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<cActivityFilterPolicy> currentActivityFilters =
            new AsyncLocal<cActivityFilterPolicy>();

        private sealed class ActivityFilterScope : IDisposable
        {
            private readonly cActivityFilterPolicy previous;

            public ActivityFilterScope(cActivityFilterPolicy filters)
            {
                previous = currentActivityFilters.Value;
                currentActivityFilters.Value = filters;
            }

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

        internal IDisposable BeginActivityFilterScope(cActivityFilterPolicy filters)
        {
            return new ActivityFilterScope(filters);
        }

        internal async Task<string> ApplyActivityFiltersAsync(string baseFilter, cActivityFilterPolicy policy)
        {
            var result = await ActivityFilterCompiler.CompileAsync(policy ?? currentActivityFilters.Value, null);
            if (!result.Success)
            {
                LogEntry($"Activity filter rejected (fail closed): {result.Error}", LogLevels.Error);
                return null;
            }

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

        internal cTicketActivityFilterCapabilities GetActivityFilterCapabilities()
        {
            return new cTicketActivityFilterCapabilities
            {
                Provider = ActivityFilterCompiler.ProviderName,
                CommonFields = new List<string> { ActivityFilterCompiler.AssignmentGroupField },
                ProviderFields = new List<string> { ActivityFilterCompiler.QueueField }
            };
        }
    }
}