var Negotiator = require('negotiator')
var mime = require('mime-types')

var slice = [].slice

module.exports = Accepts

function Accepts(req) {
  if (!( this instanceof Accepts))
    return new Accepts(req)

  this.headers = req.headers
  this.negotiator = Negotiator(req)
}

/**
 * Check if the given `type(s)` is acceptable, returning
 * the best match when true, otherwise `undefined`, in which
 * case you should respond with 406 "Not Acceptable". 
 *
 * The `type` value may be a single mime type string
 * such as "application/json", the extension name
 * such as "json" or an array `["json", "html", "text/plain"]`.  When a list
 * or array is given the _best_ match, if any is returned. 
 *
 * Examples:
 *
 *     // Accept: text/html
 *     this.types('html');
 *     // => "html"
 *
 *     // Accept: text/*, application/json
 *     this.types('html');
 *     // => "html"
 *     this.types('text/html');
 *     // => "text/html"
 *     this.types('json', 'text');
 *     // => "json"
 *     this.types('application/json');
 *     // => "application/json"
 *
 *     // Accept: text/*, application/json
 *     this.types('image/png');
 *     this.types('png');
 *     // => undefined
 *
 *     // Accept: text/*;q=.5, application/json
 *     this.types(['html', 'json']);
 *     this.types('html', 'json');
 *     // => "json"
 *
 * @param {String|Array} type(s)...
 * @return {String|Array|Boolean}
 * @api public
 */

Accepts.prototype.type =
Accepts.prototype.types = function (types) {
  if (! Array.isArray(types)) types = slice.call(arguments);
  var n = this.negotiator;
  if (! types.length) return n.mediaTypes();
  if (! this.headers.accept) return types[0];
  var mimes = types.map(extToMime);
  var accepts = n.mediaTypes(mimes.filter(validMime));
  var first = accepts[0];
  if (! first) return false;
  return types[mimes.indexOf(first)];
}

/**
 * Return accepted encodings or best fit based on `encodings`. 
 *
 * Given `Accept-Encoding: gzip, deflate`
 * an array sorted by quality is returned:
 *
 *     ['gzip', 'deflate']
 *
 * @param {String|Array} encoding(s)...
 * @return {String|Array}
 * @api public
 */

Accepts.prototype.encoding =
Accepts.prototype.encodings = function (encodings) {
  if (! Array.isArray(encodings)) encodings = slice.call(arguments);
  var n = this.negotiator;
  if (! encodings.length) return n.encodings();
  return n.encodings(encodings)[0] || false;
}

/**
 * Return accepted charsets or best fit based on `charsets`. 
 *
 * Given `Accept-Charset: utf-8, iso-8859-1;q=0.2, utf-7;q=0.5`
 * an array sorted by quality is returned:
 *
 *     ['utf-8', 'utf-7', 'iso-8859-1']
 *
 * @param {String|Array} charset(s)...
 * @return {String|Array}
 * @api public
 */

Accepts.prototype.charset =
Accepts.prototype.charsets = function (charsets) {
  if (! Array.isArray(charsets)) charsets = [].slice.call(arguments);
  var n = this.negotiator;
  if (! charsets.length) return n.charsets();
  if (! this.headers['accept-charset']) return charsets[0];
  return n.charsets(charsets)[0] || false;
}

/**
 * Return accepted languages or best fit based on `langs`. 
 *
 * Given `Accept-Language: en;q=0.8, es, pt`
 * an array sorted by quality is returned:
 *
 *     ['es', 'pt', 'en']
 *
 * @param {String|Array} lang(s)...
 * @return {Array|String}
 * @api public
 */

Accepts.prototype.lang =
Accepts.prototype.langs =
Accepts.prototype.language =
Accepts.prototype.languages = function (langs) {
  if (! Array.isArray(langs)) langs = slice.call(arguments);
  var n = this.negotiator;
  if (! langs.length) return n.languages();
  if (! this.headers['accept-language']) return langs[0];
  return n.languages(langs)[0] || false;
}

/**
 * Convert extnames to mime. 
 *
 * @param {String} type
 * @return {String}
 * @api private
 */

function extToMime(type) {
  if (~type.indexOf('/')) return type;
  return mime.lookup(type);
}

/**
 * Check if mime is valid. 
 *
 * @param {String} type
 * @return {String}
 * @api private
 */

function validMime(type) {
  return typeof type === 'string';
}
