'use strict';

/**
 * Stringify/parse functions that don't operate
 * recursively, so they avoid call stack exceeded
 * errors.
 */
exports.stringify = function stringify(input) {
  var queue = [];
  queue.push({obj: input});

  var res = '';
  var next, obj, prefix, val, i, arrayPrefix, keys, k, key, value, objPrefix;
  while ((next = queue.pop())) {
    obj = next.obj;
    prefix = next.prefix || '';
    val = next.val || '';
    res += prefix;
    if (val) {
      res += val;
    } else if (typeof obj !== 'object') {
      res += typeof obj === 'undefined' ? null : JSON.stringify(obj);
    } else if (obj === null) {
      res += 'null';
    } else if (Array.isArray(obj)) {
      queue.push({val: ']'});
      for (i = obj.length - 1; i >= 0; i--) {
        arrayPrefix = i === 0 ? '' : ',';
        queue.push({obj: obj[i], prefix: arrayPrefix});
      }
      queue.push({val: '['});
    } else { // object
      keys = [];
      for (k in obj) {
        if (obj.hasOwnProperty(k)) {
          keys.push(k);
        }
      }
      queue.push({val: '}'});
      for (i = keys.length - 1; i >= 0; i--) {
        key = keys[i];
        value = obj[key];
        objPrefix = (i > 0 ? ',' : '');
        objPrefix += JSON.stringify(key) + ':';
        queue.push({obj: value, prefix: objPrefix});
      }
      queue.push({val: '{'});
    }
  }
  return res;
};

// Convenience function for the parse function.
// This pop function is basically copied from
// pouchCollate.parseIndexableString
function pop(obj, stack, metaStack) {
  var lastMetaElement = metaStack[metaStack.length - 1];
  if (obj === lastMetaElement.element) {
    // popping a meta-element, e.g. an object whose value is another object
    metaStack.pop();
    lastMetaElement = metaStack[metaStack.length - 1];
  }
  var element = lastMetaElement.element;
  var lastElementIndex = lastMetaElement.index;
  if (Array.isArray(element)) {
    element.push(obj);
  } else if (lastElementIndex === stack.length - 2) { // obj with key+value
    var key = stack.pop();
    element[key] = obj;
  } else {
    stack.push(obj); // obj with key only
  }
}

exports.parse = function (str) {
  var stack = [];
  var metaStack = []; // stack for arrays and objects
  var i = 0;
  var collationIndex,parsedNum,numChar;
  var parsedString,lastCh,numConsecutiveSlashes,ch;
  var arrayElement, objElement;
  while (true) {
    collationIndex = str[i++];
    if (collationIndex === '}' ||
        collationIndex === ']' ||
        typeof collationIndex === 'undefined') {
      if (stack.length === 1) {
        return stack.pop();
      } else {
        pop(stack.pop(), stack, metaStack);
        continue;
      }
    }
    switch (collationIndex) {
      case ' ':
      case '\t':
      case '\n':
      case ':':
      case ',':
        break;
      case 'n':
        i += 3; // 'ull'
        pop(null, stack, metaStack);
        break;
      case 't':
        i += 3; // 'rue'
        pop(true, stack, metaStack);
        break;
      case 'f':
        i += 4; // 'alse'
        pop(false, stack, metaStack);
        break;
      case '0':
      case '1':
      case '2':
      case '3':
      case '4':
      case '5':
      case '6':
      case '7':
      case '8':
      case '9':
      case '-':
        parsedNum = '';
        i--;
        while (true) {
          numChar = str[i++];
          if (/[\d\.\-e\+]/.test(numChar)) {
            parsedNum += numChar;
          } else {
            i--;
            break;
          }
        }
        pop(parseFloat(parsedNum), stack, metaStack);
        break;
      case '"':
        parsedString = '';
        lastCh = void 0;
        numConsecutiveSlashes = 0;
        while (true) {
          ch = str[i++];
          if (ch !== '"' || (lastCh === '\\' &&
              numConsecutiveSlashes % 2 === 1)) {
            parsedString += ch;
            lastCh = ch;
            if (lastCh === '\\') {
              numConsecutiveSlashes++;
            } else {
              numConsecutiveSlashes = 0;
            }
          } else {
            break;
          }
        }
        pop(JSON.parse('"' + parsedString + '"'), stack, metaStack);
        break;
      case '[':
        arrayElement = { element: [], index: stack.length };
        stack.push(arrayElement.element);
        metaStack.push(arrayElement);
        break;
      case '{':
        objElement = { element: {}, index: stack.length };
        stack.push(objElement.element);
        metaStack.push(objElement);
        break;
      default:
        throw new Error(
          'unexpectedly reached end of input: ' + collationIndex);
    }
  }
};