/*!
 * Module dependencies.
 */

var Document = require('./document')
  , MongooseArray = require('./types/array')
  , MongooseBuffer = require('./types/buffer')
  , MongooseError = require('./error')
  , VersionError = require('./errors/version')
  , Query = require('./query')
  , Schema = require('./schema')
  , utils = require('./utils')
  , isMongooseObject = utils.isMongooseObject
  , EventEmitter = utils.EventEmitter
  , merge = utils.merge
  , Promise = require('./promise')
  , tick = utils.tick

var VERSION_WHERE = 1
  , VERSION_INC = 2
  , VERSION_ALL = VERSION_WHERE | VERSION_INC;

/**
 * Model constructor
 *
 * @param {Object} doc values to with which to create the document
 * @inherits Document
 * @event `error`: If listening to this Model event, it is emitted when a document was saved without passing a callback and an `error` occurred. If not listening, the event bubbles to the connection used to create this Model.
 * @event `index`: Emitted after `Model#ensureIndexes` completes. If an error occurred it is passed with the event.
 * @api public
 */

function Model (doc, fields, skipId) {
  Document.call(this, doc, fields, skipId);
};

/*!
 * Inherits from Document.
 *
 * All Model.prototype features are available on
 * top level (non-sub) documents.
 */

Model.prototype.__proto__ = Document.prototype;

/**
 * Connection the model uses.
 *
 * @api public
 * @property db
 */

Model.prototype.db;

/**
 * Collection the model uses.
 *
 * @api public
 * @property collection
 */

Model.prototype.collection;

/**
 * The name of the model
 *
 * @api public
 * @property modelName
 */

Model.prototype.modelName;

/**
 * Returns what paths can be populated
 *
 * @param {Query} query object
 * @return {Object|undefined} population paths
 * @api private
 */

Model.prototype._getPopulationKeys = function getPopulationKeys (query) {
  if (!(query && query.options.populate)) return;

  var names = Object.keys(query.options.populate)
    , n = names.length
    , name
    , paths = {}
    , hasKeys
    , schema

  while (n--) {
    name = names[n];
    schema = this.schema.path(name);
    hasKeys = true;

    if (!schema) {
      // if the path is not recognized, it's potentially embedded docs
      // walk path atoms from right to left to find a matching path
      var pieces = name.split('.')
        , i = pieces.length;

      while (i--) {
        var path = pieces.slice(0, i).join('.')
          , pathSchema = this.schema.path(path);

        // loop until we find an array schema
        if (pathSchema && pathSchema.caster) {
          if (!paths[path]) {
            paths[path] = { sub: {} };
          }

          paths[path].sub[pieces.slice(i).join('.')] = query.options.populate[name];
          hasKeys || (hasKeys = true);
          break;
        }
      }
    } else {
      paths[name] = query.options.populate[name];
      hasKeys || (hasKeys = true);
    }
  }

  return hasKeys && paths;
};

/**
 * Populates an object
 *
 * @param {SchemaType} schema type for the oid
 * @param {Object} oid object id or array of object ids
 * @param {Object} query object specifying query conditions, fields, and options
 * @param {Function} fn
 * @api private
 */

Model.prototype._populate = function populate (schema, oid, query, fn) {
  if (!Array.isArray(oid)) {
    var conditions = query.conditions || {};
    conditions._id = oid;

    return this
    .db.model(query.model || schema.options.ref)
    .findOne(conditions, query.fields, query.options, fn);
  }

  if (!oid.length) {
    return fn(null, oid);
  }

  var model = this.db.model(query.model || schema.caster.options.ref)
    , conditions = query && query.conditions || {};

  conditions._id || (conditions._id = { $in: oid });

  model.find(conditions, query.fields, query.options, function (err, docs) {
    if (err) return fn(err);

    // user specified sort order?
    if (query.options && query.options.sort) {
      return fn(null, docs);
    }

    // put back in original id order (using a hash reduces complexity from n*n to 2n)
    var docHash = {};
    docs.forEach(function (doc) {
      docHash[doc._id] = doc;
    });

    var arr = [];
    oid.forEach(function (id) {
      if (id in docHash) arr.push(docHash[id]);
    });

    fn(null, arr);
  });
};

/**
 * Performs auto-population of relations.
 *
 * @param {Object} doc document returned by mongo
 * @param {Query} query query that originated the initialization
 * @param {Function} fn
 * @api private
 */

Model.prototype.init = function init (doc, query, fn) {
  if ('function' == typeof query) {
    fn = query;
    query = null;
  }

  var populate = this._getPopulationKeys(query);

  if (!populate) {
    return Document.prototype.init.call(this, doc, fn);
  }

  // population from other models is necessary
  var self = this;

  init(doc, '', function (err) {
    if (err) return fn(err);
    Document.prototype.init.call(self, doc, fn);
  });

  return this;

  function init (obj, prefix, fn) {
    prefix = prefix || '';

    var keys = Object.keys(obj)
      , len = keys.length;

    return next();

    function next () {
      if (--len < 0) return fn();

      var i = keys[len]
        , path = prefix + i
        , schema = self.schema.path(path)
        , total = 0
        , inline = false
        , poppath

      if (!schema && obj[i] && 'Object' === obj[i].constructor.name) {
        // assume nested object
        return init(obj[i], path + '.', next);
      }

      if (!(obj[i] && schema && populate[path])) return next();

      // this query object is re-used and passed around. we clone
      // it to prevent query condition contamination between
      // one populate call to the next.
      poppath = utils.clone(populate[path]);

      if (poppath.sub) {
        obj[i].forEach(function (subobj) {
          inline = true;

          var pkeys = Object.keys(poppath.sub)
            , pi = pkeys.length
            , key

          while (pi--) {
            key = pkeys[pi];

            if (subobj[key]) (function (key) {
              total++;
              self._populate(schema.schema.path(key), subobj[key], poppath.sub[key], done);
              function done (err, doc) {
                if (err) return error(err);
                subobj[key] = doc;
                if (--total < 1 && !inline) {
                  next();
                }
              }
            })(key);
          }
        });

        inline = false;

        if (0 === total) return next();

