using System;
using System.Collections.Generic;
using Opc.Ua;
using Shouldly;
using Xunit;
using ZB.MOM.WW.LmxOpcUa.Host.Historian;

namespace ZB.MOM.WW.LmxOpcUa.Tests.Historian
{
    public class HistoryContinuationPointTests
    {
        private static List<DataValue> CreateTestValues(int count)
        {
            var values = new List<DataValue>();
            for (var i = 0; i < count; i++)
                values.Add(new DataValue
                {
                    Value = new Variant((double)i),
                    SourceTimestamp = DateTime.UtcNow.AddSeconds(i),
                    StatusCode = StatusCodes.Good
                });
            return values;
        }

        [Fact]
        public void Store_ReturnsNonEmptyContinuationPoint()
        {
            var mgr = new HistoryContinuationPointManager();
            var values = CreateTestValues(5);

            var cp = mgr.Store(values);

            cp.ShouldNotBeNull();
            cp.Length.ShouldBe(16); // GUID = 16 bytes
        }

        [Fact]
        public void Retrieve_ValidContinuationPoint_ReturnsStoredValues()
        {
            var mgr = new HistoryContinuationPointManager();
            var values = CreateTestValues(5);
            var cp = mgr.Store(values);

            var retrieved = mgr.Retrieve(cp);

            retrieved.ShouldNotBeNull();
            retrieved!.Count.ShouldBe(5);
        }

        [Fact]
        public void Retrieve_SameContinuationPointTwice_ReturnsNullSecondTime()
        {
            var mgr = new HistoryContinuationPointManager();
            var values = CreateTestValues(3);
            var cp = mgr.Store(values);

            mgr.Retrieve(cp).ShouldNotBeNull();
            mgr.Retrieve(cp).ShouldBeNull();
        }

        [Fact]
        public void Retrieve_InvalidBytes_ReturnsNull()
        {
            var mgr = new HistoryContinuationPointManager();

            mgr.Retrieve(new byte[] { 1, 2, 3 }).ShouldBeNull();
        }

        [Fact]
        public void Retrieve_NullBytes_ReturnsNull()
        {
            var mgr = new HistoryContinuationPointManager();

            mgr.Retrieve(null!).ShouldBeNull();
        }

        [Fact]
        public void Retrieve_UnknownGuid_ReturnsNull()
        {
            var mgr = new HistoryContinuationPointManager();

            mgr.Retrieve(Guid.NewGuid().ToByteArray()).ShouldBeNull();
        }

        [Fact]
        public void Release_RemovesContinuationPoint()
        {
            var mgr = new HistoryContinuationPointManager();
            var values = CreateTestValues(5);
            var cp = mgr.Store(values);

            mgr.Release(cp);

            mgr.Retrieve(cp).ShouldBeNull();
        }

        [Fact]
        public void Retrieve_ExpiredContinuationPoint_ReturnsNull()
        {
            var mgr = new HistoryContinuationPointManager(TimeSpan.FromMilliseconds(1));
            var values = CreateTestValues(5);
            var cp = mgr.Store(values);

            System.Threading.Thread.Sleep(50);

            mgr.Retrieve(cp).ShouldBeNull();
        }

        [Fact]
        public void Release_PurgesExpiredEntries()
        {
            var mgr = new HistoryContinuationPointManager(TimeSpan.FromMilliseconds(1));
            var cp1 = mgr.Store(CreateTestValues(3));
            var cp2 = mgr.Store(CreateTestValues(5));

            System.Threading.Thread.Sleep(50);

            // Release one — purge should clean both expired entries
            mgr.Release(cp1);
            mgr.Retrieve(cp2).ShouldBeNull();
        }

        [Fact]
        public void MultipleContinuationPoints_IndependentRetrieval()
        {
            var mgr = new HistoryContinuationPointManager();
            var values1 = CreateTestValues(3);
            var values2 = CreateTestValues(7);

            var cp1 = mgr.Store(values1);
            var cp2 = mgr.Store(values2);

            var r1 = mgr.Retrieve(cp1);
            var r2 = mgr.Retrieve(cp2);

            r1.ShouldNotBeNull();
            r1!.Count.ShouldBe(3);
            r2.ShouldNotBeNull();
            r2!.Count.ShouldBe(7);
        }
    }
}