using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Junction.App.ViewModels;
using Junction.Core.Monitoring;
using Junction.Domain;
using Junction.Domain.Models;
using Junction.Domain.Persistence;
using Microsoft.Extensions.Logging.Abstractions;
using Moq;
using Xunit;

namespace Junction.Tests.Unit
{
    /// <summary>
    /// Trend-load behaviour of the detail VM: after a load, each row whose history parses as numeric
    /// gets a populated <see cref="DataItemRowViewModel.Trend"/> (ascending order) with
    /// <c>HasTrend</c> true; a row with non-numeric history stays null / <c>HasTrend</c> false.
    /// Fixture: Moq'd <see cref="IMachineRepository"/> + <see cref="IMachineMonitor"/> + null logger.
    /// The fire-and-forget trend load is awaited via the VM's internal <c>TrendLoadTask</c>.
    /// </summary>
    public class MachineDetailViewModelTests
    {
        private const string NumericItemId = "temp";
        private const string TextItemId = "avail";

        private static readonly Guid MachineId = Guid.NewGuid();

        private static MachineSnapshot SnapshotWithBothItems()
        {
            var now = DateTimeOffset.UtcNow;
            var items = new List<DataItem>
            {
                new DataItem(NumericItemId, "Temperature", "12", "Sample", now),
                new DataItem(TextItemId, "Availability", "AVAILABLE", "Event", now),
            };
            return new MachineSnapshot(MachineId, now, ConnectionState.Connected, items);
        }

        private static IReadOnlyList<HistoryPoint> NumericHistory()
        {
            var t = DateTimeOffset.UtcNow;
            return new List<HistoryPoint>
            {
                new HistoryPoint(NumericItemId, "10", t.AddSeconds(-30)),
                new HistoryPoint(NumericItemId, "12.5", t.AddSeconds(-20)),
                new HistoryPoint(NumericItemId, "11", t.AddSeconds(-10)),
            };
        }

        private static IReadOnlyList<HistoryPoint> TextHistory()
        {
            var t = DateTimeOffset.UtcNow;
            return new List<HistoryPoint>
            {
                new HistoryPoint(TextItemId, "AVAILABLE", t.AddSeconds(-20)),
                new HistoryPoint(TextItemId, "UNAVAILABLE", t.AddSeconds(-10)),
            };
        }

        private static MachineDetailViewModel BuildVm(
            Mock<IMachineRepository> repo,
            Mock<IMachineMonitor> monitor)
        {
            var vm = new MachineDetailViewModel(
                repo.Object, monitor.Object, NullLogger<MachineDetailViewModel>.Instance);
            vm.Initialize(MachineId, "VMC Sim (mock)");
            return vm;
        }

        private static Mock<IMachineMonitor> MonitorWithSnapshot(MachineSnapshot snapshot)
        {
            var monitor = new Mock<IMachineMonitor>();
            var cache = new Dictionary<Guid, MachineSnapshot> { [MachineId] = snapshot };
            monitor.SetupGet(m => m.LatestSnapshots)
                .Returns((IReadOnlyDictionary<Guid, MachineSnapshot>)cache);
            return monitor;
        }

        private static DataItemRowViewModel Row(MachineDetailViewModel vm, string id) =>
            vm.Items.First(r => r.Id == id);

        [Fact]
        public async Task LoadAsync_NumericHistory_PopulatesTrendAscending()
        {
            var snapshot = SnapshotWithBothItems();
            var repo = new Mock<IMachineRepository>();
            repo.Setup(r => r.GetByIdAsync(MachineId, It.IsAny<CancellationToken>()))
                .ReturnsAsync(Result<Machine>.Ok(new Machine(MachineId, "VMC", "mtconnect", null, TimeSpan.FromSeconds(2))));
            repo.Setup(r => r.GetHistoryAsync(MachineId, NumericItemId, It.IsAny<DateTimeOffset>(), It.IsAny<int>(), It.IsAny<CancellationToken>()))
                .ReturnsAsync(Result<IReadOnlyList<HistoryPoint>>.Ok(NumericHistory()));
            repo.Setup(r => r.GetHistoryAsync(MachineId, TextItemId, It.IsAny<DateTimeOffset>(), It.IsAny<int>(), It.IsAny<CancellationToken>()))
                .ReturnsAsync(Result<IReadOnlyList<HistoryPoint>>.Ok(TextHistory()));

