define(["../../_base/lang", "../../_base/kernel", "./sorter"],
  function(lang, kernel, sorter){
	// module:
	//		dojo/data/util/simpleFetch
	// summary:
	//		The simpleFetch mixin is designed to serve as a set of function(s) that can
	//		be mixed into other datastore implementations to accelerate their development.

var simpleFetch = {};
lang.setObject("dojo.data.util.simpleFetch", simpleFetch);

simpleFetch.errorHandler = function(/*Object*/ errorData, /*Object*/ requestObject){
	// summary:
	//		The error handler when there is an error fetching items.  This function should not be called
	//		directly and is used by simpleFetch.fetch().
	if(requestObject.onError){
		var scope = requestObject.scope || kernel.global;
		requestObject.onError.call(scope, errorData, requestObject);
	}
};

simpleFetch.fetchHandler = function(/*Array*/ items, /*Object*/ requestObject){
	// summary:
	//		The handler when items are sucessfully fetched.  This function should not be called directly
	//		and is used by simpleFetch.fetch().
	var oldAbortFunction = requestObject.abort || null,
		aborted = false,

		startIndex = requestObject.start?requestObject.start: 0,
		endIndex = (requestObject.count && (requestObject.count !== Infinity))?(startIndex + requestObject.count):items.length;

	requestObject.abort = function(){
		aborted = true;
		if(oldAbortFunction){
			oldAbortFunction.call(requestObject);
		}
	};

	var scope = requestObject.scope || kernel.global;
	if(!requestObject.store){
		requestObject.store = this;
	}
	if(requestObject.onBegin){
		requestObject.onBegin.call(scope, items.length, requestObject);
	}
	if(requestObject.sort){
		items.sort(sorter.createSortFunction(requestObject.sort, this));
	}
	if(requestObject.onItem){
		for(var i = startIndex; (i < items.length) && (i < endIndex); ++i){
			var item = items[i];
			if(!aborted){
				requestObject.onItem.call(scope, item, requestObject);
			}
		}
	}
	if(requestObject.onComplete && !aborted){
		var subset = null;
		if(!requestObject.onItem){
			subset = items.slice(startIndex, endIndex);
		}
		requestObject.onComplete.call(scope, subset, requestObject);
	}
};