      } else {
        self._populate(schema, obj[i], poppath, function (err, doc) {
          if (err) return error(err);
          obj[i] = doc;
          next();
        });
      }
    };
  };

  function error (err) {
    if (error.err) return;
    fn(error.err = err);
  }
};

/*!
 * Handles doc.save() callbacks
 */

function handleSave (promise, self) {
  return tick(function handleSave (err, result) {
    if (err) {
      // If the initial insert fails provide a second chance.
      // (If we did this all the time we would break updates)
      if (self._inserting) {
        self.isNew = true;
        self.emit('isNew', true);
      }
      promise.error(err);
      promise = self = null;
      return;
    }

    self._storeShard();

    var numAffected;
    if (result) {
      // when inserting, the array of created docs is returned
      numAffected = result.length
        ? result.length
        : result;
    } else {
      numAffected = 0;
    }

    // was this an update that required a version bump?
    if (self.__version && !self._inserting) {
      var doIncrement = VERSION_INC === (VERSION_INC & self.__version);
      self.__version = undefined;

      // increment version if was successful
      if (numAffected > 0) {
        if (doIncrement) {
          var key = self.schema.options.versionKey;
          var version = self.getValue(key) | 0;
          self.setValue(key, version + 1);
        }
      } else {
        // the update failed. pass an error back
        promise.error(new VersionError);
        promise = self = null;
        return;
      }
    }

    self.emit('save', self, numAffected);
    promise.complete(self, numAffected);
    promise = self = null;
  });
}

/**
 * Saves this document.
 *
 * ####Example:
 *
 *     product.sold = Date.now();
 *     product.save(function (err, product) {
 *       if (err) ..
 *     })
 *
 * The `fn` callback is optional. If no `fn` is passed and validation fails, the validation error will be emitted on the connection used to create this model.
 *
 *     var db = mongoose.createConnection(..);
 *     var schema = new Schema(..);
 *     var Product = db.model('Product', schema);
 *
 *     db.on('error', handleError);
 *
 * However, if you desire more local error handling you can add an `error` listener to the model and handle errors there instead.
 *
 *     Product.on('error', handleError);
 *
 * @param {Function} [fn] optional callback
 * @api public
 * @see middleware http://mongoosejs.com/docs/middleware.html
 */

Model.prototype.save = function save (fn) {
  var promise = new Promise(fn)
    , complete = handleSave(promise, this)
    , options = {}

  if (this.schema.options.safe) {
    options.safe = this.schema.options.safe;
  }

  if (this.isNew) {
    // send entire doc
    var obj = this.toObject({ depopulate: 1 });
    this._version(true, obj);
    this.collection.insert(obj, options, complete);
    this._reset();
    this.isNew = false;
    this.emit('isNew', false);
    // Make it possible to retry the insert
    this._inserting = true;

  } else {
    // Make sure we don't treat it as a new object on error,
    // since it already exists
    this._inserting = false;

    var delta = this._delta();
    if (delta) {
      var where = this._where(delta[0]);
      this.collection.update(where, delta[1], options, complete);
    } else {
      process.nextTick(function () {
        complete(null);
      })
    }

    this._reset();
    this.emit('isNew', false);
  }
};

/*!
 * Apply the operation to the delta (update) clause as
 * well as track versioning for our where clause.
 *
 * @param {Document} self
 * @param {Object} where
 * @param {Object} delta
 * @param {Object} data
 * @param {Mixed} val
 * @param {String} [operation]
 */

function operand (self, where, delta, data, val, op) {
  // delta
  op || (op = '$set');
  if (!delta[op]) delta[op] = {};
  delta[op][data.path] = val;

  // disabled versioning?
  if (false === self.schema.options.versionKey) return;

  // already marked for versioning?
  if (VERSION_ALL === (VERSION_ALL & self.__version)) return;

  switch (op) {
    case '$set':
    case '$unset':
    case '$pop':
    case '$pull':
    case '$pullAll':
    case '$push':
    case '$pushAll':
    case '$addToSet':
      break;
    default:
      // nothing to do
      return;
  }

  // ensure updates sent with positional notation are
  // editing the correct array element.
  // only increment the version if an array position changes.
  // modifying elements of an array is ok if position does not change.

  if ('$push' == op || '$pushAll' == op || '$addToSet' == op) {
    self.__version = VERSION_INC;
  }
  else if (/^\$p/.test(op)) {
    // potentially changing array positions
    self.increment();
  }
  else if (Array.isArray(val)) {
    // $set an array
    self.increment();
  }
  // now handling $set, $unset
  else if (/\.\d+/.test(data.path)) {
    // subpath of array
    self.__version = VERSION_WHERE;
  }
}

/*!
 * Compiles an update and where clause for a `val` with _atomics.
 *
 * @param {Document} self
 * @param {Object} where
 * @param {Object} delta
 * @param {Object} data
 * @param {Array} val
 */

function handleAtomics (self, where, delta, data, val) {
  if (delta.$set && delta.$set[data.path]) {
    // $set has precedence over other atomics
    return;
  }

  var atomics = val._atomics
    , ops = Object.keys(atomics)
    , schema = data.schema
    , path = data.path
    , i = ops.length
    , val
    , op;

  if (0 === i) {
    // $set

    if (isMongooseObject(val)) {
      val = val.toObject({ depopulate: 1 });
    } else if (val.valueOf) {
      val = val.valueOf();
    }

    return operand(self, where, delta, data, val);
  }

  while (i--) {
    op = ops[i];
    val = atomics[op];
    if (isMongooseObject(val)) {
      val = val.toObject({ depopulate: 1 })
    } else if (Array.isArray(val)) {
      val = val.map(function (mem) {
        return isMongooseObject(mem)
          ? mem.toObject({ depopulate: 1 })
          : mem;
      })
    } else if (val.valueOf) {
      val = val.valueOf()
    }

    if ('$addToSet' === op)
      val = { $each: val };

    operand(self, where, delta, data, val, op);
  }
}

/**
 * Produces a special query document of the modified properties used in updates.
 *
 * @api private
 */

