/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you 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.apache.xml.security.utils.resolver.implementations;

import java.lang.System.Logger;
import java.lang.System.Logger.Level;
import java.net.URI;
import java.net.URISyntaxException;
import java.nio.file.Paths;

import org.apache.xml.security.signature.XMLSignatureInput;
import org.apache.xml.security.signature.XMLSignatureFileInput;
import org.apache.xml.security.utils.resolver.ResourceResolverContext;
import org.apache.xml.security.utils.resolver.ResourceResolverException;
import org.apache.xml.security.utils.resolver.ResourceResolverSpi;

/**
 * A simple ResourceResolver for requests into the local filesystem.
 */
public class ResolverLocalFilesystem extends ResourceResolverSpi {

    private static final Logger LOG = System.getLogger(ResolverLocalFilesystem.class.getName());

    /**
     * {@inheritDoc}
     */
    @Override
    public XMLSignatureInput engineResolveURI(ResourceResolverContext context)
        throws ResourceResolverException {
        try {
            // calculate new URI
            URI uriNew = getNewURI(context.uriToResolve, context.baseUri);
            XMLSignatureInput result = new XMLSignatureFileInput(Paths.get(uriNew));
            result.setSecureValidation(context.secureValidation);
            result.setSourceURI(uriNew.toString());
            return result;
        } catch (Exception e) {
            throw new ResourceResolverException(e, context.uriToResolve, context.baseUri, "generic.EmptyMessage");
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public boolean engineCanResolveURI(ResourceResolverContext context) {
        if (context.uriToResolve == null) {
            return false;
        }

        if (context.uriToResolve.isEmpty() || context.uriToResolve.charAt(0) == '#' ||
            context.uriToResolve.startsWith("http:")) {
            return false;
        }

        try {
            LOG.log(Level.DEBUG, "I was asked whether I can resolve {0}", context.uriToResolve);

            if (context.uriToResolve.startsWith("file:") || context.baseUri.startsWith("file:")) {
                LOG.log(Level.DEBUG, "I state that I can resolve {0}", context.uriToResolve);
                return true;
            }
        } catch (Exception e) {
            LOG.log(Level.DEBUG, e.getMessage(), e);
        }

        LOG.log(Level.DEBUG, "But I can't");

        return false;
    }

    private static URI getNewURI(String uri, String baseURI) throws URISyntaxException {
        URI newUri = null;
        if (baseURI == null || baseURI.length() == 0) {
            newUri = new URI(uri);
        } else {
            newUri = new URI(baseURI).resolve(uri);
        }

        // if the URI contains a fragment, ignore it
        if (newUri.getFragment() != null) {
            return new URI(newUri.getScheme(), newUri.getSchemeSpecificPart(), null);
        }
        return newUri;
    }
}
