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

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

/// <summary>
///     Unit tests for the S7 1-D array support: the pure
///     <see cref="S7Driver.DecodeArrayBlock"/> decode loop (the half of the contiguous
///     block read that turns a raw S7 big-endian byte block into a typed CLR array — the
///     network I/O half, <c>Plc.ReadBytesAsync</c>, has no in-process fake so only the
///     decode is unit-proven), the <see cref="ITagDiscovery"/> <c>IsArray</c>/<c>ArrayDim</c>
///     flip, and the equipment-tag resolver threading <c>arrayLength</c> into the transient
///     tag-def's array count.
/// </summary>
[Trait("Category", "Unit")]
public sealed class S7ArrayReadTests
{
    // ── Helpers ──────────────────────────────────────────────────────────────────────────

    private static S7TagDefinition ArrTag(S7DataType dt, int count) =>
        new("ArrTag", "DB1.DBW0", dt, ArrayCount: count);

    private static S7ParsedAddress Addr(S7Size size) =>
        new(S7Area.DataBlock, DbNumber: 1, size, ByteOffset: 0, BitOffset: 0);

    // S7 is big-endian: most-significant byte first.
    private static byte[] BeWords(params ushort[] words)
    {
        var b = new byte[words.Length * 2];
        for (var i = 0; i < words.Length; i++)
        {
            b[i * 2] = (byte)(words[i] >> 8);
            b[i * 2 + 1] = (byte)(words[i] & 0xFF);
        }
        return b;
    }

    private static byte[] BeDwords(params uint[] dwords)
    {
        var b = new byte[dwords.Length * 4];
        for (var i = 0; i < dwords.Length; i++)
        {
            b[i * 4] = (byte)(dwords[i] >> 24);
            b[i * 4 + 1] = (byte)(dwords[i] >> 16);
            b[i * 4 + 2] = (byte)(dwords[i] >> 8);
            b[i * 4 + 3] = (byte)(dwords[i] & 0xFF);
        }
        return b;
    }

    // ── DecodeArrayBlock — element-typed CLR arrays ───────────────────────────────────────

    /// <summary>Verifies an Int16 array decodes to a typed short[] with big-endian values.</summary>
    [Fact]
    public void DecodeArrayBlock_Int16_returns_short_array()
    {
        // 3 words: 1, -1 (0xFFFF), 32767 (0x7FFF).
        var block = BeWords(0x0001, 0xFFFF, 0x7FFF);
        var result = S7Driver.DecodeArrayBlock(ArrTag(S7DataType.Int16, 3), Addr(S7Size.Word), block);

        var arr = result.ShouldBeOfType<short[]>();
        arr.ShouldBe(new short[] { 1, -1, 32767 });
    }

    /// <summary>Verifies a UInt16 array decodes to a typed ushort[].</summary>
    [Fact]
    public void DecodeArrayBlock_UInt16_returns_ushort_array()
    {
        var block = BeWords(0, 1000, 65535);
        var result = S7Driver.DecodeArrayBlock(ArrTag(S7DataType.UInt16, 3), Addr(S7Size.Word), block);

        result.ShouldBeOfType<ushort[]>().ShouldBe(new ushort[] { 0, 1000, 65535 });
    }

    /// <summary>Verifies an Int32 array decodes to a typed int[] with big-endian dwords.</summary>
    [Fact]
    public void DecodeArrayBlock_Int32_returns_int_array()
    {
        var block = BeDwords(1u, 0xFFFF_FFFFu, 0x7FFF_FFFFu);
        var result = S7Driver.DecodeArrayBlock(ArrTag(S7DataType.Int32, 3), Addr(S7Size.DWord), block);

        result.ShouldBeOfType<int[]>().ShouldBe(new[] { 1, -1, int.MaxValue });
    }

    /// <summary>Verifies a UInt32 array decodes to a typed uint[].</summary>
    [Fact]
    public void DecodeArrayBlock_UInt32_returns_uint_array()
    {
        var block = BeDwords(0u, 70_000u, 0xFFFF_FFFFu);
        var result = S7Driver.DecodeArrayBlock(ArrTag(S7DataType.UInt32, 3), Addr(S7Size.DWord), block);

        result.ShouldBeOfType<uint[]>().ShouldBe(new uint[] { 0, 70_000, 0xFFFF_FFFF });
    }

