#region License Information
/* HeuristicLab
 * Copyright (C) 2002-2012 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
 *
 * This file is part of HeuristicLab.
 *
 * HeuristicLab is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * HeuristicLab is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
 */
#endregion

using System;
using System.Collections.Generic;
using System.Linq;
using HeuristicLab.Services.Hive.DataTransfer;
using DA = HeuristicLab.Services.Hive.DataAccess;

namespace HeuristicLab.Services.Hive {
  public class HeartbeatManager {
    private IHiveDao dao {
      get { return ServiceLocator.Instance.HiveDao; }
    }
    private ITaskScheduler taskScheduler {
      get { return ServiceLocator.Instance.TaskScheduler; }
    }

    /// <summary>
    /// This method will be called every time a slave sends a heartbeat (-> very often; concurrency is important!)
    /// </summary>
    /// <returns>a list of actions the slave should do</returns>
    public List<MessageContainer> ProcessHeartbeat(Heartbeat heartbeat) {
      List<MessageContainer> actions = new List<MessageContainer>();
      Slave slave = dao.GetSlave(heartbeat.SlaveId);
      if (slave == null) {
        actions.Add(new MessageContainer(MessageContainer.MessageType.SayHello));
      } else {
        if (heartbeat.HbInterval != slave.HbInterval) {
          actions.Add(new MessageContainer(MessageContainer.MessageType.NewHBInterval));
        }

        // update slave data
        slave.FreeCores = heartbeat.FreeCores;
        slave.FreeMemory = heartbeat.FreeMemory;
        slave.CpuUtilization = heartbeat.CpuUtilization;
        slave.IsAllowedToCalculate = SlaveIsAllowedToCalculate(slave.Id);
        slave.SlaveState = (heartbeat.JobProgress != null && heartbeat.JobProgress.Count > 0) ? SlaveState.Calculating : SlaveState.Idle;
        slave.LastHeartbeat = DateTime.Now;
        dao.UpdateSlave(slave);

        // update task data
        actions.AddRange(UpdateTasks(heartbeat, slave.IsAllowedToCalculate));

        // assign new task
        if (heartbeat.AssignJob && slave.IsAllowedToCalculate && heartbeat.FreeCores > 0) {
          var availableJobs = taskScheduler.Schedule(dao.GetWaitingTasks(slave));
          if (availableJobs.Any()) {
            var job = availableJobs.First();
            if (AssignJob(slave, job))
              actions.Add(new MessageContainer(MessageContainer.MessageType.CalculateTask, job.Id));
          }
        }
      }
      return actions;
    }

    // returns true if assignment was successful
    private bool AssignJob(Slave slave, Task task) {
      // load task again and check if it is still available (this is an attempt to reduce the race condition which causes multiple heartbeats to get the same task assigned)
      if (dao.GetTask(task.Id).State != TaskState.Waiting) return false;

      task = dao.UpdateTaskState(task.Id, DataAccess.TaskState.Transferring, slave.Id, null, null);

      // from now on the task has some time to send the next heartbeat (ApplicationConstants.TransferringJobHeartbeatTimeout)
      task.LastHeartbeat = DateTime.Now;
      dao.UpdateTask(task);
      return true;
    }

    /// <summary>
    /// Update the progress of each task
    /// Checks if all the task sent by heartbeat are supposed to be calculated by this slave
    /// </summary>
    private IEnumerable<MessageContainer> UpdateTasks(Heartbeat heartbeat, bool IsAllowedToCalculate) {
      List<MessageContainer> actions = new List<MessageContainer>();

      if (heartbeat.JobProgress == null)
        return actions;

      if (!IsAllowedToCalculate && heartbeat.JobProgress.Count != 0) {
        actions.Add(new MessageContainer(MessageContainer.MessageType.PauseAll));
      } else {
        // process the jobProgresses
        foreach (var jobProgress in heartbeat.JobProgress) {
          Task curTask = dao.GetTask(jobProgress.Key);
          if (curTask == null) {
            // task does not exist in db
            actions.Add(new MessageContainer(MessageContainer.MessageType.AbortTask, jobProgress.Key));
            DA.LogFactory.GetLogger(this.GetType().Namespace).Log("Task on slave " + heartbeat.SlaveId + " does not exist in DB: " + jobProgress.Key);
          } else {
            if (curTask.CurrentStateLog.SlaveId == Guid.Empty || curTask.CurrentStateLog.SlaveId != heartbeat.SlaveId) {
              // assigned slave does not match heartbeat
              actions.Add(new MessageContainer(MessageContainer.MessageType.AbortTask, curTask.Id));
              DA.LogFactory.GetLogger(this.GetType().Namespace).Log("The slave " + heartbeat.SlaveId + " is not supposed to calculate task: " + curTask);
            } else if (!TaskIsAllowedToBeCalculatedBySlave(heartbeat.SlaveId, curTask)) {
              // assigned resources ids of task do not match with slaveId (and parent resourceGroupIds); this might happen when slave is moved to different group
              actions.Add(new MessageContainer(MessageContainer.MessageType.PauseTask, curTask.Id));
            } else {
              // save task execution time
              curTask.ExecutionTime = jobProgress.Value;
              curTask.LastHeartbeat = DateTime.Now;

              switch (curTask.Command) {
                case Command.Stop:
                  actions.Add(new MessageContainer(MessageContainer.MessageType.StopTask, curTask.Id));
                  break;
                case Command.Pause:
                  actions.Add(new MessageContainer(MessageContainer.MessageType.PauseTask, curTask.Id));
                  break;
                case Command.Abort:
                  actions.Add(new MessageContainer(MessageContainer.MessageType.AbortTask, curTask.Id));
                  break;
              }
              dao.UpdateTask(curTask);
            }
          }
        }
      }
      return actions;
    }

    private bool TaskIsAllowedToBeCalculatedBySlave(Guid slaveId, Task curTask) {
      var assignedResourceIds = dao.GetAssignedResources(curTask.Id).Select(x => x.Id);
      var slaveResourceIds = dao.GetParentResources(slaveId).Select(x => x.Id);
      return assignedResourceIds.Any(x => slaveResourceIds.Contains(x));
    }

    private bool SlaveIsAllowedToCalculate(Guid slaveId) {
      // the slave may only calculate if there is no downtime right now. this needs to be checked for every parent resource also
      return dao.GetParentResources(slaveId).All(r => dao.GetDowntimes(x => x.ResourceId == r.Id && (DateTime.Now >= x.StartDate) && (DateTime.Now <= x.EndDate)).Count() == 0);
    }
  }
}