using System;
using System.Diagnostics;
using Xunit;
using Xunit.Abstractions;

namespace Centron.Tests.EndToEnd.Infrastructure
{
    public abstract class PerformanceTest : EndToEndTest
    {
        protected PerformanceTest(ITestOutputHelper testOutputHelper) 
            : base(testOutputHelper)
        {
        }

        public override void Execute()
        {
            this.Prepare();

            var watch = Stopwatch.StartNew();
            this.Measure();
            watch.Stop();
            
            this.AssertResults();

            bool FinishedInTime(double factor)
            {
                return this.AllowedDuration == null || 
                       watch.Elapsed.TotalSeconds <= this.AllowedDuration.Value.TotalSeconds * factor;
            }

            bool finishedPerfect = FinishedInTime(factor: 1.0);
            bool finishedGood = FinishedInTime(factor: 1.1);
            bool finishedBad = FinishedInTime(factor: 1.5);

            var status = finishedPerfect
                ? "PERFECT"
                : finishedGood
                    ? "GOOD"
                    : finishedBad
                        ? "BAD"
                        : string.Empty;

            if (string.IsNullOrWhiteSpace(status))
            {
                this.TestOutputHelper.WriteLine($"{this.GetType().Name} did not finish in time. Max duration is {this.AllowedDuration?.ToString() ?? "(infinite)"}, but it took {watch.Elapsed}");
            }
            else
            {
                this.TestOutputHelper.WriteLine($"{this.GetType().Name} did finish {status} in {watch.Elapsed}");
            }
        }
        

        protected virtual TimeSpan? AllowedDuration { get; }

        protected virtual void Prepare()
        {
        }

        protected abstract void Measure();

        protected virtual void AssertResults()
        {
        }
    }
}