#region License Information
/* HeuristicLab
 * Copyright (C) 2002-2011 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 System.Threading;
using System.Threading.Tasks;
using HeuristicLab.Clients.Hive;
using HeuristicLab.Common;
using HeuristicLab.Core;
using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;

namespace HeuristicLab.HiveEngine {
  /// <summary>
  /// Represents an engine that executes operations which can be executed in parallel on the hive
  /// </summary>
  [StorableClass]
  [Item("Hive Engine", "Engine for parallel execution on the hive. You need enable `Parallel` for at least one operator in your operator graph to have all childoperations parallelized. Also those childoperations must not have sideeffects on a higher scope.")]
  public class HiveEngine : Engine {
    private static object locker = new object();
    private static object logLocker = new object();
    private CancellationToken cancellationToken;
    private bool firstRun = true;

    [Storable]
    private IOperator currentOperator;

    [Storable]
    public string ResourceNames { get; set; }

    [Storable]
    private int priority;
    public int Priority {
      get { return priority; }
      set { priority = value; }
    }

    [Storable]
    private TimeSpan executionTimeOnHive;
    public TimeSpan ExecutionTimeOnHive {
      get { return executionTimeOnHive; }
      set {
        if (value != executionTimeOnHive) {
          executionTimeOnHive = value;
          OnExecutionTimeOnHiveChanged();
        }
      }
    }

    [Storable]
    private bool isPrivileged;
    public bool IsPrivileged {
      get { return isPrivileged; }
      set { isPrivileged = value; }
    }

    // [Storable] -> HiveExperiment can't be storable, so RefreshableHiveExperiment can't be stored
    private ItemCollection<RefreshableHiveExperiment> hiveExperiments = new ItemCollection<RefreshableHiveExperiment>();
    public ItemCollection<RefreshableHiveExperiment> HiveExperiments {
      get { return hiveExperiments; }
      set { hiveExperiments = value; }
    }

    private List<Plugin> onlinePlugins;
    public List<Plugin> OnlinePlugins {
      get { return onlinePlugins; }
      set { onlinePlugins = value; }
    }

    private List<Plugin> alreadyUploadedPlugins;
    public List<Plugin> AlreadyUploadedPlugins {
      get { return alreadyUploadedPlugins; }
      set { alreadyUploadedPlugins = value; }
    }

    #region constructors and cloning
    public HiveEngine() {
      ResourceNames = "HEAL";
      Priority = 0;
    }

    [StorableConstructor]
    protected HiveEngine(bool deserializing) : base(deserializing) { }
    protected HiveEngine(HiveEngine original, Cloner cloner)
      : base(original, cloner) {
      this.ResourceNames = original.ResourceNames;
      this.currentOperator = cloner.Clone(original.currentOperator);
      this.priority = original.priority;
      this.executionTimeOnHive = original.executionTimeOnHive;
      this.IsPrivileged = original.IsPrivileged;
      // this.hiveExperiments = cloner.Clone(original.hiveExperiments); do not clone hiveExperiments - otherwise they would be sent with every job
    }
    public override IDeepCloneable Clone(Cloner cloner) {
      return new HiveEngine(this, cloner);
    }
    #endregion

    #region Events
    protected override void OnPrepared() {
      base.OnPrepared();
      this.ExecutionTimeOnHive = TimeSpan.Zero;
    }

    public event EventHandler ExecutionTimeOnHiveChanged;
    protected virtual void OnExecutionTimeOnHiveChanged() {
      var handler = ExecutionTimeOnHiveChanged;
      if (handler != null) handler(this, EventArgs.Empty);
    }
    #endregion

    protected override void Run(CancellationToken cancellationToken) {
      this.cancellationToken = cancellationToken;
      Run(ExecutionStack);
    }

    private void Run(object state) {
      Stack<IOperation> executionStack = (Stack<IOperation>)state;
      IOperation next;
      OperationCollection coll;
      IAtomicOperation operation;

