traxxx/src/utils/cf.js

'use strict';

const arrayEqual = require('array-equal');

/* eslint-disable */
function evaluateBranch(tree, modifiers) {
	const result = tree.map((expression) => {
		if (expression.type === 'group') {
			return evaluateBranch(expression.values, expression.modifiers);
		} if (expression.modifiers.length === 0) {
			return ''; // This is a trigger to stringify the previous values
		} if (arrayEqual(['plus'], expression.modifiers)) {
			return 0;
		} if (arrayEqual(['negate', 'negate'], expression.modifiers)) {
			return true;
		} if (arrayEqual(['negate', 'plus'], expression.modifiers)) {
			return true;
		} if (arrayEqual(['plus', 'plus', 'negate'], expression.modifiers)) {
			return true;
		} if (arrayEqual(['plus', 'negate', 'negate'], expression.modifiers)) {
			return 1;
		}
		throw new Error(`Found unrecognized modifier pattern: ${expression.modifiers}`);
	}).reduce((combined, value) => {
		if (value === '') {
			return combined.toString();
		}
		if (value === true) {
			value = 1;
		}

		if (typeof combined === 'string') {
			return combined + value.toString();
		}
		return combined + value;
	}, 0);

	if (modifiers == null) {
		return result;
	}
	if (arrayEqual(['plus'], modifiers)) {
		return parseInt(result);
	}
	return result;
}

function evaluate(tree) {
	return evaluateBranch(tree);
}

function parse(string) {
	const length = string.length;
	let byte;

	let stateFinishedItem = false;
	const modifierStack = [[]];
	const itemStack = [[]];
	let currentStack = itemStack[0];
	let currentModifiers = modifierStack[0];
	let stackLevel = 0;

	for (let pos = 0; pos < length; pos++) {
		byte = string[pos];

		switch (byte) {
		case '+':
			if (pos === 0 || stateFinishedItem === false) {
				// Modifier / number-cast
				currentModifiers.push('plus');
				stateFinishedItem = false;
			} else {
				// Addition, we don't need to do anything here
			}
			break;
		case '!':
			stateFinishedItem = false;
			currentModifiers.push('negate');
			break;
		case '(':
			stateFinishedItem = false;
			stackLevel++;
			itemStack[stackLevel] = currentStack = [];
			modifierStack[stackLevel] = currentModifiers = [];
			break;
		case ')':
			if (stackLevel === 0) {
				throw new Error('Encountered ) without matching (');
			}

			stackLevel--;
			stateFinishedItem = true;

			currentStack = itemStack[stackLevel];
			currentStack.push({
				type: 'group',
				values: itemStack[stackLevel + 1],
				modifiers: modifierStack[stackLevel],
			});

			currentModifiers = modifierStack[stackLevel] = [];
			break;
		case '[':
			if (string[pos + 1] === ']') {
				// Reached the brackets; end of the modifier sequence
				currentStack.push({
					type: 'brackets',
					modifiers: currentModifiers,
				});

				currentModifiers = [];
				pos += 1; // Skip over the closing bracket
				stateFinishedItem = true;
			} else {
				throw new Error(`Invalid byte found; expected ] but got ${string[pos + 1]}`);
			}
		}
	}

	return itemStack[0];
}

function parseExpression(string) {
	return evaluate(parse(string));
}

function findAll(regex, target) {
	const results = []; let
		match;

	while (match = regex.exec(target)) {
		results.push(match);
	}

	return results;
}

function cf(testcase) {
	let [_, parent, child, initialExpression] = /var s,t,o,p,b,r,e,a,k,i,n,g,f,\s*([a-zA-Z]+)={"([a-zA-Z]+)":([^}]+)};/.exec(testcase);

	const modifyingExpressions = findAll(new RegExp(`${parent}\.${child}\s*([*+-])=\s*([^;]+)`, 'g'), testcase).map(match => ({
		operation: match[1],
		expression: match[2],
	})).map(({ operation, expression }) => ({
		operation,
		expression: parseExpression(expression),
	}));

	initialExpression = parseExpression(initialExpression);

	return { parent, child, initialExpression, modifyingExpressions };
};

module.exports = cf;