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

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

/// <summary>
///     Review 07 U2: block-read coalescing is ON by default (gap 8), and it covers coils, discrete inputs,
///     <c>BitInRegister</c> and <c>String</c> tags — 16 bit tags on one status word used to cost 16 reads of
///     the same register, and 64 adjacent coils 64 FC01s.
/// </summary>
[Trait("Category", "Unit")]
public sealed class ModbusCoalescingDefaultsTests
{
    private static async Task<(ModbusDriver, ScriptedTransport)> StartAsync(ModbusDriverOptions opts)
    {
        var t = new ScriptedTransport();
        var d = new ModbusDriver(opts, "m1", _ => t);
        await d.InitializeAsync("{}", TestContext.Current.CancellationToken);
        return (d, t);
    }

    private static ModbusDriverOptions Opts(IEnumerable<ModbusTagDefinition> tags, bool disable = false) => new()
    {
        Host = "f", RawTags = ModbusRawTags.Entries(tags), DisableReadCoalescing = disable,
        Probe = new ModbusProbeOptions { Enabled = false },
    };

    [Fact]
    public void Default_options_coalesce_with_a_gap_of_8()
    {
        new ModbusDriverOptions().MaxReadGap.ShouldBe((ushort)8);
        new ModbusDriverOptions().DisableReadCoalescing.ShouldBeFalse();
        ModbusDriverFactoryExtensions.ParseOptions("m1", """{"host":"h"}""").MaxReadGap.ShouldBe((ushort)8);
    }

    [Fact]
    public async Task Default_configured_holding_registers_are_read_in_one_PDU()
    {
        var tags = Enumerable.Range(0, 10).Select(i =>
            new ModbusTagDefinition($"HR{i}", ModbusRegion.HoldingRegisters, (ushort)(100 + i * 3), ModbusDataType.Int16)).ToArray();
        var (drv, t) = await StartAsync(Opts(tags));
        await using var _ = drv;
        for (var i = 0; i < 10; i++) t.Bank.HoldingRegisters[100 + i * 3] = (ushort)(i + 1);

        var r = await drv.ReadAsync([.. tags.Select(x => x.Name)], TestContext.Current.CancellationToken);

        t.Requests(0x03).Count.ShouldBe(1);
        r.Select(s => (short)s.Value!).ShouldBe(Enumerable.Range(1, 10).Select(i => (short)i));
    }

    /// <summary>
    ///     Fix round 1 (coordinator ruling 2): an explicitly authored maxReadGap 0 — what the pre-#741 form
    ///     persisted on every driver — keeps its old meaning, NO coalescing; the gap-8 default applies only to an
    ///     absent key (positive control).
    /// </summary>
    [Theory]
    [InlineData("""{"host":"h","maxReadGap":0,"disableFC23":false}""", 2)]
    [InlineData("""{"host":"h"}""", 1)]
    public async Task A_persisted_maxReadGap_0_keeps_coalescing_off(string legacyConfig, int expectedReads)
    {
        var parsed = ModbusDriverFactoryExtensions.ParseOptions("m1", legacyConfig);
        var tags = new[]
        {
            new ModbusTagDefinition("A", ModbusRegion.HoldingRegisters, 100, ModbusDataType.Int16),
            new ModbusTagDefinition("B", ModbusRegion.HoldingRegisters, 101, ModbusDataType.Int16),
        };
        var (drv, t) = await StartAsync(new ModbusDriverOptions
        {
            Host = "f", MaxReadGap = parsed.MaxReadGap, DisableReadCoalescing = parsed.DisableReadCoalescing,
            RawTags = ModbusRawTags.Entries(tags), Probe = new ModbusProbeOptions { Enabled = false },
        });
        await using var _ = drv;
        await drv.ReadAsync(["A", "B"], TestContext.Current.CancellationToken);
        t.Requests(0x03).Count.ShouldBe(expectedReads);
    }

    [Fact]
    public async Task DisableReadCoalescing_reads_every_tag_alone()
    {
        // Positive control for the default-on test: the off switch really is per-tag.
        var tags = new[]
        {
            new ModbusTagDefinition("A", ModbusRegion.HoldingRegisters, 100, ModbusDataType.Int16),
            new ModbusTagDefinition("B", ModbusRegion.HoldingRegisters, 101, ModbusDataType.Int16),
        };
        var (drv, t) = await StartAsync(Opts(tags, disable: true));
        await using var _ = drv;
        await drv.ReadAsync(["A", "B"], TestContext.Current.CancellationToken);
        t.Requests(0x03).Count.ShouldBe(2);
    }

