overlookmotel / livepack / 6937739311

/* --------------------

 * livepack module

 * Functions to create unique var names.

 * ------------------*/

'use strict';

// Imports

const {isReservedVarName} = require('../shared/functions.js');

// Exports

const CHARS = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ',

        NUM_CHARS = CHARS.length,

        PRIVATE_PREFIX = '_';

/**

 * Factory superclass.

 * Extended by `MangledVarNameFactory` and `UnmangledVarNameFactory`.

 * @param {Set<string>} reservedNames - Set of reserved names

 */

class VarNameFactory {

        constructor(reservedNames) {

                this.reservedNames = reservedNames;

        }

        isReserved(name) {

                // Check if reserved name

                if (this.reservedNames?.has(name)) return true;

                // Check if JS reserved var name

                return isReservedVarName(name);

        }

}

/**

 * Factory for mangled var names.

 *   - First name is 'a'

 *   - Then 'b', 'c', ...'z', 'A', 'B', 'C', ...'Z'

 *   - Then 'aa', 'ab', ...'aZ'

 *   - Then 'ba', 'bb', ...'bZ', ...'ZZ'

 *   - Then 'aaa', 'aab'...

 *

 * Names present in reserved names set and JS reserved words are avoided.

 *

 * @param {Set<string>} reservedNames - Set of reserved names

 */

class MangledVarNameFactory extends VarNameFactory {

                super(reservedNames);

                this.counter = 0;

                this.privateCounter = 0;

        }

        transform(originalName, isPrivate) {

                let name;

                do {

                        let remainder = isPrivate ? this.privateCounter++ : this.counter++;

                        name = '';

                        while (true) { // eslint-disable-line no-constant-condition

                                const code = remainder % NUM_CHARS;

                                name = `${CHARS[code]}${name}`;

                                remainder = (remainder - code) / NUM_CHARS - 1;

                                if (remainder === -1) break;

                        }

                        if (isPrivate) name = `${PRIVATE_PREFIX}${name}`;

                } while (this.isReserved(name));

                return name;

        }

}

function createMangledVarNameTransform(reservedNames) {

        const factory = new MangledVarNameFactory(reservedNames);

        return factory.transform.bind(factory);

}

/**

 * Factory for unmangled var names.

 * Aims to not change var names if possible, but ensure all names are unique.

 * Where a name has been used before, name is postpended with '$0', '$1', '$2' etc

 *

 * Names present in reserved names set and JS reserved words are avoided.

 *

 * @param {Set<string>} reservedNames - Set of reserved names

 */

const NAME_REGEX = /^(.*?)(?:\$(\d+))?$/;

class UnmangledVarNameFactory extends VarNameFactory {

        constructor(reservedNames) {

                super(reservedNames);

                this.used = new Map();

        }

        transform(name, isPrivate) {

                if (isPrivate) name = `${PRIVATE_PREFIX}${name}`;

                const [, nameWithoutPostfix, numStr] = name.match(NAME_REGEX);

                let num = numStr ? numStr * 1 : -1;

                const usedNum = this.used.get(nameWithoutPostfix);

                if (usedNum !== undefined && num <= usedNum) num = usedNum + 1;

                let outName = nameWithoutPostfix;

                while (true) { // eslint-disable-line no-constant-condition

                        if (num > -1) outName = `${nameWithoutPostfix}$${num}`;

                        if (!this.isReserved(outName)) break;

                        num++;

                }

                this.used.set(nameWithoutPostfix, num);

function createUnmangledVarNameTransform(reservedNames) {

        const factory = new UnmangledVarNameFactory(reservedNames);

        return factory.transform.bind(factory);

}

module.exports = {

        createMangledVarNameTransform,

        createUnmangledVarNameTransform,

        // Classes only exported for unit testing

        MangledVarNameFactory,

        UnmangledVarNameFactory

};