/**
 * Module dependencies.
 */

var mime = require('connect').mime
  , crc32 = require('buffer-crc32');

/**
 * toString ref.
 */

var toString = {}.toString;

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

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

/**
 * Make `locals()` bound to the given `obj`.
 *
 * This is used for `app.locals` and `res.locals`.
 *
 * @param {Object} obj
 * @return {Function}
 * @api private
 */

exports.locals = function(obj){
  function locals(obj){
    for (var key in obj) locals[key] = obj[key];
    return obj;
  };

  return locals;
};

/**
 * 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;
};

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

exports.flatten = function(arr, ret){
  var ret = ret || []
    , 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;
};

/**
 * Return the acceptable type in `types`, if any.
 *
 * @param {Array} types
 * @param {String} str
 * @return {String}
 * @api private
 */

exports.acceptsArray = function(types, str){
  // accept anything when Accept is not present
  if (!str) return types[0];

  // parse
  var accepted = exports.parseAccept(str)
    , normalized = exports.normalizeTypes(types)
    , len = accepted.length;

  for (var i = 0; i < len; ++i) {
    for (var j = 0, jlen = types.length; j < jlen; ++j) {
      if (exports.accept(normalized[j], accepted[i])) {
        return types[j];
      }
    }
  }
};

/**
 * Check if `type(s)` are acceptable based on
 * the given `str`.
 *
 * @param {String|Array} type(s)
 * @param {String} str
 * @return {Boolean|String}
 * @api private
 */

exports.accepts = function(type, str){
  if ('string' == typeof type) type = type.split(/ *, */);
  return exports.acceptsArray(type, str);
};

/**
 * Check if `type` array is acceptable for `other`.
 *
 * @param {Object} type
 * @param {Object} other
 * @return {Boolean}
 * @api private
 */

exports.accept = function(type, other){
  var t = type.value.split('/');
  return (t[0] == other.type || '*' == other.type)
    && (t[1] == other.subtype || '*' == other.subtype)
    && paramsEqual(type.params, other.params);
};

/**
 * Check if accept params are equal.
 *
 * @param {Object} a
 * @param {Object} b
 * @return {Boolean}
 * @api private
 */

function paramsEqual(a, b){
  return !Object.keys(a).some(function(k) {
    return a[k] != b[k];
  });
}

/**
 * Parse accept `str`, returning
 * an array objects containing
 * `.type` and `.subtype` along
 * with the values provided by
 * `parseQuality()`.
 *
 * @param {Type} name
 * @return {Type}
 * @api private
 */

exports.parseAccept = function(str){
  return exports
    .parseParams(str)
    .map(function(obj){
      var parts = obj.value.split('/');
      obj.type = parts[0];
      obj.subtype = parts[1];
      return obj;
    });
};

/**
 * Parse quality `str`, returning an
 * array of objects with `.value`,
 * `.quality` and optional `.params`
 *
 * @param {String} str
 * @return {Array}
 * @api private
 */

exports.parseParams = function(str){
  return str
    .split(/ *, */)
    .map(acceptParams)
    .filter(function(obj){
      return obj.quality;
    })
    .sort(function(a, b){
      if (a.quality === b.quality) {
        return a.originalIndex - b.originalIndex;
      } else {
        return b.quality - a.quality;
      }
    });
};

/**
 * 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;
}

/**
 * Escape special characters in the given string of html.
 *
 * @param  {String} html
 * @return {String}
 * @api private
 */

exports.escape = function(html) {
  return String(html)
    .replace(/&/g, '&amp;')
    .replace(/"/g, '&quot;')
    .replace(/</g, '&lt;')
    .replace(/>/g, '&gt;');
};

/**
 * Normalize the given path string,
 * returning a regular expression.
 *
 * An empty array should be passed,
 * which will contain the placeholder
 * key names. For example "/user/:id" will
 * then contain ["id"].
 *
 * @param  {String|RegExp|Array} path
 * @param  {Array} keys
 * @param  {Boolean} sensitive
 * @param  {Boolean} strict
 * @return {RegExp}
 * @api private
 */

exports.pathRegexp = function(path, keys, sensitive, strict) {
  if (toString.call(path) == '[object RegExp]') return path;
  if (Array.isArray(path)) path = '(' + path.join('|') + ')';
  path = path
    .concat(strict ? '' : '/?')
    .replace(/\/\(/g, '(?:/')
    .replace(/(\/)?(\.)?:(\w+)(?:(\(.*?\)))?(\?)?(\*)?/g, function(_, slash, format, key, capture, optional, star){
      keys.push({ name: key, optional: !! optional });
      slash = slash || '';
      return ''
        + (optional ? '' : slash)
        + '(?:'
        + (optional ? slash : '')
        + (format || '') + (capture || (format && '([^/.]+?)' || '([^/]+?)')) + ')'
        + (optional || '')
        + (star ? '(/*)?' : '');
    })
    .replace(/([\/.])/g, '\\$1')
    .replace(/\*/g, '(.*)');
  return new RegExp('^' + path + '$', sensitive ? '' : 'i');
}