source: trunk/sources/HeuristicLab.ExtLibs/HeuristicLab.NRefactory/5.5.0/NRefactory.CSharp-5.5.0/QueryExpressionExpander.cs @ 15529

// Copyright (c) 2010-2013 AlphaSierraPapa for the SharpDevelop Team
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// 
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// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
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using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Globalization;
using System.Linq;
using System.Text;
using ICSharpCode.NRefactory.PatternMatching;

namespace ICSharpCode.NRefactory.CSharp {
  public class QueryExpressionExpansionResult {
    public AstNode AstNode { get; private set; }

    /// <summary>
    /// Maps original range variables to some node in the new tree that represents them.
    /// </summary>
    public IDictionary<Identifier, AstNode> RangeVariables { get; private set; }

    /// <summary>
    /// Maps clauses to method calls. The keys will always be either a <see cref="QueryClause"/> or a <see cref="QueryOrdering"/>
    /// </summary>
    public IDictionary<AstNode, Expression> Expressions { get; private set; }

    public QueryExpressionExpansionResult(AstNode astNode, IDictionary<Identifier, AstNode> rangeVariables, IDictionary<AstNode, Expression> expressions) {
      AstNode = astNode;
      RangeVariables = rangeVariables;
      Expressions = expressions;
    }
  }

  public class QueryExpressionExpander {
    class Visitor : DepthFirstAstVisitor<AstNode> {
      internal IEnumerator<string> TransparentIdentifierNamePicker;

      protected override AstNode VisitChildren(AstNode node) {
        List<AstNode> newChildren = null;
        
        int i = 0;
        foreach (var child in node.Children) {
          var newChild = child.AcceptVisitor(this);
          if (newChild != null) {
            newChildren = newChildren ?? Enumerable.Repeat((AstNode)null, i).ToList();
            newChildren.Add(newChild);
          }
          else if (newChildren != null) {
            newChildren.Add(null);
          }
          i++;
        }

        if (newChildren == null)
          return null;

        var result = node.Clone();

        i = 0;
        foreach (var children in result.Children) {
          if (newChildren[i] != null)
            children.ReplaceWith(newChildren[i]);
          i++;
        }

        return result;
      }

      Expression MakeNestedMemberAccess(Expression target, IEnumerable<string> members) {
        return members.Aggregate(target, (current, m) => current.Member(m));
      }

      Expression VisitNested(Expression node, ParameterDeclaration transparentParameter) {
        var oldRangeVariableSubstitutions = activeRangeVariableSubstitutions;
        try {
          if (transparentParameter != null && currentTransparentType.Count > 1) {
            activeRangeVariableSubstitutions = new Dictionary<string, Expression>(activeRangeVariableSubstitutions);
            foreach (var t in currentTransparentType)
              activeRangeVariableSubstitutions[t.Item1.Name] = MakeNestedMemberAccess(new IdentifierExpression(transparentParameter.Name), t.Item2);
          }
          var result = node.AcceptVisitor(this);
          return (Expression)(result ?? node.Clone());
        }
        finally {
          activeRangeVariableSubstitutions = oldRangeVariableSubstitutions;
        }
      }

      QueryClause GetNextQueryClause(QueryClause clause) {
        for (AstNode node = clause.NextSibling; node != null; node = node.NextSibling) {
          if (node.Role == QueryExpression.ClauseRole)
            return (QueryClause)node;
        }
        return null;
      }

      public IDictionary<Identifier, AstNode> rangeVariables = new Dictionary<Identifier, AstNode>();
      public IDictionary<AstNode, Expression> expressions = new Dictionary<AstNode, Expression>();

      Dictionary<string, Expression> activeRangeVariableSubstitutions = new Dictionary<string, Expression>();
      List<Tuple<Identifier, List<string>>> currentTransparentType = new List<Tuple<Identifier, List<string>>>();
      Expression currentResult;
      bool eatSelect;

      void MapExpression(AstNode orig, Expression newExpr) {
        Debug.Assert(orig is QueryClause || orig is QueryOrdering);
        expressions[orig] = newExpr;
      }

      internal static IEnumerable<string> FallbackTransparentIdentifierNamePicker()
      {
        const string TransparentParameterNameTemplate = "x{0}";
        int currentTransparentParameter = 0;
        for (;;) {
          yield return string.Format(CultureInfo.InvariantCulture, TransparentParameterNameTemplate, currentTransparentParameter++);
        }
      }

