/*******************************************************************************
 * Copyright (c) 2000, 2001, 2002 International Business Machines Corp. and others.
 * All rights reserved. This program and the accompanying materials 
 * are made available under the terms of the Common Public License v0.5 
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/cpl-v05.html
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 ******************************************************************************/
package net.sourceforge.phpdt.internal.compiler.ast;

import net.sourceforge.phpdt.internal.compiler.impl.*;
import net.sourceforge.phpdt.internal.compiler.codegen.*;
import net.sourceforge.phpdt.internal.compiler.flow.*;
import net.sourceforge.phpdt.internal.compiler.lookup.*;
import net.sourceforge.phpdt.internal.compiler.problem.*;
import net.sourceforge.phpdt.internal.compiler.util.Util;

public abstract class Expression extends Statement {
	
	//some expression may not be used - from a java semantic point
	//of view only - as statements. Other may. In order to avoid the creation
	//of wrappers around expression in order to tune them as expression
	//Expression is a subclass of Statement. See the message isValidJavaStatement()

	public int implicitConversion;

	public Constant constant;

	public Expression() {
		super();
	}

	public FlowInfo analyseCode(
		BlockScope currentScope,
		FlowContext flowContext,
		FlowInfo flowInfo,
		boolean valueRequired) {

		return analyseCode(currentScope, flowContext, flowInfo);
	}

	public Constant conditionalConstant() {

		return constant;
	}

	public static final boolean isConstantValueRepresentable(
		Constant constant,
		int constantTypeID,
		int targetTypeID) {

		//true if there is no loss of precision while casting.
		// constantTypeID == constant.typeID
		if (targetTypeID == constantTypeID)
			return true;
		switch (targetTypeID) {
			case T_char :
				switch (constantTypeID) {
					case T_char :
						return true;
					case T_double :
						return constant.doubleValue() == constant.charValue();
					case T_float :
						return constant.floatValue() == constant.charValue();
					case T_int :
						return constant.intValue() == constant.charValue();
					case T_short :
						return constant.shortValue() == constant.charValue();
					case T_byte :
						return constant.byteValue() == constant.charValue();
					case T_long :
						return constant.longValue() == constant.charValue();
					default :
						return false;//boolean
				} 

			case T_float :
				switch (constantTypeID) {
					case T_char :
						return constant.charValue() == constant.floatValue();
					case T_double :
						return constant.doubleValue() == constant.floatValue();
					case T_float :
						return true;
					case T_int :
						return constant.intValue() == constant.floatValue();
					case T_short :
						return constant.shortValue() == constant.floatValue();
					case T_byte :
						return constant.byteValue() == constant.floatValue();
					case T_long :
						return constant.longValue() == constant.floatValue();
					default :
						return false;//boolean
				} 
				
			case T_double :
				switch (constantTypeID) {
					case T_char :
						return constant.charValue() == constant.doubleValue();
					case T_double :
						return true;
					case T_float :
						return constant.floatValue() == constant.doubleValue();
					case T_int :
						return constant.intValue() == constant.doubleValue();
					case T_short :
						return constant.shortValue() == constant.doubleValue();
					case T_byte :
						return constant.byteValue() == constant.doubleValue();
					case T_long :
						return constant.longValue() == constant.doubleValue();
					default :
						return false; //boolean
				} 
				
			case T_byte :
				switch (constantTypeID) {
					case T_char :
						return constant.charValue() == constant.byteValue();
					case T_double :
						return constant.doubleValue() == constant.byteValue();
					case T_float :
						return constant.floatValue() == constant.byteValue();
					case T_int :
						return constant.intValue() == constant.byteValue();
					case T_short :
						return constant.shortValue() == constant.byteValue();
					case T_byte :
						return true;
					case T_long :
						return constant.longValue() == constant.byteValue();
					default :
						return false; //boolean
				} 
				
			case T_short :
				switch (constantTypeID) {
					case T_char :
						return constant.charValue() == constant.shortValue();
					case T_double :
						return constant.doubleValue() == constant.shortValue();
					case T_float :
						return constant.floatValue() == constant.shortValue();
					case T_int :
						return constant.intValue() == constant.shortValue();
					case T_short :
						return true;
					case T_byte :
						return constant.byteValue() == constant.shortValue();
					case T_long :
						return constant.longValue() == constant.shortValue();
					default :
						return false; //boolean
				} 
				
			case T_int :
				switch (constantTypeID) {
					case T_char :
						return constant.charValue() == constant.intValue();
					case T_double :
						return constant.doubleValue() == constant.intValue();
					case T_float :
						return constant.floatValue() == constant.intValue();
					case T_int :
						return true;
					case T_short :
						return constant.shortValue() == constant.intValue();
					case T_byte :
						return constant.byteValue() == constant.intValue();
					case T_long :
						return constant.longValue() == constant.intValue();
					default :
						return false; //boolean
				} 
				
