/*
    * This file is part of dependency-check-core.
    *
    * 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.
   *
   * Copyright (c) 2024 Jeremy Long. All Rights Reserved.
   */
  package org.owasp.dependencycheck.data.update;
  
  import org.jspecify.annotations.NonNull;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.FileOutputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.time.Duration;
  import java.time.Instant;
  import java.util.Properties;
  
  import static org.owasp.dependencycheck.utils.FileUtils.existsWithContent;
  
  /**
   *
   * @author Jeremy Long
   */
  public abstract class LocalDataSource implements CachedWebDataSource {
  
      /**
       * Static logger.
       */
      private static final Logger LOGGER = LoggerFactory.getLogger(LocalDataSource.class);
  
      /**
       * Saves the timestamp in a properties file adjacent to the provided repo file
       *
       * @param repo the local file data source
       */
      protected void saveLastUpdated(@NonNull File repo) {
          final File timestampFile = new File(repo + ".properties");
          try (OutputStream out = new FileOutputStream(timestampFile)) {
              final Properties prop = new Properties();
              prop.setProperty("LAST_UPDATED", String.valueOf(System.currentTimeMillis()));
              prop.store(out, null);
          } catch (IOException ex) {
              throw new RuntimeException(ex);
          }
      }
  
      /**
       * Retrieves the last updated date from the local file system (in a file
       * next to the repo file).
       *
       * @param repo the local file data source
       * @return the instant of the last updated date/time
       */
      protected Instant getLastUpdated(@NonNull File repo) {
          long lastUpdatedOn = 0;
          final File timestampFile = new File(repo + ".properties");
          if (timestampFile.isFile()) {
              try (InputStream is = new FileInputStream(timestampFile)) {
                  final Properties props = new Properties();
                  props.load(is);
                  lastUpdatedOn = Long.parseLong(props.getProperty("LAST_UPDATED", "0"));
              } catch (IOException | NumberFormatException ex) {
                  LOGGER.debug("error reading timestamp file", ex);
              }
              if (lastUpdatedOn <= 0) {
                  //fall back on conversion from file last modified
                  lastUpdatedOn = repo.lastModified();
              }
          }
          return Instant.ofEpochMilli(lastUpdatedOn);
      }
  
      /**
       * Determines if we should update the local data source.
       *
       * @param repo the local file data source
       * @param validFor the duration for which the local data source should be considered valid
       * @return <code>true</code> if an update to the data source should be performed; otherwise <code>false</code>.
       *         If the repo does not exist, or is an empty file, it is considered stale.
       */
      protected boolean isStale(@NonNull File repo, @NonNull Duration validFor) {
          boolean stale = true;
          if (existsWithContent(repo)) {
             final Instant lastUpdatedOn = getLastUpdated(repo);
             final Instant now = Instant.now();
             LOGGER.debug("{} last updated: {}, now: {}", getClass().getSimpleName(), lastUpdatedOn, now);
             stale = lastUpdatedOn.plus(validFor).isBefore(now);
             if (!stale) {
                 LOGGER.info("Should skip {} update since last update was within period {}.", getClass().getSimpleName(), validFor);
             }
         }
         return stale;
     }
 }