using System;
using System.Collections.Generic;
using System.IO;
using System.Net;
using System.Net.Http;
using System.Threading;
using System.Threading.Tasks;
using Junction.Domain.Models;
using Junction.Domain.Protocols;
using Junction.Protocols.MTConnect;
using Xunit;

namespace Junction.Tests.Unit
{
    public sealed class MtconnectDriverTests
    {
        private static readonly Guid MachineId = Guid.Parse("aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee");
        private const string AgentUrl = "http://mtconnect-agent.test:5000";

        private static string LoadCurrentFixture()
        {
            var path = Path.Combine(AppContext.BaseDirectory, "Fixtures", "mtconnect", "current.xml");
            return File.ReadAllText(path);
        }

        /// <summary>Stub handler: canned response or thrown exception, per configuration.</summary>
        private sealed class StubHandler : HttpMessageHandler
        {
            private readonly Func<HttpRequestMessage, CancellationToken, Task<HttpResponseMessage>> _responder;

            public Uri? LastRequestUri { get; private set; }

            public StubHandler(HttpStatusCode status, string body)
            {
                _responder = (_, __) => Task.FromResult(new HttpResponseMessage(status)
                {
                    Content = new StringContent(body),
                });
            }

            public StubHandler(Func<HttpRequestMessage, CancellationToken, Task<HttpResponseMessage>> responder)
            {
                _responder = responder;
            }

            protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
            {
                LastRequestUri = request.RequestUri;
                return _responder(request, cancellationToken);
            }
        }

        private static readonly TimeSpan GenerousTimeout = TimeSpan.FromSeconds(30);

        // Shared client with infinite global timeout mirrors production; per-request timeout enforced in driver.
        private static MtconnectDriver DriverWith(HttpMessageHandler handler, TimeSpan? requestTimeout = null) =>
            new MtconnectDriver(
                MachineId,
                AgentUrl,
                new HttpClient(handler) { Timeout = Timeout.InfiniteTimeSpan },
                requestTimeout ?? GenerousTimeout);

        // ---- ReadCurrentAsync: happy path ----

        [Fact]
        public async Task ReadCurrentAsync_200WithValidXml_ReturnsOkSnapshotStampedWithMachineId()
        {
            var handler = new StubHandler(HttpStatusCode.OK, LoadCurrentFixture());
            var driver = DriverWith(handler);

            var result = await driver.ReadCurrentAsync(CancellationToken.None);

            Assert.True(result.IsSuccess);
            Assert.False(result.WasCancelled);
            Assert.NotNull(result.Value);
            Assert.Equal(MachineId, result.Value.MachineId);
            Assert.True(result.Value.Items.Count > 0);
            Assert.Equal(ConnectionState.Connected, result.Value.ConnectionState);

            // Driver hits the agent's /current endpoint.
            Assert.NotNull(handler.LastRequestUri);
            Assert.EndsWith("/current", handler.LastRequestUri!.AbsoluteUri);
        }

        [Fact]
        public void ProtocolId_IsMtconnect()
        {
            var driver = DriverWith(new StubHandler(HttpStatusCode.OK, "<x/>"));
            Assert.Equal("mtconnect", driver.ProtocolId);
        }

        // ---- ReadCurrentAsync: HTTP failure statuses ----

        [Theory]
        [InlineData(HttpStatusCode.NotFound)]
        [InlineData(HttpStatusCode.InternalServerError)]
        public async Task ReadCurrentAsync_NonSuccessStatus_ReturnsFailNoThrow(HttpStatusCode status)
        {
            var handler = new StubHandler(status, "irrelevant");
            var driver = DriverWith(handler);

            var result = await driver.ReadCurrentAsync(CancellationToken.None);

            Assert.False(result.IsSuccess);
            Assert.False(result.WasCancelled);
            Assert.NotEmpty(result.Errors);
        }

        // ---- ReadCurrentAsync: network down ----

        [Fact]
        public async Task ReadCurrentAsync_HttpRequestException_ReturnsFailNoThrow()
        {
            var handler = new StubHandler((_, __) =>
                throw new HttpRequestException("connection refused"));
            var driver = DriverWith(handler);

            var result = await driver.ReadCurrentAsync(CancellationToken.None);

            Assert.False(result.IsSuccess);
            Assert.False(result.WasCancelled);
            Assert.NotEmpty(result.Errors);
        }

        // ---- ReadCurrentAsync: cancellation ----

        [Fact]
        public async Task ReadCurrentAsync_CancelledBeforeCall_ReturnsCancelled()
        {
            var handler = new StubHandler(HttpStatusCode.OK, LoadCurrentFixture());
            var driver = DriverWith(handler);
            using var cts = new CancellationTokenSource();
            cts.Cancel();

            var result = await driver.ReadCurrentAsync(cts.Token);