            var monitor = MonitorWithSnapshot(snapshot);
            var vm = BuildVm(repo, monitor);

            await vm.LoadAsync();
            if (vm.TrendLoadTask != null)
            {
                await vm.TrendLoadTask;
            }

            var numericRow = Row(vm, NumericItemId);
            Assert.True(numericRow.HasTrend);
            Assert.NotNull(numericRow.Trend);
            Assert.Equal(new double[] { 10, 12.5, 11 }, numericRow.Trend!.ToArray());
        }

        [Fact]
        public async Task LoadAsync_NonNumericHistory_LeavesTrendNull()
        {
            var snapshot = SnapshotWithBothItems();
            var repo = new Mock<IMachineRepository>();
            repo.Setup(r => r.GetByIdAsync(MachineId, It.IsAny<CancellationToken>()))
                .ReturnsAsync(Result<Machine>.Ok(new Machine(MachineId, "VMC", "mtconnect", null, TimeSpan.FromSeconds(2))));
            repo.Setup(r => r.GetHistoryAsync(MachineId, NumericItemId, It.IsAny<DateTimeOffset>(), It.IsAny<int>(), It.IsAny<CancellationToken>()))
                .ReturnsAsync(Result<IReadOnlyList<HistoryPoint>>.Ok(NumericHistory()));
            repo.Setup(r => r.GetHistoryAsync(MachineId, TextItemId, It.IsAny<DateTimeOffset>(), It.IsAny<int>(), It.IsAny<CancellationToken>()))
                .ReturnsAsync(Result<IReadOnlyList<HistoryPoint>>.Ok(TextHistory()));

            var monitor = MonitorWithSnapshot(snapshot);
            var vm = BuildVm(repo, monitor);

            await vm.LoadAsync();
            if (vm.TrendLoadTask != null)
            {
                await vm.TrendLoadTask;
            }

            var textRow = Row(vm, TextItemId);
            Assert.False(textRow.HasTrend);
            Assert.Null(textRow.Trend);
        }

        [Fact]
        public async Task LoadAsync_HistoryFailureForOneItem_DoesNotThrowOrBlockOthers()
        {
            var snapshot = SnapshotWithBothItems();
            var repo = new Mock<IMachineRepository>();
            repo.Setup(r => r.GetByIdAsync(MachineId, It.IsAny<CancellationToken>()))
                .ReturnsAsync(Result<Machine>.Ok(new Machine(MachineId, "VMC", "mtconnect", null, TimeSpan.FromSeconds(2))));
            // Numeric item succeeds; text item fails hard.
            repo.Setup(r => r.GetHistoryAsync(MachineId, NumericItemId, It.IsAny<DateTimeOffset>(), It.IsAny<int>(), It.IsAny<CancellationToken>()))
                .ReturnsAsync(Result<IReadOnlyList<HistoryPoint>>.Ok(NumericHistory()));
            repo.Setup(r => r.GetHistoryAsync(MachineId, TextItemId, It.IsAny<DateTimeOffset>(), It.IsAny<int>(), It.IsAny<CancellationToken>()))
                .ThrowsAsync(new InvalidOperationException("boom"));

            var monitor = MonitorWithSnapshot(snapshot);
            var vm = BuildVm(repo, monitor);

            await vm.LoadAsync();
            if (vm.TrendLoadTask != null)
            {
                await vm.TrendLoadTask;
            }

            // The failing item leaves the successful item's trend intact.
            Assert.True(Row(vm, NumericItemId).HasTrend);
            Assert.False(Row(vm, TextItemId).HasTrend);
        }
    }
}