simpleFetch.fetch = function(/* Object? */ request){
	// summary:
	//		The simpleFetch mixin is designed to serve as a set of function(s) that can
	//		be mixed into other datastore implementations to accelerate their development.
	// description:
	//		The simpleFetch mixin should work well for any datastore that can respond to a _fetchItems()
	//		call by returning an array of all the found items that matched the query.  The simpleFetch mixin
	//		is not designed to work for datastores that respond to a fetch() call by incrementally
	//		loading items, or sequentially loading partial batches of the result
	//		set.  For datastores that mixin simpleFetch, simpleFetch
	//		implements a fetch method that automatically handles eight of the fetch()
	//		arguments -- onBegin, onItem, onComplete, onError, start, count, sort and scope
	//		The class mixing in simpleFetch should not implement fetch(),
	//		but should instead implement a _fetchItems() method.  The _fetchItems()
	//		method takes three arguments, the keywordArgs object that was passed
	//		to fetch(), a callback function to be called when the result array is
	//		available, and an error callback to be called if something goes wrong.
	//		The _fetchItems() method should ignore any keywordArgs parameters for
	//		start, count, onBegin, onItem, onComplete, onError, sort, and scope.
	//		The _fetchItems() method needs to correctly handle any other keywordArgs
	//		parameters, including the query parameter and any optional parameters
	//		(such as includeChildren).  The _fetchItems() method should create an array of
	//		result items and pass it to the fetchHandler along with the original request object --
	//		or, the _fetchItems() method may, if it wants to, create an new request object
	//		with other specifics about the request that are specific to the datastore and pass
	//		that as the request object to the handler.
	//
	//		For more information on this specific function, see dojo/data/api/Read.fetch()
	//
	// request:
	//		The keywordArgs parameter may either be an instance of
	//		conforming to dojo/data/api/Request or may be a simple anonymous object
	//		that may contain any of the following:
	// |	{
	// |		query: query-object or query-string,
	// |		queryOptions: object,
	// |		onBegin: Function,
	// |		onItem: Function,
	// |		onComplete: Function,
	// |		onError: Function,
	// |		scope: object,
	// |		start: int
	// |		count: int
	// |		sort: array
	// |	}
	//		All implementations should accept keywordArgs objects with any of
	//		the 9 standard properties: query, onBegin, onItem, onComplete, onError
	//		scope, sort, start, and count.  Some implementations may accept additional
	//		properties in the keywordArgs object as valid parameters, such as
	//		{includeOutliers:true}.
	//
	//		####The *query* parameter
	//
	//		The query may be optional in some data store implementations.
	//		The dojo/data/api/Read API does not specify the syntax or semantics
	//		of the query itself -- each different data store implementation
	//		may have its own notion of what a query should look like.
	//		However, as of dojo 0.9, 1.0, and 1.1, all the provided datastores in dojo.data
	//		and dojox.data support an object structure query, where the object is a set of
	//		name/value parameters such as { attrFoo: valueBar, attrFoo1: valueBar1}.  Most of the
	//		dijit widgets, such as ComboBox assume this to be the case when working with a datastore
	//		when they dynamically update the query.  Therefore, for maximum compatibility with dijit
	//		widgets the recommended query parameter is a key/value object.  That does not mean that the
	//		the datastore may not take alternative query forms, such as a simple string, a Date, a number,
	//		or a mix of such.  Ultimately, The dojo/data/api/Read API is agnostic about what the query
	//		format.
	//
	//		Further note:  In general for query objects that accept strings as attribute
	//		value matches, the store should also support basic filtering capability, such as *
	//		(match any character) and ? (match single character).  An example query that is a query object
	//		would be like: { attrFoo: "value*"}.  Which generally means match all items where they have
	//		an attribute named attrFoo, with a value that starts with 'value'.
	//
	//		####The *queryOptions* parameter
	//
	//		The queryOptions parameter is an optional parameter used to specify options that may modify
	//		the query in some fashion, such as doing a case insensitive search, or doing a deep search
	//		where all items in a hierarchical representation of data are scanned instead of just the root
	//		items.  It currently defines two options that all datastores should attempt to honor if possible:
	// |	{
	// |		ignoreCase: boolean, // Whether or not the query should match case sensitively or not.  Default behaviour is false.
	// |		deep: boolean	// Whether or not a fetch should do a deep search of items and all child
	// |						// items instead of just root-level items in a datastore.  Default is false.
	// |	}
	//
	//		####The *onBegin* parameter.
	//
	//		function(size, request);
	//		If an onBegin callback function is provided, the callback function
	//		will be called just once, before the first onItem callback is called.
	//		The onBegin callback function will be passed two arguments, the
	//		the total number of items identified and the Request object.  If the total number is
	//		unknown, then size will be -1.  Note that size is not necessarily the size of the
	//		collection of items returned from the query, as the request may have specified to return only a
	//		subset of the total set of items through the use of the start and count parameters.
	//
	//		####The *onItem* parameter.
	//
	//		function(item, request);
	//
	//		If an onItem callback function is provided, the callback function
	//		will be called as each item in the result is received. The callback
	//		function will be passed two arguments: the item itself, and the
	//		Request object.
	//
	//		####The *onComplete* parameter.
	//
	//		function(items, request);
	//
	//		If an onComplete callback function is provided, the callback function
	//		will be called just once, after the last onItem callback is called.
	//		Note that if the onItem callback is not present, then onComplete will be passed
	//		an array containing all items which matched the query and the request object.
	//		If the onItem callback is present, then onComplete is called as:
	//		onComplete(null, request).
	//
	//		####The *onError* parameter.
	//
	//		function(errorData, request);
	//
	//		If an onError callback function is provided, the callback function
	//		will be called if there is any sort of error while attempting to
	//		execute the query.
	//		The onError callback function will be passed two arguments:
	//		an Error object and the Request object.
	//
	//		####The *scope* parameter.
	//
	//		If a scope object is provided, all of the callback functions (onItem,
	//		onComplete, onError, etc) will be invoked in the context of the scope
	//		object.  In the body of the callback function, the value of the "this"
	//		keyword will be the scope object.   If no scope object is provided,
	//		the callback functions will be called in the context of dojo.global().
	//		For example, onItem.call(scope, item, request) vs.
	//		onItem.call(dojo.global(), item, request)
	//
	//		####The *start* parameter.
	//
	//		If a start parameter is specified, this is a indication to the datastore to
	//		only start returning items once the start number of items have been located and
	//		skipped.  When this parameter is paired with 'count', the store should be able
	//		to page across queries with millions of hits by only returning subsets of the
	//		hits for each query
	//
	//		####The *count* parameter.
	//
	//		If a count parameter is specified, this is a indication to the datastore to
	//		only return up to that many items.  This allows a fetch call that may have
	//		millions of item matches to be paired down to something reasonable.
	//
	//		####The *sort* parameter.
	//
	//		If a sort parameter is specified, this is a indication to the datastore to
	//		sort the items in some manner before returning the items.  The array is an array of
	//		javascript objects that must conform to the following format to be applied to the
	//		fetching of items:
	// |	{
	// |		attribute: attribute || attribute-name-string,
	// |		descending: true|false;   // Optional.  Default is false.
	// |	}
	//		Note that when comparing attributes, if an item contains no value for the attribute
	//		(undefined), then it the default ascending sort logic should push it to the bottom
	//		of the list.  In the descending order case, it such items should appear at the top of the list.

	request = request || {};
	if(!request.store){
		request.store = this;
	}

	this._fetchItems(request, lang.hitch(this, "fetchHandler"), lang.hitch(this, "errorHandler"));
	return request;	// Object
};

return simpleFetch;
});
