'use strict';

const path = require("path");

function fixDependencyPaths(dependencies) {
	/* When generating a parser on runtime, the parser source will be evaluated
	 * from within the PEG.js source code, which means that relative dependency
	 * paths will not work. This function patches all relative paths, by
	 * resolving them to absolute paths relative from this file. */

	return Object.keys(dependencies).reduce((obj, key) => {
		obj[key] = path.join(__dirname, dependencies[key]);
		return obj;
	}, {});
}

module.exports = function(body, options = {}) {
	let expressionParser, parserOptions;

	if (options.tracer != null) {
		const pegjs = require("pegjs");
		const fs = require("fs");
		const path = require("path");

		let grammar = fs.readFileSync(path.join(__dirname, "../src/expression.pegjs"), {encoding: "utf8"});

		let pegOptions = require("../pegjs-options.js");

		if (pegOptions.dependencies != null) {
			pegOptions.dependencies = fixDependencyPaths(pegOptions.dependencies);
		}

		expressionParser = pegjs.generate(grammar, Object.assign({
			trace: true,
			format: "commonjs"
		}, pegOptions));

		parserOptions = {
			tracer: options.tracer
		};
	} else {
		expressionParser = require("./expression");

		parserOptions = {};
	}

	return expressionParser.parse(body, parserOptions);
}