a-miyashita/gulp-custom-filter

'use strict';

var Promise = Promise || require('promise');
var assertIsFunction = require('./assertions').isFunction;

function promisenize(fn) {
    assertIsFunction(fn, null, 'target');
    if (fn.length < 3) {
        return function(file, encode) {
            try {
                return Promise.resolve(fn(file, encode));
            } catch (err) {
                return Promise.reject(err);
            }
        }
    } else {
        return function(file, encode) {
            return new Promise(function(resolve, reject) {
                fn(file, encode, function(err, result) {
                    if (err) {
                        reject(err);
                    } else {
                        resolve(result);
                    }
                });
            });
        }
    }
}

module.exports = promisenize;