using System;

using System.Collections.Generic;

using System.Linq;

using System.Text.RegularExpressions;

using System.Xml.Linq;

namespace SimpleBrowser.Query

{

/* Some simple rules about jQuery:

*

* parsing operates in a context which is a set of included elements

* no elements are selected in a blank query- a selector is required in order to obtain a subset of elements from the context

* a new (raw) context draws from any available node in the tree, unlike an empty context which is the result of selections with no matches

* a filtered context only operates on nodes that are selected within the context (which could be none if selectors have filtered out all nodes)

* a query should always start and end with a selector- a query starting or ending with a shift operator is invalid

* context is cloned for subqueries, as the context may alter during a subquery but need to be reset upon resolution of the subquery e.g. :not(p > b)

* there are five types of selectors:

* #id - select an element by its 'id' attribute - starts with a hash

* .class - select an element by its 'class' attribute - starts with a period

* tag - selects an element according to its tag name - starts with a letter

* [attribute filter] - selects an element by the existence of, or value of, an attribute with a given name - starts with a square bracket

* :named filter - selects elements that match a defined rule (note that this type of selector can select and include elements outside of the current selection) - starts with a colon

* shift operators traverse the context - they are:

* > filter context to children of existing selection

* [space] filter context to descendents of existing selection

* + filter context to next adjacent siblings of existing selection

* usage examples: http://ejohn.org/files/selectors.html

*/

public static class XQuery

{

internal static IXQuerySelector[] Parse(XQueryParserContext context)

{

var list = new List<IXQuerySelector>();

while(!context.EndOfQuery)

{

var selector = context.MatchNextSelector();

if(selector == null)

throw new XQueryException("Unexpected character at position " + context.Index + " in query: " + context.Query.Substring(context.Index), context.Query, context.Index, 1);

list.Add(selector);

}

return list.ToArray();

}

public static XElement[] Execute(string query, XDocument doc, params XElement[] baseElements)

{

var parserContext = new XQueryParserContext(new SelectorParserCatalog(), query);

var selectors = Parse(parserContext);

var resultsContext = new XQueryResultsContext(doc);

if(baseElements.Length > 0)

resultsContext.ResultSetInternal = baseElements;

if(selectors.Length > 0)

if(selectors.Last().IsTransposeSelector || selectors.First().IsTransposeSelector)

throw new XQueryException("A query may not start or end with a transposal selector (e.g. >)", query, 0, query.Length);

foreach(var selector in selectors)

selector.Execute(resultsContext);

return resultsContext.ResultSet;

}

}

}