using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Text;

namespace Wayne.Lib.Log.SlowLog
{
    internal class Slowlogger : DisposableBase, ISlowLogger
    {
        private static readonly IIdentifiableEntity LoggingEntity = new IdentifiableEntity(IdentifiableEntity.NoId, "SlowLog", "", null);
        private readonly Stopwatch stopwatch = Stopwatch.StartNew();
        private readonly string context;
        private readonly TimeSpan threshold;
        readonly List<CheckpointInstant> checkpoints = new List<CheckpointInstant>();

        class CheckpointInstant
        {
            public TimeSpan At { get; set; }
            public string Name { get; set; }
        }

        public Slowlogger(string context, TimeSpan threshold)
        {
            this.context = context;
            this.threshold = threshold;
        }

        protected override void DoDispose()
        {
            stopwatch.Stop();
            if (stopwatch.Elapsed > threshold)
            {
                using (DebugLogger debugLogger = new DebugLogger(LoggingEntity))
                {
                    if (debugLogger.IsActive())
                    {
                        StringBuilder sb = new StringBuilder();
                        sb.AppendFormat("::::::  SLOWLOG ::::: [{0}] Expected to take less than {1} but took {2}", context, threshold, stopwatch.Elapsed);
                        if (checkpoints.Count > 0)
                        {
                            TimeSpan lastTimeSpan = checkpoints[0].At;
                            foreach (var checkpointInstant in checkpoints)
                            {
                                sb.AppendLine();
                                sb.AppendFormat("     Checkpoint {0,45} @ {1}, delta {2}", checkpointInstant.Name, checkpointInstant.At, checkpointInstant.At - lastTimeSpan);
                                lastTimeSpan = checkpointInstant.At;
                            }
                        }
                        debugLogger.Add(sb);
                    }
                }
            }
        }

        public void Checkpoint(string checkpointName)
        {
            checkpoints.Add(new CheckpointInstant()
            {
                Name = checkpointName,
                At = stopwatch.Elapsed
            });
        }
    }
}