      if (firstRun) {
        TaskScheduler.UnobservedTaskException += new EventHandler<UnobservedTaskExceptionEventArgs>(TaskScheduler_UnobservedTaskException);
        this.OnlinePlugins = ServiceLocator.Instance.CallHiveService(s => s.GetPlugins()).Where(x => x.Hash != null).ToList();
        this.AlreadyUploadedPlugins = new List<Plugin>();
        firstRun = false;
      }

      while (executionStack.Count > 0) {
        cancellationToken.ThrowIfCancellationRequested();

        next = executionStack.Pop();
        //bool isOpCollection = next is OperationCollection;
        //int collCount = isOpCollection ? ((OperationCollection)next).Count : 0;
        //string opName = !isOpCollection ? ((IAtomicOperation)next).Operator.Name : "OpCollection";

        if (next is OperationCollection) {
          coll = (OperationCollection)next;

          //bool isPMOEvaluator = coll.Count > 0 && coll.First() is HeuristicLab.Core.ExecutionContext && ((HeuristicLab.Core.ExecutionContext)coll.First()).Operator.GetType().Name == "PMOEvaluator";
          //bool isAlgorithmEvaluator = coll.Count > 0 && coll.First() is HeuristicLab.Core.ExecutionContext && ((HeuristicLab.Core.ExecutionContext)coll.First()).Operator.GetType().Name == "AlgorithmEvaluator";

          //if (coll.Parallel && isPMOEvaluator) {
          //  Task[] tasks = new Task[coll.Count];
          //  Stack<IOperation>[] stacks = new Stack<IOperation>[coll.Count];
          //  for (int i = 0; i < coll.Count; i++) {
          //    stacks[i] = new Stack<IOperation>();
          //    stacks[i].Push(coll[i]);
          //    tasks[i] = Task.Factory.StartNew(Run, stacks[i], cancellationToken);
          //  }
          //  try {
          //    Task.WaitAll(tasks);
          //  }
          //  catch (AggregateException ex) {
          //    OperationCollection remaining = new OperationCollection() { Parallel = true };
          //    for (int i = 0; i < stacks.Length; i++) {
          //      if (stacks[i].Count == 1)
          //        remaining.Add(stacks[i].Pop());
          //      if (stacks[i].Count > 1) {
          //        OperationCollection ops = new OperationCollection();
          //        while (stacks[i].Count > 0)
          //          ops.Add(stacks[i].Pop());
          //        remaining.Add(ops);
          //      }
          //    }
          //    if (remaining.Count > 0) executionStack.Push(remaining);
          //    throw ex;
          //  }
          //} else if (coll.Parallel) {
          if (coll.Parallel) {
            try {
              // clone the parent scope here and reuse it for each operation. otherwise for each job the whole scope-tree first needs to be copied and then cleaned, which causes a lot of work for the Garbage Collector
              IScope parentScopeClone = (IScope)((IAtomicOperation)coll.First()).Scope.Parent.Clone();
              parentScopeClone.SubScopes.Clear();
              parentScopeClone.ClearParentScopes();

              EngineJob[] jobs = new EngineJob[coll.Count];
              for (int i = 0; i < coll.Count; i++) {
                jobs[i] = new EngineJob(coll[i], new SequentialEngine.SequentialEngine());
              }

              var experiment = CreateHiveExperiment();
              IScope[] scopes = ExecuteOnHive(experiment, jobs, parentScopeClone, cancellationToken);

              for (int i = 0; i < coll.Count; i++) {
                if (coll[i] is IAtomicOperation) {
                  ExchangeScope(scopes[i], ((IAtomicOperation)coll[i]).Scope);
                } else if (coll[i] is OperationCollection) {
                  // todo ??
                }
              }
            }
            catch {
              executionStack.Push(coll); throw;
            }
          } else {
            for (int i = coll.Count - 1; i >= 0; i--)
              if (coll[i] != null) executionStack.Push(coll[i]);
          }
        } else if (next is IAtomicOperation) {
          operation = (IAtomicOperation)next;
          try {
            next = operation.Operator.Execute((IExecutionContext)operation, cancellationToken);
          }
          catch (Exception ex) {
            executionStack.Push(operation);
            if (ex is OperationCanceledException) throw ex;
            else throw new OperatorExecutionException(operation.Operator, ex);
          }
          if (next != null) executionStack.Push(next);

