using System.Collections.Generic;
using System;
using System.Threading;
using System.Threading.Tasks;

using C4IT.FASD.Base;
using C4IT.Logging;

using static C4IT.Logging.cLogManager;

namespace C4IT.F4SD
{
    public partial class F4SDHelperService
    {
        private static readonly AsyncLocal<cTicketFilterPolicy> currentTicketFilters =
            new AsyncLocal<cTicketFilterPolicy>();

        private sealed class TicketFilterScope : IDisposable
        {
            private readonly cTicketFilterPolicy previous;

            public TicketFilterScope(cTicketFilterPolicy filters)
            {
                previous = currentTicketFilters.Value;
                currentTicketFilters.Value = filters;
            }

            public void Dispose()
            {
                currentTicketFilters.Value = previous;
            }
        }

        internal IDisposable BeginTicketFilterScope(cTicketFilterPolicy filters)
        {
            return new TicketFilterScope(filters);
        }

        internal async Task<string> ApplyTicketFiltersAsync(string baseFilter, cTicketFilterPolicy policy)
        {
            var result = await TicketFilterCompiler.CompileAsync(policy ?? currentTicketFilters.Value, null);
            if (!result.Success)
            {
                LogEntry($"Ticket filter rejected (fail closed): {result.Error}", LogLevels.Error);
                return null;
            }

            return string.IsNullOrWhiteSpace(result.Clause)
                ? baseFilter
                : $"({baseFilter}) AND ({result.Clause})";
        }

        internal cTicketFilterCapabilities GetTicketFilterCapabilities()
        {
            return new cTicketFilterCapabilities
            {
                Provider = TicketFilterCompiler.ProviderName,
                CommonFields = new List<string> { TicketFilterCompiler.AssignmentGroupField },
                ProviderFields = new List<string> { TicketFilterCompiler.QueueField }
            };
        }
    }
}