Model.prototype._delta = function _delta () {
  var dirty = this._dirty();
  if (!dirty.length) return;

  var self = this
    , where = {}
    , delta = {}
    , len = dirty.length
    , d = 0
    , val
    , obj

  for (; d < len; ++d) {
    var data = dirty[d]
    var value = data.value
    var schema = data.schema

    if (undefined === value) {
      operand(self, where, delta, data, 1, '$unset');

    } else if (null === value) {
      operand(self, where, delta, data, null);

    } else if (value._path && value._atomics) {
      // arrays and other custom types (support plugins etc)
      handleAtomics(self, where, delta, data, value);

    } else if (value._path && Buffer.isBuffer(value)) {
      // MongooseBuffer
      value = value.toObject();
      operand(self, where, delta, data, value);

    } else {
      value = utils.clone(value);
      operand(self, where, delta, data, value);
    }
  }

  if (this.__version) {
    this._version(where, delta);
  }

  return [where, delta];
}

/**
 * Appends versioning to the where and update clauses.
 *
 * @api private
 */

Model.prototype._version = function _version (where, delta) {
  var key = this.schema.options.versionKey;

  if (true === where) {
    // this is an insert
    if (key) this.setValue(key, delta[key] = 0);
    return;
  }

  // updates

  // only apply versioning if our versionKey was selected. else
  // there is no way to select the correct version. we could fail
  // fast here and force them to include the versionKey but
  // thats a bit intrusive. can we do this automatically?
  // TODO fail fast option?
  if (!this.isSelected(key)) {
    return;
  }

  // $push $addToSet don't need the where clause set
  if (VERSION_WHERE === (VERSION_WHERE & this.__version)) {
    where[key] = this.getValue(key);
  }

  if (VERSION_INC === (VERSION_INC & this.__version)) {
    delta.$inc || (delta.$inc = {});
    delta.$inc[key] = 1;
  }
}

/**
 * Signal that we desire an increment of this documents version.
 *
 * @see versionKeys http://mongoosejs.com/docs/guide.html#versionKey
 * @api public
 */

Model.prototype.increment = function increment () {
  this.__version = VERSION_ALL;
  return this;
}

/**
 * Returns a query object which applies shardkeys if they exist.
 *
 * @api private
 */

Model.prototype._where = function _where (where) {
  where || (where = {});

  var paths
    , len

  if (this._shardval) {
    paths = Object.keys(this._shardval)
    len = paths.length

    for (var i = 0; i < len; ++i) {
      where[paths[i]] = this._shardval[paths[i]];
    }
  }

  where._id = this._doc._id;
  return where;
}

/**
 * Removes this document from the db.
 *
 * ####Example:
 *
 *     product.remove(function (err, product) {
 *       if (err) return handleError(err);
 *       Product.findById(product._id, function (err, product) {
 *         console.log(product) // null
 *       })
 *     })
 *
 * @param {Function} [fn] optional callback
 * @api public
 */

Model.prototype.remove = function remove (fn) {
  if (this._removing) {
    this._removing.addBack(fn);
    return this;
  }

  var promise = this._removing = new Promise(fn)
    , where = this._where()
    , self = this
    , options = {}

  if (this.schema.options.safe) {
    options.safe = this.schema.options.safe;
  }

  this.collection.remove(where, options, tick(function (err) {
    if (err) {
      promise.error(err);
      promise = self = self._removing = where = options = null;
      return;
    }
    self.emit('remove', self);
    promise.complete();
    promise = self = where = options = null;
  }));

  return this;
};

/**
 * Register hooks override
 *
 * @api private
 */

Model.prototype._registerHooks = function registerHooks () {
  Document.prototype._registerHooks.call(this);
};

/**
 * Returns another Model instance.
 *
 * ####Example:
 *
 *     var doc = new Tank;
 *     doc.model('User').findById(id, callback);
 *
 * @param {String} name model name
 * @api public
 */

Model.prototype.model = function model (name) {
  return this.db.model(name);
};

// Model (class) features

/*!
 * Give the constructor the ability to emit events.
 */

for (var i in EventEmitter.prototype)
  Model[i] = EventEmitter.prototype[i];

/**
 * Called when the model compiles.
 *
 * @api private
 */

Model.init = function init () {
  if (this.schema.options.autoIndex) {
    this.ensureIndexes();
  }

  this.schema.emit('init', this);
};

/**
 * Sends `ensureIndex` commands to mongo for each index declared in the schema.
 *
 * After completion, an `index` event is emitted on this `Model` passing an error if one occurred.
 *
 * _NOTE: It is not recommended that you run this in production. Index creation may impact database performance depending on your load. Use with caution._
 *
 * ####Example:
 *
 *     Event.ensureIndexes(function (err) {
 *       if (err) return handleError(err);
 *     });
 *
 * @param {Function} [cb] optional callback
 * @api public
 */

