source: trunk/HeuristicLab.ExtLibs/HeuristicLab.NRefactory/5.5.0/NRefactory.CSharp-5.5.0/CombineQueryExpressions.cs @ 16433

//
// CombineQueryExpressions.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.Linq;
using ICSharpCode.NRefactory.CSharp;
using ICSharpCode.NRefactory.PatternMatching;

namespace ICSharpCode.NRefactory.CSharp
{
  /// <summary>
  /// Combines query expressions and removes transparent identifiers.
  /// </summary>
  public class CombineQueryExpressions
  {
    static readonly InvocationExpression castPattern = new InvocationExpression {
      Target = new MemberReferenceExpression {
        Target = new AnyNode("inExpr"),
        MemberName = "Cast",
        TypeArguments = { new AnyNode("targetType") }
      }};

    public string CombineQuery(AstNode node, AstNode rootQuery = null)
    {
      if (rootQuery == null) {
        rootQuery = node;
      }

      QueryExpression query = node as QueryExpression;
      if (query != null) {
        string continuationIdentifier = null;

        foreach (var clause in query.Clauses) {
          var continuation = clause as QueryContinuationClause;
          if (continuation != null) {
            CombineQuery(continuation.PrecedingQuery);
          }

          var from = clause as QueryFromClause;
          if (from != null) {
            continuationIdentifier = CombineQuery(from.Expression, rootQuery);
          }
        }

        QueryFromClause fromClause = (QueryFromClause)query.Clauses.First();
        QueryExpression innerQuery = fromClause.Expression as QueryExpression;
        if (innerQuery != null) {
          continuationIdentifier = continuationIdentifier ?? ((QueryFromClause)innerQuery.Clauses.First()).Identifier;

          string transparentIdentifier;
          if (TryRemoveTransparentIdentifier(query, fromClause, innerQuery, continuationIdentifier, out transparentIdentifier)) {
            RemoveTransparentIdentifierReferences(rootQuery, transparentIdentifier);
          } else if (fromClause.Type.IsNull) {
            QueryContinuationClause continuation = new QueryContinuationClause();
            continuation.PrecedingQuery = innerQuery.Detach();
            continuation.Identifier = fromClause.Identifier;
            fromClause.ReplaceWith(continuation);
          }

          return transparentIdentifier;
        } else {
          Match m = castPattern.Match(fromClause.Expression);
          if (m.Success) {
            fromClause.Type = m.Get<AstType>("targetType").Single().Detach();
            fromClause.Expression = m.Get<Expression>("inExpr").Single().Detach();
          }
        }
      }

      return null;
    }

    static readonly QuerySelectClause selectTransparentIdentifierPattern = new QuerySelectClause {
      Expression = new AnonymousTypeCreateExpression {
          Initializers = {
            new AnyNode("nae1"),
            new AnyNode("nae2")
          }
        }
      };

    bool TryRemoveTransparentIdentifier(QueryExpression query, QueryFromClause fromClause, QueryExpression innerQuery, string continuationIdentifier, out string transparentIdentifier)
    {
      transparentIdentifier = fromClause.Identifier;

      Match match = selectTransparentIdentifierPattern.Match(innerQuery.Clauses.Last());
      if (!match.Success)
        return false;
      QuerySelectClause selectClause = (QuerySelectClause)innerQuery.Clauses.Last();
      Expression nae1 = match.Get<Expression>("nae1").SingleOrDefault();
      string nae1Name = ExtractExpressionName(ref nae1);
      if (nae1Name == null)
        return false;

      Expression nae2 = match.Get<Expression>("nae2").SingleOrDefault();
      string nae2Name = ExtractExpressionName(ref nae2);
      if (nae1Name == null)
        return false;

      bool introduceLetClause = true;
      var nae1Identifier = nae1 as IdentifierExpression;
      var nae2Identifier = nae2 as IdentifierExpression;
      if (nae1Identifier != null && nae2Identifier != null && nae1Identifier.Identifier == nae1Name && nae2Identifier.Identifier == nae2Name) {
        introduceLetClause = false;
      }

      if (nae1Name != continuationIdentifier) {
        if (nae2Name == continuationIdentifier) {
          //Members are in reversed order
          string tempName = nae1Name;
          Expression tempNae = nae1;

          nae1Name = nae2Name;
          nae1 = nae2;
          nae2Name = tempName;
          nae2 = tempNae;
        } else {
          return false;
        }
      }

      if (introduceLetClause && innerQuery.Clauses.OfType<QueryFromClause>().Any(from => from.Identifier == nae2Name)) {
        return false;
      }
      if (introduceLetClause && innerQuery.Clauses.OfType<QueryJoinClause>().Any(join => join.JoinIdentifier == nae2Name)) {
        return false;
      }

      // from * in (from x in ... select new { x = x, y = expr }) ...
      // =>
      // from x in ... let y = expr ...
      fromClause.Remove();
      selectClause.Remove();
      // Move clauses from innerQuery to query
      QueryClause insertionPos = null;
      foreach (var clause in innerQuery.Clauses) {
        query.Clauses.InsertAfter(insertionPos, insertionPos = clause.Detach());
      }
      if (introduceLetClause) {
        query.Clauses.InsertAfter(insertionPos, new QueryLetClause { Identifier = nae2Name, Expression = nae2.Detach() });
      }
      return true;
    }

    /// <summary>
    /// Removes all occurrences of transparent identifiers
    /// </summary>
    void RemoveTransparentIdentifierReferences(AstNode node, string transparentIdentifier)
    {
      foreach (AstNode child in node.Children) {
        RemoveTransparentIdentifierReferences(child, transparentIdentifier);
      }
      MemberReferenceExpression mre = node as MemberReferenceExpression;
      if (mre != null) {
        IdentifierExpression ident = mre.Target as IdentifierExpression;
        if (ident != null && ident.Identifier == transparentIdentifier) {
          IdentifierExpression newIdent = new IdentifierExpression(mre.MemberName);
          mre.TypeArguments.MoveTo(newIdent.TypeArguments);
          newIdent.CopyAnnotationsFrom(mre);
          newIdent.RemoveAnnotations<PropertyDeclaration>(); // remove the reference to the property of the anonymous type
          mre.ReplaceWith(newIdent);
          return;
        } else if (mre.MemberName == transparentIdentifier) {
          var newVar = mre.Target.Detach();
          newVar.CopyAnnotationsFrom(mre);
          newVar.RemoveAnnotations<PropertyDeclaration>(); // remove the reference to the property of the anonymous type
          mre.ReplaceWith(newVar);
          return;
        }
      }
    }

    string ExtractExpressionName(ref Expression expr)
    {
      NamedExpression namedExpr = expr as NamedExpression;
      if (namedExpr != null) {
        expr = namedExpr.Expression;
        return namedExpr.Name;
      }

      IdentifierExpression identifier = expr as IdentifierExpression;
      if (identifier != null) {
        return identifier.Identifier;
      }

      MemberReferenceExpression memberRef = expr as MemberReferenceExpression;
      if (memberRef != null) {
        return memberRef.MemberName;
      }

      return null;
    }
  }
}