/* Expression 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.
 *
 * $Id$
 */

package net.sf.jode.expr;
import net.sf.jode.type.Type;
import net.sf.jode.GlobalOptions;
import net.sf.jode.decompiler.TabbedPrintWriter;

///#def COLLECTIONS java.util
import java.util.Collection;
import java.util.Set;
///#enddef

public abstract class Expression {
    protected Type type;

    Operator parent = null;

    public Expression(Type type) {
        this.type = type;
    }

    public void setType(Type otherType) {
	Type newType = otherType.intersection(type);
	if (type.equals(newType))
	    return;
	if (newType == Type.tError && otherType != Type.tError) {
	    GlobalOptions.err.println("setType: Type error in "+this
				      +": merging "+type+" and "+otherType);
	    if (parent != null)
		GlobalOptions.err.println("\tparent is "+parent);
	    if ((GlobalOptions.debuggingFlags
		 & GlobalOptions.DEBUG_TYPES) != 0)
		Thread.dumpStack();
	}
	type = newType;
	if (type != Type.tError)
	    updateSubTypes();
    }

    public void updateParentType(Type otherType) {
	setType(otherType);
	if (parent != null)
	    parent.updateType();
    }

    /**
     * Tells an expression that an inner expression may have changed and
     * that the type should be recalculated.
     * 
     * This may call setType of the caller again.
     */
    public abstract void updateType();

    /**
     * Tells an expression that an outer expression has changed our type
     * and that the inner types should be recalculated.
     */
    public abstract void updateSubTypes();

    public Type getType() {
        return type;
    }

    public Operator getParent() {
        return parent;
    }

    /**
     * Get priority of the operator.
     * Currently this priorities are known:
     * <ul><li> 1000 constant
     * </li><li> 950 new, .(field access), []
     * </li><li> 900 new[]
     * </li><li> 800 ++,-- (post)
     * </li><li> 700 ++,--(pre), +,-(unary), ~, !, cast
     * </li><li> 650 *,/, % 
     * </li><li> 610 +,-
     * </li><li> 600 <<, >>, >>> 
     * </li><li> 550 >, <, >=, <=, instanceof
     * </li><li> 500 ==, != 
     * </li><li> 450 & 
     * </li><li> 420 ^ 
     * </li><li> 410 | 
     * </li><li> 350 && 
     * </li><li> 310 || 
     * </li><li> 200 ?:
     * </li><li> 100 =, +=, -=, etc.
     * </li></ul>
     */
    public abstract int getPriority();

    /**
     * Get the penalty for splitting up this operator.
     */
    public int getBreakPenalty() {
	return 0;
    }

    /**
     * Get the number of operands.
     * @return The number of stack entries this expression needs.
     */
    public abstract int getFreeOperandCount();

    public abstract Expression addOperand(Expression op);

    public Expression negate() {
        Operator negop = 
            new UnaryOperator(Type.tBoolean, Operator.LOG_NOT_OP);
	negop.addOperand(this);
	return negop;
    }

    /**
     * Checks if the value of the given expression can change, due to
     * side effects in this expression.  If this returns false, the 
     * expression can safely be moved behind the current expresion.
     * @param expr the expression that should not change.
     */
    public boolean hasSideEffects(Expression expr) {
	return false;
    }

    /**
     * Checks if the given Expression (which should be a CombineableOperator)
     * can be combined into this expression.
     * @param e The store expression, must be of type void.
     * @return 1, if it can, 0, if no match was found and -1, if a
     * conflict was found.  You may wish to check for >0.
     */
    public int canCombine(CombineableOperator combOp) {
	return 0;
    }

    /**
     * Checks if this expression contains a load, that matches the
     * given CombineableOperator (which must be an Operator)
     * @param e The store expression.
     * @return if this expression contains a matching load.
     * @exception ClassCastException, if e.getOperator 
     * is not a CombineableOperator.
     */
    public boolean containsMatchingLoad(CombineableOperator e) {
	return false;
    }

    /**
     * Checks if this expression contains a conflicting load, that
     * matches the given CombineableOperator.  The sub expressions are
     * not checked.
     * @param op The combineable operator.
     * @return if this expression contains a matching load.  */
    public boolean containsConflictingLoad(MatchableOperator op) {
        return false;
    }

