/*******************************************************************************
 * Copyright (c) 2000, 2003 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials 
 * are made available under the terms of the Common Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/cpl-v10.html
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package net.sourceforge.phpdt.internal.compiler.ast;

import net.sourceforge.phpdt.internal.compiler.flow.FlowContext;
import net.sourceforge.phpdt.internal.compiler.flow.FlowInfo;
import net.sourceforge.phpdt.internal.compiler.impl.Constant;
import net.sourceforge.phpdt.internal.compiler.lookup.BaseTypeBinding;
import net.sourceforge.phpdt.internal.compiler.lookup.BlockScope;
import net.sourceforge.phpdt.internal.compiler.lookup.TypeBinding;

public 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 TypeBinding resolvedType;

	public Constant constant;

	public Expression() {
		super();
	}

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

		return flowInfo;
	}

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

		return analyseCode(currentScope, flowContext, flowInfo);
	}

	/**
	 * Constant usable for bytecode pattern optimizations, but cannot be inlined
	 * since it is not strictly equivalent to the definition of constant
	 * expressions. In particular, some side-effects may be required to occur
	 * (only the end value is known). Constant is known to be of boolean type
	 */
	public Constant optimizedBooleanConstant() {

		return this.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
	 *            net.sourceforge.phpdt.internal.compiler.lookup.BlockScope
	 * @param codeStream
	 *            net.sourceforge.phpdt.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
	 *            net.sourceforge.phpdt.internal.compiler.lookup.BlockScope
	 * @param codeStream
	 *            net.sourceforge.phpdt.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(ProjectPrefUtil.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 StringBuffer print(int indent, StringBuffer output) {
		printIndent(indent, output);
		return printExpression(indent, output);
	}

	public StringBuffer printExpression(int indent, StringBuffer output) {
		output.append(super.toString(0));
		return output;
	}

	public StringBuffer printStatement(int indent, StringBuffer output) {
		return print(indent, output).append(";"); //$NON-NLS-1$
	}

	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 expectedType) {

		TypeBinding expressionType = this.resolveType(scope);
		if (expressionType == null)
			return null;
		if (expressionType == expectedType)
			return expressionType;

		if (!expressionType.isCompatibleWith(expectedType)) {
			scope.problemReporter().typeMismatchError(expressionType,
					expectedType, this);
			return null;
		}
		return expressionType;
	}

	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;
	}
}