/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the  "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * $Id$
 */

package org.apache.xalan.xsltc.compiler.util;

import org.apache.bcel.generic.ALOAD;
import org.apache.bcel.generic.ASTORE;
import org.apache.bcel.generic.BranchHandle;
import org.apache.bcel.generic.ConstantPoolGen;
import org.apache.bcel.generic.GOTO;
import org.apache.bcel.generic.IFEQ;
import org.apache.bcel.generic.IFNONNULL;
import org.apache.bcel.generic.INVOKESTATIC;
import org.apache.bcel.generic.INVOKEVIRTUAL;
import org.apache.bcel.generic.Instruction;
import org.apache.bcel.generic.InstructionList;
import org.apache.bcel.generic.PUSH;
import org.apache.xalan.xsltc.compiler.Constants;
import org.apache.xalan.xsltc.compiler.FlowList;

/**
 * @author Jacek Ambroziak
 * @author Santiago Pericas-Geertsen
 */
public class StringType extends Type {
    protected StringType() {}

    public String toString() {
	return "string";
    }

    public boolean identicalTo(Type other) {
	return this == other;
    }

    public String toSignature() {
	return "Ljava/lang/String;";
    }

    public boolean isSimple() {
	return true;
    }

    public org.apache.bcel.generic.Type toJCType() {
	return org.apache.bcel.generic.Type.STRING;
    }

    /**
     * Translates a string into an object of internal type <code>type</code>.
     * The translation to int is undefined since strings are always converted
     * to reals in arithmetic expressions.
     *
     * @see	org.apache.xalan.xsltc.compiler.util.Type#translateTo
     */
    public void translateTo(ClassGenerator classGen, MethodGenerator methodGen, 
			    Type type) {
	if (type == Type.Boolean) {
	    translateTo(classGen, methodGen, (BooleanType) type);
	}
	else if (type == Type.Real) {
	    translateTo(classGen, methodGen, (RealType) type);
	}
	else if (type == Type.Reference) {
	    translateTo(classGen, methodGen, (ReferenceType) type);
	}
	else {
	    ErrorMsg err = new ErrorMsg(ErrorMsg.DATA_CONVERSION_ERR,
					toString(), type.toString());
	    classGen.getParser().reportError(Constants.FATAL, err);
	}
    }

    /**
     * Translates a string into a synthesized boolean.
     *
     * @see	org.apache.xalan.xsltc.compiler.util.Type#translateTo
     */
    public void translateTo(ClassGenerator classGen, MethodGenerator methodGen, 
			    BooleanType type) {
	final InstructionList il = methodGen.getInstructionList();
	FlowList falsel = translateToDesynthesized(classGen, methodGen, type);
	il.append(ICONST_1);
	final BranchHandle truec = il.append(new GOTO(null));
	falsel.backPatch(il.append(ICONST_0));
	truec.setTarget(il.append(NOP));
    }

    /**
     * Translates a string into a real by calling stringToReal() from the
     * basis library.
     *
     * @see	org.apache.xalan.xsltc.compiler.util.Type#translateTo
     */
    public void translateTo(ClassGenerator classGen, MethodGenerator methodGen,
			    RealType type) {
	final ConstantPoolGen cpg = classGen.getConstantPool();
	final InstructionList il = methodGen.getInstructionList();
	il.append(new INVOKESTATIC(cpg.addMethodref(BASIS_LIBRARY_CLASS,
						    STRING_TO_REAL,
						    STRING_TO_REAL_SIG)));
    }

    /**
     * Translates a string into a non-synthesized boolean. It does not push a 
     * 0 or a 1 but instead returns branchhandle list to be appended to the 
     * false list.
     *
     * @see	org.apache.xalan.xsltc.compiler.util.Type#translateToDesynthesized
     */
    public FlowList translateToDesynthesized(ClassGenerator classGen, 
					     MethodGenerator methodGen, 
					     BooleanType type) {
	final ConstantPoolGen cpg = classGen.getConstantPool();
	final InstructionList il = methodGen.getInstructionList();

	il.append(new INVOKEVIRTUAL(cpg.addMethodref(STRING_CLASS,
						     "length", "()I")));
	return new FlowList(il.append(new IFEQ(null)));
    }

    /**
     * Expects a string on the stack and pushes a boxed string.
     * Strings are already boxed so the translation is just a NOP.
     *
     * @see	org.apache.xalan.xsltc.compiler.util.Type#translateTo
     */
    public void translateTo(ClassGenerator classGen, MethodGenerator methodGen, 
			    ReferenceType type) {
	methodGen.getInstructionList().append(NOP);
    }

    /**
     * Translates a internal string into an external (Java) string. 
     *
     * @see	org.apache.xalan.xsltc.compiler.util.Type#translateFrom
     */
    public void translateTo(ClassGenerator classGen, MethodGenerator methodGen, 
			    Class clazz) 
    {
        // Is String <: clazz? I.e. clazz in { String, Object }
        if (clazz.isAssignableFrom(java.lang.String.class)) {
	    methodGen.getInstructionList().append(NOP);
	}
	else {
	    ErrorMsg err = new ErrorMsg(ErrorMsg.DATA_CONVERSION_ERR,
					toString(), clazz.getName());
	    classGen.getParser().reportError(Constants.FATAL, err);
	}
    }
    
    /**
     * Translates an external (primitive) Java type into a string. 
     *
     * @see	org.apache.xalan.xsltc.compiler.util.Type#translateFrom
     */
    public void translateFrom(ClassGenerator classGen, 
	MethodGenerator methodGen, Class clazz) 
    {
	final ConstantPoolGen cpg = classGen.getConstantPool();
	final InstructionList il = methodGen.getInstructionList();

	if (clazz.getName().equals("java.lang.String")) {
	    // same internal representation, convert null to ""
	    il.append(DUP);
	    final BranchHandle ifNonNull = il.append(new IFNONNULL(null));
	    il.append(POP);
	    il.append(new PUSH(cpg, ""));
	    ifNonNull.setTarget(il.append(NOP));
	}
	else {
	    ErrorMsg err = new ErrorMsg(ErrorMsg.DATA_CONVERSION_ERR,
					toString(), clazz.getName());
	    classGen.getParser().reportError(Constants.FATAL, err);
	}
    }

    /**
     * Translates an object of this type to its boxed representation.
     */ 
    public void translateBox(ClassGenerator classGen,
			     MethodGenerator methodGen) {
	translateTo(classGen, methodGen, Type.Reference);
    }

    /**
     * Translates an object of this type to its unboxed representation.
     */ 
    public void translateUnBox(ClassGenerator classGen,
			       MethodGenerator methodGen) {
	methodGen.getInstructionList().append(NOP);
    }

    /**
     * Returns the class name of an internal type's external representation.
     */
    public String getClassName() {
	return(STRING_CLASS);
    }


    public Instruction LOAD(int slot) {
	return new ALOAD(slot);
    }
	
    public Instruction STORE(int slot) {
	return new ASTORE(slot);
    }
}
