/*
 * Copyright 2005-2008 Les Hazlewood
 *
 * Licensed 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.
 */
package org.jsecurity.codec;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import java.io.UnsupportedEncodingException;

/**
 * @author Les Hazlewood
 * @since 0.9
 */
public abstract class CodecSupport {
    
    protected transient final Log log = LogFactory.getLog( getClass() );

    public static final String PREFERRED_ENCODING = "UTF-8";

    public static byte[] toBytes( char[] chars ) {
        return toBytes( new String( chars ), PREFERRED_ENCODING );
    }

    public static byte[] toBytes( char[] chars, String encoding ) {
        return toBytes( new String( chars ), encoding );
    }

    public static byte[] toBytes( String source ) {
        return toBytes( source, PREFERRED_ENCODING );
    }

    public static byte[] toBytes( String source, String encoding ) {
        try {
            return source.getBytes( encoding );
        } catch (UnsupportedEncodingException e) {
            String msg = "Unable to convert source [" + source + "] to byte array using " +
                "encoding '" + encoding + "'";
            throw new CodecException( msg, e );
        }
    }

    public static String toString( byte[] bytes ) {
        return toString( bytes, PREFERRED_ENCODING );
    }

    public static String toString( byte[] bytes, String encoding ) {
        try {
            return new String( bytes, encoding );
        } catch (UnsupportedEncodingException e) {
            String msg = "Unable to convert byte array to String with encoding '" + encoding + "'.";
            throw new CodecException( msg, e );
        }
    }

    public static char[] toChars( byte[] bytes ) {
        return toChars( bytes, PREFERRED_ENCODING );
    }

    public static char[] toChars( byte[] bytes, String encoding ) {
        return toString( bytes, encoding ).toCharArray();
    }

    /**
     * Converts the specified Object into a byte array.
     *
     * <p>If the argument is a <tt>byte[]</tt>, <tt>char[]</tt>, or <tt>String</tt> it will be converted
     * automatically and returned.</tt>
     *
     * <p>If the argument is anything other than these three types, it is passed to the
     * {@link #objectToBytes(Object) objectToBytes} method which must be overridden by subclasses.
     * @param o the Object to convert into a byte array
     * @return a byte array representation of the Object argument.
     */
    protected byte[] toBytes( Object o ) {
        if ( o == null ) {
            String msg = "Argument for byte conversion cannot be null.";
            throw new IllegalArgumentException( msg );
        }
        if ( o instanceof byte[] ) {
            return (byte[])o;
        } else if (o instanceof char[] ) {
            return toBytes( (char[])o );
        } else if (o instanceof String ) {
            return toBytes( (String)o );
        } else {
            return objectToBytes( o );
        }
    }

    /**
     * Converts the specified Object into a String.
     *
     * <p>If the argument is a <tt>byte[]</tt>, <tt>char[]</tt>, or <tt>String</tt> it will be converted
     * automatically and returned.</tt>
     *
     * <p>If the argument is anything other than these three types, it is passed to the
     * {@link #objectToString(Object) objectToString} method which must be overridden by subclasses.
     * @param o the Object to convert into a byte array
     * @return a byte array representation of the Object argument.
     */
    protected String toString( Object o ) {
        if ( o == null ) {
            String msg = "Argument for String conversion cannot be null.";
            throw new IllegalArgumentException( msg );
        }
        if ( o instanceof byte[] ) {
            return toString( (byte[])o );
        } else if (o instanceof char[] ) {
            return new String( (char[])o );
        } else if (o instanceof String ) {
            return (String)o;
        } else {
            return objectToString( o );
        }
    }

    /**
     * Default implementation throws a CodecException immediately since it can't infer how to convert the Object
     * to a byte array.  This method must be overridden by subclasses if anything other than the three default
     * types (listed in the {@link #toBytes(Object) toBytes(Object)} JavaDoc) are to be converted to a byte array.
     *
     * @param o the Object to convert to a byte array.
     * @return a byte array representation of the Object argument.
     */
    protected byte[] objectToBytes( Object o ) {
        String msg = "The " + getClass().getName() + " implementation only supports conversion to " +
            "byte[] if the source is of type byte[], char[] or String.  The instance provided as a method " +
            "argument is of type [" + o.getClass().getName() + "].  If you would like to convert " +
            "this argument type to a byte[], you can 1) convert the argument to a byte[], char[] or String " +
            "yourself and then use that as the method argument or 2) subclass " + getClass().getName() +
            " and override the objectToBytes(Object o) method.";
        throw new CodecException( msg );
    }

    /**
     * Default implementation merely returns <code>objectArgument.toString()</code>.  Subclasses can override this
     * method for different mechanisms of converting an object to a String.
     *
     * @param o the Object to convert to a byte array.
     * @return a String representation of the Object argument.
     */
    protected String objectToString( Object o ) {
        return o.toString();
    }
}