var util = require('./util');
var Queue = require('./Queue');

/**
 * DataSet
 *
 * Usage:
 *     var dataSet = new DataSet({
 *         fieldId: '_id',
 *         type: {
 *             // ...
 *         }
 *     });
 *
 *     dataSet.add(item);
 *     dataSet.add(data);
 *     dataSet.update(item);
 *     dataSet.update(data);
 *     dataSet.remove(id);
 *     dataSet.remove(ids);
 *     var data = dataSet.get();
 *     var data = dataSet.get(id);
 *     var data = dataSet.get(ids);
 *     var data = dataSet.get(ids, options, data);
 *     dataSet.clear();
 *
 * A data set can:
 * - add/remove/update data
 * - gives triggers upon changes in the data
 * - can  import/export data in various data formats
 *
 * @param {Array} [data]    Optional array with initial data
 * @param {Object} [options]   Available options:
 *                             {String} fieldId Field name of the id in the
 *                                              items, 'id' by default.
 *                             {Object.<String, String} type
 *                                              A map with field names as key,
 *                                              and the field type as value.
 *                             {Object} queue   Queue changes to the DataSet,
 *                                              flush them all at once.
 *                                              Queue options:
 *                                              - {number} delay  Delay in ms, null by default
 *                                              - {number} max    Maximum number of entries in the queue, Infinity by default
 * @constructor DataSet
 */
// TODO: add a DataSet constructor DataSet(data, options)
function DataSet (data, options) {
  // correctly read optional arguments
  if (data && !Array.isArray(data)) {
    options = data;
    data = null;
  }

  this._options = options || {};
  this._data = {};                                 // map with data indexed by id
  this.length = 0;                                 // number of items in the DataSet
  this._fieldId = this._options.fieldId || 'id';   // name of the field containing id
  this._type = {};                                 // internal field types (NOTE: this can differ from this._options.type)

  // all variants of a Date are internally stored as Date, so we can convert
  // from everything to everything (also from ISODate to Number for example)
  if (this._options.type) {
    var fields = Object.keys(this._options.type);
    for (var i = 0, len = fields.length; i < len; i++) {
      var field = fields[i];
      var value = this._options.type[field];
      if (value == 'Date' || value == 'ISODate' || value == 'ASPDate') {
        this._type[field] = 'Date';
      }
      else {
        this._type[field] = value;
      }
    }
  }

  // TODO: deprecated since version 1.1.1 (or 2.0.0?)
  if (this._options.convert) {
    throw new Error('Option "convert" is deprecated. Use "type" instead.');
  }

  this._subscribers = {};  // event subscribers

  // add initial data when provided
  if (data) {
    this.add(data);
  }

  this.setOptions(options);
}

/**
 * @param {Object} [options]   Available options:
 *                             {Object} queue   Queue changes to the DataSet,
 *                                              flush them all at once.
 *                                              Queue options:
 *                                              - {number} delay  Delay in ms, null by default
 *                                              - {number} max    Maximum number of entries in the queue, Infinity by default
 * @param options
 */
DataSet.prototype.setOptions = function(options) {
  if (options && options.queue !== undefined) {
    if (options.queue === false) {
      // delete queue if loaded
      if (this._queue) {
        this._queue.destroy();
        delete this._queue;
      }
    }
    else {
      // create queue and update its options
      if (!this._queue) {
        this._queue = Queue.extend(this, {
          replace: ['add', 'update', 'remove']
        });
      }

      if (typeof options.queue === 'object') {
        this._queue.setOptions(options.queue);
      }
    }
  }
};

/**
 * Subscribe to an event, add an event listener
 * @param {String} event        Event name. Available events: 'put', 'update',
 *                              'remove'
 * @param {function} callback   Callback method. Called with three parameters:
 *                                  {String} event
 *                                  {Object | null} params
 *                                  {String | Number} senderId
 */
DataSet.prototype.on = function(event, callback) {
  var subscribers = this._subscribers[event];
  if (!subscribers) {
    subscribers = [];
    this._subscribers[event] = subscribers;
  }

  subscribers.push({
    callback: callback
  });
};

// TODO: remove this deprecated function some day (replaced with `on` since version 0.5, deprecated since v4.0)
DataSet.prototype.subscribe = function () {
  throw new Error('DataSet.subscribe is deprecated. Use DataSet.on instead.');
};

/**
 * Unsubscribe from an event, remove an event listener
 * @param {String} event
 * @param {function} callback
 */
DataSet.prototype.off = function(event, callback) {
  var subscribers = this._subscribers[event];
  if (subscribers) {
    this._subscribers[event] = subscribers.filter(listener => listener.callback != callback);
  }
};