			case T_long :
				switch (constantTypeID) {
					case T_char :
						return constant.charValue() == constant.longValue();
					case T_double :
						return constant.doubleValue() == constant.longValue();
					case T_float :
						return constant.floatValue() == constant.longValue();
					case T_int :
						return constant.intValue() == constant.longValue();
					case T_short :
						return constant.shortValue() == constant.longValue();
					case T_byte :
						return constant.byteValue() == constant.longValue();
					case T_long :
						return true;
					default :
						return false; //boolean
				} 
				
			default :
				return false; //boolean
		} 
	}

	/**
	 * Expression statements are plain expressions, however they generate like
	 * normal expressions with no value required.
	 *
	 * @param currentScope org.eclipse.jdt.internal.compiler.lookup.BlockScope
	 * @param codeStream org.eclipse.jdt.internal.compiler.codegen.CodeStream 
	 */
	public void generateCode(BlockScope currentScope, CodeStream codeStream) {

		if ((bits & IsReachableMASK) == 0) {
			return;
		}
		generateCode(currentScope, codeStream, false);
	}

	/**
	 * Every expression is responsible for generating its implicit conversion when necessary.
	 *
	 * @param currentScope org.eclipse.jdt.internal.compiler.lookup.BlockScope
	 * @param codeStream org.eclipse.jdt.internal.compiler.codegen.CodeStream
	 * @param valueRequired boolean
	 */
	public void generateCode(
		BlockScope currentScope,
		CodeStream codeStream,
		boolean valueRequired) {

		if (constant != NotAConstant) {
			// generate a constant expression
			int pc = codeStream.position;
			codeStream.generateConstant(constant, implicitConversion);
			codeStream.recordPositionsFrom(pc, this.sourceStart);
		} else {
			// actual non-constant code generation
			throw new ShouldNotImplement(Util.bind("ast.missingCode")); //$NON-NLS-1$
		}
	}

	/**
	 * Default generation of a boolean value
	 */
	public void generateOptimizedBoolean(
		BlockScope currentScope,
		CodeStream codeStream,
		Label trueLabel,
		Label falseLabel,
		boolean valueRequired) {

		// a label valued to nil means: by default we fall through the case... 
		// both nil means we leave the value on the stack

		if ((constant != Constant.NotAConstant) && (constant.typeID() == T_boolean)) {
			int pc = codeStream.position;
			if (constant.booleanValue() == true) {
				// constant == true
				if (valueRequired) {
					if (falseLabel == null) {
						// implicit falling through the FALSE case
						if (trueLabel != null) {
							codeStream.goto_(trueLabel);
						}
					}
				}
			} else {
				if (valueRequired) {
					if (falseLabel != null) {
						// implicit falling through the TRUE case
						if (trueLabel == null) {
							codeStream.goto_(falseLabel);
						}
					}
				}
			}
			codeStream.recordPositionsFrom(pc, this.sourceStart);
			return;
		}
		generateCode(currentScope, codeStream, valueRequired);
		// branching
		int position = codeStream.position;
		if (valueRequired) {
			if (falseLabel == null) {
				if (trueLabel != null) {
					// Implicit falling through the FALSE case
					codeStream.ifne(trueLabel);
				}
			} else {
				if (trueLabel == null) {
					// Implicit falling through the TRUE case
					codeStream.ifeq(falseLabel);
				} else {
					// No implicit fall through TRUE/FALSE --> should never occur
				}
			}
		}
		// reposition the endPC
		codeStream.updateLastRecordedEndPC(position);
	}

	/* Optimized (java) code generation for string concatenations that involve StringBuffer
	 * creation: going through this path means that there is no need for a new StringBuffer
	 * creation, further operands should rather be only appended to the current one.
	 * By default: no optimization.
	 */
	public void generateOptimizedStringBuffer(
		BlockScope blockScope,
		net.sourceforge.phpdt.internal.compiler.codegen.CodeStream codeStream,
		int typeID) {

		generateCode(blockScope, codeStream, true);
		codeStream.invokeStringBufferAppendForType(typeID);
	}

	/* Optimized (java) code generation for string concatenations that involve StringBuffer
	 * creation: going through this path means that there is no need for a new StringBuffer
	 * creation, further operands should rather be only appended to the current one.
	 */
	public void generateOptimizedStringBufferCreation(
		BlockScope blockScope,
		CodeStream codeStream,
		int typeID) {

