/*
 * Copyright © 2011, Petro Protsyk, Denys Vuika
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *  http://www.apache.org/licenses/LICENSE-2.0
 *  
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

using System.Collections.Generic;

namespace Scripting.SSharp.Execution.Compilers
{
  using Dom;
  using VM;

  [CompilerType(typeof(CodeSwitchStatement))]
  internal class CodeSwitchStatementCompiler : IVMCompiler
  {
    #region IVMCompiler Members
    private static long _sid;

    public ExecutableMachine Compile(CodeObject code, ExecutableMachine machine)
    {
      var codeSwitch = (CodeSwitchStatement)code;

      //switch(a) { case c1 : s1; case c2 : s2; default : s3 }
      //~
      //switch_expr = a;
      //if (a == c1) s1
      //else if (a == c2) s2
      //else s3

      _sid++;

      var block = new CodeBlockStatement { SourceSpan = codeSwitch.SourceSpan };

      var switchExpr = new CodeAssignExpression(
        "#switch_"+_sid, codeSwitch.Expression);
         
      var ifStatement = BuildNextIf(codeSwitch.Cases, 0);

      block.Statements.Add(new CodeExpressionStatement(switchExpr));
      block.Statements.Add(ifStatement);

      CodeDomCompiler.Compile(block, machine);

      return machine;
    }

    private static CodeStatement BuildNextIf(IList<CodeSwitchCase> list, int index)
    {
      if (index < 0 || list.Count <= index) return null;

      var current = list[index];

      //Default case
      if (current.Condition == null) return current.Statement;

      CodeStatement next = new CodeIfStatement(
        new CodeBinaryOperator { Left = new CodeVariableReference("#switch_" + _sid), Right = current.Condition, Type = OperatorType.Eq },
        current.Statement,
        BuildNextIf(list, index + 1));

      return next;
    }


    #endregion
  }
}