source: branches/2990_VariableImpactBasedFeatureSelection/HeuristicLab.ExtLibs/HeuristicLab.NRefactory/5.5.0/NRefactory.CSharp-5.5.0/IntroduceQueryExpressions.cs @ 16612

//
// 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;
    }
  }
}