using S7.Net;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;

namespace ZB.MOM.WW.OtOpcUa.Driver.S7.Tests;

/// <summary>
///     R07:H4 — a deterministic PLC refusal (S7.Net <c>ReadData</c> / <c>WriteData</c> carrying an S7
///     item error such as "object does not exist", not a socket/timeout/framing fault) proves the CPU
///     answered. It is per-tag Bad with a once-per-tag Warning and NO Degraded; it advances
///     <c>LastSuccessfulRead</c>, so a driver whose every tag is refused (wrong DB number) no longer
///     trips the 90 s comms-loss watchdog against a reachable PLC.
/// </summary>
[Trait("Category", "Unit")]
public sealed class S7RefusalHealthTests
{
    private const uint BadDeviceFailure = 0x808B0000u;

    /// <summary>
    ///     The shape S7.Net's READ paths really raise for a CPU item error — a BARE
    ///     <see cref="Exception"/>, live-probed against the snap7 fixture (not a PlcException).
    /// </summary>
    private static Exception ReadRefusal() => new("Received error from PLC: Object does not exist.");

    private static PlcException WriteRefusal() =>
        new(ErrorCode.WriteData, new Exception("Received error from PLC: Address out of range."));

    private static S7DriverOptions Options() => new()
    {
        Host = "192.0.2.1",
        Timeout = TimeSpan.FromSeconds(5),
        Probe = new S7ProbeOptions { Enabled = false },
        // Grouping off: one wire request per tag keeps each tag's outcome its own.
        SpanReadMaxGapBytes = -1,
        RawTags = S7RawTags.Entries(
            new S7TagDefinition("Missing", "DB99.DBW0", S7DataType.UInt16),
            new S7TagDefinition("Good", "DB1.DBW0", S7DataType.UInt16)),
    };

    /// <summary>A stepped pass clock, so "LastSuccessfulRead advanced" is asserted STRICTLY.</summary>
    private sealed class PassClock
    {
        public DateTime Now { get; private set; } = new(2026, 10, 22, 12, 0, 0, DateTimeKind.Utc);

        /// <summary>Moves the clock one second on and returns the new time.</summary>
        public DateTime Step() => Now = Now.AddSeconds(1);
    }

    private static async Task<(S7Driver Driver, ScriptedS7PlcFactory Factory, CapturingS7Logger Log, PassClock Clock)> StartAsync()
    {
        var factory = new ScriptedS7PlcFactory();
        var log = new CapturingS7Logger();
        var clock = new PassClock();
        var drv = new S7Driver(Options(), "s7-refusal", factory, log) { UtcNow = () => clock.Now };
        await drv.InitializeAsync("{}", TestContext.Current.CancellationToken);
        drv.GetHealth().LastSuccessfulRead.ShouldBe(clock.Now, "init stamps the pass clock");
        return (drv, factory, log, clock);
    }

    /// <summary>A refused tag is Bad, health stays Healthy, LastSuccessfulRead advances, and it warns once.</summary>
    [Fact]
    public async Task A_read_refusal_is_per_tag_bad_with_no_health_impact_and_one_warning()
    {
        var ct = TestContext.Current.CancellationToken;
        var (drv, factory, log, clock) = await StartAsync();
        using var _ = drv;
        factory.Read = (addr, _) => addr == "DB99.DBW0" ? throw ReadRefusal() : Task.FromResult<object?>((ushort)7);

        for (var pass = 0; pass < 3; pass++)
        {
            var at = clock.Step();
            var r = await drv.ReadAsync(["Missing"], ct);
            r[0].StatusCode.ShouldBe(BadDeviceFailure);
            drv.GetHealth().State.ShouldBe(DriverState.Healthy, "a refusal is not a comms fault");
            drv.GetHealth().LastSuccessfulRead.ShouldBe(at,
                "the CPU answered, so the all-refused pass advances LastSuccessfulRead to the pass time");
        }
        log.Warnings.Count(w => w.Contains("Missing")).ShouldBe(1, "one Warning per refused tag, not one per poll");

        // Positive control: the good tag still reads, and nothing reopened the connection.
        (await drv.ReadAsync(["Good"], ct))[0].StatusCode.ShouldBe(0u);
        factory.Created.Count.ShouldBe(1);
    }

    /// <summary>
    ///     A refusal after a comms fault restores Healthy — the CPU is back and answering. Before the
    ///     fix the refusal latched Degraded with LastSuccessfulRead frozen, which is exactly the
    ///     watchdog's trip condition.
    /// </summary>
    [Fact]
    public async Task A_refusal_after_a_comms_fault_restores_healthy()
    {
        var ct = TestContext.Current.CancellationToken;
        var (drv, factory, _, clock) = await StartAsync();
        using var __ = drv;