Model.ensureIndexes = function ensureIndexes (cb) {
  var indexes = this.schema.indexes();
  if (!indexes.length) {
    return cb && cb();
  }

  var self = this
    , safe = self.schema.options.safe
    , count = indexes.length
    , error

  indexes.forEach(function (index) {
    var options = index[1];
    options.safe = safe;
    self.collection.ensureIndex(index[0], options, tick(function (err) {
      if (err) error = err;
      if (--count) return;

      self.emit('index', error);
      cb && cb(error);
    }));
  });
}

/**
 * Schema the model uses.
 *
 * @property schema
 * @receiver Model
 * @api public
 */

Model.schema;

/**
 * Database instance the model uses.
 *
 * @property db
 * @receiver Model
 * @api public
 */

Model.db;

/**
 * Collection the model uses.
 *
 * @property collection
 * @receiver Model
 * @api public
 */

Model.collection;

/**
 * Base Mongoose instance the model uses.
 *
 * @property base
 * @receiver Model
 * @api public
 */

Model.base;

/**
 * Removes documents from the collection.
 *
 * ####Note:
 *
 * To remove documents without waiting for a response from MongoDB, do not pass a `callback`, then call `exec` on the returned [Query](#query-js):
 *
 *     Comment.remove({ _id: id }).exec();
 *
 * ####Note:
 *
 * This method sends a remove command directly to MongoDB, no Mongoose documents are involved. Because no Mongoose documents are involved, _no middleware (hooks) are executed_.
 *
 * @param {Object} conditions
 * @param {Function} [callback]
 * @return {Query}
 * @api public
 */

Model.remove = function remove (conditions, callback) {
  if ('function' === typeof conditions) {
    callback = conditions;
    conditions = {};
  }

  var query = new Query(conditions).bind(this, 'remove');

  if ('undefined' === typeof callback)
    return query;

  this._applyNamedScope(query);
  return query.remove(callback);
};

/**
 * Finds documents
 *
 * ####Examples:
 *
 *     // retrieve only certain keys
 *     MyModel.find({ name: /john/i }, 'name friends', function () { })
 *
 *     // pass options
 *     MyModel.find({ name: /john/i }, null, { skip: 10 } )
 *
 * @param {Object} conditions
 * @param {Object} [fields] optional fields to select
 * @param {Object} [options] optional
 * @param {Function} [callback]
 * @return {Query}
 * @see field selection #query_Query-select
 * @api public
 */

Model.find = function find (conditions, fields, options, callback) {
  if ('function' == typeof conditions) {
    callback = conditions;
    conditions = {};
    fields = null;
    options = null;
  } else if ('function' == typeof fields) {
    callback = fields;
    fields = null;
    options = null;
  } else if ('function' == typeof options) {
    callback = options;
    options = null;
  }

  var query = new Query(conditions, options);
  query.bind(this, 'find');
  query.select(fields);

  if ('undefined' === typeof callback)
    return query;

  this._applyNamedScope(query);
  return query.find(callback);
};

/**
 * Merges the current named scope query into `query`.
 *
 * @param {Query} query
 * @return {Query}
 * @api private
 */

Model._applyNamedScope = function _applyNamedScope (query) {
  var cQuery = this._cumulativeQuery;

  if (cQuery) {
    merge(query._conditions, cQuery._conditions);
    if (query._fields && cQuery._fields)
      merge(query._fields, cQuery._fields);
    if (query.options && cQuery.options)
      merge(query.options, cQuery.options);
    delete this._cumulativeQuery;
  }

  return query;
}

/**
 * Finds a single document by id.
 *
 * The `id` is cast to an ObjectId before sending the command.
 *
 * ####Example:
 *
 *     Adventure.findById(id, callback);
 *
 * @param {ObjectId|HexId} id objectid, or a value that can be casted to one
 * @param {Object} [fields] optional fields to select
 * @param {Object} [options] optional
 * @param {Function} [callback]
 * @return {Query}
 * @see field selection #query_Query-select
 * @api public
 */

Model.findById = function findById (id, fields, options, callback) {
  return this.findOne({ _id: id }, fields, options, callback);
};

/**
 * Finds one document.
 *
 * The `conditions` are cast to their respective SchemaTypes before the command is sent.
 *
 * ####Example:
 *
 *     Adventure.findOne({ type: 'iphone' }, 'name', { safe: true }, callback);
 *
 * @param {Object} conditions
 * @param {Object} [fields] optional fields to select
 * @param {Object} [options] optional
 * @param {Function} [callback]
 * @return {Query}
 * @see field selection #query_Query-select
 * @api public
 */

Model.findOne = function findOne (conditions, fields, options, callback) {
  if ('function' == typeof options) {
    callback = options;
    options = null;
  } else if ('function' == typeof fields) {
    callback = fields;
    fields = null;
    options = null;
  } else if ('function' == typeof conditions) {
    callback = conditions;
    conditions = {};
    fields = null;
    options = null;
  }

  var query = new Query(conditions, options).select(fields).bind(this, 'findOne');

  if ('undefined' == typeof callback)
    return query;

  this._applyNamedScope(query);
  return query.findOne(callback);
};

/**
 * Counts number of matching documents in a database collection.
 *
 * ####Example:
 *
 *     Adventure.count({ type: 'jungle' }, function (err, count) {
 *       if (err) ..
 *       console.log('there are %d jungle adventures', count);
 *     });
 *
 * @param {Object} conditions
 * @param {Function} [callback]
 * @return {Query}
 * @api public
 */

Model.count = function count (conditions, callback) {
  if ('function' === typeof conditions)
    callback = conditions, conditions = {};

  var query = new Query(conditions).bind(this, 'count');
  if ('undefined' == typeof callback)
    return query;

  this._applyNamedScope(query);
  return query.count(callback);
};

/**
 * Executes a DISTINCT command
 *
 * @param {String} field
 * @param {Object} [conditions] optional
 * @param {Function} [callback]
 * @return {Query}
 * @api public
 */

