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//
// ConvertSwitchToIfAction.cs
//
// Author:
// Mansheng Yang <lightyang0@gmail.com>
//
// Copyright (c) 2012 Mansheng Yang <lightyang0@gmail.com>
//
// 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.Linq;
namespace ICSharpCode.NRefactory.CSharp.Refactoring
{
[ContextAction ("Convert 'switch' to 'if'", Description = "Convert 'switch' statement to 'if' statement")]
public class ConvertSwitchToIfAction : SpecializedCodeAction<SwitchStatement>
{
static readonly InsertParenthesesVisitor insertParenthesesVisitor = new InsertParenthesesVisitor ();
protected override CodeAction GetAction (RefactoringContext context, SwitchStatement node)
{
if (!node.SwitchToken.Contains (context.Location))
return null;
// empty switch
if (node.SwitchSections.Count == 0)
return null;
// switch with default only
if (node.SwitchSections.First ().CaseLabels.Any (label => label.Expression.IsNull))
return null;
// check non-trailing breaks
foreach (var switchSection in node.SwitchSections) {
var lastStatement = switchSection.Statements.LastOrDefault ();
var finder = new NonTrailingBreakFinder (lastStatement as BreakStatement);
if (switchSection.AcceptVisitor (finder))
return null;
}
return new CodeAction (context.TranslateString ("Convert 'switch' to 'if'"),
script =>
{
IfElseStatement ifStatement = null;
IfElseStatement currentStatement = null;
foreach (var switchSection in node.SwitchSections) {
var condition = CollectCondition (node.Expression, switchSection.CaseLabels);
var bodyStatement = new BlockStatement ();
var lastStatement = switchSection.Statements.LastOrDefault ();
foreach (var statement in switchSection.Statements) {
// skip trailing break
if (statement == lastStatement && statement is BreakStatement)
continue;
bodyStatement.Add (statement.Clone ());
}
// default -> else
if (condition == null) {
currentStatement.FalseStatement = bodyStatement;
break;
}
var elseIfStatement = new IfElseStatement (condition, bodyStatement);
if (ifStatement == null)
ifStatement = elseIfStatement;
else
currentStatement.FalseStatement = elseIfStatement;
currentStatement = elseIfStatement;
}
script.Replace (node, ifStatement);
script.FormatText (ifStatement);
}, node);
}
static Expression CollectCondition(Expression switchExpr, AstNodeCollection<CaseLabel> caseLabels)
{
// default
if (caseLabels.Count == 0 || caseLabels.Any (label => label.Expression.IsNull))
return null;
var conditionList = caseLabels.Select (
label => new BinaryOperatorExpression (switchExpr.Clone (), BinaryOperatorType.Equality, label.Expression.Clone ()))
.ToArray ();
// insert necessary parentheses
foreach (var expr in conditionList)
expr.AcceptVisitor (insertParenthesesVisitor);
if (conditionList.Length == 1)
return conditionList [0];
// combine case labels into an conditional or expression
BinaryOperatorExpression condition = null;
BinaryOperatorExpression currentCondition = null;
for (int i = 0; i < conditionList.Length - 1; i++) {
var newCondition = new BinaryOperatorExpression
{
Operator = BinaryOperatorType.ConditionalOr,
Left = conditionList[i]
};
if (currentCondition == null)
condition = newCondition;
else
currentCondition.Right = newCondition;
currentCondition = newCondition;
}
currentCondition.Right = conditionList [conditionList.Length - 1];
return condition;
}
class NonTrailingBreakFinder : DepthFirstAstVisitor<bool>
{
BreakStatement trailingBreakStatement;
public NonTrailingBreakFinder (BreakStatement trailingBreak)
{
trailingBreakStatement = trailingBreak;
}
protected override bool VisitChildren (AstNode node)
{
return node.Children.Any (child => child.AcceptVisitor (this));
}
public override bool VisitBreakStatement (BreakStatement breakStatement)
{
return breakStatement != trailingBreakStatement;
}
}
}
}
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