    /// <summary>Verifies a Float32 array decodes to a typed float[] from IEEE-754 big-endian dwords.</summary>
    [Fact]
    public void DecodeArrayBlock_Float32_returns_float_array()
    {
        var bits0 = BitConverter.SingleToUInt32Bits(1.5f);
        var bits1 = BitConverter.SingleToUInt32Bits(-2.25f);
        var bits2 = BitConverter.SingleToUInt32Bits(3.14f);
        var block = BeDwords(bits0, bits1, bits2);

        var result = S7Driver.DecodeArrayBlock(ArrTag(S7DataType.Float32, 3), Addr(S7Size.DWord), block);

        var arr = result.ShouldBeOfType<float[]>();
        arr.Length.ShouldBe(3);
        arr[0].ShouldBe(1.5f, tolerance: 1e-6f);
        arr[1].ShouldBe(-2.25f, tolerance: 1e-6f);
        arr[2].ShouldBe(3.14f, tolerance: 1e-6f);
    }

    /// <summary>Verifies a Byte array decodes to a typed byte[] (one element per byte).</summary>
    [Fact]
    public void DecodeArrayBlock_Byte_returns_byte_array()
    {
        var block = new byte[] { 0, 42, 200, 255 };
        var result = S7Driver.DecodeArrayBlock(ArrTag(S7DataType.Byte, 4), Addr(S7Size.Byte), block);

        result.ShouldBeOfType<byte[]>().ShouldBe(new byte[] { 0, 42, 200, 255 });
    }

    /// <summary>Verifies a Bool array decodes from packed bits (one byte → low bit per element).</summary>
    [Fact]
    public void DecodeArrayBlock_Bool_returns_bool_array()
    {
        // Bit array: one byte per element, low bit carries the value (S7 contiguous bit access
        // is byte-granular over the wire so each element occupies its own byte slot).
        var block = new byte[] { 0x01, 0x00, 0x01 };
        var result = S7Driver.DecodeArrayBlock(
            new S7TagDefinition("B", "DB1.DBX0.0", S7DataType.Bool, ArrayCount: 3),
            new S7ParsedAddress(S7Area.DataBlock, 1, S7Size.Bit, 0, 0),
            block);

        result.ShouldBeOfType<bool[]>().ShouldBe(new[] { true, false, true });
    }

    /// <summary>Verifies the array length matches the tag's declared count.</summary>
    [Fact]
    public void DecodeArrayBlock_length_matches_declared_count()
    {
        var block = BeWords(10, 20, 30, 40, 50);
        var result = S7Driver.DecodeArrayBlock(ArrTag(S7DataType.UInt16, 5), Addr(S7Size.Word), block);

        result.ShouldBeOfType<ushort[]>().Length.ShouldBe(5);
    }

    /// <summary>Verifies unsupported element types throw NotSupportedException in the array path.</summary>
    /// <param name="dt">The unsupported S7 data type.</param>
    [Theory]
    [InlineData(S7DataType.Int64)]
    [InlineData(S7DataType.Float64)]
    [InlineData(S7DataType.String)]
    public void DecodeArrayBlock_unsupported_element_type_throws(S7DataType dt)
    {
        Should.Throw<NotSupportedException>(() =>
            S7Driver.DecodeArrayBlock(ArrTag(dt, 2), Addr(S7Size.DWord), new byte[16]));
    }

    // ── ElementByteSize — block-read sizing ───────────────────────────────────────────────

    /// <summary>Verifies element byte sizes used to size the contiguous block read.</summary>
    [Theory]
    [InlineData(S7Size.Bit, 1)]
    [InlineData(S7Size.Byte, 1)]
    [InlineData(S7Size.Word, 2)]
    [InlineData(S7Size.DWord, 4)]
    public void ElementByteSize_matches_size_width(S7Size size, int expected)
        => S7Driver.ElementByteSize(size).ShouldBe(expected);

    // ── Discovery — IsArray / ArrayDim flip ───────────────────────────────────────────────

    private sealed class RecordingBuilder : IAddressSpaceBuilder
    {
        public readonly List<(string Name, DriverAttributeInfo Attr)> Variables = new();
        public IAddressSpaceBuilder Folder(string browseName, string displayName) => this;
        public IVariableHandle Variable(string browseName, string displayName, DriverAttributeInfo attr)
        {
            Variables.Add((browseName, attr));
            return new Handle();
        }
        public void AddProperty(string browseName, DriverDataType dataType, object? value) { }
        public void AttachAlarmCondition(IVariableHandle sourceVariable, string alarmName, DriverAttributeInfo alarmInfo) { }
        private sealed class Handle : IVariableHandle
        {
            public string FullReference => "stub";
            public IAlarmConditionSink MarkAsAlarmCondition(AlarmConditionInfo info) => throw new NotImplementedException();
        }
    }