      ParameterDeclaration CreateParameterForCurrentRangeVariable() {
        var param = new ParameterDeclaration();

        if (currentTransparentType.Count == 1) {
          var clonedRangeVariable = (Identifier)currentTransparentType[0].Item1.Clone();
          if (!rangeVariables.ContainsKey(currentTransparentType[0].Item1))
            rangeVariables[currentTransparentType[0].Item1] = param;
          param.AddChild(clonedRangeVariable, Roles.Identifier);
        }
        else {
          if (!TransparentIdentifierNamePicker.MoveNext()) {
            TransparentIdentifierNamePicker = FallbackTransparentIdentifierNamePicker().GetEnumerator();
            TransparentIdentifierNamePicker.MoveNext();
          }
          string name = TransparentIdentifierNamePicker.Current;
          param.AddChild(Identifier.Create(name), Roles.Identifier);
        }
        return param;
      }

      LambdaExpression CreateLambda(IList<ParameterDeclaration> parameters, Expression body) {
        var result = new LambdaExpression();
        if (parameters.Count > 1)
          result.AddChild(new CSharpTokenNode(TextLocation.Empty, Roles.LPar), Roles.LPar);
        result.AddChild(parameters[0], Roles.Parameter);
        for (int i = 1; i < parameters.Count; i++) {
          result.AddChild(new CSharpTokenNode(TextLocation.Empty, Roles.Comma), Roles.Comma);
          result.AddChild(parameters[i], Roles.Parameter);
        }
        if (parameters.Count > 1)
          result.AddChild(new CSharpTokenNode(TextLocation.Empty, Roles.RPar), Roles.RPar);
        result.AddChild(body, LambdaExpression.BodyRole);

        return result;
      }

      ParameterDeclaration CreateParameter(Identifier identifier) {
        var result = new ParameterDeclaration();
        result.AddChild(identifier, Roles.Identifier);
        return result;
      }

      Expression AddMemberToCurrentTransparentType(ParameterDeclaration param, Identifier name, Expression value, bool namedExpression) {
        Expression newAssignment = VisitNested(value, param);
        if (namedExpression) {
          newAssignment = new NamedExpression(name.Name, VisitNested(value, param));
          if (!rangeVariables.ContainsKey(name) )
            rangeVariables[name] = ((NamedExpression)newAssignment).NameToken;
        }

        foreach (var t in currentTransparentType)
          t.Item2.Insert(0, param.Name);

        currentTransparentType.Add(Tuple.Create(name, new List<string> { name.Name }));
        return new AnonymousTypeCreateExpression(new[] { new IdentifierExpression(param.Name), newAssignment });
      }

      void AddFirstMemberToCurrentTransparentType(Identifier identifier) {
        Debug.Assert(currentTransparentType.Count == 0);
        currentTransparentType.Add(Tuple.Create(identifier, new List<string>()));
      }

      public override AstNode VisitQueryExpression(QueryExpression queryExpression) {
        var oldTransparentType = currentTransparentType;
        var oldResult = currentResult;
        var oldEatSelect = eatSelect;
        try {
          currentTransparentType = new List<Tuple<Identifier, List<string>>>();
          currentResult = null;
          eatSelect = false;

          foreach (var clause in queryExpression.Clauses) {
            var result = (Expression)clause.AcceptVisitor(this);
            MapExpression(clause, result ?? currentResult);
            currentResult = result;
          }

          return currentResult; 
        }
        finally {
          currentTransparentType = oldTransparentType;
          currentResult = oldResult;
          eatSelect = oldEatSelect;
        }
      }

      public override AstNode VisitQueryContinuationClause(QueryContinuationClause queryContinuationClause) {
        var prev = VisitNested(queryContinuationClause.PrecedingQuery, null);
        AddFirstMemberToCurrentTransparentType(queryContinuationClause.IdentifierToken);
        return prev;
      }

      static bool NeedsToBeParenthesized(Expression expr)
      {
        UnaryOperatorExpression unary = expr as UnaryOperatorExpression;
        if (unary != null) {
          if (unary.Operator == UnaryOperatorType.PostIncrement || unary.Operator == UnaryOperatorType.PostDecrement) {
            return false;
          }
          return true;
        }
      
        if (expr is BinaryOperatorExpression || expr is ConditionalExpression || expr is AssignmentExpression) {
          return true;
        }

        return false;
      }

      static Expression ParenthesizeIfNeeded(Expression expr)
      {
        return NeedsToBeParenthesized(expr) ? new ParenthesizedExpression(expr.Clone()) : expr;
      }