    [Theory]
    [InlineData(ModbusRegion.Coils, (byte)0x01)]
    [InlineData(ModbusRegion.DiscreteInputs, (byte)0x02)]
    public async Task Adjacent_bit_tags_fold_into_one_bit_read(ModbusRegion region, byte fc)
    {
        var tags = Enumerable.Range(0, 64).Select(i =>
            new ModbusTagDefinition($"B{i}", region, (ushort)(10 + i), ModbusDataType.Bool)).ToArray();
        var (drv, t) = await StartAsync(Opts(tags));
        await using var _ = drv;
        var bank = region == ModbusRegion.Coils ? t.Bank.Coils : t.Bank.DiscreteInputs;
        for (var i = 0; i < 64; i++) bank[10 + i] = i % 3 == 0;

        var r = await drv.ReadAsync([.. tags.Select(x => x.Name)], TestContext.Current.CancellationToken);

        t.Requests(fc).ShouldBe([(fc, (ushort)10, (ushort)64)]);
        for (var i = 0; i < 64; i++) r[i].Value.ShouldBe(i % 3 == 0, $"bit {i}");
    }

    [Fact]
    public async Task Bit_tags_on_one_status_word_fold_into_one_register_read()
    {
        var tags = Enumerable.Range(0, 16).Select(b =>
            new ModbusTagDefinition($"S{b}", ModbusRegion.HoldingRegisters, 40, ModbusDataType.BitInRegister, BitIndex: (byte)b)).ToArray();
        var (drv, t) = await StartAsync(Opts(tags));
        await using var _ = drv;
        t.Bank.HoldingRegisters[40] = 0b1010_0000_0000_0101;

        var r = await drv.ReadAsync([.. tags.Select(x => x.Name)], TestContext.Current.CancellationToken);

        t.Requests(0x03).ShouldBe([((byte)0x03, (ushort)40, (ushort)1)]);
        for (var b = 0; b < 16; b++) r[b].Value.ShouldBe(((0b1010_0000_0000_0101 >> b) & 1) == 1, $"bit {b}");
    }

    [Fact]
    public async Task A_string_tag_coalesces_with_its_neighbours()
    {
        var tags = new[]
        {
            new ModbusTagDefinition("Num", ModbusRegion.HoldingRegisters, 50, ModbusDataType.Int16),
            new ModbusTagDefinition("Str", ModbusRegion.HoldingRegisters, 51, ModbusDataType.String, StringLength: 4),
            new ModbusTagDefinition("After", ModbusRegion.HoldingRegisters, 53, ModbusDataType.UInt16),
        };
        var (drv, t) = await StartAsync(Opts(tags));
        await using var _ = drv;
        t.Bank.HoldingRegisters[50] = 7;
        t.Bank.HoldingRegisters[51] = ('A' << 8) | 'B';
        t.Bank.HoldingRegisters[52] = ('C' << 8) | 'D';
        t.Bank.HoldingRegisters[53] = 9;

        var r = await drv.ReadAsync(["Num", "Str", "After"], TestContext.Current.CancellationToken);

        t.Requests(0x03).ShouldBe([((byte)0x03, (ushort)50, (ushort)4)]);
        r[0].Value.ShouldBe((short)7);
        r[1].Value.ShouldBe("ABCD");
        r[2].Value.ShouldBe((ushort)9);
    }

    [Fact]
    public async Task A_refused_coil_range_is_prohibited_and_reprobed_with_FC01()
    {
        var tags = Enumerable.Range(0, 4).Select(i =>
            new ModbusTagDefinition($"C{i}", ModbusRegion.Coils, (ushort)(20 + i), ModbusDataType.Bool)).ToArray();
        var opts = new ModbusDriverOptions
        {
            Host = "f", RawTags = ModbusRawTags.Entries(tags), Probe = new ModbusProbeOptions { Enabled = false },
            AutoProhibitReprobeInterval = TimeSpan.FromHours(1),
        };
        var (drv, t) = await StartAsync(opts);
        await using var _ = drv;
        var refuseMerged = true;
        t.Handler = (_, pdu, _) =>
        {
            var qty = (pdu[3] << 8) | pdu[4];
            return pdu[0] == 0x01 && qty > 1 && refuseMerged
                ? Task.FromException<byte[]>(new ModbusException(0x01, 0x02, "protected"))
                : null;
        };

        var r = await drv.ReadAsync([.. tags.Select(x => x.Name)], TestContext.Current.CancellationToken);
        r.ShouldAllBe(s => s.StatusCode == 0u, "the per-tag fallback still reads every coil");
        drv.AutoProhibitedRangeCount.ShouldBe(1);

        refuseMerged = false;
        while (t.Sent.TryDequeue(out var _1)) { }
        await drv.RunReprobeOnceForTestAsync(TestContext.Current.CancellationToken);
        t.Sent.ShouldAllBe(s => s.Pdu[0] == 0x01, "a coil range is re-probed with FC01, never a register read");
        drv.AutoProhibitedRangeCount.ShouldBe(0);
    }
}