Model.distinct = function distinct (field, conditions, callback) {
  var query = new Query(conditions).bind(this, 'distinct');
  if ('undefined' == typeof callback) {
    query._distinctArg = field;
    return query;
  }

  this._applyNamedScope(query);
  return query.distinct(field, callback);
};

/**
 * Creates a Query, applies the passed conditions, and returns the Query.
 *
 * For example, instead of writing:
 *
 *     User.find({age: {$gte: 21, $lte: 65}}, callback);
 *
 * we can instead write:
 *
 *     User.where('age').gte(21).lte(65).exec(callback);
 *
 * Since the Query class also supports `where` you can continue chaining
 *
 *     User
 *     .where('age').gte(21).lte(65)
 *     .where('name', /^b/i)
 *     ... etc
 *
 * @param {String} path
 * @param {Object} [val] optional value
 * @return {Query}
 * @api public
 */

Model.where = function where (path, val) {
  var q = new Query().bind(this, 'find');
  return q.where.apply(q, arguments);
};

/**
 * Creates a `Query` and specifies a `$where` condition.
 *
 * Sometimes you need to query for things in mongodb using a JavaScript expression. You can do so via `find({ $where: javascript })`, or you can use the mongoose shortcut method $where via a Query chain or from your mongoose Model.
 *
 *     Blog.$where('this.comments.length > 5');
 *
 * @param {String|Function} argument is a javascript string or anonymous function
 * @method $where
 * @memberOf Model
 * @return {Query}
 * @see Query.$where #query_Query-%24where
 * @api public
 */

Model.$where = function $where () {
  var q = new Query().bind(this, 'find');
  return q.$where.apply(q, arguments);
};

/**
 * Issues a mongodb findAndModify update command.
 *
 * Finds a matching document, updates it according to the `update` arg, passing any `options`, and returns the found document (if any) to the callback. The query executes immediately if `callback` is passed else a Query object is returned.
 *
 * ####Options:
 *
 * - `new`: bool - true to return the modified document rather than the original. defaults to true
 * - `upsert`: bool - creates the object if it doesn't exist. defaults to false.
 * - `sort`: if multiple docs are found by the conditions, sets the sort order to choose which doc to update
 * - `select`: sets the document fields to return
 *
 * ####Examples:
 *
 *     A.findOneAndUpdate(conditions, update, options, callback) // executes
 *     A.findOneAndUpdate(conditions, update, options)  // returns Query
 *     A.findOneAndUpdate(conditions, update, callback) // executes
 *     A.findOneAndUpdate(conditions, update)           // returns Query
 *     A.findOneAndUpdate()                             // returns Query
 *
 * ####Note:
 *
 * All top level update keys which are not `atomic` operation names are treated as set operations:
 *
 * ####Example:
 *
 *     var query = { name: 'borne' };
 *     Model.findOneAndUpdate(query, { name: 'jason borne' }, options, callback)
 *
 *     // is sent as
 *     Model.findOneAndUpdate(query, { $set: { name: 'jason borne' }}, options, callback)
 *
 * This helps prevent accidentally overwriting your document with `{ name: 'jason borne' }`.
 *
 * ####Note:
 *
 * Although values are cast to their appropriate types when using the findAndModify helpers, the following are *not* applied:
 *
 * - defaults
 * - setters
 * - validators
 * - middleware
 *
 * If you need those features, use the traditional approach of first retrieving the document.
 *
 *     Model.findOne({ name: 'borne' }, function (err, doc) {
 *       if (err) ..
 *       doc.name = 'jason borne';
 *       doc.save(callback);
 *     })
 *
 * @param {Object} [conditions]
 * @param {Object} [update]
 * @param {Object} [options]
 * @param {Function} [callback]
 * @return {Query}
 * @see mongodb http://www.mongodb.org/display/DOCS/findAndModify+Command
 * @api public
 */

Model.findOneAndUpdate = function (conditions, update, options, callback) {
  if ('function' == typeof options) {
    callback = options;
    options = null;
  }
  else if (1 === arguments.length) {
    if ('function' == typeof conditions) {
      var msg = 'Model.findOneAndUpdate(): First argument must not be a function.\n\n'
              + '  ' + this.modelName + '.findOneAndUpdate(conditions, update, options, callback)\n'
              + '  ' + this.modelName + '.findOneAndUpdate(conditions, update, options)\n'
              + '  ' + this.modelName + '.findOneAndUpdate(conditions, update)\n'
              + '  ' + this.modelName + '.findOneAndUpdate(update)\n'
              + '  ' + this.modelName + '.findOneAndUpdate()\n';
      throw new TypeError(msg)
    }
    update = conditions;
    conditions = undefined;
  }

  var fields;
  if (options && options.fields) {
    fields = options.fields;
    options.fields = undefined;
  }

  var query = new Query(conditions);
  query.setOptions(options);
  query.select(fields);
  query.bind(this, 'findOneAndUpdate', update);

  if ('undefined' == typeof callback)
    return query;