        // Positive control: a genuine comms fault DOES degrade, and leaves LastSuccessfulRead frozen.
        var initStamp = clock.Now;
        clock.Step();
        factory.Read = (_, _) => throw new TimeoutException("frozen peer");
        await drv.ReadAsync(["Missing"], ct);
        var degraded = drv.GetHealth();
        degraded.State.ShouldBe(DriverState.Degraded);
        degraded.LastSuccessfulRead.ShouldBe(initStamp);

        var at = clock.Step();
        factory.Read = (addr, _) => addr == "DB99.DBW0" ? throw ReadRefusal() : Task.FromResult<object?>((ushort)7);
        var r = await drv.ReadAsync(["Missing"], ct);
        r[0].StatusCode.ShouldBe(BadDeviceFailure);
        var after = drv.GetHealth();
        after.State.ShouldBe(DriverState.Healthy);
        after.LastSuccessfulRead.ShouldBe(at);
    }

    /// <summary>The ReadData-wrapped shape of a refusal is classified the same way.</summary>
    [Fact]
    public async Task A_read_data_wrapped_refusal_is_also_a_refusal()
    {
        var ct = TestContext.Current.CancellationToken;
        var (drv, factory, _, clock) = await StartAsync();
        using var __ = drv;
        factory.Read = (_, _) => throw new PlcException(ErrorCode.ReadData, ReadRefusal());

        (await drv.ReadAsync(["Missing"], ct))[0].StatusCode.ShouldBe(BadDeviceFailure);
        drv.GetHealth().State.ShouldBe(DriverState.Healthy);
    }

    /// <summary>
    ///     The bare read-path shape of access denied (PUT/GET disabled) is the Faulted config alert.
    ///     Before, only a PlcException-wrapped "not allowed" was recognised, so a real CPU's read
    ///     refusal fell through to BadCommunicationError + Degraded.
    /// </summary>
    [Fact]
    public async Task A_bare_access_denied_read_is_the_faulted_config_alert()
    {
        var ct = TestContext.Current.CancellationToken;
        var (drv, factory, _, clock) = await StartAsync();
        using var __ = drv;
        factory.Read = (_, _) => throw new Exception("Received error from PLC: Accessing object not allowed.");

        (await drv.ReadAsync(["Good"], ct))[0].StatusCode.ShouldBe(0x803D0000u); // BadNotSupported
        drv.GetHealth().State.ShouldBe(DriverState.Faulted);
        drv.GetHealth().LastError!.ShouldContain("PUT/GET");
    }

    /// <summary>
    ///     Review I-1: an access-denied CPU (PUT/GET left at its factory default — EVERY read denied) is
    ///     reachable and answering, so each pass advances LastSuccessfulRead while staying Faulted.
    ///     Before, the pass stayed Faulted with the stamp frozen — the comms-loss watchdog's trip
    ///     condition, so the actor reconnected + re-subscribed every 90 s, forever, which can never fix
    ///     a PUT/GET setting. The control: a comms fault afterwards leaves the stamp frozen.
    /// </summary>
    [Fact]
    public async Task An_all_access_denied_pass_stays_faulted_but_advances_last_successful_read()
    {
        var ct = TestContext.Current.CancellationToken;
        var (drv, factory, _, clock) = await StartAsync();
        using var __ = drv;
        factory.Read = (_, _) => throw new Exception("Received error from PLC: Accessing object not allowed.");

        DateTime last = default;
        for (var pass = 0; pass < 2; pass++)
        {
            last = clock.Step();
            await drv.ReadAsync(["Good", "Missing"], ct);
            var h = drv.GetHealth();
            h.State.ShouldBe(DriverState.Faulted, "the config alert is kept");
            h.LastSuccessfulRead.ShouldBe(last, "the CPU answered, so the stamp advances every pass");
        }

        // Positive control: a real comms loss does NOT advance it (and the sticky Faulted outranks it).
        clock.Step();
        factory.Read = (_, _) => throw new TimeoutException("frozen peer");
        await drv.ReadAsync(["Good"], ct);
        drv.GetHealth().LastSuccessfulRead.ShouldBe(last);
    }

    /// <summary>The write-side access-denied is an answer too, and its sticky Faulted still clears only on a real success.</summary>
    [Fact]
    public async Task A_write_access_denied_advances_last_successful_read_and_stays_sticky()
    {
        var ct = TestContext.Current.CancellationToken;
        var (drv, factory, _, clock) = await StartAsync();
        using var __ = drv;
        factory.Write = (_, _, _) => throw new PlcException(ErrorCode.WriteData,
            new Exception("Received error from PLC: Accessing object not allowed."));

        var at = clock.Step();
        (await drv.WriteAsync([new WriteRequest("Good", (ushort)1)], ct))[0].StatusCode.ShouldBe(0x803D0000u);
        drv.GetHealth().State.ShouldBe(DriverState.Faulted);
        drv.GetHealth().LastSuccessfulRead.ShouldBe(at);

        // A clean read leaves the write-side Faulted in place (sticky) …
        clock.Step();
        await drv.ReadAsync(["Good"], ct);
        drv.GetHealth().State.ShouldBe(DriverState.Faulted);

