/*
 * Copyright 2012 the original author or authors.
 *
 * 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.gradle.api.internal.externalresource.transport.http;

import org.cyberneko.html.parsers.SAXParser;
import org.gradle.api.internal.resource.ResourceException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.xml.sax.Attributes;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

import java.io.IOException;
import java.io.StringReader;
import java.net.MalformedURLException;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.ArrayList;
import java.util.List;

public class ApacheDirectoryListingParser {

    private static final Logger LOGGER = LoggerFactory.getLogger(ApacheDirectoryListingParser.class);

    public ApacheDirectoryListingParser() {
    }

    public List<URI> parse(URI baseURI, byte[] content, String contentType) throws Exception {
        baseURI = addTrailingSlashes(baseURI);
        if (contentType == null || !contentType.startsWith("text/html")) {
            throw new ResourceException(String.format("Unsupported ContentType %s for DirectoryListing", contentType));
        }
        String contentEncoding = contentType.contains("charset=") ? contentType.substring(contentType.indexOf('=') + 1) : "utf-8";
        final String htmlText = new String(content, contentEncoding);
        final InputSource inputSource = new InputSource(new StringReader(htmlText));
        final SAXParser htmlParser = new SAXParser();
        final AnchorListerHandler anchorListerHandler = new AnchorListerHandler();
        htmlParser.setContentHandler(anchorListerHandler);
        htmlParser.parse(inputSource);

        List<String> hrefs = anchorListerHandler.getHrefs();
        List<URI> uris = resolveURIs(baseURI, hrefs);
        return filterNonDirectChilds(baseURI, uris);
    }

    private URI addTrailingSlashes(URI uri) throws IOException, URISyntaxException {
        if(uri.getPath() == null){
            uri = new URI(uri.getScheme(), uri.getUserInfo(), uri.getHost(), uri.getPort(), "/", uri.getQuery(), uri.getFragment());
        }else if (!uri.getPath().endsWith("/") && !uri.getPath().endsWith(".html")) {
            uri = new URI(uri.getScheme(), uri.getUserInfo(), uri.getHost(), uri.getPort(), uri.getPath() + "/", uri.getQuery(), uri.getFragment());

        }
        return uri;
    }

    private List<URI> filterNonDirectChilds(URI baseURI, List<URI> inputURIs) throws MalformedURLException {
        final int baseURIPort = baseURI.getPort();
        final String baseURIHost = baseURI.getHost();
        final String baseURIScheme = baseURI.getScheme();

        List<URI> uris = new ArrayList<URI>();
        final String prefixPath = baseURI.getPath();
        for (URI parsedURI : inputURIs) {
            if (parsedURI.getHost() != null && !parsedURI.getHost().equals(baseURIHost)) {
                continue;
            }
            if (parsedURI.getScheme() != null && !parsedURI.getScheme().equals(baseURIScheme)) {
                continue;
            }
            if (parsedURI.getPort() != baseURIPort) {
                continue;
            }
            if (parsedURI.getPath() != null && !parsedURI.getPath().startsWith(prefixPath)) {
                continue;
            }
            String childPathPart = parsedURI.getPath().substring(prefixPath.length(), parsedURI.getPath().length());
            if (childPathPart.startsWith("../")) {
                continue;
            }
            if (childPathPart.equals("") || childPathPart.split("/").length > 1) {
                continue;
            }

            uris.add(parsedURI);
        }
        return uris;
    }

    private List<URI> resolveURIs(URI baseURI, List<String> hrefs) {
        List<URI> uris = new ArrayList<URI>();
        for (String href : hrefs) {
            try {
                uris.add(baseURI.resolve(href));
            } catch (IllegalArgumentException ex) {
                LOGGER.debug(String.format("Cannot resolve anchor: %s", href));
            }
        }
        return uris;
    }

    private class AnchorListerHandler extends DefaultHandler {
        List<String> hrefs = new ArrayList<String>();

        public List<String> getHrefs() {
            return hrefs;
        }

        public void startElement(String uri, String localName, String qName, Attributes atts) throws SAXException {
            if (qName.equalsIgnoreCase("A")) {
                final String href = atts.getValue("href");
                if (href != null) {
                    hrefs.add(href);
                }
            }
        }
    }
}