          if (operation.Operator.Breakpoint) {
            LogMessage(string.Format("Breakpoint: {0}", operation.Operator.Name != string.Empty ? operation.Operator.Name : operation.Operator.ItemName));
            Pause();
          }
        }
      }
    }

    private void TaskScheduler_UnobservedTaskException(object sender, UnobservedTaskExceptionEventArgs e) {
      e.SetObserved(); // avoid crash of process
    }

    private IRandom FindRandomParameter(IExecutionContext ec) {
      try {
        if (ec == null)
          return null;

        foreach (var p in ec.Parameters) {
          if (p.Name == "Random" && p is IValueParameter)
            return ((IValueParameter)p).Value as IRandom;
        }
        return FindRandomParameter(ec.Parent);
      }
      catch { return null; }
    }

    private static void ReIntegrateScope(IAtomicOperation source, IAtomicOperation target) {
      ExchangeScope(source.Scope, target.Scope);
    }

    private static void ExchangeScope(IScope source, IScope target) {
      target.Variables.Clear();
      target.Variables.AddRange(source.Variables);
      target.SubScopes.Clear();
      target.SubScopes.AddRange(source.SubScopes);
      // TODO: validate if parent scopes match - otherwise source is invalid
    }

    /// <summary>
    /// This method blocks until all jobs are finished
    /// TODO: Cancelation needs to be refined; all tasks currently stay in Semaphore.WaitOne after cancelation
    /// </summary>
    /// <param name="jobs"></param>
    private IScope[] ExecuteOnHive(RefreshableHiveExperiment refreshableHiveExperiment, EngineJob[] jobs, IScope parentScopeClone, CancellationToken cancellationToken) {
      LogMessage(string.Format("Executing {0} operations on the hive.", jobs.Length));
      IScope[] scopes = new Scope[jobs.Length];
      object locker = new object();
      var hiveExperiment = refreshableHiveExperiment.HiveExperiment;

      try {
        // create upload-tasks
        for (int i = 0; i < jobs.Length; i++) {
          var engineHiveJob = new EngineHiveJob(jobs[i], parentScopeClone);
          engineHiveJob.Job.Priority = this.Priority;
          hiveExperiment.HiveJobs.Add(engineHiveJob);

          // shuffle random variable to avoid the same random sequence in each operation; todo: does not yet work (it cannot find the random variable)
          IRandom random = FindRandomParameter(jobs[i].InitialOperation as IExecutionContext);
          if (random != null)
            random.Reset(random.Next());
        }
        HiveClient.StartExperiment((e) => { LogException(e); }, refreshableHiveExperiment);

        // do polling until experiment is finished and all jobs are downloaded
        while (!refreshableHiveExperiment.AllJobsFinished()) {
          Thread.Sleep(2000);
          this.ExecutionTimeOnHive = TimeSpan.FromMilliseconds(hiveExperiments.Sum(x => x.HiveExperiment.ExecutionTime.TotalMilliseconds));
          cancellationToken.ThrowIfCancellationRequested();
        }
        LogMessage(string.Format("{0} finished (TotalExecutionTime: {1}).", refreshableHiveExperiment.ToString(), refreshableHiveExperiment.HiveExperiment.ExecutionTime));

        var failedJobs = hiveExperiment.HiveJobs.Where(x => x.Job.State == JobState.Failed);
        if (failedJobs.Count() > 0) {
          throw new HiveEngineException("Job failed: " + failedJobs.First().Job.StateLog.Last().Exception);
        }