		// Optimization only for integers and strings
		if (typeID == T_Object) {
			// in the case the runtime value of valueOf(Object) returns null, we have to use append(Object) instead of directly valueOf(Object)
			// append(Object) returns append(valueOf(Object)), which means that the null case is handled by append(String).
			codeStream.newStringBuffer();
			codeStream.dup();
			codeStream.invokeStringBufferDefaultConstructor();
			generateCode(blockScope, codeStream, true);
			codeStream.invokeStringBufferAppendForType(T_Object);
			return;
		}
		codeStream.newStringBuffer();
		codeStream.dup();
		if ((typeID == T_String) || (typeID == T_null)) {
			if (constant != NotAConstant) {
				codeStream.ldc(constant.stringValue());
			} else {
				generateCode(blockScope, codeStream, true);
				codeStream.invokeStringValueOf(T_Object);
			}
		} else {
			generateCode(blockScope, codeStream, true);
			codeStream.invokeStringValueOf(typeID);
		}
		codeStream.invokeStringBufferStringConstructor();
	}

	// Base types need that the widening is explicitly done by the compiler using some bytecode like i2f
	public void implicitWidening(
		TypeBinding runtimeTimeType,
		TypeBinding compileTimeType) {

		if (runtimeTimeType == null || compileTimeType == null)
			return;

		if (compileTimeType.id == T_null) {
			// this case is possible only for constant null
			// The type of runtime is a reference type
			// The code gen use the constant id thus any value
			// for the runtime id (akak the <<4) could be used.
			// T_Object is used as some general T_reference
			implicitConversion = (T_Object << 4) + T_null;
			return;
		}

		switch (runtimeTimeType.id) {
			case T_byte :
			case T_short :
			case T_char :
				implicitConversion = (T_int << 4) + compileTimeType.id;
				break;
			case T_String :
			case T_float :
			case T_boolean :
			case T_double :
			case T_int : //implicitConversion may result in i2i which will result in NO code gen
			case T_long :
				implicitConversion = (runtimeTimeType.id << 4) + compileTimeType.id;
				break;
			default : //nothing on regular object ref
		}
	}

	public boolean isCompactableOperation() {

		return false;
	}

	//Return true if the conversion is done AUTOMATICALLY by the vm
	//while the javaVM is an int based-machine, thus for example pushing
	//a byte onto the stack , will automatically creates a int on the stack
	//(this request some work d be done by the VM on signed numbers)
	public boolean isConstantValueOfTypeAssignableToType(
		TypeBinding constantType,
		TypeBinding targetType) {

		if (constant == Constant.NotAConstant)
			return false;
		if (constantType == targetType)
			return true;
		if (constantType.isBaseType() && targetType.isBaseType()) {
			//No free assignment conversion from anything but to integral ones.
			if ((constantType == IntBinding
				|| BaseTypeBinding.isWidening(T_int, constantType.id))
				&& (BaseTypeBinding.isNarrowing(targetType.id, T_int))) {
				//use current explicit conversion in order to get some new value to compare with current one
				return isConstantValueRepresentable(constant, constantType.id, targetType.id);
			}
		}
		return false;
	}

	public boolean isTypeReference() {
		return false;
	}

	public void resolve(BlockScope scope) {
		// drops the returning expression's type whatever the type is.

		this.resolveType(scope);
		return;
	}

	public TypeBinding resolveType(BlockScope scope) {
		// by default... subclasses should implement a better TC if required.

		return null;
	}

	public TypeBinding resolveTypeExpecting(
		BlockScope scope,
		TypeBinding expectedTb) {

		TypeBinding thisTb = this.resolveType(scope);
		if (thisTb == null)
			return null;
		if (!scope.areTypesCompatible(thisTb, expectedTb)) {
			scope.problemReporter().typeMismatchError(thisTb, expectedTb, this);
			return null;
		}
		return thisTb;
	}

	public String toString(int tab) {

		//Subclass re-define toStringExpression
		String s = tabString(tab);
		if (constant != null)
			//before TC has runned
			if (constant != NotAConstant)
				//after the TC has runned
				s += " /*cst:" + constant.toString() + "*/ "; //$NON-NLS-1$ //$NON-NLS-2$
		return s + toStringExpression(tab);
	}

	//Subclass re-define toStringExpression
	//This method is abstract and should never be called
	//but we provide some code that is running.....just in case
	//of developpement time (while every  thing is not built)
	public String toStringExpression() {

		return super.toString(0);
	}

	public String toStringExpression(int tab) {
		// default is regular toString expression (qualified allocation expressions redifine this method)
		return this.toStringExpression();
	}

	public Expression toTypeReference() {
		//by default undefined

		//this method is meanly used by the parser in order to transform
		//an expression that is used as a type reference in a cast ....
		//--appreciate the fact that castExpression and ExpressionWithParenthesis
		//--starts with the same pattern.....

		return this;
	}
}