//
// IntroduceQueryExpressions.cs
//
// Modified by Luís Reis <luiscubal@gmail.com> (Copyright (C) 2013)
//
// Copyright header of the original version follows:
//
// Copyright (c) 2011 AlphaSierraPapa for the SharpDevelop Team
// 
// Permission is hereby granted, free of charge, to any person obtaining a copy of this
// software and associated documentation files (the "Software"), to deal in the Software
// without restriction, including without limitation the rights to use, copy, modify, merge,
// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
// to whom the Software is furnished to do so, subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in all copies or
// substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
using System;
using System.Diagnostics;
using System.Linq;
using ICSharpCode.NRefactory.CSharp;
using ICSharpCode.NRefactory.PatternMatching;

namespace ICSharpCode.NRefactory.CSharp
{
	static class NRefactoryExtensions
	{
		public static T Detach<T>(this T node) where T : AstNode
		{
			node.Remove();
			return node;
		}

		public static T CopyAnnotationsFrom<T>(this T node, AstNode other) where T : AstNode
		{
			foreach (object annotation in other.Annotations) {
				node.AddAnnotation(annotation);
			}
			return node;
		}

		public static Expression WithName(this Expression node, string patternGroupName)
		{
			return new NamedNode(patternGroupName, node);
		}
	}

	/// <summary>
	/// Decompiles query expressions.
	/// Based on C# 4.0 spec, §7.16.2 Query expression translation
	/// </summary>
	public class IntroduceQueryExpressions
	{
		static readonly InvocationExpression castPattern = new InvocationExpression {
			Target = new MemberReferenceExpression {
				Target = new AnyNode("inExpr"),
				MemberName = "Cast",
				TypeArguments = { new AnyNode("targetType") }
			}};

		public Expression ConvertFluentToQuery(Expression node)
		{
			node = node.Clone();

			var artificialParent = new ExpressionStatement();
			artificialParent.Expression = node;

			DecompileQueries(node);
			// After all queries were decompiled, detect degenerate queries (queries not property terminated with 'select' or 'group')
			// and fix them, either by adding a degenerate select, or by combining them with another query.
			foreach (QueryExpression query in artificialParent.Descendants.OfType<QueryExpression>()) {
				QueryFromClause fromClause = (QueryFromClause)query.Clauses.First();
				if (IsDegenerateQuery(query)) {
					string identifierName = fromClause.Identifier;

					// introduce select for degenerate query
					query.Clauses.Add(new QuerySelectClause { Expression = new IdentifierExpression(identifierName) });
				}

				if (fromClause.Type.IsNull) {
					// See if the data source of this query is a degenerate query,
					// and combine the queries if possible.
					QueryExpression innerQuery = fromClause.Expression as QueryExpression;
					while (IsDegenerateQuery(innerQuery)) {
						QueryFromClause innerFromClause = (QueryFromClause)innerQuery.Clauses.First();
						if (fromClause.Identifier != innerFromClause.Identifier && !innerFromClause.Identifier.StartsWith("<>"))
							break;
						// Replace the fromClause with all clauses from the inner query
						fromClause.Remove();
						foreach (var identifierChild in innerQuery.Descendants.OfType<Identifier>().Where(identifier => identifier.Name == innerFromClause.Identifier)) {
							//When the identifier is "<>X", then replace it with the outer one
							identifierChild.ReplaceWith(fromClause.IdentifierToken.Clone());
						}
						QueryClause insertionPos = null;
						foreach (var clause in innerQuery.Clauses) {
							query.Clauses.InsertAfter(insertionPos, insertionPos = clause.Detach());
						}
						fromClause = innerFromClause;
						innerQuery = fromClause.Expression as QueryExpression;
					}
				}
			}

			return artificialParent.Expression.Clone();
		}

		bool IsDegenerateQuery(QueryExpression query)
		{
			if (query == null)
				return false;
			var lastClause = query.Clauses.LastOrDefault();
			return !(lastClause is QuerySelectClause || lastClause is QueryGroupClause);
		}

		void DecompileQueries(AstNode node)
		{
			QueryExpression query = DecompileQuery(node as InvocationExpression);
			if (query != null)
				node.ReplaceWith(query);
		}

		Expression ExtractQuery(MemberReferenceExpression mre)
		{
			var inExpression = mre.Target.Clone();
			var inContent = DecompileQuery(inExpression as InvocationExpression) ?? inExpression;
			return inContent;
		}

