/**
 * Module dependencies.
 */

var mime = require('send').mime;
var crc32 = require('buffer-crc32');
var basename = require('path').basename;

/**
 * Return ETag for `body`.
 *
 * @param {String|Buffer} body
 * @return {String}
 * @api private
 */

exports.etag = function(body){
  return '"' + crc32.signed(body) + '"';
};

/**
 * Check if `path` looks absolute.
 *
 * @param {String} path
 * @return {Boolean}
 * @api private
 */

exports.isAbsolute = function(path){
  if ('/' == path[0]) return true;
  if (':' == path[1] && '\\' == path[2]) return true;
  if ('\\\\' == path.substring(0, 2)) return true; // Microsoft Azure absolute path
};

/**
 * Flatten the given `arr`.
 *
 * @param {Array} arr
 * @return {Array}
 * @api private
 */

exports.flatten = function(arr, ret){
  ret = ret || [];
  var len = arr.length;
  for (var i = 0; i < len; ++i) {
    if (Array.isArray(arr[i])) {
      exports.flatten(arr[i], ret);
    } else {
      ret.push(arr[i]);
    }
  }
  return ret;
};

/**
 * Normalize the given `type`, for example "html" becomes "text/html".
 *
 * @param {String} type
 * @return {Object}
 * @api private
 */

exports.normalizeType = function(type){
  return ~type.indexOf('/')
    ? acceptParams(type)
    : { value: mime.lookup(type), params: {} };
};

/**
 * Normalize `types`, for example "html" becomes "text/html".
 *
 * @param {Array} types
 * @return {Array}
 * @api private
 */

exports.normalizeTypes = function(types){
  var ret = [];

  for (var i = 0; i < types.length; ++i) {
    ret.push(exports.normalizeType(types[i]));
  }

  return ret;
};

/**
 * Generate Content-Disposition header appropriate for the filename.
 * non-ascii filenames are urlencoded and a filename* parameter is added
 *
 * @param {String} filename
 * @return {String}
 * @api private
 */

exports.contentDisposition = function(filename){
  var ret = 'attachment';
  if (filename) {
    filename = basename(filename);
    // if filename contains non-ascii characters, add a utf-8 version ala RFC 5987
    ret = /[^\040-\176]/.test(filename)
      ? 'attachment; filename=' + encodeURI(filename) + '; filename*=UTF-8\'\'' + encodeURI(filename)
      : 'attachment; filename="' + filename + '"';
  }

  return ret;
};

/**
 * Parse accept params `str` returning an
 * object with `.value`, `.quality` and `.params`.
 * also includes `.originalIndex` for stable sorting
 *
 * @param {String} str
 * @return {Object}
 * @api private
 */

function acceptParams(str, index) {
  var parts = str.split(/ *; */);
  var ret = { value: parts[0], quality: 1, params: {}, originalIndex: index };

  for (var i = 1; i < parts.length; ++i) {
    var pms = parts[i].split(/ *= */);
    if ('q' == pms[0]) {
      ret.quality = parseFloat(pms[1]);
    } else {
      ret.params[pms[0]] = pms[1];
    }
  }

  return ret;
}
