
        filter = opts.filter || null;
    }
    assert(count >= 0, "options.count should be zero or a positive integer.");
    assert(!filter || typeof filter === "function", "options.filter should be a function.");

    return factory.createCursor(tokens, comments, indexMap, startLoc, endLoc, includeComments, filter, 0, countExists ? count : -1);
}

/**
 * Creates the cursor iterates tokens with options.
 * This is overload function of the below.
 *
 * @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 {Function|Object} opts - The option object. If this is a function then it's `opts.filter`.
 * @param {boolean} [opts.includeComments] - The flag to iterate comments as well.
 * @param {Function|null} [opts.filter=null] - The predicate function to choose tokens.
 * @param {number} [opts.count=0] - The maximum count of tokens the cursor iterates. Zero is no iteration for backward compatibility.
 * @returns {Cursor} The created cursor.
 * @private
 */
/**
 * Creates the cursor iterates tokens with 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 {number} [beforeCount=0] - The number of tokens before the node to retrieve.
 * @param {boolean} [afterCount=0] - The number of tokens after the node to retrieve.
 * @returns {Cursor} The created cursor.
 * @private
 */
function createCursorWithPadding(tokens, comments, indexMap, startLoc, endLoc, beforeCount, afterCount) {
    if (typeof beforeCount === "undefined" && typeof afterCount === "undefined") {
        return new ForwardTokenCursor(tokens, comments, indexMap, startLoc, endLoc);
    }
    if (typeof beforeCount === "number" || typeof beforeCount === "undefined") {
        return new PaddedTokenCursor(tokens, comments, indexMap, startLoc, endLoc, beforeCount | 0, afterCount | 0);
    }
    return createCursorWithCount(cursors.forward, tokens, comments, indexMap, startLoc, endLoc, beforeCount);
}

/**
 * Gets comment tokens that are adjacent to the current cursor position.
 * @param {Cursor} cursor - A cursor instance.
 * @returns {Array} An array of comment tokens adjacent to the current cursor position.
 * @private
 */
function getAdjacentCommentTokensFromCursor(cursor) {
    const tokens = [];
    let currentToken = cursor.getOneToken();

    while (currentToken && isCommentToken(currentToken)) {
        tokens.push(currentToken);
        currentToken = cursor.getOneToken();
    }

    return tokens;
}

//------------------------------------------------------------------------------
// Exports
//------------------------------------------------------------------------------

/**
 * The token store.
 *
 * This class provides methods to get tokens by locations as fast as possible.
 * The methods are a part of public API, so we should be careful if it changes this class.
 *
 * People can get tokens in O(1) by the hash map which is mapping from the location of tokens/comments to tokens.
 * Also people can get a mix of tokens and comments in O(log k), the k is the number of comments.
 * Assuming that comments to be much fewer than tokens, this does not make hash map from token's locations to comments to reduce memory cost.
 * This uses binary-searching instead for comments.
 */
module.exports = class TokenStore {

    /**
     * Initializes this token store.
     * @param {Token[]} tokens - The array of tokens.
     * @param {Comment[]} comments - The array of comments.
     */
    constructor(tokens, comments) {
        this[TOKENS] = tokens;
        this[COMMENTS] = comments;
        this[INDEX_MAP] = createIndexMap(tokens, comments);
    }

    //--------------------------------------------------------------------------
    // Gets single token.
    //--------------------------------------------------------------------------

    /**
     * Gets the token starting at the specified index.
     * @param {number} offset - Index of the start of the token's range.
     * @param {Object} [options=0] - The option object.
     * @param {boolean} [options.includeComments=false] - The flag to iterate comments as well.
     * @returns {Token|null} The token starting at index, or null if no such token.
     */
    getTokenByRangeStart(offset, options) {
        const includeComments = options && options.includeComments;
        const token = cursors.forward.createBaseCursor(
            this[TOKENS],
            this[COMMENTS],
            this[INDEX_MAP],
            offset,
            -1,
            includeComments
        ).getOneToken();

        if (token && token.range[0] === offset) {
            return token;
        }
        return null;
    }

