using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using HeuristicLab.Clients.Hive;
using HeuristicLab.Core;

namespace HeuristicLab.Problems.Modifiers {
  /// <summary>
  /// non-storable poller that downloads hive jobs 
  /// </summary>
  public class HiveEvaluationResultPoller {
    protected static readonly object LogLocker = new object();
    protected static readonly Semaphore Throttle = new Semaphore(90, 90); //The Hive server throttles connections down to 100 
  }
  public class HiveEvaluationResultPoller<T> : HiveEvaluationResultPoller where T : IExecutable {
    private Thread thread;
    private readonly object locker = new object();
    private readonly Dictionary<Guid, TaskCompletionSource<T>> jobs = new Dictionary<Guid, TaskCompletionSource<T>>();

    public TimeSpan Interval { get; set; }
    public string LogFile;
    public HiveEvaluationResultPoller(TimeSpan interval) {
      Interval = interval;
    }

    public TaskCompletionSource<T> StartEvaluation(T evaluation, HiveApi.Options options) {
      HiveApi.RefreshHiveClient(out var projects, out _);
      var projectId = HiveApi.GuardProjectId(options.ProjectId, projects);
      var resourceIds = options.ResourceIds;
      var jobName = HiveApi.GuardJobName(new[] { evaluation }, options.JobName);
      var distribute = options.Distribute;
      using (var refreshableJob = HiveApi.PackJob(new[] { evaluation }, projectId, resourceIds, jobName, distribute)) {
        Throttle.WaitOne();
        try {
          HiveClient.Store(refreshableJob, CancellationToken.None);
        } catch (Exception e) {
          WriteToLog(new[] { "Exception occured when uploading Job : " + DateTime.Now, e.ToString(), "========" });
          throw;
        } finally {
          Throttle.Release();
        }
        var comp = new TaskCompletionSource<T>();
        lock (locker) {
          var startNew = jobs.Count == 0;
          jobs.Add(refreshableJob.Id, comp);
          if (startNew) Start();
        }
        return comp;
      }
    }

    #region Helpers
    private void Start() {
      thread = new Thread(RunPolling);
      thread.Start();
    }

    private void RunPolling() {
      var stopRequested = false;
      do {
        try {
          Thread.Sleep(Interval);
          stopRequested = FetchJobResults();
          HiveApi.RefreshHiveClient(out _, out _);
        } catch (Exception e) {
          WriteToLog(new[] { "Poller Exception occurred at : " + DateTime.Now, e.ToString(), "========" });
        }
      } while (!stopRequested);
    }

    private bool FetchJobResults() {
      var stopping = false;
      HiveServiceLocator.Instance.CallHiveService(service => {
        Guid[] tasks1;
        lock (locker) {
          tasks1 = jobs.Keys.ToArray();
        }

        var toRemoves = new HashSet<Guid>();
        foreach (var x in tasks1) {
          LightweightTask task;
          try {
            task = service.GetLightweightJobTasksWithoutStateLog(x).Single();
          } catch (Exception e) {
            toRemoves.Add(x);
            lock (locker) {
              if (jobs.ContainsKey(x)) jobs[x].SetException(e);
            }
            continue;
          }
          switch (task.State) {
            case TaskState.Offline:
            case TaskState.Waiting:
            case TaskState.Transferring:
            case TaskState.Calculating:
            case TaskState.Paused:
              break;
            case TaskState.Finished:
              var evaluation = (T)PersistenceUtil.Deserialize<ItemTask>(service.GetTaskData(task.Id).Data).Item;
              HiveClient.Delete(service.GetJob(x));
              toRemoves.Add(x);
              lock (locker) {
                if (jobs.ContainsKey(x))
                  jobs[x].SetResult(evaluation);
              }
              break;
            case TaskState.Aborted:
            case TaskState.Failed:
              toRemoves.Add(x);
              lock (locker) {
                if (jobs.ContainsKey(x))
                  jobs[x].SetException(new HiveException($"The evaluation with job id {x} and task id {task.Id} failed. Please consult the Hive Job-Manager for further information"));
              }
              break;
            default:
              throw new ArgumentOutOfRangeException();
          }
        }

        lock (locker) {
          foreach (var x in toRemoves.Where(x => jobs.ContainsKey(x))) {
            jobs.Remove(x);
            if (jobs.Count != 0) continue;
            stopping = true;
            thread = null;
          }
        }

      });
      return stopping;
    }
    private void WriteToLog(IEnumerable<string> lines) {
      if (LogFile == null) return;
      lock (LogLocker) {
        try {
          File.AppendAllLines(LogFile, lines);
        } catch { // ignored
        }
      }
    }
    #endregion
  }
}