using System;
using System.Collections.Concurrent;
using System.Diagnostics;
using Microsoft.Extensions.Logging;

namespace AyaNova.Util
{

    //Track processes and kill any that go past their expiry date
    internal static class ReportRenderManager
    {

        //thread safe collection for unordered items, optimized for single thread produce/consume (which is the norm here) but supports multithread produce / consume (which is needed for separate cleanup job)
        internal static ConcurrentBag<ReportRenderInstanceInfo> _baginstances;// = new ConcurrentBag<ReportRenderInstanceInfo>();


        static ReportRenderManager()
        {
            _baginstances = new ConcurrentBag<ReportRenderInstanceInfo>();
        }

        internal class ReportRenderInstanceInfo
        {
            internal int ReporterProcessId { get; set; }
            internal DateTime Expires { get; set; }

            internal ReportRenderInstanceInfo(int processId, DateTime expires)
            {
                ReporterProcessId = processId;
                Expires = expires;
            }
        }


        internal static void KillExpiredRenders(ILogger log)
        {
            log.LogDebug("Clear potential expired render jobs check");
            //check for expired and remove
            var Instances = _baginstances.ToArray();
            var dtNow = DateTime.UtcNow;
            foreach (ReportRenderInstanceInfo i in Instances)
            {
                if (i.Expires < dtNow)
                {
// #if (DEBUG)
//                     log.LogInformation($"DBG: KillExpiredRenders attempting kill of expired process {i.ReporterProcessId}");
// #endif
                    ForceCloseProcess(i, log);
                }
            }
        }

        internal static bool ForceCloseProcess(ReportRenderInstanceInfo instance, ILogger log)
        {
            log.LogDebug($"ForceCloseProcess on report render instance id {instance.ReporterProcessId} expired {instance.Expires.ToString()} utc");
            try
            {
                var p = Process.GetProcessById(instance.ReporterProcessId);
                
                if (p != null)
                {
                    //we have an existing process                   
                    //try to kill it                   
                    p.Kill(true);
                    if (p.HasExited == false)
                    {
                        log.LogDebug($"Expired report render instance id {instance.ReporterProcessId} could not be force closed");
                        return false;//can't kill it so can't free up a slot
                    }
                }
                //remove it from the list, it's either gone or killed at this point
                //this would not be unexpected since it will normally just close on it's own
                //at the finally in render report
                _baginstances.TryTake(out instance);
                return true;//process that was there is now not there so while not perfect system we will consider it free

            }
            catch (ArgumentException)
            {
                //do nothing, this is normal, the process could not be found and this means it's already been removed:
                //ArgumentException
                //The process specified by the processId parameter is not running. The identifier might be expired.
                _baginstances.TryTake(out instance);
                return true;
            }
        }

        internal static void AddProcess(int processId, DateTime expires, ILogger log)
        {
            // #if (DEBUG)
            //             log.LogInformation($"DBG: RenderSlotAvailable::AddProcess {processId} in the bag");
            // #endif
            _baginstances.Add(new ReportRenderInstanceInfo(processId, expires));

            // #if (DEBUG)
            //             log.LogInformation($"DBG: RenderSlotAvailable::AddProcess, there are currently {_baginstances.Count} instances in the bag");
            // #endif
        }

        internal static void RemoveProcess(int processId, ILogger log)
        {
            // #if (DEBUG)
            //             log.LogInformation($"DBG: RenderSlotAvailable::RemoveProcess {processId} from the bag");
            // #endif
            foreach (var i in _baginstances)
            {
                if (i.ReporterProcessId == processId)
                {
                    ForceCloseProcess(i, log);
                    break;
                }
            }
        }

    }//eoc
}//eons