var util = require('util');
/**
 * Module exports.
 */

exports.parse = parse;
exports.format = format;
/**
 * Parse extensions header value
 */

function parse (value) {
    value = value || '';
    var extensions = {};
    value.split(',').forEach(function(v) {
        var params = v.split(';');
        var token = params.shift().trim();
        var paramsList = extensions[token] = extensions[token] || [];
        var parsedParams = {};
        params.forEach(function(param) {
            var parts = param.trim().split('=');
            var key = parts[0];
            var value = parts[1];
            if (typeof value === 'undefined') {
                value = true;
            }
            else {
                // unquote value
                if (value[0] === '"') {
                    value = value.slice(1);
                }
                if (value[value.length - 1] === '"') {
                    value = value.slice(0, value.length - 1);
                }
            }
            (parsedParams[key] = parsedParams[key] || []).push(value);
        });
        paramsList.push(parsedParams);
    });
    return extensions;
}
/**
 * Format extensions header value
 */

function format (value) {
    return Object.keys(value).map(function(token) {
        var paramsList = value[token];
        if (!util.isArray(paramsList)) {
            paramsList = [paramsList];
        }
        return paramsList.map(function(params) {
            return [token].concat(Object.keys(params).map(function(k) {
                var p = params[k];
                if (!util.isArray(p)) {
                    p = [p];
                }
                return p.map(function(v) {
                    return v === true ? k : k + '=' + v;
                }).join('; ');
            })).join('; ');
        }).join(', ');
    }).join(', ');
}
