/**
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */
'use strict';

const babylon = require('babylon');
const fs = require('fs');
const path = require('path');
const traverse = require('babel-traverse').default;
const evalToString = require('../shared/evalToString');
const invertObject = require('./invertObject');

const babylonOptions = {
 sourceType: 'module',
 // As a parser, babylon has its own options and we can't directly
 // import/require a babel preset. It should be kept **the same** as
 // the `babel-plugin-syntax-*` ones specified in
 // https://github.com/facebook/fbjs/blob/master/packages/babel-preset-fbjs/configure.js
 plugins: [
 'classProperties',
 'flow',
 'jsx',
 'trailingFunctionCommas',
 'objectRestSpread',
 ],
};

module.exports = function(opts) {
 if (!opts || !('errorMapFilePath' in opts)) {
 throw new Error(
 'Missing options. Ensure you pass an object with `errorMapFilePath`.'
 );
 }

 const errorMapFilePath = opts.errorMapFilePath;
 let existingErrorMap;
 try {
 // Using `fs.readFileSync` instead of `require` here, because `require()`
 // calls are cached, and the cache map is not properly invalidated after
 // file changes.
 existingErrorMap = JSON.parse(
 fs.readFileSync(
 path.join(__dirname, path.basename(errorMapFilePath)),
 'utf8'
 )
 );
 } catch (e) {
 existingErrorMap = {};
 }

 const allErrorIDs = Object.keys(existingErrorMap);
 let currentID;

 if (allErrorIDs.length === 0) {
 // Map is empty
 currentID = 0;
 } else {
 currentID = Math.max.apply(null, allErrorIDs) + 1;
 }

 // Here we invert the map object in memory for faster error code lookup
 existingErrorMap = invertObject(existingErrorMap);

 function transform(source) {
 const ast = babylon.parse(source, babylonOptions);

 traverse(ast, {
 CallExpression: {
 exit(astPath) {
 if (astPath.get('callee').isIdentifier({name: 'invariant'})) {
 const node = astPath.node;

 // error messages can be concatenated (`+`) at runtime, so here's a
 // trivial partial evaluator that interprets the literal value
 const errorMsgLiteral = evalToString(node.arguments[1]);
 if (existingErrorMap.hasOwnProperty(errorMsgLiteral)) {
 return;
 }

 existingErrorMap[errorMsgLiteral] = '' + currentID++;
 }
 },
 },
 });
 }

 function flush(cb) {
 fs.writeFileSync(
 errorMapFilePath,
 JSON.stringify(invertObject(existingErrorMap), null, 2) + '\n',
 'utf-8'
 );
 }

 return function extractErrors(source) {
 transform(source);
 flush();
 };
};