/**
    * Copyright 2010 The Kuali Foundation Licensed under the
    * Educational Community 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.osedu.org/licenses/ECL-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.kuali.student.common.util;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.util.jar.Attributes;
  import java.util.jar.Manifest;
  
  import javax.servlet.ServletContext;
  
  import static org.apache.commons.io.IOUtils.*;
  import static org.apache.commons.lang.StringUtils.*;
  
  /**
   * Obtains version information about the application from the META-INF/MANIFEST.MF file contained inside a .war file
   */
  public class ManifestInspector {
  
  	/**
  	 * Location of the MANIFEST.MF file
  	 */
  	public static final String MANIFEST_LOCATION = "/META-INF/MANIFEST.MF";
  	public static final String BUNDLE_NAME = "Bundle-Name";
  	public static final String BUNDLE_VERSION = "Bundle-Version";
  	public static final String BUNDLE_TIMESTAMP = "Bundle-Timestamp";
  	public static final String BUNDLE_BUILD_NUMBER = "Bundle-BuildNumber";
  	public static final String NO_BUILD_INFORMATION_AVAILABLE = "No build information available";
  
  	/**
  	 * Return a Manifest object
  	 */
  	protected Manifest getManifest(ServletContext servletContext) throws IOException {
  		InputStream in = null;
  		try {
  			in = servletContext.getResourceAsStream(MANIFEST_LOCATION);
  			if (in == null) {
  				return null;
  			} else {
  				return new Manifest(in);
  			}
  		} catch (IOException e) {
  			throw e;
  		} finally {
  			closeQuietly(in);
  		}
  	}
  
  	/**
  	 * Examine the manifest provided for build information. Returns null if manifest is null
  	 */
  	protected BuildInformation getBuildInformation(Manifest manifest) {
  		// No Manifest is available
  		if (manifest == null) {
  			return null;
  		}
  
  		// Extract the attributes
  		Attributes attributes = manifest.getMainAttributes();
  
  		// Manifest attributes containing the build information
  		String name = attributes.getValue(BUNDLE_NAME);
  		String version = attributes.getValue(BUNDLE_VERSION);
  		String buildNumber = attributes.getValue(BUNDLE_BUILD_NUMBER);
  		String timestamp = attributes.getValue(BUNDLE_TIMESTAMP);
  
  		// Create and populate a BuildInformation object
  		BuildInformation bi = new BuildInformation();
  		bi.setName(name);
  		bi.setVersion(version);
  		bi.setBuildNumber(buildNumber);
  		bi.setTimestamp(timestamp);
  		return bi;
  	}
  
  	/**
  	 * Obtain version information from MANIFEST.MF
  	 */
  	public String getBuildInformationString(ServletContext context) throws IOException {
  		// Get a handle to a Manifest object
  		Manifest manifest = getManifest(context);
  
  		// Store build information attributes from the manifest into a POJO
  		BuildInformation buildInformation = getBuildInformation(manifest);
  
  		// Convert the POJO to a string
 		return toString(buildInformation);
 	}
 
 	/**
 	 * Return true if BuildInformation is null or does not contain any meaningful information.
 	 */
 	protected boolean isNullOrEmpty(BuildInformation bi) {
 		if (bi == null) {
 			return true;
 		}
 		if (!isEmpty(bi.getName())) {
 			return false;
 		}
 		if (!isEmpty(bi.getVersion())) {
 			return false;
 		}
 		if (!isEmpty(bi.getBuildNumber())) {
 			return false;
 		}
 		if (!isEmpty(bi.getTimestamp())) {
 			return false;
 		}
 		return true;
 	}
 
 	/**
 	 * Convert the build information POJO to a display String
 	 */
 	public String toString(BuildInformation bi) {
 		/**
 		 * For developers pointed at a local build, MANIFEST.MF may not be present
 		 * 
 		 * Since we overlay the Rice war file, the MANIFEST.MF from Rice may be present but doesn't contain build
 		 * information
 		 */
 		if (isNullOrEmpty(bi)) {
 			return NO_BUILD_INFORMATION_AVAILABLE;
 		}
 
 		/**
 		 * Build number is only present if Hudson has done the build
 		 */
 		if (!isEmpty(bi.getBuildNumber())) {
 			bi.setBuildNumber("#" + bi.getBuildNumber());
 		}
 
 		/**
 		 * Build a string out of the build information
 		 */
 		StringBuffer sb = new StringBuffer();
 		if (!isEmpty(bi.getName())) {
 			sb.append(bi.getName());
 			sb.append(" :: ");
 		}
 		if (!isEmpty(bi.getVersion())) {
 			sb.append(bi.getVersion());
 			sb.append(" :: ");
 		}
 		if (!isEmpty(bi.getBuildNumber())) {
 			sb.append(bi.getBuildNumber());
 			sb.append(" :: ");
 		}
 		if (!isEmpty(bi.getTimestamp())) {
 			sb.append(bi.getTimestamp());
 		}
 		return sb.toString();
 	}
 }