		QueryExpression DecompileQuery(InvocationExpression invocation)
		{
			if (invocation == null)
				return null;
			MemberReferenceExpression mre = invocation.Target as MemberReferenceExpression;
			if (mre == null)
				return null;

			switch (mre.MemberName) {
				case "Select":
					{
						if (invocation.Arguments.Count != 1)
							return null;
						string parameterName;
						Expression body;
						if (MatchSimpleLambda(invocation.Arguments.Single(), out parameterName, out body)) {
							QueryExpression query = new QueryExpression();
							query.Clauses.Add(new QueryFromClause { Identifier = parameterName, Expression = ExtractQuery(mre) });
							query.Clauses.Add(new QuerySelectClause { Expression = body.Detach() });
							return query;
						}
						return null;
					}
				case "Cast":
					{
						if (invocation.Arguments.Count == 0 && mre.TypeArguments.Count == 1) {
							var typeArgument = mre.TypeArguments.First();

							QueryExpression query = new QueryExpression();
							string varName = GenerateVariableName();
							query.Clauses.Add(new QueryFromClause {
								Identifier = varName,
								Expression = ExtractQuery(mre),
								Type = typeArgument.Detach()
							});
							return query;

						}
						return null;
					}
				case "GroupBy":
					{
						if (invocation.Arguments.Count == 2) {
							string parameterName1, parameterName2;
							Expression keySelector, elementSelector;
							if (MatchSimpleLambda(invocation.Arguments.ElementAt(0), out parameterName1, out keySelector)
								&& MatchSimpleLambda(invocation.Arguments.ElementAt(1), out parameterName2, out elementSelector)
								&& parameterName1 == parameterName2) {
								QueryExpression query = new QueryExpression();
								query.Clauses.Add(new QueryFromClause { Identifier = parameterName1, Expression = ExtractQuery(mre) });
								query.Clauses.Add(new QueryGroupClause { Projection = elementSelector.Detach(), Key = keySelector.Detach() });
								return query;
							}
						} else if (invocation.Arguments.Count == 1) {
							string parameterName;
							Expression keySelector;
							if (MatchSimpleLambda(invocation.Arguments.Single(), out parameterName, out keySelector)) {
								QueryExpression query = new QueryExpression();
								query.Clauses.Add(new QueryFromClause { Identifier = parameterName, Expression = ExtractQuery(mre) });
								query.Clauses.Add(new QueryGroupClause {
									Projection = new IdentifierExpression(parameterName),
									Key = keySelector.Detach()
								});
								return query;
							}
						}
						return null;
					}
				case "SelectMany":
					{
						if (invocation.Arguments.Count != 2)
							return null;
						string parameterName;
						Expression collectionSelector;
						if (!MatchSimpleLambda(invocation.Arguments.ElementAt(0), out parameterName, out collectionSelector))
							return null;
						LambdaExpression lambda = invocation.Arguments.ElementAt(1) as LambdaExpression;
						if (lambda != null && lambda.Parameters.Count == 2 && lambda.Body is Expression) {
							ParameterDeclaration p1 = lambda.Parameters.ElementAt(0);
							ParameterDeclaration p2 = lambda.Parameters.ElementAt(1);
							QueryExpression query = new QueryExpression();
							query.Clauses.Add(new QueryFromClause { Identifier = p1.Name, Expression = ExtractQuery(mre) });
							query.Clauses.Add(new QueryFromClause { Identifier = p2.Name, Expression = collectionSelector.Detach() });
							query.Clauses.Add(new QuerySelectClause { Expression = ((Expression)lambda.Body).Detach() });
							return query;
						}
						return null;
					}
				case "Where":
					{
						if (invocation.Arguments.Count != 1)
							return null;
						string parameterName;
						Expression body;
						if (MatchSimpleLambda(invocation.Arguments.Single(), out parameterName, out body)) {
							QueryExpression query = new QueryExpression();
							query.Clauses.Add(new QueryFromClause { Identifier = parameterName, Expression = ExtractQuery(mre) });
							query.Clauses.Add(new QueryWhereClause { Condition = body.Detach() });
							return query;
						}
						return null;
					}
				case "OrderBy":
				case "OrderByDescending":
				case "ThenBy":
				case "ThenByDescending":
					{
						if (invocation.Arguments.Count != 1)
							return null;
						string parameterName;
						Expression orderExpression;
						if (MatchSimpleLambda(invocation.Arguments.Single(), out parameterName, out orderExpression)) {
							if (ValidateThenByChain(invocation, parameterName)) {
								QueryOrderClause orderClause = new QueryOrderClause();
								InvocationExpression tmp = invocation;
								while (mre.MemberName == "ThenBy" || mre.MemberName == "ThenByDescending") {
									// insert new ordering at beginning
									orderClause.Orderings.InsertAfter(
										null, new QueryOrdering {
										Expression = orderExpression.Detach(),
										Direction = (mre.MemberName == "ThenBy" ? QueryOrderingDirection.None : QueryOrderingDirection.Descending)
									});

									tmp = (InvocationExpression)mre.Target;
									mre = (MemberReferenceExpression)tmp.Target;
									MatchSimpleLambda(tmp.Arguments.Single(), out parameterName, out orderExpression);
								}
								// insert new ordering at beginning
								orderClause.Orderings.InsertAfter(
									null, new QueryOrdering {
									Expression = orderExpression.Detach(),
									Direction = (mre.MemberName == "OrderBy" ? QueryOrderingDirection.None : QueryOrderingDirection.Descending)
								});

