package com.atlassian.scheduler.core.impl;
   
   import com.atlassian.scheduler.config.JobId;
   import com.atlassian.scheduler.core.spi.RunDetailsDao;
   import com.atlassian.scheduler.status.RunDetails;
   import com.atlassian.scheduler.status.RunOutcome;
   import com.google.common.cache.Cache;
   import com.google.common.cache.CacheBuilder;
   
  import static java.util.concurrent.TimeUnit.DAYS;
  
  /**
   * An implementation of the {@code RunDetailsDao} that keeps the scheduler history in memory.
   * This implementation does not share information across nodes in the cluster or persist it
   * across restarts, but provides an otherwise functional implementation.  By default, each
   * job's history is expired 30 days after it is last updated.
   *
   * @since v1.0
   */
  public class MemoryRunDetailsDao implements RunDetailsDao {
      private final Cache<JobId, JobRecord> store;
  
      public MemoryRunDetailsDao() {
          this(30);
      }
  
      public MemoryRunDetailsDao(int daysToKeepIdleHistory) {
          this.store = CacheBuilder.newBuilder()
                  .expireAfterWrite(daysToKeepIdleHistory, DAYS)
                  .<JobId, JobRecord>build();
      }
  
  
      @Override
      public RunDetails getLastRunForJob(JobId jobId) {
          final JobRecord record = store.getIfPresent(jobId);
          return (record != null) ? record.lastRun : null;
      }
  
      @Override
      public RunDetails getLastSuccessfulRunForJob(JobId jobId) {
          final JobRecord record = store.getIfPresent(jobId);
          return (record != null) ? record.lastRun : null;
      }
  
      @Override
      public void addRunDetails(JobId jobId, RunDetails runDetails) {
          // Concurrency note: while we won't get concurrent modification exceptions or anything like
          // that, little effort is made here to keep this information consistent if multiple instances
          // of the same JobId attempt to record run details at once.  This is not supposed to happen,
          // anyway, so it should not be important.
          final JobRecord record;
          if (runDetails.getRunOutcome() == RunOutcome.SUCCESS) {
              record = new JobRecord(runDetails, runDetails);
          } else {
              record = new JobRecord(runDetails, getLastSuccessfulRunForJob(jobId));
          }
          store.put(jobId, record);
      }
  
  
      static class JobRecord {
          final RunDetails lastRun;
          final RunDetails lastSuccessfulRun;
  
          JobRecord(RunDetails lastRun, RunDetails lastSuccessfulRun) {
              this.lastRun = lastRun;
              this.lastSuccessfulRun = lastSuccessfulRun;
          }
      }
  }