    /**
     * Gets the first token of the given node.
     * @param {ASTNode} node - The AST node.
     * @param {number|Function|Object} [options=0] - The option object. If this is a number then it's `options.skip`. If this is a function then it's `options.filter`.
     * @param {boolean} [options.includeComments=false] - The flag to iterate comments as well.
     * @param {Function|null} [options.filter=null] - The predicate function to choose tokens.
     * @param {number} [options.skip=0] - The count of tokens the cursor skips.
     * @returns {Token|null} An object representing the token.
     */
    getFirstToken(node, options) {
        return createCursorWithSkip(
            cursors.forward,
            this[TOKENS],
            this[COMMENTS],
            this[INDEX_MAP],
            node.range[0],
            node.range[1],
            options
        ).getOneToken();
    }

    /**
     * Gets the last token of the given node.
     * @param {ASTNode} node - The AST node.
     * @param {number|Function|Object} [options=0] - The option object. Same options as getFirstToken()
     * @returns {Token|null} An object representing the token.
     */
    getLastToken(node, options) {
        return createCursorWithSkip(
            cursors.backward,
            this[TOKENS],
            this[COMMENTS],
            this[INDEX_MAP],
            node.range[0],
            node.range[1],
            options
        ).getOneToken();
    }

    /**
     * Gets the token that precedes a given node or token.
     * @param {ASTNode|Token|Comment} node - The AST node or token.
     * @param {number|Function|Object} [options=0] - The option object. Same options as getFirstToken()
     * @returns {Token|null} An object representing the token.
     */
    getTokenBefore(node, options) {
        return createCursorWithSkip(
            cursors.backward,
            this[TOKENS],
            this[COMMENTS],
            this[INDEX_MAP],
            -1,
            node.range[0],
            options
        ).getOneToken();
    }

    /**
     * Gets the token that follows a given node or token.
     * @param {ASTNode|Token|Comment} node - The AST node or token.
     * @param {number|Function|Object} [options=0] - The option object. Same options as getFirstToken()
     * @returns {Token|null} An object representing the token.
     */
    getTokenAfter(node, options) {
        return createCursorWithSkip(
            cursors.forward,
            this[TOKENS],
            this[COMMENTS],
            this[INDEX_MAP],
            node.range[1],
            -1,
            options
        ).getOneToken();
    }

    /**
     * Gets the first token between two non-overlapping nodes.
     * @param {ASTNode|Token|Comment} left - Node before the desired token range.
     * @param {ASTNode|Token|Comment} right - Node after the desired token range.
     * @param {number|Function|Object} [options=0] - The option object. Same options as getFirstToken()
     * @returns {Token|null} An object representing the token.
     */
    getFirstTokenBetween(left, right, options) {
        return createCursorWithSkip(
            cursors.forward,
            this[TOKENS],
            this[COMMENTS],
            this[INDEX_MAP],
            left.range[1],
            right.range[0],
            options
        ).getOneToken();
    }

    /**
     * Gets the last token between two non-overlapping nodes.
     * @param {ASTNode|Token|Comment} left Node before the desired token range.
     * @param {ASTNode|Token|Comment} right Node after the desired token range.
     * @param {number|Function|Object} [options=0] - The option object. Same options as getFirstToken()
     * @returns {Token|null} An object representing the token.
     */
    getLastTokenBetween(left, right, options) {
        return createCursorWithSkip(
            cursors.backward,
            this[TOKENS],
            this[COMMENTS],
            this[INDEX_MAP],
            left.range[1],
            right.range[0],
            options
        ).getOneToken();
    }

    /**
     * Gets the token that precedes a given node or token in the token stream.
     * This is defined for backward compatibility. Use `includeComments` option instead.
     * TODO: We have a plan to remove this in a future major version.
     * @param {ASTNode|Token|Comment} node The AST node or token.
     * @param {number} [skip=0] A number of tokens to skip.
     * @returns {Token|null} An object representing the token.
     * @deprecated
     */
    getTokenOrCommentBefore(node, skip) {
        return this.getTokenBefore(node, { includeComments: true, skip });
    }

    /**
     * Gets the token that follows a given node or token in the token stream.
     * This is defined for backward compatibility. Use `includeComments` option instead.
     * TODO: We have a plan to remove this in a future major version.
     * @param {ASTNode|Token|Comment} node The AST node or token.
     * @param {number} [skip=0] A number of tokens to skip.
     * @returns {Token|null} An object representing the token.
     * @deprecated
     */
    getTokenOrCommentAfter(node, skip) {
        return this.getTokenAfter(node, { includeComments: true, skip });
    }