      public override AstNode VisitQueryFromClause(QueryFromClause queryFromClause) {
        if (currentResult == null) {
          AddFirstMemberToCurrentTransparentType(queryFromClause.IdentifierToken);
          if (queryFromClause.Type.IsNull) {
            return VisitNested(ParenthesizeIfNeeded(queryFromClause.Expression), null);
          }
          else {
            return VisitNested(ParenthesizeIfNeeded(queryFromClause.Expression), null).Invoke("Cast", new[] { queryFromClause.Type.Clone() }, new Expression[0]);
          }
        }
        else {
          var innerSelectorParam = CreateParameterForCurrentRangeVariable();
          var lambdaContent = VisitNested(queryFromClause.Expression, innerSelectorParam);
          if (!queryFromClause.Type.IsNull) {
            lambdaContent = lambdaContent.Invoke("Cast", new[] { queryFromClause.Type.Clone() }, new Expression[0]);
          }
          var innerSelector = CreateLambda(new[] { innerSelectorParam }, lambdaContent);

          var clonedIdentifier = (Identifier)queryFromClause.IdentifierToken.Clone();

          var resultParam = CreateParameterForCurrentRangeVariable();
          Expression body;
          // Second from clause - SelectMany
          var select = GetNextQueryClause(queryFromClause) as QuerySelectClause;
          if (select != null) {
            body = VisitNested(select.Expression, resultParam);
            eatSelect = true;
          }
          else {
            body = AddMemberToCurrentTransparentType(resultParam, queryFromClause.IdentifierToken, new IdentifierExpression(queryFromClause.Identifier), false);
          }

          var resultSelectorParam2 = CreateParameter(clonedIdentifier);
          var resultSelector = CreateLambda(new[] { resultParam, resultSelectorParam2 }, body);
          rangeVariables[queryFromClause.IdentifierToken] = resultSelectorParam2;

          return currentResult.Invoke("SelectMany", innerSelector, resultSelector);
        }
      }

      public override AstNode VisitQueryLetClause(QueryLetClause queryLetClause) {
        var param = CreateParameterForCurrentRangeVariable();
        var body = AddMemberToCurrentTransparentType(param, queryLetClause.IdentifierToken, queryLetClause.Expression, true);
        var lambda = CreateLambda(new[] { param }, body);

        return currentResult.Invoke("Select", lambda);
      }

      public override AstNode VisitQueryWhereClause(QueryWhereClause queryWhereClause) {
        var param = CreateParameterForCurrentRangeVariable();
        return currentResult.Invoke("Where", CreateLambda(new[] { param }, VisitNested(queryWhereClause.Condition, param)));
      }

      public override AstNode VisitQueryJoinClause(QueryJoinClause queryJoinClause) {
        Expression resultSelectorBody = null;
        var inExpression = VisitNested(queryJoinClause.InExpression, null);
        if (!queryJoinClause.Type.IsNull) {
          inExpression = inExpression.Invoke("Cast", new[] { queryJoinClause.Type.Clone() }, EmptyList<Expression>.Instance);
        }
        var key1SelectorFirstParam = CreateParameterForCurrentRangeVariable();
        var key1Selector = CreateLambda(new[] { key1SelectorFirstParam }, VisitNested(queryJoinClause.OnExpression, key1SelectorFirstParam));
        var key2Param = CreateParameter(Identifier.Create(queryJoinClause.JoinIdentifier));
        var key2Selector = CreateLambda(new[] { key2Param }, VisitNested(queryJoinClause.EqualsExpression, null));

        var resultSelectorFirstParam = CreateParameterForCurrentRangeVariable();

        var select = GetNextQueryClause(queryJoinClause) as QuerySelectClause;
        if (select != null) {
          resultSelectorBody = VisitNested(select.Expression, resultSelectorFirstParam);
          eatSelect = true;
        }

        if (queryJoinClause.IntoKeyword.IsNull) {
          // Normal join
          if (resultSelectorBody == null)
            resultSelectorBody = AddMemberToCurrentTransparentType(resultSelectorFirstParam, queryJoinClause.JoinIdentifierToken, new IdentifierExpression(queryJoinClause.JoinIdentifier), false);

          var resultSelector = CreateLambda(new[] { resultSelectorFirstParam, CreateParameter(Identifier.Create(queryJoinClause.JoinIdentifier)) }, resultSelectorBody);
          rangeVariables[queryJoinClause.JoinIdentifierToken] = key2Param;
          return currentResult.Invoke("Join", inExpression, key1Selector, key2Selector, resultSelector);
        }
        else {
          // Group join
          if (resultSelectorBody == null)
            resultSelectorBody = AddMemberToCurrentTransparentType(resultSelectorFirstParam, queryJoinClause.IntoIdentifierToken, new IdentifierExpression(queryJoinClause.IntoIdentifier), false);