  this._applyNamedScope(query);
  return query.findOneAndUpdate(callback);
}

/**
 * Issues a mongodb findAndModify update command by a documents id.
 *
 * Finds a matching document, updates it according to the `update` arg, passing any `options`, and returns the found document (if any) to the callback. The query executes immediately if `callback` is passed else a Query object is returned.
 *
 * ####Options:
 *
 * - `new`: bool - true to return the modified document rather than the original. defaults to true
 * - `upsert`: bool - creates the object if it doesn't exist. defaults to false.
 * - `sort`: if multiple docs are found by the conditions, sets the sort order to choose which doc to update
 * - `select`: sets the document fields to return
 *
 * ####Examples:
 *
 *     A.findByIdAndUpdate(id, update, options, callback) // executes
 *     A.findByIdAndUpdate(id, update, options)  // returns Query
 *     A.findByIdAndUpdate(id, update, callback) // executes
 *     A.findByIdAndUpdate(id, update)           // returns Query
 *     A.findByIdAndUpdate()                     // returns Query
 *
 * Finds a matching document, updates it according to the `update` arg, passing any `options`, and returns the found document (if any) to the callback. The query executes      immediately if `callback` is passed else a Query object is returned.
 *
 * ####Options:
 *
 * - `new`: bool - true to return the modified document rather than the original. defaults to true
 * - `upsert`: bool - creates the object if it doesn't exist. defaults to false.
 * - `sort`: if multiple docs are found by the conditions, sets the sort order to choose which doc to update
 *
 * ####Note:
 *
 * All top level update keys which are not `atomic` operation names are treated as set operations:
 *
 * ####Example:
 *
 *     Model.findByIdAndUpdate(id, { name: 'jason borne' }, options, callback)
 *
 *     // is sent as
 *     Model.findByIdAndUpdate(id, { $set: { name: 'jason borne' }}, options, callback)
 *
 * This helps prevent accidentally overwriting your document with `{ name: 'jason borne' }`.
 *
 * ####Note:
 *
 * Although values are cast to their appropriate types when using the findAndModify helpers, the following are *not* applied:
 *
 * - defaults
 * - setters
 * - validators
 * - middleware
 *
 * If you need those features, use the traditional approach of first retrieving the document.
 *
 *     Model.findById(id, function (err, doc) {
 *       if (err) ..
 *       doc.name = 'jason borne';
 *       doc.save(callback);
 *     })
 *
 * @param {ObjectId|HexId} id an ObjectId or string that can be cast to one.
 * @param {Object} [update]
 * @param {Object} [options]
 * @param {Function} [callback]
 * @return {Query}
 * @see Model.findOneAndUpdate #model_Model-findOneAndUpdate
 * @see mongodb http://www.mongodb.org/display/DOCS/findAndModify+Command
 * @api public
 */

Model.findByIdAndUpdate = function (id, update, options, callback) {
  var args;

  if (1 === arguments.length) {
    if ('function' == typeof id) {
      var msg = 'Model.findByIdAndUpdate(): First argument must not be a function.\n\n'
                + '  ' + this.modelName + '.findByIdAndUpdate(id, callback)\n'
                + '  ' + this.modelName + '.findByIdAndUpdate(id)\n'
                + '  ' + this.modelName + '.findByIdAndUpdate()\n';
      throw new TypeError(msg)
    }
    return this.findOneAndUpdate({_id: id }, undefined);
  }

  args = utils.args(arguments, 1);
  args.unshift({ _id: id });
  return this.findOneAndUpdate.apply(this, args);
}

/**
 * Issue a mongodb findAndModify remove command.
 *
 * Finds a matching document, removes it, passing the found document (if any) to the callback.
 *
 * Executes immediately if `callback` is passed else a Query object is returned.
 *
 * ####Options:
 *
 * - `sort`: if multiple docs are found by the conditions, sets the sort order to choose which doc to update
 * - `select`: sets the document fields to return
 *
 * ####Examples:
 *
 *     A.findOneAndRemove(conditions, options, callback) // executes
 *     A.findOneAndRemove(conditions, options)  // return Query
 *     A.findOneAndRemove(conditions, callback) // executes
 *     A.findOneAndRemove(conditions) // returns Query
 *     A.findOneAndRemove()           // returns Query
 *
 * @param {Object} conditions
 * @param {Object} [options]
 * @param {Function} [callback]
 * @return {Query}
 * @see mongodb http://www.mongodb.org/display/DOCS/findAndModify+Command
 * @api public
 */

Model.findOneAndRemove = function (conditions, options, callback) {
  if (1 === arguments.length && 'function' == typeof conditions) {
    var msg = 'Model.findOneAndRemove(): First argument must not be a function.\n\n'
              + '  ' + this.modelName + '.findOneAndRemove(conditions, callback)\n'
              + '  ' + this.modelName + '.findOneAndRemove(conditions)\n'
              + '  ' + this.modelName + '.findOneAndRemove()\n';
    throw new TypeError(msg)
  }

  if ('function' == typeof options) {
    callback = options;
    options = undefined;
  }

  var fields;
  if (options) {
    fields = options.select;
    options.select = undefined;
  }

  var query = new Query(conditions);
  query.setOptions(options);
  query.select(fields);
  query.bind(this, 'findOneAndRemove');

  if ('undefined' == typeof callback)
    return query;

  this._applyNamedScope(query);
  return query.findOneAndRemove(callback);
}

/**
 * Issue a mongodb findAndModify remove command by a documents id.
 *
 * Finds a matching document, removes it, passing the found document (if any) to the callback.
 *
 * Executes immediately if `callback` is passed, else a `Query` object is returned.
 *
 * ####Options:
 *
 * - `sort`: if multiple docs are found by the conditions, sets the sort order to choose which doc to update
 * - `select`: sets the document fields to return
 *
 * ####Examples:
 *
 *     A.findByIdAndRemove(id, options, callback) // executes
 *     A.findByIdAndRemove(id, options)  // return Query
 *     A.findByIdAndRemove(id, callback) // executes
 *     A.findByIdAndRemove(id) // returns Query
 *     A.findByIdAndRemove()           // returns Query
 *
 * @param {ObjectId|HexString} id ObjectId or string that can be cast to one
 * @param {Object} [options]
 * @param {Function} [callback]
 * @return {Query}
 * @see Model.findOneAndRemove #model_Model-findOneAndRemove
 * @see mongodb http://www.mongodb.org/display/DOCS/findAndModify+Command
 */