    //--------------------------------------------------------------------------
    // Gets multiple tokens.
    //--------------------------------------------------------------------------

    /**
     * Gets the first `count` tokens of the given node.
     * @param {ASTNode} node - The AST node.
     * @param {number|Function|Object} [options=0] - The option object. If this is a number then it's `options.count`. If this is a function then it's `options.filter`.
     * @param {boolean} [options.includeComments=false] - The flag to iterate comments as well.
     * @param {Function|null} [options.filter=null] - The predicate function to choose tokens.
     * @param {number} [options.count=0] - The maximum count of tokens the cursor iterates.
     * @returns {Token[]} Tokens.
     */
    getFirstTokens(node, options) {
        return createCursorWithCount(
            cursors.forward,
            this[TOKENS],
            this[COMMENTS],
            this[INDEX_MAP],
            node.range[0],
            node.range[1],
            options
        ).getAllTokens();
    }

    /**
     * Gets the last `count` tokens of the given node.
     * @param {ASTNode} node - The AST node.
     * @param {number|Function|Object} [options=0] - The option object. Same options as getFirstTokens()
     * @returns {Token[]} Tokens.
     */
    getLastTokens(node, options) {
        return createCursorWithCount(
            cursors.backward,
            this[TOKENS],
            this[COMMENTS],
            this[INDEX_MAP],
            node.range[0],
            node.range[1],
            options
        ).getAllTokens().reverse();
    }

    /**
     * Gets the `count` tokens that precedes a given node or token.
     * @param {ASTNode|Token|Comment} node - The AST node or token.
     * @param {number|Function|Object} [options=0] - The option object. Same options as getFirstTokens()
     * @returns {Token[]} Tokens.
     */
    getTokensBefore(node, options) {
        return createCursorWithCount(
            cursors.backward,
            this[TOKENS],
            this[COMMENTS],
            this[INDEX_MAP],
            -1,
            node.range[0],
            options
        ).getAllTokens().reverse();
    }

    /**
     * Gets the `count` tokens that follows a given node or token.
     * @param {ASTNode|Token|Comment} node - The AST node or token.
     * @param {number|Function|Object} [options=0] - The option object. Same options as getFirstTokens()
     * @returns {Token[]} Tokens.
     */
    getTokensAfter(node, options) {
        return createCursorWithCount(
            cursors.forward,
            this[TOKENS],
            this[COMMENTS],
            this[INDEX_MAP],
            node.range[1],
            -1,
            options
        ).getAllTokens();
    }

    /**
     * Gets the first `count` tokens between two non-overlapping nodes.
     * @param {ASTNode|Token|Comment} left - Node before the desired token range.
     * @param {ASTNode|Token|Comment} right - Node after the desired token range.
     * @param {number|Function|Object} [options=0] - The option object. Same options as getFirstTokens()
     * @returns {Token[]} Tokens between left and right.
     */
    getFirstTokensBetween(left, right, options) {
        return createCursorWithCount(
            cursors.forward,
            this[TOKENS],
            this[COMMENTS],
            this[INDEX_MAP],
            left.range[1],
            right.range[0],
            options
        ).getAllTokens();
    }

    /**
     * Gets the last `count` tokens between two non-overlapping nodes.
     * @param {ASTNode|Token|Comment} left Node before the desired token range.
     * @param {ASTNode|Token|Comment} right Node after the desired token range.
     * @param {number|Function|Object} [options=0] - The option object. Same options as getFirstTokens()
     * @returns {Token[]} Tokens between left and right.
     */
    getLastTokensBetween(left, right, options) {
        return createCursorWithCount(
            cursors.backward,
            this[TOKENS],
            this[COMMENTS],
            this[INDEX_MAP],
            left.range[1],
            right.range[0],
            options
        ).getAllTokens().reverse();
    }

