/*!
 * content-type
 * Copyright(c) 2015 Douglas Christopher Wilson
 * MIT Licensed
 */

'use strict'

/**
 * RegExp to match *( ";" parameter ) in RFC 7231 sec 3.1.1.1
 *
 * parameter     = token "=" ( token / quoted-string )
 * token         = 1*tchar
 * tchar         = "!" / "#" / "$" / "%" / "&" / "'" / "*"
 *               / "+" / "-" / "." / "^" / "_" / "`" / "|" / "~"
 *               / DIGIT / ALPHA
 *               ; any VCHAR, except delimiters
 * quoted-string = DQUOTE *( qdtext / quoted-pair ) DQUOTE
 * qdtext        = HTAB / SP / %x21 / %x23-5B / %x5D-7E / obs-text
 * obs-text      = %x80-FF
 * quoted-pair   = "\" ( HTAB / SP / VCHAR / obs-text )
 */
var paramRegExp = /; *([!#$%&'\*\+\-\.\^_`\|~0-9A-Za-z]+) *= *("(?:[\u000b\u0020\u0021\u0023-\u005b\u005d-\u007e\u0080-\u00ff]|\\[\u000b\u0020-\u00ff])*"|[!#$%&'\*\+\-\.\^_`\|~0-9A-Za-z]+) */g
var textRegExp = /^[\u000b\u0020-\u007e\u0080-\u00ff]+$/
var tokenRegExp = /^[!#$%&'\*\+\-\.\^_`\|~0-9A-Za-z]+$/

/**
 * RegExp to match quoted-pair in RFC 7230 sec 3.2.6
 *
 * quoted-pair = "\" ( HTAB / SP / VCHAR / obs-text )
 * obs-text    = %x80-FF
 */
var qescRegExp = /\\([\u000b\u0020-\u00ff])/g

/**
 * RegExp to match chars that must be quoted-pair in RFC 7230 sec 3.2.6
 */
var quoteRegExp = /([\\"])/g

/**
 * RegExp to match type in RFC 6838
 *
 * media-type = type "/" subtype
 * type       = token
 * subtype    = token
 */
var typeRegExp = /^[!#$%&'\*\+\-\.\^_`\|~0-9A-Za-z]+\/[!#$%&'\*\+\-\.\^_`\|~0-9A-Za-z]+$/

/**
 * Module exports.
 * @public
 */

exports.format = format
exports.parse = parse

/**
 * Format object to media type.
 *
 * @param {object} obj
 * @return {string}
 * @public
 */

function format(obj) {
  if (!obj || typeof obj !== 'object') {
    throw new TypeError('argument obj is required')
  }

  var parameters = obj.parameters
  var type = obj.type

  if (!type || !typeRegExp.test(type)) {
    throw new TypeError('invalid type')
  }

  var string = type

  // append parameters
  if (parameters && typeof parameters === 'object') {
    var param
    var params = Object.keys(parameters).sort()

    for (var i = 0; i < params.length; i++) {
      param = params[i]

      if (!tokenRegExp.test(param)) {
        throw new TypeError('invalid parameter name')
      }

      string += '; ' + param + '=' + qstring(parameters[param])
    }
  }

  return string
}

/**
 * Parse media type to object.
 *
 * @param {string|object} string
 * @return {Object}
 * @public
 */

function parse(string) {
  if (!string) {
    throw new TypeError('argument string is required')
  }

  if (typeof string === 'object') {
    // support req/res-like objects as argument
    string = getcontenttype(string)

    if (typeof string !== 'string') {
      throw new TypeError('content-type header is missing from object');
    }
  }

  if (typeof string !== 'string') {
    throw new TypeError('argument string is required to be a string')
  }

  var index = string.indexOf(';')
  var type = index !== -1
    ? string.substr(0, index).trim()
    : string.trim()

  if (!typeRegExp.test(type)) {
    throw new TypeError('invalid media type')
  }

  var key
  var match
  var obj = new ContentType(type.toLowerCase())
  var value

  paramRegExp.lastIndex = index

  while (match = paramRegExp.exec(string)) {
    if (match.index !== index) {
      throw new TypeError('invalid parameter format')
    }

    index += match[0].length
    key = match[1].toLowerCase()
    value = match[2]

    if (value[0] === '"') {
      // remove quotes and escapes
      value = value
        .substr(1, value.length - 2)
        .replace(qescRegExp, '$1')
    }

    obj.parameters[key] = value
  }

  if (index !== -1 && index !== string.length) {
    throw new TypeError('invalid parameter format')
  }

  return obj
}

/**
 * Get content-type from req/res objects.
 *
 * @param {object}
 * @return {Object}
 * @private
 */

function getcontenttype(obj) {
  if (typeof obj.getHeader === 'function') {
    // res-like
    return obj.getHeader('content-type')
  }

  if (typeof obj.headers === 'object') {
    // req-like
    return obj.headers && obj.headers['content-type']
  }
}

/**
 * Quote a string if necessary.
 *
 * @param {string} val
 * @return {string}
 * @private
 */

function qstring(val) {
  var str = String(val)

  // no need to quote tokens
  if (tokenRegExp.test(str)) {
    return str
  }

  if (str.length > 0 && !textRegExp.test(str)) {
    throw new TypeError('invalid parameter value')
  }

  return '"' + str.replace(quoteRegExp, '\\$1') + '"'
}

/**
 * Class to represent a content type.
 * @private
 */
function ContentType(type) {
  this.parameters = Object.create(null)
  this.type = type
}