/*=============================================================================#
 # Copyright (c) 2018, 2021 Stephan Wahlbrink and others.
 # 
 # This program and the accompanying materials are made available under the
 # terms of the Eclipse Public License 2.0 which is available at
 # https://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
 # which is available at https://www.apache.org/licenses/LICENSE-2.0.
 # 
 # SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
 # 
 # Contributors:
 #     Stephan Wahlbrink <sw@wahlbrink.eu> - initial API and implementation
 #=============================================================================*/

package org.eclipse.statet.internal.rhelp.core.index;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.eclipse.statet.jcommons.lang.NonNullByDefault;

import org.eclipse.statet.rhelp.core.RHelpSearchMatch;


@NonNullByDefault
public class RHelpHtmlUtils {
	
	
	public static final String HR_PREFIX= "<hr"; //$NON-NLS-1$
	public static final Pattern HR_LINE_PATTERN= Pattern.compile("\\A\\<hr\\ ?\\/\\>"); //$NON-NLS-1$
	
	public static final int indexOfLastHr(final String html) {
		Matcher matcher= null;
		int idx= html.length();
		while ((idx= html.lastIndexOf(HR_PREFIX, idx - 1)) != -1) {
			if (matcher == null) {
				matcher= HR_LINE_PATTERN.matcher(html);
			}
			matcher.region(idx, html.length());
			if (matcher.find()) {
				return idx;
			}
		}
		return -1;
	}
	
	
	public static final int indexOfSectionEnd(final String html, final int idxBegin) {
		final int idx= html.indexOf("<h3", idxBegin); //$NON-NLS-1$
		return idx;
	}
	
	
	public static final String MATCH_HIGHTLIGHT_CLASS_PREFIX= "SMATCH-";
	
	private static final Pattern START_TAG_PATTERN= Pattern.compile("\\A\\<SMATCH\\-([A-J])\\>");
	
	public static String formatHtmlMatches(final String html) {
		final StringBuilder sb= new StringBuilder(html.length() + 64);
		final Matcher startMatcher= START_TAG_PATTERN.matcher(html);
		int idx= 0;
		int beginIdx= 0;
		while (idx < html.length()) {
			final int nextIdx= html.indexOf('<', idx);
			if (nextIdx != -1) {
				if (startMatcher.region(nextIdx, html.length()).find()) {
					sb.append(html, beginIdx, nextIdx);
					idx= formatHtmlMatch(startMatcher.group(1).charAt(0), html, startMatcher.end(), sb);
					beginIdx= idx;
					continue;
				}
			}
			idx++;
		}
		sb.append(html, beginIdx, html.length());
		return sb.toString();
	}
	
	private static int formatHtmlMatch(final char matchClass,
			final String html, final int beginIdx, final StringBuilder sb) {
		final int endIdx= html.indexOf(RHelpSearchMatch.POST_TAGS[matchClass - 'A'], beginIdx);
		if (endIdx == -1) {
			return beginIdx;
		}
		
		sb.append("<span class=\"");
		sb.append(MATCH_HIGHTLIGHT_CLASS_PREFIX);
		sb.append(matchClass);
		sb.append("\">");
		
		// TODO check tag balance?
		sb.append(html, beginIdx, endIdx);
		
		sb.append("</span>");
		
		return endIdx + RHelpSearchMatch.POST_TAGS_PREFIX.length() + 2;
	}
	
}