								QueryExpression query = new QueryExpression();
								query.Clauses.Add(new QueryFromClause { Identifier = parameterName, Expression = ExtractQuery(mre) });
								query.Clauses.Add(orderClause);
								return query;
							}
						}
						return null;
					}
				case "Join":
				case "GroupJoin":
					{
						if (invocation.Arguments.Count != 4)
							return null;
						Expression source1 = mre.Target;
						Expression source2 = invocation.Arguments.ElementAt(0);
						string elementName1, elementName2;
						Expression key1, key2;
						if (!MatchSimpleLambda(invocation.Arguments.ElementAt(1), out elementName1, out key1))
							return null;
						if (!MatchSimpleLambda(invocation.Arguments.ElementAt(2), out elementName2, out key2))
							return null;
						LambdaExpression lambda = invocation.Arguments.ElementAt(3) as LambdaExpression;
						if (lambda != null && lambda.Parameters.Count == 2 && lambda.Body is Expression) {
							ParameterDeclaration p1 = lambda.Parameters.ElementAt(0);
							ParameterDeclaration p2 = lambda.Parameters.ElementAt(1);
							QueryExpression query = new QueryExpression();
							query.Clauses.Add(new QueryFromClause { Identifier = elementName1, Expression = source1.Detach() });
							QueryJoinClause joinClause = new QueryJoinClause();
							
							joinClause.JoinIdentifier = elementName2;    // join elementName2
							joinClause.InExpression = source2.Detach();  // in source2

							Match castMatch = castPattern.Match(source2);
							if (castMatch.Success) {
								Expression target = castMatch.Get<Expression>("inExpr").Single().Detach();
								joinClause.Type = castMatch.Get<AstType>("targetType").Single().Detach();
								joinClause.InExpression = target;
							}
							
							joinClause.OnExpression = key1.Detach();     // on key1
							joinClause.EqualsExpression = key2.Detach(); // equals key2
							if (mre.MemberName == "GroupJoin") {
								joinClause.IntoIdentifier = p2.Name; // into p2.Name
							}
							query.Clauses.Add(joinClause);
							Expression resultExpr = ((Expression)lambda.Body).Detach();
							if (p1.Name != elementName1) {
								foreach (var identifier in resultExpr.Descendants.OfType<Identifier>().Where(id => id.Name == p1.Name))
								{
									identifier.Name = elementName1;
								}
							}
							if (p2.Name != elementName2 && mre.MemberName != "GroupJoin") {
								foreach (var identifier in resultExpr.Descendants.OfType<Identifier>().Where(id => id.Name == p2.Name))
								{
									identifier.Name = elementName2;
								}
							}
							query.Clauses.Add(new QuerySelectClause { Expression = resultExpr });
							return query;
						}
						return null;
					}
				default:
					return null;
			}
		}

		int id = 1;
		string GenerateVariableName()
		{
			return "<>" + id++;
		}

		/// <summary>
		/// Ensure that all ThenBy's are correct, and that the list of ThenBy's is terminated by an 'OrderBy' invocation.
		/// </summary>
		bool ValidateThenByChain(InvocationExpression invocation, string expectedParameterName)
		{
			if (invocation == null || invocation.Arguments.Count != 1)
				return false;
			MemberReferenceExpression mre = invocation.Target as MemberReferenceExpression;
			if (mre == null)
				return false;
			string parameterName;
			Expression body;
			if (!MatchSimpleLambda(invocation.Arguments.Single(), out parameterName, out body))
				return false;
			if (parameterName != expectedParameterName)
				return false;

			if (mre.MemberName == "OrderBy" || mre.MemberName == "OrderByDescending")
				return true;
			else if (mre.MemberName == "ThenBy" || mre.MemberName == "ThenByDescending")
				return ValidateThenByChain(mre.Target as InvocationExpression, expectedParameterName);
			else
				return false;
		}

		/// <summary>Matches simple lambdas of the form "a => b"</summary>
		bool MatchSimpleLambda(Expression expr, out string parameterName, out Expression body)
		{
			LambdaExpression lambda = expr as LambdaExpression;
			if (lambda != null && lambda.Parameters.Count == 1 && lambda.Body is Expression) {
				ParameterDeclaration p = lambda.Parameters.Single();
				if (p.ParameterModifier == ParameterModifier.None) {
					parameterName = p.Name;
					body = (Expression)lambda.Body;
					return true;
				}
			}
			parameterName = null;
			body = null;
			return false;
		}
	}
}