/**
 * gitignore-to-glob
 * https://github.com/EE/gitignore-to-glob
 *
 * Author Michał Gołębiowski <m.goleb@gmail.com>
 * Licensed under the MIT license.
 */

'use strict';

const fs = require('fs');
const path = require('path');

module.exports = (gitignorePath, dirsToCheck) => {
    gitignorePath = path.resolve(gitignorePath || '.gitignore');

    return fs.readFileSync(gitignorePath, {encoding: 'utf8'})
        .split('\n')

        // Filter out empty lines and comments.
        .filter(pattern => !!pattern && pattern[0] !== '#')

        // '!' in .gitignore and glob mean opposite things so we need to swap it.
        // Return pairt [ignoreFlag, pattern], we'll concatenate it later.
        .map(pattern => pattern[0] === '!' ? ['', pattern.substring(1)] : ['!', pattern])

        // Filter out hidden files/directories (i.e. starting with a dot).
        .filter(patternPair => {
            const pattern = patternPair[1];
            return pattern.indexOf('/.') === -1 && pattern.indexOf('.') !== 0;
        })

        // There may be a lot of files outside of directories from `dirsToCheck`, don't ignore
        // them wasting time.
        .filter(patternPair => {
            const pattern = patternPair[1];
            return pattern[0] !== '/' || !dirsToCheck ||
                new RegExp(`^/(?:${ dirsToCheck.join('|') })(?:/|$)`).test(pattern);
        })

        // Patterns not starting with '/' are in fact "starting" with '**/'. Since that would
        // catch a lot of files, restrict it to directories we check.
        // Patterns starting with '/' are relative to the project directory and glob would
        // treat them as relative to the OS root directory so strip the slash then.
        .map(patternPair => {
            const pattern = patternPair[1];
            if (pattern[0] !== '/') {
                return [patternPair[0],
                    `${ dirsToCheck ? `{${ dirsToCheck }}/` : '' }**/${ pattern }`];
            }
            return [patternPair[0], pattern.substring(1)];
        })

        // We don't know whether a pattern points to a directory or a file and we need files.
        // Therefore, include both `pattern` and `pattern/**` for every pattern in the array.
        .reduce((result, patternPair) => {
            const pattern = patternPair.join('');
            result.push(pattern);
            result.push(`${ pattern }/**`);
            return result;
        }, []);
};