var gutil = require('gulp-util');
var through = require('through2');

module.exports = function (varName) {
    return through.obj(function (file, enc, cb) {

        var moduleExportsAddition = '\nexport = ' + varName + ';\n';

        if (file.isNull()) {
            cb(null, file);
            return;
        }

        if (file.isStream()) {
            //streams not supported, no need for now.
            return;
        }

        try {
            file.contents = new Buffer(String(file.contents) + moduleExportsAddition);
            this.push(file);

        } catch (err) {
            this.emit('error', new gutil.PluginError('gulp-add-module-exports', err, { fileName: file.path }));
        }
        cb();
    });
};