/* IfThenElseBlock Copyright (C) 1998-2002 Jochen Hoenicke.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; see the file COPYING.LESSER.  If not, write to
 * the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 * $Id: IfThenElseBlock.java.in,v 4.3.2.1 2002/05/28 17:34:09 hoenicke Exp $
 */

package alterrs.jode.flow;

import java.util.Set;

import alterrs.jode.decompiler.TabbedPrintWriter;
import alterrs.jode.expr.Expression;
import alterrs.jode.util.SimpleSet;

/**
 * An IfThenElseBlock is the structured block representing an if instruction.
 * The else part may be null.
 */
public class IfThenElseBlock extends StructuredBlock {

	/**
	 * The condition. Must be of boolean type.
	 */
	Expression cond;
	/**
	 * The loads that are on the stack before cond is executed.
	 */
	VariableStack condStack;

	/**
	 * The then part. This is always a valid block and not null
	 */
	StructuredBlock thenBlock;

	/**
	 * The else part, may be null, and mustn't be the then part.
	 */
	StructuredBlock elseBlock;

	/**
	 * Creates a new if then else block. The method setThenBlock must be called
	 * shortly after the creation.
	 */
	public IfThenElseBlock(Expression cond) {
		this.cond = cond;
	}

	/**
	 * Sets the then block.
	 * 
	 * @param thenBlock
	 *            the then block, must be non null.
	 */
	public void setThenBlock(StructuredBlock thenBlock) {
		this.thenBlock = thenBlock;
		thenBlock.outer = this;
		thenBlock.setFlowBlock(flowBlock);
	}

	/**
	 * Sets the else block.
	 * 
	 * @param elseBlock
	 *            the else block
	 */
	public void setElseBlock(StructuredBlock elseBlock) {
		this.elseBlock = elseBlock;
		elseBlock.outer = this;
		elseBlock.setFlowBlock(flowBlock);
	}

	/*
	 * The implementation of getNext[Flow]Block is the standard implementation
	 */

	/**
	 * Replaces the given sub block with a new block.
	 * 
	 * @param oldBlock
	 *            the old sub block.
	 * @param newBlock
	 *            the new sub block.
	 * @return false, if oldBlock wasn't a direct sub block.
	 */
	public boolean replaceSubBlock(StructuredBlock oldBlock,
			StructuredBlock newBlock) {
		if (thenBlock == oldBlock)
			thenBlock = newBlock;
		else if (elseBlock == oldBlock)
			elseBlock = newBlock;
		else
			return false;
		return true;
	}

	/**
	 * This does take the instr into account and modifies stack accordingly. It
	 * then calls super.mapStackToLocal.
	 * 
	 * @param stack
	 *            the stack before the instruction is called
	 * @return stack the stack afterwards.
	 */
	public VariableStack mapStackToLocal(VariableStack stack) {
		VariableStack newStack;
		int params = cond.getFreeOperandCount();
		if (params > 0) {
			condStack = stack.peek(params);
			newStack = stack.pop(params);
		} else
			newStack = stack;

		VariableStack after = VariableStack.merge(thenBlock
				.mapStackToLocal(newStack), elseBlock == null ? newStack
				: elseBlock.mapStackToLocal(newStack));
		if (jump != null) {
			jump.stackMap = after;
			return null;
		}
		return after;
	}

	public void removePush() {
		if (condStack != null)
			cond = condStack.mergeIntoExpression(cond);
		thenBlock.removePush();
		if (elseBlock != null)
			elseBlock.removePush();
	}

	public Set getDeclarables() {
		Set used = new SimpleSet();
		cond.fillDeclarables(used);
		return used;
	}

	/**
	 * Make the declarations, i.e. initialize the declare variable to correct
	 * values. This will declare every variable that is marked as used, but not
	 * done.<br>
	 * <p/>
	 * This will now also combine locals, that use the same slot, have
	 * compatible types and are declared in the same block. <br>
	 * 
	 * @param done
	 *            The set of the already declare variables.
	 */
	public void makeDeclaration(Set done) {
		cond.makeDeclaration(done);
		super.makeDeclaration(done);
	}

	/**
	 * Print the source code for this structured block. This may be called only
	 * once, because it remembers which local variables were declared.
	 */
	public void dumpInstruction(TabbedPrintWriter writer)
			throws java.io.IOException {
		boolean needBrace = thenBlock.needsBraces();
		writer.print("if (");
		cond.dumpExpression(writer.EXPL_PAREN, writer);
		writer.print(")");
		if (needBrace)
			writer.openBrace();
		else
			writer.println();
		writer.tab();
		thenBlock.dumpSource(writer);
		writer.untab();
		if (elseBlock != null) {
			if (needBrace)
				writer.closeBraceContinue();

			if (elseBlock instanceof IfThenElseBlock
					&& (elseBlock.declare == null || elseBlock.declare
							.isEmpty())) {
				needBrace = false;
				writer.print("else ");
				elseBlock.dumpSource(writer);
			} else {
				needBrace = elseBlock.needsBraces();
				writer.print("else");
				if (needBrace)
					writer.openBrace();
				else
					writer.println();
				writer.tab();
				elseBlock.dumpSource(writer);
				writer.untab();
			}
		}
		if (needBrace)
			writer.closeBrace();
	}

	/**
	 * Returns all sub block of this structured block.
	 */
	public StructuredBlock[] getSubBlocks() {
		return (elseBlock == null) ? new StructuredBlock[] { thenBlock }
				: new StructuredBlock[] { thenBlock, elseBlock };
	}

	/**
	 * Determines if there is a sub block, that flows through to the end of this
	 * block. If this returns true, you know that jump is null.
	 * 
	 * @return true, if the jump may be safely changed.
	 */
	public boolean jumpMayBeChanged() {
		return (thenBlock.jump != null || thenBlock.jumpMayBeChanged())
				&& elseBlock != null
				&& (elseBlock.jump != null || elseBlock.jumpMayBeChanged());
	}

	public void simplify() {
		cond = cond.simplify();
		super.simplify();
	}

	public boolean doTransformations() {
		StructuredBlock last = flowBlock.lastModified;
		return CreateCheckNull.transformJikes(this, last)
				|| CreateClassField.transform(this, last);
	}
}