Model.findByIdAndRemove = function (id, options, callback) {
  if (1 === arguments.length && 'function' == typeof id) {
    var msg = 'Model.findByIdAndRemove(): First argument must not be a function.\n\n'
              + '  ' + this.modelName + '.findByIdAndRemove(id, callback)\n'
              + '  ' + this.modelName + '.findByIdAndRemove(id)\n'
              + '  ' + this.modelName + '.findByIdAndRemove()\n';
    throw new TypeError(msg)
  }

  return this.findOneAndRemove({ _id: id }, options, callback);
}

/**
 * Shortcut for creating a new Document that is automatically saved to the db if valid.
 *
 * ####Example:
 *
 *     Candy.create({ type: 'jelly bean' }, { type: 'snickers' }, function (err, jellybean, snickers) {
 *       if (err) // ...
 *     });
 *
 *     var array = [{ type: 'jelly bean' }, { type: 'snickers' }];
 *     Candy.create(array, function (err, jellybean, snickers) {
 *       if (err) // ...
 *     });
 *
 * @param {Array|Object...} doc
 * @param {Function} fn callback
 * @api public
 */

Model.create = function create (doc, fn) {
  if (1 === arguments.length) {
    return 'function' === typeof doc && doc(null);
  }

  var self = this
    , docs = [null]
    , promise
    , count
    , args

  if (Array.isArray(doc)) {
    args = doc;
  } else {
    args = utils.args(arguments, 0, arguments.length - 1);
    fn = arguments[arguments.length - 1];
  }

  if (0 === args.length) return fn(null);

  promise = new Promise(fn);
  count = args.length;

  args.forEach(function (arg, i) {
    var doc = new self(arg);
    docs[i+1] = doc;
    doc.save(function (err) {
      if (err) return promise.error(err);
      --count || fn.apply(null, docs);
    });
  });

  // TODO
  // utilize collection.insertAll for batch processing?
};

/**
 * Updates documents in the database without returning them.
 *
 * ####Examples:
 *
 *     MyModel.update({ age: { $gt: 18 } }, { oldEnough: true }, fn);
 *     MyModel.update({ name: 'Tobi' }, { ferret: true }, { multi: true }, function (err, numberAffected, raw) {
 *       if (err) return handleError(err);
 *       console.log('The number of updated documents was %d', numberAffected);
 *       console.log('The raw response from Mongo was ', raw);
 *     });
 *
 * ####Valid options:
 *
 *  - `safe` (boolean) safe mode (defaults to value set in schema (true))
 *  - `upsert` (boolean) whether to create the doc if it doesn't match (false)
 *  - `multi` (boolean) whether multiple documents should be updated (false)
 *
 * All `update` values are cast to their appropriate SchemaTypes before being sent.
 *
 * The `callback` function receives `(err, numberAffected, rawResponse)`.
 *
 * - `err` is the error if any occurred
 * - `numberAffected` is the count of updated documents Mongo reported
 * - `rawResponse` is the full response from Mongo
 *
 * ####Note:
 *
 * All top level keys which are not `atomic` operation names are treated as set operations:
 *
 * ####Example:
 *
 *     var query = { name: 'borne' };
 *     Model.update(query, { name: 'jason borne' }, options, callback)
 *
 *     // is sent as
 *     Model.update(query, { $set: { name: 'jason borne' }}, options, callback)
 *
 * This helps prevent accidentally overwriting all documents in your collection with `{ name: 'jason borne' }`.
 *
 * ####Note:
 *
 * To update documents without waiting for a response from MongoDB, do not pass a `callback`, then call `exec` on the returned [Query](#query-js):
 *
 *     Comment.update({ _id: id }, { $set: { text: 'changed' }}).exec();
 *
 * ####Note:
 *
 * Although values are casted to their appropriate types when using update, the following are *not* applied:
 *
 * - defaults
 * - setters
 * - validators
 * - middleware
 *
 * If you need those features, use the traditional approach of first retrieving the document.
 *
 *     Model.findOne({ name: 'borne' }, function (err, doc) {
 *       if (err) ..
 *       doc.name = 'jason borne';
 *       doc.save(callback);
 *     })
 *
 * @param {Object} conditions
 * @param {Object} update
 * @param {Object} [options]
 * @param {Function} [callback]
 * @return {Query}
 * @api public
 */

Model.update = function update (conditions, doc, options, callback) {
  if (arguments.length < 4) {
    if ('function' === typeof options) {
      // Scenario: update(conditions, doc, callback)
      callback = options;
      options = null;
    } else if ('function' === typeof doc) {
      // Scenario: update(doc, callback);
      callback = doc;
      doc = conditions;
      conditions = {};
      options = null;
    }
  }

  var query = new Query(conditions, options).bind(this, 'update', doc);

  if ('undefined' == typeof callback)
    return query;

  this._applyNamedScope(query);
  return query.update(doc, callback);
};