    /**
     * Gets all tokens that are related to the given node.
     * @param {ASTNode} node - The AST node.
     * @param {Function|Object} options The option object. If this is a function then it's `options.filter`.
     * @param {boolean} [options.includeComments=false] - The flag to iterate comments as well.
     * @param {Function|null} [options.filter=null] - The predicate function to choose tokens.
     * @param {number} [options.count=0] - The maximum count of tokens the cursor iterates.
     * @returns {Token[]} Array of objects representing tokens.
     */
    /**
     * Gets all tokens that are related to the given node.
     * @param {ASTNode} node - The AST node.
     * @param {int} [beforeCount=0] - The number of tokens before the node to retrieve.
     * @param {int} [afterCount=0] - The number of tokens after the node to retrieve.
     * @returns {Token[]} Array of objects representing tokens.
     */
    getTokens(node, beforeCount, afterCount) {
        return createCursorWithPadding(
            this[TOKENS],
            this[COMMENTS],
            this[INDEX_MAP],
            node.range[0],
            node.range[1],
            beforeCount,
            afterCount
        ).getAllTokens();
    }

    /**
     * Gets all of the tokens between two non-overlapping nodes.
     * @param {ASTNode|Token|Comment} left Node before the desired token range.
     * @param {ASTNode|Token|Comment} right Node after the desired token range.
     * @param {Function|Object} options The option object. If this is a function then it's `options.filter`.
     * @param {boolean} [options.includeComments=false] - The flag to iterate comments as well.
     * @param {Function|null} [options.filter=null] - The predicate function to choose tokens.
     * @param {number} [options.count=0] - The maximum count of tokens the cursor iterates.
     * @returns {Token[]} Tokens between left and right.
     */
    /**
     * Gets all of the tokens between two non-overlapping nodes.
     * @param {ASTNode|Token|Comment} left Node before the desired token range.
     * @param {ASTNode|Token|Comment} right Node after the desired token range.
     * @param {int} [padding=0] Number of extra tokens on either side of center.
     * @returns {Token[]} Tokens between left and right.
     */
    getTokensBetween(left, right, padding) {
        return createCursorWithPadding(
            this[TOKENS],
            this[COMMENTS],
            this[INDEX_MAP],
            left.range[1],
            right.range[0],
            padding,
            padding
        ).getAllTokens();
    }

    //--------------------------------------------------------------------------
    // Others.
    //--------------------------------------------------------------------------

    /**
     * Checks whether any comments exist or not between the given 2 nodes.
     *
     * @param {ASTNode} left - The node to check.
     * @param {ASTNode} right - The node to check.
     * @returns {boolean} `true` if one or more comments exist.
     */
    commentsExistBetween(left, right) {
        const index = utils.search(this[COMMENTS], left.range[1]);

        return (
            index < this[COMMENTS].length &&
            this[COMMENTS][index].range[1] <= right.range[0]
        );
    }

    /**
     * Gets all comment tokens directly before the given node or token.
     * @param {ASTNode|token} nodeOrToken The AST node or token to check for adjacent comment tokens.
     * @returns {Array} An array of comments in occurrence order.
     */
    getCommentsBefore(nodeOrToken) {
        const cursor = createCursorWithCount(
            cursors.backward,
            this[TOKENS],
            this[COMMENTS],
            this[INDEX_MAP],
            -1,
            nodeOrToken.range[0],
            { includeComments: true }
        );

        return getAdjacentCommentTokensFromCursor(cursor).reverse();
    }

    /**
     * Gets all comment tokens directly after the given node or token.
     * @param {ASTNode|token} nodeOrToken The AST node or token to check for adjacent comment tokens.
     * @returns {Array} An array of comments in occurrence order.
     */
    getCommentsAfter(nodeOrToken) {
        const cursor = createCursorWithCount(
            cursors.forward,
            this[TOKENS],
            this[COMMENTS],
            this[INDEX_MAP],
            nodeOrToken.range[1],
            -1,
            { includeComments: true }
        );

        return getAdjacentCommentTokensFromCursor(cursor);
    }

    /**
     * Gets all comment tokens inside the given node.
     * @param {ASTNode} node The AST node to get the comments for.
     * @returns {Array} An array of comments in occurrence order.
     */
    getCommentsInside(node) {
        return this.getTokens(node, {
            includeComments: true,
            filter: isCommentToken
        });
    }
};