          var intoParam = CreateParameter(Identifier.Create(queryJoinClause.IntoIdentifier));
          var resultSelector = CreateLambda(new[] { resultSelectorFirstParam, intoParam }, resultSelectorBody);
          rangeVariables[queryJoinClause.IntoIdentifierToken] = intoParam;

          return currentResult.Invoke("GroupJoin", inExpression, key1Selector, key2Selector, resultSelector);
        }
      }

      public override AstNode VisitQueryOrderClause(QueryOrderClause queryOrderClause) {
        var current = currentResult;
        bool first = true;
        foreach (var o in queryOrderClause.Orderings) {
          string methodName = first ? (o.Direction == QueryOrderingDirection.Descending ? "OrderByDescending" : "OrderBy")
                                    : (o.Direction == QueryOrderingDirection.Descending ? "ThenByDescending" : "ThenBy");

          var param = CreateParameterForCurrentRangeVariable();
          current = current.Invoke(methodName, CreateLambda(new[] { param }, VisitNested(o.Expression, param)));
          MapExpression(o, current);
          first = false;
        }
        return current;
      }

      bool IsSingleRangeVariable(Expression expr) {
        if (currentTransparentType.Count > 1)
          return false;
        var unpacked = ParenthesizedExpression.UnpackParenthesizedExpression(expr);
        return unpacked is IdentifierExpression && ((IdentifierExpression)unpacked).Identifier == currentTransparentType[0].Item1.Name;
      }

      public override AstNode VisitQuerySelectClause(QuerySelectClause querySelectClause) {
        if (eatSelect) {
          eatSelect = false;
          return currentResult;
        }
        else if (((QueryExpression)querySelectClause.Parent).Clauses.Count > 2 && IsSingleRangeVariable(querySelectClause.Expression)) {
          // A simple query that ends with a trivial select should be removed.
          return currentResult;
        }

        var param = CreateParameterForCurrentRangeVariable();
        var lambda = CreateLambda(new[] { param }, VisitNested(querySelectClause.Expression, param));
        return currentResult.Invoke("Select", lambda);
      }

      public override AstNode VisitQueryGroupClause(QueryGroupClause queryGroupClause) {
        var param = CreateParameterForCurrentRangeVariable();
        var keyLambda = CreateLambda(new[] { param }, VisitNested(queryGroupClause.Key, param));

        if (IsSingleRangeVariable(queryGroupClause.Projection)) {
          // We are grouping by the single active range variable, so we can use the single argument form of GroupBy
          return currentResult.Invoke("GroupBy", keyLambda);
        }
        else {
          var projectionParam = CreateParameterForCurrentRangeVariable();
          var projectionLambda = CreateLambda(new[] { projectionParam }, VisitNested(queryGroupClause.Projection, projectionParam));
          return currentResult.Invoke("GroupBy", keyLambda, projectionLambda);
        }
      }

      public override AstNode VisitIdentifierExpression(IdentifierExpression identifierExpression) {
        Expression subst;
        activeRangeVariableSubstitutions.TryGetValue(identifierExpression.Identifier, out subst);
        return subst != null ? subst.Clone() : null;
      }
    }

    /// <summary>
    /// Expands all occurances of query patterns in the specified node. Returns a clone of the node with all query patterns expanded, or null if there was no query pattern to expand.
    /// </summary>
    /// <param name="node"></param>
    /// <param name="transparentIdentifierNamePicker">A sequence of names to use for transparent identifiers. Once the sequence is over, a fallback name generator is used</param> 
    /// <returns></returns>
    public QueryExpressionExpansionResult ExpandQueryExpressions(AstNode node, IEnumerable<string> transparentIdentifierNamePicker) {
      var visitor = new Visitor();
      visitor.TransparentIdentifierNamePicker = transparentIdentifierNamePicker.GetEnumerator();
      var astNode = node.AcceptVisitor(visitor);
      if (astNode != null) {
        astNode.Freeze();
        return new QueryExpressionExpansionResult(astNode, visitor.rangeVariables, visitor.expressions);
      }
      else {
        return null;
      }
    }

    
    /// <summary>
    /// Expands all occurances of query patterns in the specified node. Returns a clone of the node with all query patterns expanded, or null if there was no query pattern to expand.
    /// </summary>
    /// <param name="node"></param>
    /// <returns></returns>
    public QueryExpressionExpansionResult ExpandQueryExpressions(AstNode node)
    {
      return ExpandQueryExpressions(node, Enumerable.Empty<string>());
    }
  }
}