            Assert.False(result.IsSuccess);
            Assert.True(result.WasCancelled);
        }

        [Fact]
        public async Task ReadCurrentAsync_CancelledDuringSend_ReturnsCancelledNoThrow()
        {
            var handler = new StubHandler(async (_, ct) =>
            {
                await Task.Delay(Timeout.Infinite, ct).ConfigureAwait(false);
                return new HttpResponseMessage(HttpStatusCode.OK);
            });
            var driver = DriverWith(handler);
            using var cts = new CancellationTokenSource();

            var task = driver.ReadCurrentAsync(cts.Token);
            cts.Cancel();
            var result = await task;

            Assert.False(result.IsSuccess);
            Assert.True(result.WasCancelled);
        }

        // ---- ReadCurrentAsync: per-request timeout (linked CTS) ----

        [Fact]
        public async Task ReadCurrentAsync_RequestExceedsPerRequestTimeout_ReturnsFailCurrentTimeoutNotCancelled()
        {
            // Handler stalls until its token trips; only the driver's linked CTS (CancelAfter) can trip it.
            var handler = new StubHandler(async (_, ct) =>
            {
                await Task.Delay(Timeout.Infinite, ct).ConfigureAwait(false);
                return new HttpResponseMessage(HttpStatusCode.OK);
            });
            var driver = DriverWith(handler, TimeSpan.FromMilliseconds(50));

            // Caller token never cancelled: any cancellation here is the per-request timeout.
            var result = await driver.ReadCurrentAsync(CancellationToken.None);

            Assert.False(result.IsSuccess);
            Assert.False(result.WasCancelled);
            Assert.NotEmpty(result.Errors);
            Assert.Contains(result.Errors, e => e.Code == "CURRENT_TIMEOUT");
        }

        [Fact]
        public async Task ReadCurrentAsync_CallerCancelBeatsTimeout_ReturnsCancelled()
        {
            var handler = new StubHandler(async (_, ct) =>
            {
                await Task.Delay(Timeout.Infinite, ct).ConfigureAwait(false);
                return new HttpResponseMessage(HttpStatusCode.OK);
            });
            // Generous per-request timeout so the caller cancel wins the race, not the timeout.
            var driver = DriverWith(handler, GenerousTimeout);
            using var cts = new CancellationTokenSource();

            var task = driver.ReadCurrentAsync(cts.Token);
            cts.Cancel();
            var result = await task;

            Assert.False(result.IsSuccess);
            Assert.True(result.WasCancelled);
        }

        // ---- Factory: config validation ----

        private static Machine MachineWithConfig(IReadOnlyDictionary<string, string>? config) =>
            new Machine(MachineId, "VMC-01", "mtconnect", config, TimeSpan.FromSeconds(5));

        [Fact]
        public void Factory_ProtocolId_IsMtconnect()
        {
            Assert.Equal("mtconnect", new MtconnectDriverFactory().ProtocolId);
        }

        [Fact]
        public void Factory_MissingAgentUrl_ReturnsFail()
        {
            var factory = new MtconnectDriverFactory();
            var machine = MachineWithConfig(new Dictionary<string, string>());

            var result = factory.Create(machine);

            Assert.False(result.IsSuccess);
            Assert.NotEmpty(result.Errors);
        }

        [Fact]
        public void Factory_EmptyAgentUrl_ReturnsFail()
        {
            var factory = new MtconnectDriverFactory();
            var machine = MachineWithConfig(new Dictionary<string, string> { ["AgentUrl"] = "   " });

            var result = factory.Create(machine);

            Assert.False(result.IsSuccess);
        }

        [Fact]
        public void Factory_ValidAgentUrl_ReturnsOkDriverWithMtconnectProtocolId()
        {
            var factory = new MtconnectDriverFactory();
            var machine = MachineWithConfig(new Dictionary<string, string> { ["AgentUrl"] = AgentUrl });

            var result = factory.Create(machine);

            Assert.True(result.IsSuccess);
            Assert.NotNull(result.Value);
            Assert.Equal("mtconnect", result.Value.ProtocolId);
        }

        [Fact]
        public void Factory_AgentUrlKeyIsCaseInsensitive()
        {
            var factory = new MtconnectDriverFactory();
            var machine = MachineWithConfig(new Dictionary<string, string> { ["agenturl"] = AgentUrl });

            var result = factory.Create(machine);

            Assert.True(result.IsSuccess);
        }

        [Fact]
        public void Factory_InvalidTimeout_ReturnsFail()
        {
            var factory = new MtconnectDriverFactory();
            var machine = MachineWithConfig(new Dictionary<string, string>
            {
                ["AgentUrl"] = AgentUrl,
                ["TimeoutSeconds"] = "not-a-number",
            });

            var result = factory.Create(machine);

            Assert.False(result.IsSuccess);
        }
    }
}