OoasTools

/**

  *

  *                      OOAS Compiler

  *

  *       Copyright 2015, AIT Austrian Institute of Technology.

  * This code is based on the C# Version of the OOAS Compiler, which is

  * copyright 2015 by the Institute of Software Technology, Graz University

  * of Technology with portions copyright by the AIT Austrian Institute of

  * Technology. All rights reserved.

  *

  * SEE THE "LICENSE" FILE FOR THE TERMS UNDER WHICH THIS FILE IS PROVIDED.

  *

  * If you modify the file please update the list of contributors below to in-

  * clude your name. Please also stick to the coding convention of using TABs

  * to do the basic (block-level) indentation and spaces for anything after

  * that. (Enable the display of special chars and it should be pretty obvious

  * what this means.) Also, remove all trailing whitespace.

  *

  * Contributors:

  *               Willibald Krenn (AIT)

  *               Stephan Zimmerer (AIT)

  *               Markus Demetz (AIT)

  *               Christoph Czurda (AIT)

  *

  */

package org.momut.ooas.visitors.optimisation;

import org.momut.ooas.utils.exceptions.InternalCompilerException;

/**

 * Removes Seq blocks that only have one element...

 * @author KrennW

 */

public final class OoaRemoveTrivialSequentialCompositionVisitor extends OoaCompleteAstTraversalVisitor {

	private void setNewParent(Statement s, final IScope oldScope,final IScope newParentScope) {

		class ParentScopeVis extends OoaCompleteAstTraversalVisitor {

			@Override

			protected void VisitAstElement(IAst element, IAst parent) {

				if (element instanceof IScope) {

					final IScope scope = (IScope) element;

					if (scope.GetParentScope() == oldScope)

						scope.SetParentScope(newParentScope);

				}

				super.VisitAstElement(element, parent);

			}

			public ParentScopeVis() {

				super(null);

			}

		}

		if (s instanceof IScope)

			((IScope)s).SetParentScope(newParentScope);

		final ParentScopeVis visitor = new ParentScopeVis();

		s.Accept(visitor);

	}

	/// <summary>

	/// replaces the seqBlock by its child

	/// </summary>

	private IAst ConvertNondetBlock(SeqBlock seqBlock, IAst parent)

	{

		if (seqBlock.statements().size() <= 1 &&            // max one statement in block

		    seqBlock.isSimpleBlock() &&                     // block must not have local vars etc.

		    parent.nodeType() !=  AstNodeTypeEnum.type)     // we cannot simplify if block is owned by an OoActionSystem since dood always is a block

		{

			final Statement stmt = seqBlock.statements().peekFirst();

			setNewParent(stmt, seqBlock, seqBlock.GetParentScope()); // change AST and correct all parentscope pointers to this seqblock

			switch (parent.nodeType())

			{

			case statement:

				switch (((Statement)parent).kind())

				{

				case SeqBlock:

				case NondetBlock:

				case PrioBlock:

					final Block aBlock = (Block)parent;

					final int idx = aBlock.statements().indexOf(seqBlock);

					if (idx == -1)

						throw new OoasCompilerRuntimeException(); // must not happen?!

					aBlock.statements().set(idx, stmt);

					break;

				case GuardedCommand:

					final GuardedCommand gc = (GuardedCommand)parent;

					if(gc.body() != seqBlock) // ref equ.

						throw new InternalCompilerException("Internal Error: Cannot replace guarded command body.");

					gc.SetBody(stmt);

					break;

				default:

					throw new NotImplementedException();

				}

				break;

			case identifier:

				switch (((Identifier)parent).kind())

				{

				case NamedActionIdentifier:

				case MethodIdentifier:

					final FunctionIdentifier method = (FunctionIdentifier)parent;

					if (method.body() != seqBlock) // ref equ.

						throw new InternalCompilerException("Internal Error: Cannot replace method body.");

					method.SetBody(stmt);

					break;

				default:

					throw new NotImplementedException();

				}

				break;

			default:

				throw new NotImplementedException();

			}

			m_changes = true;

			return stmt;

		}

		else

			return seqBlock;

	}

	@Override

	protected void VisitAstElement(IAst element, IAst parent)

	{

		if ( (element.nodeType() == AstNodeTypeEnum.statement) &&

		     (((Statement)element).kind() == StatementKind.SeqBlock) &&

		      // we're only interested in actionblock and actionbody composition, not in type composition

		     !(parent.nodeType() == AstNodeTypeEnum.identifier &&

		       ((Identifier)parent).kind() == IdentifierKind.List))

		{

			final IAst newchild = ConvertNondetBlock((SeqBlock)element, parent);

			super.VisitAstElement(newchild, parent);

		}

		else

			super.VisitAstElement(element, parent);

	}

	private boolean m_changes = false;

	public OoaRemoveTrivialSequentialCompositionVisitor(ParserState aState)

	{

		super (aState);

	}

	public boolean changedAst() {

		return m_changes;

	}

}