/*
 * 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.flink.runtime.clusterframework.overlays;

import org.apache.flink.configuration.Configuration;
import org.apache.flink.configuration.SecurityOptions;
import org.apache.flink.core.fs.Path;
import org.apache.flink.runtime.clusterframework.ContainerSpecification;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.annotation.Nullable;
import java.io.File;
import java.io.IOException;


/**
 * Overlays cluster-level Kerberos credentials (i.e. keytab) into a container.
 *
 * The folloowing Flink configuration entries are updated:
 *  - security.kerberos.login.keytab
 */
public class KeytabOverlay extends AbstractContainerOverlay {

	private static final Logger LOG = LoggerFactory.getLogger(KeytabOverlay.class);

	static final Path TARGET_PATH = new Path("krb5.keytab");

	final Path keytab;

	public KeytabOverlay(@Nullable File keytab) {
		this.keytab = keytab != null ? new Path(keytab.toURI()) : null;
	}

	public KeytabOverlay(@Nullable Path keytab) {
		this.keytab = keytab;
	}

	@Override
	public void configure(ContainerSpecification container) throws IOException {
		if(keytab != null) {
			container.getArtifacts().add(ContainerSpecification.Artifact.newBuilder()
				.setSource(keytab)
				.setDest(TARGET_PATH)
				.setCachable(false)
				.build());
			container.getDynamicConfiguration().setString(SecurityOptions.KERBEROS_LOGIN_KEYTAB, TARGET_PATH.getPath());
		}
	}

	public static Builder newBuilder() {
		return new Builder();
	}

	/**
	 * A builder for the {@link KeytabOverlay}.
	 */
	public static class Builder {

		File keytabPath;

		/**
		 * Configures the overlay using the current environment (and global configuration).
		 *
		 * The following Flink configuration settings are checked for a keytab:
		 *  - security.kerberos.login.keytab
		 */
		public Builder fromEnvironment(Configuration globalConfiguration) {
			String keytab = globalConfiguration.getString(SecurityOptions.KERBEROS_LOGIN_KEYTAB);
			if(keytab != null) {
				keytabPath = new File(keytab);
				if(!keytabPath.exists()) {
					throw new IllegalStateException("Invalid configuration for " +
						SecurityOptions.KERBEROS_LOGIN_KEYTAB +
						"; '" + keytab + "' not found.");
				}
			}

			return this;
		}

		public KeytabOverlay build() {
			return new KeytabOverlay(keytabPath);
		}
	}
}