/*
 * 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 1.3 2006-10-21 23:14:13 pombredanne Exp $
 */

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

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

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

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

/**
 * 
 * 
 * @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;
	}
}