namespace Diligent.WebAPI.Host.Middlewares
{
    public class CorrelationMiddleware
    {
        private const string DefaultHeader = "X-Correlation-ID";
        private readonly RequestDelegate next;
        private readonly ILogger<CorrelationMiddleware> logger;
        public CorrelationMiddleware(RequestDelegate next, ILogger<CorrelationMiddleware> logger) => (this.next,this.logger) = (next,logger);

        public async Task Invoke(HttpContext context)
        {
            if (!context.Request.Headers.TryGetValue(DefaultHeader, out var correlation))
            {
                correlation = Guid.NewGuid().ToString();
            }

            context.Response.OnStarting(() =>
            {
                if (!context.Response.Headers.ContainsKey(DefaultHeader))
                {
                    context.Response.Headers.Add(DefaultHeader, correlation);
                }

                return Task.CompletedTask;
            });
            using (logger.BeginScope(new Dictionary<string, object>
            {
                ["CorrelationId"] = correlation
            }))
            {
                context.Items.Add(DefaultHeader, correlation);
                await next(context);
                
            }
        }
    }
}