using System;
using System.Configuration;
using System.Linq;
using System.Reflection;
using System.Threading;
using System.Threading.Tasks;
using log4net;

namespace Watson.Integration
{
    public static class RetryHelper
    {
        //I am using log4net but swap in your favourite
        private static readonly ILog Log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);

        public static async Task RetryOnExceptionAsync(int times, TimeSpan delay, Func<Task> operation)
        {
            await RetryOnExceptionAsync<Exception>(times, delay, operation);
        }

        public static async Task RetryOnExceptionAsync<TException>(int times, TimeSpan delay, Func<Task> operation) where TException : Exception
        {
            if (times <= 0) throw new ArgumentOutOfRangeException(nameof(times));

            var attempts = 0;
            do
            {
                try
                {
                    attempts++;
                    await operation();
                    break;
                }
                catch (TException ex)
                {
                    if (attempts == times)
                        throw;

                    await CreateDelayForException(times, attempts, delay, ex);
                }
            } while (true);
        }

        private static Task CreateDelayForException(int times, int attempts, TimeSpan delay, Exception ex)
        {
            var delay = IncreasingDelayInSeconds(attempts);
            Log.Warn($"Exception on attempt {attempts} - Retying max {times} times. Sleeping for {delay}s.", ex);
            return Task.Delay(delay);
        }
    }
}