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(', ');
}