/**
 * Executes a mapReduce command.
 *
 * `o` is an object specifying all mapReduce options as well as the map and reduce functions. All options are delegated to the driver implementation.
 *
 * ####Example:
 *
 *     var o = {};
 *     o.map = function () { emit(this.name, 1) }
 *     o.reduce = function (k, vals) { return vals.length }
 *     User.mapReduce(o, function (err, results) {
 *       console.log(results)
 *     })
 *
 * ####Other options:
 *
 * - `query` {Object} query filter object.
 * - `limit` {Number} max number of documents
 * - `keeptemp` {Boolean, default:false} keep temporary data
 * - `finalize` {Function} finalize function
 * - `scope` {Object} scope variables exposed to map/reduce/finalize during execution
 * - `jsMode` {Boolean, default:false} it is possible to make the execution stay in JS. Provided in MongoDB > 2.0.X
 * - `verbose` {Boolean, default:false} provide statistics on job execution time.
 * - `out*` {Object, default: {inline:1}} sets the output target for the map reduce job.
 *
 * ####* out options:
 *
 * - `{inline:1}` the results are returned in an array
 * - `{replace: 'collectionName'}` add the results to collectionName: the results replace the collection
 * - `{reduce: 'collectionName'}` add the results to collectionName: if dups are detected, uses the reducer / finalize functions
 * - `{merge: 'collectionName'}` add the results to collectionName: if dups exist the new docs overwrite the old
 *
 * If `options.out` is set to `replace`, `merge`, or `reduce`, a Model instance is returned that can be used for further querying. Queries run against this model are all executed with the `lean` option; meaning only the js object is returned and no Mongoose magic is applied (getters, setters, etc).
 *
 * ####Example:
 *
 *     var o = {};
 *     o.map = function () { emit(this.name, 1) }
 *     o.reduce = function (k, vals) { return vals.length }
 *     o.out = { replace: 'createdCollectionNameForResults' }
 *     o.verbose = true;
 *     User.mapReduce(o, function (err, model, stats) {
 *       console.log('map reduce took %d ms', stats.processtime)
 *       model.find().where('value').gt(10).exec(function (err, docs) {
 *         console.log(docs);
 *       });
 *     })
 *
 * @param {Object} o an object specifying map-reduce options
 * @param {Function} callback
 * @see http://www.mongodb.org/display/DOCS/MapReduce
 * @api public
 */

Model.mapReduce = function mapReduce (o, callback) {
  if ('function' != typeof callback) throw new Error('missing callback');

  var self = this;

  if (!Model.mapReduce.schema) {
    var opts = { noId: true, noVirtualId: true, strict: false }
    Model.mapReduce.schema = new Schema({}, opts);
  }

  if (!o.out) o.out = { inline: 1 };

  o.map = String(o.map);
  o.reduce = String(o.reduce);

  if (o.query) {
    var q = new Query(o.query);
    q.cast(this);
    o.query = q._conditions;
    q = undefined;
  }

  this.collection.mapReduce(null, null, o, function (err, ret, stats) {
    if (err) return callback(err);

    if (ret.findOne && ret.mapReduce) {
      // returned a collection, convert to Model
      var model = Model.compile(
          '_mapreduce_' + ret.collectionName
        , Model.mapReduce.schema
        , ret.collectionName
        , self.db
        , self.base);

      model._mapreduce = true;

      return callback(err, model, stats);
    }

    callback(err, ret, stats);
  });
}

/**
 * Executes an aggregate command on this models collection.
 *
 * ####Example:
 *
 *     // find the max age of all users
 *     Users.aggregate(
 *         { $group: { _id: null, maxAge: { $max: '$age' }}}
 *       , { $project: { _id: 0, maxAge: 1 }}
 *       , function (err, res) {
 *       if (err) return handleError(err);
 *       console.log(res); // [ { maxAge: 98 } ]
 *     });
 *
 * _NOTE: the documents returned are plain javascript objects, not mongoose documents cast to this models schema definition (since any shape of document can be returned)._
 *
 * _NOTE: this requires running MongoDB >= 2.1_
 *
 * @param {Array} array an array of pipeline commands
 * @param {Object} [options]
 * @param {Function} callback
 * @see aggregation http://docs.mongodb.org/manual/applications/aggregation/
 * @see driver http://mongodb.github.com/node-mongodb-native/api-generated/collection.html#aggregate
 * @api public
 */

Model.aggregate = function aggregate () {
  return this.collection.aggregate.apply(this.collection, arguments);
}

/*!
 * Compiler utility.
 *
 * @param {String} name model name
 * @param {Schema} schema
 * @param {String} collectionName
 * @param {Connection} connection
 * @param {Mongoose} base mongoose instance
 */

Model.compile = function compile (name, schema, collectionName, connection, base) {
  // generate new class
  function model (doc, fields, skipId) {
    if (!(this instanceof model))
      return new model(doc, fields, skipId);
    Model.call(this, doc, fields, skipId);
  };

  model.modelName = name;
  model.__proto__ = Model;
  model.prototype.__proto__ = Model.prototype;
  model.prototype.db = connection;
  model.prototype._setSchema(schema);
  model.prototype.collection = connection.collection(
      collectionName
    , schema.options.capped
  );

  // apply methods
  for (var i in schema.methods)
    model.prototype[i] = schema.methods[i];

  // apply statics
  for (var i in schema.statics)
    model[i] = schema.statics[i];

  // apply named scopes
  if (schema.namedScopes) schema.namedScopes.compile(model);

  model.model = model.prototype.model;
  model.options = model.prototype.options;
  model.db = model.prototype.db;
  model.schema = model.prototype.schema;
  model.collection = model.prototype.collection;
  model.base = base;

  return model;
};

/*!
 * Subclass this model with `conn`, `schema`, and `collection` settings.
 *
 * @param {Connection} conn
 * @param {Schema} [schema]
 * @param {String} [collection]
 * @return {Model}
 */

Model.__subclass = function subclass (conn, schema, collection) {
  // subclass model using this connection and collection name
  var model = this;

  var Model = function Model (doc, fields, skipId) {
    if (!(this instanceof Model)) {
      return new Model(doc, fields, skipId);
    }
    model.call(this, doc, fields, skipId);
  }

  Model.__proto__ = model;
  Model.prototype.__proto__ = model.prototype;
  Model.db = Model.prototype.db = conn;

  var s = 'string' != typeof schema
    ? schema
    : model.prototype.schema;

  if (!collection) {
    collection = model.prototype.schema.get('collection')
              || utils.toCollectionName(model.modelName);
  }

  Model.prototype.collection = conn.collection(collection, s && s.options.capped);
  Model.collection = Model.prototype.collection;
  Model.init();
  return Model;
}

/*!
 * Module exports.
 */

module.exports = exports = Model;