// TODO: remove this deprecated function some day (replaced with `on` since version 0.5, deprecated since v4.0)
DataSet.prototype.unsubscribe = function () {
  throw new Error('DataSet.unsubscribe is deprecated. Use DataSet.off instead.');
};

/**
 * Trigger an event
 * @param {String} event
 * @param {Object | null} params
 * @param {String} [senderId]       Optional id of the sender.
 * @private
 */
DataSet.prototype._trigger = function (event, params, senderId) {
  if (event == '*') {
    throw new Error('Cannot trigger event *');
  }

  var subscribers = [];
  if (event in this._subscribers) {
    subscribers = subscribers.concat(this._subscribers[event]);
  }
  if ('*' in this._subscribers) {
    subscribers = subscribers.concat(this._subscribers['*']);
  }

  for (var i = 0, len = subscribers.length; i < len; i++) {
    var subscriber = subscribers[i];
    if (subscriber.callback) {
      subscriber.callback(event, params, senderId || null);
    }
  }
};

/**
 * Add data.
 * Adding an item will fail when there already is an item with the same id.
 * @param {Object | Array} data
 * @param {String} [senderId] Optional sender id
 * @return {Array} addedIds      Array with the ids of the added items
 */
DataSet.prototype.add = function (data, senderId) {
  var addedIds = [],
      id,
      me = this;

  if (Array.isArray(data)) {
    // Array
    for (var i = 0, len = data.length; i < len; i++) {
      id = me._addItem(data[i]);
      addedIds.push(id);
    }
  }
  else if (data instanceof Object) {
    // Single item
    id = me._addItem(data);
    addedIds.push(id);
  }
  else {
    throw new Error('Unknown dataType');
  }

  if (addedIds.length) {
    this._trigger('add', {items: addedIds}, senderId);
  }

  return addedIds;
};

/**
 * Update existing items. When an item does not exist, it will be created
 * @param {Object | Array} data
 * @param {String} [senderId] Optional sender id
 * @return {Array} updatedIds     The ids of the added or updated items
 */
DataSet.prototype.update = function (data, senderId) {
  var addedIds = [];
  var updatedIds = [];
  var updatedData = [];
  var me = this;
  var fieldId = me._fieldId;

  var addOrUpdate = function (item) {
    var id = item[fieldId];
    if (me._data[id]) {
      var oldData = util.extend({}, me._data[id]);
      // update item
      id = me._updateItem(item);
      updatedIds.push(id);
      updatedData.push(oldData);
    }
    else {
      // add new item
      id = me._addItem(item);
      addedIds.push(id);
    }
  };

  if (Array.isArray(data)) {
    // Array
    for (var i = 0, len = data.length; i < len; i++) {
      addOrUpdate(data[i]);
    }
  }
  else if (data instanceof Object) {
    // Single item
    addOrUpdate(data);
  }
  else {
    throw new Error('Unknown dataType');
  }

  if (addedIds.length) {
    this._trigger('add', {items: addedIds}, senderId);
  }
  if (updatedIds.length) {
    this._trigger('update', {items: updatedIds, data: updatedData}, senderId);
  }

  return addedIds.concat(updatedIds);
};

/**
 * Get a data item or multiple items.
 *
 * Usage:
 *
 *     get()
 *     get(options: Object)
 *
 *     get(id: Number | String)
 *     get(id: Number | String, options: Object)
 *
 *     get(ids: Number[] | String[])
 *     get(ids: Number[] | String[], options: Object)
 *
 * Where:
 *
 * {Number | String} id         The id of an item
 * {Number[] | String{}} ids    An array with ids of items
 * {Object} options             An Object with options. Available options:
 * {String} [returnType]        Type of data to be returned.
 *                              Can be 'Array' (default) or 'Object'.
 * {Object.<String, String>} [type]
 * {String[]} [fields]          field names to be returned
 * {function} [filter]          filter items
 * {String | function} [order]  Order the items by a field name or custom sort function.
 * @throws Error
 */
DataSet.prototype.get = function (args) {
  var me = this;

  // parse the arguments
  var id, ids, options;
  var firstType = util.getType(arguments[0]);
  if (firstType == 'String' || firstType == 'Number') {
    // get(id [, options])
    id = arguments[0];
    options = arguments[1];
  }
  else if (firstType == 'Array') {
    // get(ids [, options])
    ids = arguments[0];
    options = arguments[1];
  }
  else {
    // get([, options])
    options = arguments[0];
  }