        // get scopes
        int j = 0;
        foreach (var hiveJob in hiveExperiment.HiveJobs) {
          var scope = ((IAtomicOperation)((EngineJob)hiveJob.ItemJob).InitialOperation).Scope;
          scopes[j++] = scope;
        }
        return scopes;
      }
      catch (OperationCanceledException e) {
        throw e;
      }
      catch (Exception e) {
        LogException(e);
        throw e;
      }
      finally {
        DisposeHiveExperiment(refreshableHiveExperiment);
      }
    }

    private RefreshableHiveExperiment CreateHiveExperiment() {
      lock (locker) {
        var hiveExperiment = new HiveExperiment();
        hiveExperiment.Name = "HiveEngine Run " + hiveExperiments.Count;
        hiveExperiment.DateCreated = DateTime.Now;
        hiveExperiment.ResourceNames = this.ResourceNames;
        hiveExperiment.IsPrivileged = this.IsPrivileged;
        var refreshableHiveExperiment = new RefreshableHiveExperiment(hiveExperiment);
        refreshableHiveExperiment.IsControllable = false;
        hiveExperiments.Add(refreshableHiveExperiment);
        return refreshableHiveExperiment;
      }
    }

    private void DisposeHiveExperiment(RefreshableHiveExperiment refreshableHiveExperiment) {
      refreshableHiveExperiment.RefreshAutomatically = false;
      DeleteHiveExperiment(refreshableHiveExperiment.HiveExperiment.Id);
      ClearData(refreshableHiveExperiment);
    }

    private void ClearData(RefreshableHiveExperiment refreshableHiveExperiment) {
      var jobs = refreshableHiveExperiment.HiveExperiment.GetAllHiveJobs();
      foreach (var job in jobs) {
        job.ClearData();
      }
    }

    private void DeleteHiveExperiment(Guid hiveExperimentId) {
      HiveClient.TryAndRepeat(() => {
        ServiceLocator.Instance.CallHiveService(s => s.DeleteHiveExperiment(hiveExperimentId));
      }, 5, string.Format("Could not delete jobs"));
    }

    private List<Guid> GetResourceIds() {
      return ServiceLocator.Instance.CallHiveService(service => {
        var resourceNames = ResourceNames.Split(';');
        var resourceIds = new List<Guid>();
        foreach (var resourceName in resourceNames) {
          Guid resourceId = service.GetResourceId(resourceName);
          if (resourceId == Guid.Empty) {
            throw new ResourceNotFoundException(string.Format("Could not find the resource '{0}'", resourceName));
          }
          resourceIds.Add(resourceId);
        }
        return resourceIds;
      });
    }

    /// <summary>
    /// Threadsafe message logging
    /// </summary>
    private void LogMessage(string message) {
      lock (logLocker) {
        Log.LogMessage(message);
      }
    }

    /// <summary>
    /// Threadsafe exception logging
    /// </summary>
    private void LogException(Exception exception) {
      lock (logLocker) {
        Log.LogException(exception);
      }
    }

    // testfunction:
    //private IScope[] ExecuteLocally(EngineJob[] jobs, IScope parentScopeClone, CancellationToken cancellationToken) {
    //  IScope[] scopes = new Scope[jobs.Length];
    //  for (int i = 0; i < jobs.Length; i++) {
    //    var serialized = PersistenceUtil.Serialize(jobs[i]);
    //    var deserialized = PersistenceUtil.Deserialize<IJob>(serialized);
    //    deserialized.Start();
    //    while (deserialized.ExecutionState != ExecutionState.Stopped) {
    //      Thread.Sleep(100);
    //    }
    //    var serialized2 = PersistenceUtil.Serialize(deserialized);
    //    var deserialized2 = PersistenceUtil.Deserialize<EngineJob>(serialized2);
    //    var newScope = ((IAtomicOperation)deserialized2.InitialOperation).Scope;
    //    scopes[i] = newScope;
    //  }
    //  return scopes;
    //}
  }
}