        // … and a real write success clears it.
        factory.Write = (_, _, _) => Task.CompletedTask;
        clock.Step();
        await drv.WriteAsync([new WriteRequest("Good", (ushort)1)], ct);
        drv.GetHealth().State.ShouldBe(DriverState.Healthy);
    }

    /// <summary>
    ///     Review m-7: a transport fault whose text happens to contain "not allowed" reopens (Degraded),
    ///     and only S7.Net's exact "Accessing object not allowed" is the access-denied alert.
    /// </summary>
    [Fact]
    public async Task Only_the_exact_access_denied_wording_without_a_transport_fault_is_access_denied()
    {
        var ct = TestContext.Current.CancellationToken;
        var (drv, factory, _, clock) = await StartAsync();
        using var __ = drv;

        clock.Step();
        factory.Write = (_, _, _) => throw new PlcException(ErrorCode.WriteData,
            new System.IO.IOException("Accessing object not allowed: socket closed by peer"));
        (await drv.WriteAsync([new WriteRequest("Good", (ushort)1)], ct))[0].StatusCode
            .ShouldNotBe(0x803D0000u, "not the access-denied BadNotSupported");
        drv.GetHealth().State.ShouldBe(DriverState.Degraded, "a transport fault is not a config alert");

        S7Driver.IsAccessDenied(new PlcException(ErrorCode.WriteData, new Exception("operation not allowed"))).ShouldBeFalse();
        S7Driver.IsAccessDenied(new Exception("Received error from PLC: Accessing object not allowed.")).ShouldBeTrue();
    }

    /// <summary>A ReadData wrapping a socket fault is still a comms fault (Degraded), not a refusal.</summary>
    [Fact]
    public async Task A_read_data_wrapping_a_socket_fault_still_degrades()
    {
        var ct = TestContext.Current.CancellationToken;
        var (drv, factory, _, clock) = await StartAsync();
        using var __ = drv;
        factory.Read = (_, _) => throw new PlcException(ErrorCode.ReadData, new System.IO.IOException("connection reset"));

        await drv.ReadAsync(["Good"], ct);
        drv.GetHealth().State.ShouldBe(DriverState.Degraded);
    }

    /// <summary>A write refusal is per-tag Bad, counts as answered and leaves health alone.</summary>
    [Fact]
    public async Task A_write_refusal_is_per_tag_bad_and_counts_as_answered()
    {
        var ct = TestContext.Current.CancellationToken;
        var (drv, factory, log, clock) = await StartAsync();
        using var _ = drv;
        factory.Write = (addr, _, _) => addr == "DB99.DBW0" ? throw WriteRefusal() : Task.CompletedTask;

        // Put the driver into a comms-fault Degraded first; the refusal must lift it.
        factory.Read = (_, _) => throw new TimeoutException("frozen peer");
        await drv.ReadAsync(["Good"], ct);
        var degraded = drv.GetHealth();
        degraded.State.ShouldBe(DriverState.Degraded);

        for (var i = 0; i < 2; i++)
        {
            var at = clock.Step();
            var w = await drv.WriteAsync([new WriteRequest("Missing", (ushort)1)], ct);
            w[0].StatusCode.ShouldBe(BadDeviceFailure);
            var h = drv.GetHealth();
            h.LastSuccessfulRead.ShouldBe(at, "a write refusal is an answer: the stamp advances strictly");
            // The Degraded was written by the READ side (its own message), so it is the read pass's to clear.
            h.State.ShouldBe(DriverState.Degraded);
        }

        var after = drv.GetHealth();
        after.LastSuccessfulRead!.Value.ShouldBeGreaterThan(degraded.LastSuccessfulRead!.Value);
        log.Warnings.Count(m => m.Contains("Missing")).ShouldBe(1);
    }

    /// <summary>
    ///     A good write clears a Degraded the write side wrote. Before the fix a success-only batch
    ///     never wrote health, so a transient write fault latched Degraded until some read pass ran.
    /// </summary>
    [Fact]
    public async Task A_good_write_clears_a_write_side_degraded()
    {
        var ct = TestContext.Current.CancellationToken;
        var (drv, factory, _, clock) = await StartAsync();
        using var _ = drv;

        factory.Write = (_, _, _) => throw new System.IO.IOException("connection reset");
        var bad = await drv.WriteAsync([new WriteRequest("Good", (ushort)1)], ct);
        bad[0].StatusCode.ShouldNotBe(0u);
        drv.GetHealth().State.ShouldBe(DriverState.Degraded, "positive control: a comms fault on write degrades");

        factory.Write = (_, _, _) => Task.CompletedTask;
        var good = await drv.WriteAsync([new WriteRequest("Good", (ushort)2)], ct);
        good[0].StatusCode.ShouldBe(0u);
        drv.GetHealth().State.ShouldBe(DriverState.Healthy);
    }
}