    /**
     * Combines the given Expression (which should be a StoreInstruction)
     * into this expression.  You must only call this if
     * canCombine returns the value 1.
     * @param e The store expression, 
     * the operator must be a CombineableOperator.
     * @return The combined expression.
     * @exception ClassCastException, if e.getOperator 
     * is not a CombineableOperator.
     */
    public Expression combine(CombineableOperator comb) {
        return null;
    }

    /** 
     * This method should remove local variables that are only written
     * and read one time directly after another.  <br>
     *
     * In this case this is a non void LocalStoreOperator, whose local
     * isn't used in other places.
     * @return an expression where the locals are removed.
     */
    public Expression removeOnetimeLocals() {
	return this;
    }

    public Expression simplify() {
        return this;
    }
    public Expression simplifyString() {
        return this;
    }

    public static Expression EMPTYSTRING = new ConstOperator("");

    public Expression simplifyStringBuffer() {
        return null;
    }

    public void makeInitializer(Type type) {
    }

    public boolean isConstant() {
        return true;
    }

    public void fillInGenSet(Collection in, Collection gen) {
    }

    public void fillDeclarables(Collection used) {
    }

    public void makeDeclaration(Set done) {
    }

    public abstract void dumpExpression(TabbedPrintWriter writer) 
	throws java.io.IOException;

    public void dumpExpression(int options, TabbedPrintWriter writer)
	throws java.io.IOException 
    {
	writer.startOp(options, getBreakPenalty());
	dumpExpression(writer);
	writer.endOp();
    }

    public void dumpExpression(TabbedPrintWriter writer, int minPriority)
	throws java.io.IOException {
	boolean needParen1 = false, needParen2 = false;
	boolean needEndOp1 = false, needEndOp2 = false;

	String typecast = "";

	if (type == Type.tError)
	    typecast = "/*TYPE_ERROR*/";
	else if ((GlobalOptions.debuggingFlags
		  & GlobalOptions.DEBUG_TYPES) != 0)
	    typecast = "(TYPE "+type+")";

	if (typecast != "") {
	    if (minPriority > 700) {
		needParen1 = true;
		needEndOp1 = true;
		writer.print("(");
		writer.startOp(TabbedPrintWriter.EXPL_PAREN, 0);
	    } else if (minPriority < 700) {
		needEndOp1 = true;
		writer.startOp(TabbedPrintWriter.IMPL_PAREN, 1);
	    }
	    writer.print(typecast);
	    writer.breakOp();
	    writer.print(" ");
	    minPriority = 700;
	}

	int priority = getPriority();
	if (priority < minPriority) {
	    needParen2 = true;
	    needEndOp2 = true;
	    writer.print("(");
	    writer.startOp(TabbedPrintWriter.EXPL_PAREN, getBreakPenalty());
	} else if (priority != minPriority) {
	    needEndOp2 = true;
	    if (getType() == Type.tVoid)
		writer.startOp(TabbedPrintWriter.NO_PAREN, getBreakPenalty());
	    else
		writer.startOp(TabbedPrintWriter.IMPL_PAREN, 1 + getBreakPenalty());
	}

	try {
	    dumpExpression(writer);
	} catch (RuntimeException ex) {
	    writer.print("(RUNTIME ERROR IN EXPRESSION)");
	    ex.printStackTrace();
	}

	if (needEndOp2) {
	    writer.endOp();
	    if (needParen2)
		writer.print(")");
	}
	if (needEndOp1) {
	    writer.endOp();
	    if (needParen1)
		writer.print(")");
	}
    }

    public String toString() {
	try {
	    java.io.StringWriter strw = new java.io.StringWriter();
	    TabbedPrintWriter writer = new TabbedPrintWriter(strw);
	    dumpExpression(writer);
	    writer.close();
	    return strw.toString();
	} catch (java.io.IOException ex) {
	    return "/*IOException*/"+super.toString();
	} catch (RuntimeException ex) {
	    return "/*RuntimeException*/"+super.toString();
	}
    }	

    public boolean isVoid() {
        return getType() == Type.tVoid;
    }
}