  // determine the return type
  var returnType;
  if (options && options.returnType) {
    var allowedValues = ['Array', 'Object'];
    returnType = allowedValues.indexOf(options.returnType) == -1 ? 'Array' : options.returnType;
  }
  else {
    returnType = 'Array';
  }

  // build options
  var type = options && options.type || this._options.type;
  var filter = options && options.filter;
  var items = [], item, itemIds, itemId, i, len;

  // convert items
  if (id != undefined) {
    // return a single item
    item = me._getItem(id, type);
    if (filter && !filter(item)) {
      item = null;
    }
  }
  else if (ids != undefined) {
    // return a subset of items
    for (i = 0, len = ids.length; i < len; i++) {
      item = me._getItem(ids[i], type);
      if (!filter || filter(item)) {
        items.push(item);
      }
    }
  }
  else {
    // return all items
    itemIds = Object.keys(this._data);
    for (i = 0, len = itemIds.length; i < len; i++) {
      itemId = itemIds[i];
      item = me._getItem(itemId, type);
      if (!filter || filter(item)) {
        items.push(item);
      }
    }
  }

  // order the results
  if (options && options.order && id == undefined) {
    this._sort(items, options.order);
  }

  // filter fields of the items
  if (options && options.fields) {
    var fields = options.fields;
    if (id != undefined) {
      item = this._filterFields(item, fields);
    }
    else {
      for (i = 0, len = items.length; i < len; i++) {
        items[i] = this._filterFields(items[i], fields);
      }
    }
  }

  // return the results
  if (returnType == 'Object') {
    var result = {},
        resultant;
    for (i = 0, len = items.length; i < len; i++) {
      resultant = items[i];
      result[resultant.id] = resultant;
    }
    return result;
  }
  else {
    if (id != undefined) {
      // a single item
      return item;
    }
    else {
      // just return our array
      return items;
    }
  }
};

/**
 * Get ids of all items or from a filtered set of items.
 * @param {Object} [options]    An Object with options. Available options:
 *                              {function} [filter] filter items
 *                              {String | function} [order] Order the items by
 *                                  a field name or custom sort function.
 * @return {Array} ids
 */
DataSet.prototype.getIds = function (options) {
  var data = this._data,
      filter = options && options.filter,
      order = options && options.order,
      type = options && options.type || this._options.type,
      itemIds = Object.keys(data),
      i,
      len,
      id,
      item,
      items,
      ids = [];

  if (filter) {
    // get filtered items
    if (order) {
      // create ordered list
      items = [];
      for (i = 0, len = itemIds.length; i < len; i++) {
        id = itemIds[i];
        item = this._getItem(id, type);
        if (filter(item)) {
          items.push(item);
        }
      }

      this._sort(items, order);

      for (i = 0, len = items.length; i < len; i++) {
        ids.push(items[i][this._fieldId]);
      }
    }
    else {
      // create unordered list
      for (i = 0, len = itemIds.length; i < len; i++) {
        id = itemIds[i];
        item = this._getItem(id, type);
        if (filter(item)) {
          ids.push(item[this._fieldId]);
        }
      }
    }
  }
  else {
    // get all items
    if (order) {
      // create an ordered list
      items = [];
      for (i = 0, len = itemIds.length; i < len; i++) {
        id = itemIds[i];
        items.push(data[id]);
      }

      this._sort(items, order);

      for (i = 0, len = items.length; i < len; i++) {
        ids.push(items[i][this._fieldId]);
      }
    }
    else {
      // create unordered list
      for (i = 0, len = itemIds.length; i < len; i++) {
        id = itemIds[i];
        item = data[id];
        ids.push(item[this._fieldId]);
      }
    }
  }

  return ids;
};

/**
 * Returns the DataSet itself. Is overwritten for example by the DataView,
 * which returns the DataSet it is connected to instead.
 */
DataSet.prototype.getDataSet = function () {
  return this;
};

/**
 * Execute a callback function for every item in the dataset.
 * @param {function} callback
 * @param {Object} [options]    Available options:
 *                              {Object.<String, String>} [type]
 *                              {String[]} [fields] filter fields
 *                              {function} [filter] filter items
 *                              {String | function} [order] Order the items by
 *                                  a field name or custom sort function.
 */
DataSet.prototype.forEach = function (callback, options) {
  var filter = options && options.filter,
      type = options && options.type || this._options.type,
      data = this._data,
      itemIds = Object.keys(data),
      i,
      len,
      item,
      id;

  if (options && options.order) {
    // execute forEach on ordered list
    var items = this.get(options);

    for (i = 0, len = items.length; i < len; i++) {
      item = items[i];
      id = item[this._fieldId];
      callback(item, id);
    }
  }
  else {
    // unordered
    for (i = 0, len = itemIds.length; i < len; i++) {
      id = itemIds[i];
      item = this._getItem(id, type);
      if (!filter || filter(item)) {
        callback(item, id);
      }
    }
  }
};

