/*
 * Copyright (c) 2002-2004 Widespace, OU 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:
 *     Igor Malinin - initial contribution
 *
 * $Id: AbstractDocumentProvider.java,v 1.1 2004-09-02 18:28:03 jsurfer Exp $
 */

package net.sourceforge.phpeclipse.xml.ui.internal.text;

import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.InputStream;

import org.eclipse.jface.text.rules.IWhitespaceDetector;

import net.sourceforge.phpeclipse.ui.editor.I18NDocumentProvider;


/**
 * 
 * 
 * @author Igor Malinin
 */
public abstract class AbstractDocumentProvider extends I18NDocumentProvider {
	protected IWhitespaceDetector detector = new WhitespaceDetector();

	/*
	 * @see org.eclipse.ui.editors.text.IStorageDocumentProvider#getDefaultEncoding()
	 */
	public String getDefaultEncoding() {
		return "UTF-8";
	}

	public String getDeclaredEncoding( InputStream in ) throws IOException {
		if ( !in.markSupported() ) {
			in = new BufferedInputStream( in, 512 );
		}

		in.mark( 512 );
		String encoding = super.getDeclaredEncoding( in );
		if ( encoding != null ) {
			return encoding;
		}

		in.reset();

		// check Prolog-Start <?xml
		if ( !skipXMLDecl(in) ) {
			return null;
		}

		// detect 'encoding'
		skipEncoding( in );

		// read encoding
		int delimiter;

		while ( true ) {
			int ch = in.read();
			if ( ch < 0 ) {
				return null;
			}

			if ( detector.isWhitespace((char) ch) ) {
				continue;
			}

			if ( ch == '"' || ch == '\'' ) {
				delimiter = ch;
				break;
			}

			return null;
		}

		StringBuffer buf = new StringBuffer();

		while ( true ) {
			int ch = in.read();
			if ( ch < 0 ) {
				return null;
			}

			if ( ch == delimiter ) {
				break;
			}

			buf.append( (char) ch );
		}

		return buf.toString();
	}

	private boolean skipXMLDecl( InputStream in ) throws IOException {
		int ch = in.read();
		if ( ch != '<' ) {
			return false;
		}

		ch = in.read();
		if ( ch != '?' ) {
			return false;
		}

		ch = in.read();
		if ( ch != 'x' ) {
			return false;
		}

		ch = in.read();
		if ( ch != 'm' ) {
			return false;
		}

		ch = in.read();
		if ( ch != 'l' ) {
			return false;
		}

		return true;
	}

	private boolean skipEncoding( InputStream in ) throws IOException {
		int ch = in.read();

		boolean whitespace = false;

		while ( true ) {
			if ( ch < 0 ) {
				return false;
			}

			if ( detector.isWhitespace((char) ch) ) {
				ch = in.read();
				whitespace = true;
				continue;
			}

			if ( ch == '?' || ch == '<' ) {
				return false;
			}

			if ( ch != 'e' ) {
				ch = in.read();
				whitespace = false;
				continue;
			}

			if ( !whitespace ) {
				ch = in.read();
				continue;
			}

			if ( (ch = in.read()) == 'n' &&
					(ch = in.read()) == 'c' &&
					(ch = in.read()) == 'o' &&
					(ch = in.read()) == 'd' &&
					(ch = in.read()) == 'i' &&
					(ch = in.read()) == 'n' &&
					(ch = in.read()) == 'g' ) {
				break;
			}

			whitespace = false;
		}

		// '='
		while ( true ) {
			ch = in.read();
			if ( ch < 0 ) {
				return false;
			}

			if ( detector.isWhitespace((char) ch) ) {
				continue;
			}

			if ( ch == '=' ) {
				break;
			}

			return false;
		}

		return true;
	}
}