// Query String Utilities

'use strict';

var QueryString = exports;
var util = require('util');


// If obj.hasOwnProperty has been overridden, then calling
// obj.hasOwnProperty(prop) will break.
// See: https://github.com/joyent/node/issues/1707
function hasOwnProperty(obj, prop) {
  return Object.prototype.hasOwnProperty.call(obj, prop);
}


function charCode(c) {
  return c.charCodeAt(0);
}


// a safe fast alternative to decodeURIComponent
QueryString.unescapeBuffer = function(s, decodeSpaces) {
  var out = new Buffer(s.length);
  var state = 'CHAR'; // states: CHAR, HEX0, HEX1
  var n, m, hexchar;

  for (var inIndex = 0, outIndex = 0; inIndex <= s.length; inIndex++) {
    var c = s.charCodeAt(inIndex);
    switch (state) {
      case 'CHAR':
        switch (c) {
          case charCode('%'):
            n = 0;
            m = 0;
            state = 'HEX0';
            break;
          case charCode('+'):
            if (decodeSpaces) c = charCode(' ');
            // pass thru
          default:
            out[outIndex++] = c;
            break;
        }
        break;

      case 'HEX0':
        state = 'HEX1';
        hexchar = c;
        if (charCode('0') <= c && c <= charCode('9')) {
          n = c - charCode('0');
        } else if (charCode('a') <= c && c <= charCode('f')) {
          n = c - charCode('a') + 10;
        } else if (charCode('A') <= c && c <= charCode('F')) {
          n = c - charCode('A') + 10;
        } else {
          out[outIndex++] = charCode('%');
          out[outIndex++] = c;
          state = 'CHAR';
          break;
        }
        break;

      case 'HEX1':
        state = 'CHAR';
        if (charCode('0') <= c && c <= charCode('9')) {
          m = c - charCode('0');
        } else if (charCode('a') <= c && c <= charCode('f')) {
          m = c - charCode('a') + 10;
        } else if (charCode('A') <= c && c <= charCode('F')) {
          m = c - charCode('A') + 10;
        } else {
          out[outIndex++] = charCode('%');
          out[outIndex++] = hexchar;
          out[outIndex++] = c;
          break;
        }
        out[outIndex++] = 16 * n + m;
        break;
    }
  }

  // TODO support returning arbitrary buffers.

  return out.slice(0, outIndex - 1);
};


QueryString.unescape = function(s, decodeSpaces) {
  try {
    return decodeURIComponent(s);
  } catch (e) {
    return QueryString.unescapeBuffer(s, decodeSpaces).toString();
  }
};


QueryString.escape = function(str) {
  return encodeURIComponent(str);
};

var stringifyPrimitive = function(v) {
  if (util.isString(v))
    return v;
  if (util.isBoolean(v))
    return v ? 'true' : 'false';
  if (util.isNumber(v))
    return isFinite(v) ? v : '';
  return '';
};


QueryString.stringify = QueryString.encode = function(obj, sep, eq, options) {
  sep = sep || '&';
  eq = eq || '=';

  var encode = QueryString.escape;
  if (options && typeof options.encodeURIComponent === 'function') {
    encode = options.encodeURIComponent;
  }

  if (util.isObject(obj)) {
    var keys = Object.keys(obj);
    var fields = [];

    for (var i = 0; i < keys.length; i++) {
      var k = keys[i];
      var v = obj[k];
      var ks = encode(stringifyPrimitive(k)) + eq;

      if (util.isArray(v)) {
        for (var j = 0; j < v.length; j++)
          fields.push(ks + encode(stringifyPrimitive(v[j])));
      } else {
        fields.push(ks + encode(stringifyPrimitive(v)));
      }
    }
    return fields.join(sep);
  }
  return '';
};

// Parse a key=val string.
QueryString.parse = QueryString.decode = function(qs, sep, eq, options) {
  sep = sep || '&';
  eq = eq || '=';
  var obj = {};

  if (!util.isString(qs) || qs.length === 0) {
    return obj;
  }

  var regexp = /\+/g;
  qs = qs.split(sep);

  var maxKeys = 1000;
  if (options && util.isNumber(options.maxKeys)) {
    maxKeys = options.maxKeys;
  }

  var len = qs.length;
  // maxKeys <= 0 means that we should not limit keys count
  if (maxKeys > 0 && len > maxKeys) {
    len = maxKeys;
  }

  var decode = QueryString.unescape;
  if (options && typeof options.decodeURIComponent === 'function') {
    decode = options.decodeURIComponent;
  }

  for (var i = 0; i < len; ++i) {
    var x = qs[i].replace(regexp, '%20'),
        idx = x.indexOf(eq),
        kstr, vstr, k, v;

    if (idx >= 0) {
      kstr = x.substr(0, idx);
      vstr = x.substr(idx + 1);
    } else {
      kstr = x;
      vstr = '';
    }

    try {
      k = decode(kstr);
      v = decode(vstr);
    } catch (e) {
      k = QueryString.unescape(kstr, true);
      v = QueryString.unescape(vstr, true);
    }

    if (!hasOwnProperty(obj, k)) {
      obj[k] = v;
    } else if (util.isArray(obj[k])) {
      obj[k].push(v);
    } else {
      obj[k] = [obj[k], v];
    }
  }

  return obj;
};