/**
 * Map every item in the dataset.
 * @param {function} callback
 * @param {Object} [options]    Available options:
 *                              {Object.<String, String>} [type]
 *                              {String[]} [fields] filter fields
 *                              {function} [filter] filter items
 *                              {String | function} [order] Order the items by
 *                                  a field name or custom sort function.
 * @return {Object[]} mappedItems
 */
DataSet.prototype.map = function (callback, options) {
  var filter = options && options.filter,
      type = options && options.type || this._options.type,
      mappedItems = [],
      data = this._data,
      itemIds = Object.keys(data),
      i,
      len,
      id,
      item;

  // convert and filter items
  for (i = 0, len = itemIds.length; i < len; i++) {
    id = itemIds[i];
    item = this._getItem(id, type);
    if (!filter || filter(item)) {
      mappedItems.push(callback(item, id));
    }
  }

  // order items
  if (options && options.order) {
    this._sort(mappedItems, options.order);
  }

  return mappedItems;
};

/**
 * Filter the fields of an item
 * @param {Object | null} item
 * @param {String[]} fields     Field names
 * @return {Object | null} filteredItem or null if no item is provided
 * @private
 */
DataSet.prototype._filterFields = function (item, fields) {
  if (!item) { // item is null
    return item;
  }

  var filteredItem = {},
      itemFields = Object.keys(item),
      len = itemFields.length,
      i,
      field;

  if(Array.isArray(fields)){
    for (i = 0; i < len; i++) {
      field = itemFields[i];
      if (fields.indexOf(field) != -1) {
        filteredItem[field] = item[field];
      }
    }
  }else{
    for (i = 0; i < len; i++) {
      field = itemFields[i];
      if (fields.hasOwnProperty(field)) {
        filteredItem[fields[field]] = item[field];
      }
    }
  }

  return filteredItem;
};

/**
 * Sort the provided array with items
 * @param {Object[]} items
 * @param {String | function} order      A field name or custom sort function.
 * @private
 */
DataSet.prototype._sort = function (items, order) {
  if (util.isString(order)) {
    // order by provided field name
    var name = order; // field name
    items.sort(function (a, b) {
      var av = a[name];
      var bv = b[name];
      return (av > bv) ? 1 : ((av < bv) ? -1 : 0);
    });
  }
  else if (typeof order === 'function') {
    // order by sort function
    items.sort(order);
  }
  // TODO: extend order by an Object {field:String, direction:String}
  //       where direction can be 'asc' or 'desc'
  else {
    throw new TypeError('Order must be a function or a string');
  }
};

/**
 * Remove an object by pointer or by id
 * @param {String | Number | Object | Array} id Object or id, or an array with
 *                                              objects or ids to be removed
 * @param {String} [senderId] Optional sender id
 * @return {Array} removedIds
 */
DataSet.prototype.remove = function (id, senderId) {
  var removedIds = [],
      i, len, removedId;

  if (Array.isArray(id)) {
    for (i = 0, len = id.length; i < len; i++) {
      removedId = this._remove(id[i]);
      if (removedId != null) {
        removedIds.push(removedId);
      }
    }
  }
  else {
    removedId = this._remove(id);
    if (removedId != null) {
      removedIds.push(removedId);
    }
  }

  if (removedIds.length) {
    this._trigger('remove', {items: removedIds}, senderId);
  }

  return removedIds;
};

/**
 * Remove an item by its id
 * @param {Number | String | Object} id   id or item
 * @returns {Number | String | null} id
 * @private
 */
DataSet.prototype._remove = function (id) {
  if (util.isNumber(id) || util.isString(id)) {
    if (this._data[id]) {
      delete this._data[id];
      this.length--;
      return id;
    }
  }
  else if (id instanceof Object) {
    var itemId = id[this._fieldId];
    if (itemId && this._data[itemId]) {
      delete this._data[itemId];
      this.length--;
      return itemId;
    }
  }
  return null;
};

/**
 * Clear the data
 * @param {String} [senderId] Optional sender id
 * @return {Array} removedIds    The ids of all removed items
 */
DataSet.prototype.clear = function (senderId) {
  var ids = Object.keys(this._data);

  this._data = {};
  this.length = 0;

  this._trigger('remove', {items: ids}, senderId);

  return ids;
};

