const fs = require('fs');
const path = require('path');
const readFile = promisify(fs.readFile);
const writeFile = promisify(fs.writeFile);
const glob = promisify(require('glob'));

const GLOB_PATTERN = `**/*.{md,html,js}`;

const EACH_AS_REGEX = /([^\}+]*)#each\s+([^\s]*)\s+as\s+([^\s|\}]*)/gm;
const HELPER_EXPRESSION_REGEX = /(\{+)(#if|#unless|#each|#with|log|deubgger|#eq|#is|#switch|#case|#default|joinbase|#routeCurrent|routeUrl)\s+([^\}]*)/gm;
const ARGUMENT_DELIMITER_REGEX = /,?\s+/gm;
const ROUTE_HELPERS = /#routeCurrent|routeUrl/;


module.exports = {
	getOptions: function () {
		return [];
	},
	run: function (directory) {
        return glob(GLOB_PATTERN, { cwd: directory }).then(fileNames => {
            let fileIndex = {};
            return Promise.all(fileNames.map(fileName => {
                let filePath = path.join(directory, fileName);
                return readFile(filePath, 'utf8').then(fileContent => fileIndex[filePath] = fileContent);
            })).then(() => fileIndex);
        }).then((fileIndex) => {
            for(let fileName in fileIndex){
                let newFileContents = replace(fileIndex[fileName]);
                if(newFileContents !== null){
                    fileIndex[fileName] = newFileContents;
                }
            }
            return fileIndex;
        }).then((fileIndex) => {
            return Promise.all(Object.keys(fileIndex).map(fileName => writeFile(fileName, fileIndex[fileName], 'utf8')));
        });
	}
};

function replaceAsWithHash(fileContents){
    let matches =  EACH_AS_REGEX.exec(fileContents);
    if(matches && matches[0] && matches[1] && matches[2] && matches[3]){
        fileContents = fileContents.replace(matches[0], `${matches[1]}#each(${matches[2]}, ${matches[3]}=value)`);
        return replaceAsWithHash(fileContents);
    }
    return fileContents;
}

function replaceCallExpression(fileContents){
    let matches = HELPER_EXPRESSION_REGEX.exec(fileContents);
    if(matches && matches[0] && matches[1] && matches[2]){
        let args = (matches[3] || '').trim();
        if(ROUTE_HELPERS.test(matches[2])){
            let argString = '';
            args = args.split(ARGUMENT_DELIMITER_REGEX);
            args.forEach((arg, i) => {
                argString += arg;
                let nextArg = args[i + 1];
                if(nextArg){
                    if(arg === 'true' || nextArg === 'true'){
                        argString += ',';
                    }
                    argString += ' ';
                }
            });
            args = argString;
        }else{
            args = args.replace(ARGUMENT_DELIMITER_REGEX, ', ');
        }
        fileContents = fileContents.replace(matches[0], `${matches[1]}${matches[2]}(${args})`);
        return replaceCallExpression(fileContents);
    }
    return fileContents;
}

function replace(fileContents){
    let originalFileContents = fileContents;
    fileContents = replaceAsWithHash(fileContents);
    fileContents = replaceCallExpression(fileContents);
    return originalFileContents === fileContents ? null : fileContents;
}

function promisify(fn){
	return function(){
		return new Promise((resolve, reject) => {
			fn.apply(fn, [...arguments, (err, result) => {
				if(err){
					return reject(err);
				}
				resolve(result);
			}]);
		});
	};
}