/*

* Copyright (c) 2007 Nokia Corporation and/or its subsidiary(-ies). 

* All rights reserved.

* This component and the accompanying materials are made available

* under the terms of "Eclipse Public License v1.0"

* which accompanies this distribution, and is available

* at the URL "http://www.eclipse.org/legal/epl-v10.html".

*

* Initial Contributors:

* Nokia Corporation - initial contribution.

*

* Contributors:

*

* Description:  File Reader for DTD Files. Filters out UTF-8 and 16 byte order

 *                marks.

 *

*/

package com.nokia.tools.themeinstaller.xmlparser;

import java.io.ByteArrayInputStream;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileNotFoundException;

import java.io.FileReader;

import java.io.IOException;

import java.io.Reader;

import java.util.Arrays;

import org.xml.sax.InputSource;

import com.nokia.tools.themeinstaller.installationmanager.InstallationManager;

/**

 * File Reader for DTD Files. Filters out UTF-8 and 16 byte order marks. Byte

 * order marks need to be filtered because FileReader can not tolerate BOMs.

 */

public class DTDInputSource extends InputSource {

	// CONSTANTS

	private final static int BUFFER_LENGTH = 3;

	private final static byte[] BOM_UTF8 = { (byte) 0xEF, (byte) 0xBB,

			(byte) 0xBF };

	private final static byte[] BOM_UTF16_BIG = { (byte) 0xFE, (byte) 0xFF };

	private final static byte[] BOM_UTF16_LIT = { (byte) 0xFF, (byte) 0xFE };

	// DTD File name

	private String iFileName;

	/**

	 * Constructor.

	 * 

	 * @param aFileName

	 *            DTD file name

	 * @throws FileNotFoundException

	 *             if the file can not be found

	 */

	public DTDInputSource(String aFileName) throws FileNotFoundException {

		super( new FileReader( aFileName ) );

		try {

			preprocess(aFileName);

		} catch (IOException e) {			

			e.printStackTrace();

		}

		iFileName = aFileName;

	}

	/**

	 * XML-DTD files should not contain invalid entity references. For example,

	 * %N; is valid while %N is not. This method will validate and correct such

	 * instances. Note: This was introduced because of a defect found in loc to

	 * dtd converter tool. Once loc-dtd tool works fine, this step will not be

	 * required.

	 * 

	 * @param fileName

	 *            the dtd file that needs correction.

	 * @throws IOException

	 */

	private void preprocess(String fileName) throws IOException {

		/**

		 * We won't use this parameter as of now. If required, use

		 * boolean fixDTD = InstallationManager.isFixDTD();

		 * We may remove this if we find no use in future.

		 */

		boolean fixDTD = true;

		if (!fixDTD) {

			this.setCharacterStream(new FileReader(fileName));

			return;

		}

		long fileLen = (new File(fileName)).length();

		byte[] fileContents = new byte[(int) fileLen];

		FileInputStream fis = new FileInputStream(fileName);

		fis.read(fileContents);

		fis.close();

		String fileContentsString = new String(fileContents);

		fileContentsString = fileContentsString.replace("(%N)", "(%N;)");

		fileContentsString = fileContentsString.replace("(%U)", " (%U;)");

		fileContentsString = fileContentsString.replace("%0U;", "%U;");

		fileContentsString = fileContentsString.replace("%U(", "%U;(");

		fileContentsString = fileContentsString.replace("%0U(", "%U;(");

		fileContentsString = fileContentsString.replace("%U%N;", "%U;%N;");

		fileContentsString = fileContentsString.replace("%U%N", "%U;%N;");

		setByteStream(new ByteArrayInputStream(fileContentsString.getBytes()));

	}

	/*

	 * (non-Javadoc)

	 * 

	 * @see org.xml.sax.InputSource#getCharacterStream()

	 */

	public Reader getCharacterStream() {

		// Get the reader from the base class

		Reader reader = super.getCharacterStream();

		// Read the beginning of the file to get the BOM

		byte[] buffer = new byte[BUFFER_LENGTH];

		try {

			// Read 3 bytes

			for (int i = 0; i < buffer.length; i++) {

				buffer[i] = (byte) reader.read();

			}

			int skip = 0;

			// UTF-8 byte order mark (length 3 bytes)

			if (Arrays.equals(BOM_UTF8, buffer)) {

				skip = BOM_UTF8.length;

			}

			// UTF-16 byte order mark (length 2 bytes)

			else {

				byte[] compareBuffer = new byte[BOM_UTF16_BIG.length];

				System.arraycopy(buffer, 0, compareBuffer, 0,

						compareBuffer.length);

				// Big and little endian

				if (Arrays.equals(BOM_UTF16_BIG, compareBuffer)

						|| Arrays.equals(BOM_UTF16_LIT, compareBuffer)) {

					skip = BOM_UTF16_BIG.length;

				}

			}

			// Reset not supported, a new reader must be created

			FileReader fr = new FileReader(iFileName);

			fr.skip(skip);

			// Close the old reader

			reader.close();

			// Set the new reader back to the super class

			super.setCharacterStream(fr);

		} catch (Exception e) {

			// Ignore errors, original (unfiltered) stream will be returned

		}

		return super.getCharacterStream();

	}

}