/**
 * Find the item with maximum value of a specified field
 * @param {String} field
 * @return {Object | null} item  Item containing max value, or null if no items
 */
DataSet.prototype.max = function (field) {
  var data = this._data,
      itemIds = Object.keys(data),
      max = null,
      maxField = null,
      i,
      len;

  for (i = 0, len = itemIds.length; i < len; i++) {
    var id = itemIds[i];
    var item = data[id];
    var itemField = item[field];
    if (itemField != null && (!max || itemField > maxField)) {
      max = item;
      maxField = itemField;
    }
  }

  return max;
};

/**
 * Find the item with minimum value of a specified field
 * @param {String} field
 * @return {Object | null} item  Item containing max value, or null if no items
 */
DataSet.prototype.min = function (field) {
  var data = this._data,
      itemIds = Object.keys(data),
      min = null,
      minField = null,
      i,
      len;

  for (i = 0, len = itemIds.length; i < len; i++) {
    var id = itemIds[i];
    var item = data[id];
    var itemField = item[field];
    if (itemField != null && (!min || itemField < minField)) {
      min = item;
      minField = itemField;
    }
  }

  return min;
};

/**
 * Find all distinct values of a specified field
 * @param {String} field
 * @return {Array} values  Array containing all distinct values. If data items
 *                         do not contain the specified field are ignored.
 *                         The returned array is unordered.
 */
DataSet.prototype.distinct = function (field) {
  var data = this._data;
  var itemIds = Object.keys(data);
  var values = [];
  var fieldType = this._options.type && this._options.type[field] || null;
  var count = 0;
  var i,
      j,
      len;

  for (i = 0, len = itemIds.length; i < len; i++) {
    var id = itemIds[i];
    var item = data[id];
    var value = item[field];
    var exists = false;
    for (j = 0; j < count; j++) {
      if (values[j] == value) {
        exists = true;
        break;
      }
    }
    if (!exists && (value !== undefined)) {
      values[count] = value;
      count++;
    }
  }

  if (fieldType) {
    for (i = 0, len = values.length; i < len; i++) {
      values[i] = util.convert(values[i], fieldType);
    }
  }

  return values;
};

/**
 * Add a single item. Will fail when an item with the same id already exists.
 * @param {Object} item
 * @return {String} id
 * @private
 */
DataSet.prototype._addItem = function (item) {
  var id = item[this._fieldId];

  if (id != undefined) {
    // check whether this id is already taken
    if (this._data[id]) {
      // item already exists
      throw new Error('Cannot add item: item with id ' + id + ' already exists');
    }
  }
  else {
    // generate an id
    id = util.randomUUID();
    item[this._fieldId] = id;
  }

  var d = {},
      fields = Object.keys(item),
      i,
      len;
  for (i = 0, len = fields.length; i < len; i++) {
    var field = fields[i];
    var fieldType = this._type[field];  // type may be undefined
    d[field] = util.convert(item[field], fieldType);
  }
  this._data[id] = d;
  this.length++;

  return id;
};

/**
 * Get an item. Fields can be converted to a specific type
 * @param {String} id
 * @param {Object.<String, String>} [types]  field types to convert
 * @return {Object | null} item
 * @private
 */
DataSet.prototype._getItem = function (id, types) {
  var field, value, i, len;

  // get the item from the dataset
  var raw = this._data[id];
  if (!raw) {
    return null;
  }

  // convert the items field types
  var converted = {},
      fields = Object.keys(raw);

  if (types) {
    for (i = 0, len = fields.length; i < len; i++) {
      field = fields[i];
      value = raw[field];
      converted[field] = util.convert(value, types[field]);
    }
  }
  else {
    // no field types specified, no converting needed
    for (i = 0, len = fields.length; i < len; i++) {
      field = fields[i];
      value = raw[field];
      converted[field] = value;
    }
  }
  return converted;
};

/**
 * Update a single item: merge with existing item.
 * Will fail when the item has no id, or when there does not exist an item
 * with the same id.
 * @param {Object} item
 * @return {String} id
 * @private
 */
DataSet.prototype._updateItem = function (item) {
  var id = item[this._fieldId];
  if (id == undefined) {
    throw new Error('Cannot update item: item has no id (item: ' + JSON.stringify(item) + ')');
  }
  var d = this._data[id];
  if (!d) {
    // item doesn't exist
    throw new Error('Cannot update item: no item with id ' + id + ' found');
  }

  // merge with current item
  var fields = Object.keys(item);
  for (var i = 0, len = fields.length; i < len; i++) {
    var field = fields[i];
    var fieldType = this._type[field];  // type may be undefined
    d[field] = util.convert(item[field], fieldType);
  }

  return id;
};

module.exports = DataSet;