    /// <summary>Verifies an array tag is discovered with IsArray=true and ArrayDim=count.</summary>
    [Fact]
    public async Task DiscoverAsync_flips_IsArray_for_array_tag()
    {
        var opts = new S7DriverOptions
        {
            Host = "192.0.2.1",
            Tags =
            [
                new("Scalar", "DB1.DBW0", S7DataType.Int16),
                new("Arr", "DB1.DBW10", S7DataType.Int16, ArrayCount: 8),
            ],
        };
        using var drv = new S7Driver(opts, "s7-arr-disco");

        var builder = new RecordingBuilder();
        await drv.DiscoverAsync(builder, TestContext.Current.CancellationToken);

        var scalar = builder.Variables.Single(v => v.Name == "Scalar").Attr;
        scalar.IsArray.ShouldBeFalse();
        scalar.ArrayDim.ShouldBeNull();

        var arr = builder.Variables.Single(v => v.Name == "Arr").Attr;
        arr.IsArray.ShouldBeTrue();
        arr.ArrayDim.ShouldBe(8u);
    }

    /// <summary>Verifies a tag with ArrayCount of 1 is treated as a 1-element array (not scalar).
    /// The foundation materialises a [1] OPC UA array node when IsArray=true, so the driver must
    /// honour isArray:true + arrayLength:1 — a 1-element array IS a valid array.</summary>
    [Fact]
    public async Task DiscoverAsync_count_of_one_is_array()
    {
        var opts = new S7DriverOptions
        {
            Host = "192.0.2.1",
            Tags = [new("One", "DB1.DBW0", S7DataType.Int16, ArrayCount: 1)],
        };
        using var drv = new S7Driver(opts, "s7-arr-one");

        var builder = new RecordingBuilder();
        await drv.DiscoverAsync(builder, TestContext.Current.CancellationToken);

        var one = builder.Variables.Single().Attr;
        one.IsArray.ShouldBeTrue("ArrayCount=1 is a 1-element array, not scalar");
        one.ArrayDim.ShouldBe(1u);
    }

    /// <summary>Verifies that a tag with a null ArrayCount (scalar) is still discovered as scalar.</summary>
    [Fact]
    public async Task DiscoverAsync_null_ArrayCount_is_scalar()
    {
        var opts = new S7DriverOptions
        {
            Host = "192.0.2.1",
            Tags = [new("Scalar", "DB1.DBW0", S7DataType.Int16, ArrayCount: null)],
        };
        using var drv = new S7Driver(opts, "s7-arr-null");

        var builder = new RecordingBuilder();
        await drv.DiscoverAsync(builder, TestContext.Current.CancellationToken);

        var scalar = builder.Variables.Single().Attr;
        scalar.IsArray.ShouldBeFalse("null ArrayCount is scalar");
        scalar.ArrayDim.ShouldBeNull();
    }

    /// <summary>Verifies a read of an isArray:true arrayLength:1 equipment tag returns a 1-element typed array.</summary>
    [Fact]
    public void DecodeArrayBlock_count_of_one_returns_single_element_array()
    {
        // A 1-element Int16 array: one big-endian word.
        var block = BeWords(0x0064); // 100
        var result = S7Driver.DecodeArrayBlock(ArrTag(S7DataType.Int16, 1), Addr(S7Size.Word), block);

        var arr = result.ShouldBeOfType<short[]>();
        arr.Length.ShouldBe(1);
        arr[0].ShouldBe((short)100);
    }

    // ── Equipment-tag resolver threads arrayLength → ArrayCount ───────────────────────────

    /// <summary>Verifies the equipment-tag parser threads isArray/arrayLength into ArrayCount.</summary>
    [Fact]
    public void EquipmentTagParser_threads_array_length_into_ArrayCount()
    {
        var json = """{"address":"DB1.DBW0","dataType":"Int16","isArray":true,"arrayLength":16}""";
        S7EquipmentTagParser.TryParse(json, out var def).ShouldBeTrue();
        def!.ArrayCount.ShouldBe(16);
    }

    /// <summary>Verifies arrayLength is ignored when isArray is false (mirrors the sink foundation).</summary>
    [Fact]
    public void EquipmentTagParser_ignores_arrayLength_when_isArray_false()
    {
        var json = """{"address":"DB1.DBW0","dataType":"Int16","isArray":false,"arrayLength":16}""";
        S7EquipmentTagParser.TryParse(json, out var def).ShouldBeTrue();
        def!.ArrayCount.ShouldBeNull("arrayLength is honoured only when isArray is true");
    }

    /// <summary>Verifies a scalar equipment tag (no array keys) has a null ArrayCount.</summary>
    [Fact]
    public void EquipmentTagParser_scalar_has_null_ArrayCount()
    {
        var json = """{"address":"DB1.DBW0","dataType":"Int16"}""";
        S7EquipmentTagParser.TryParse(json, out var def).ShouldBeTrue();
        def!.ArrayCount.ShouldBeNull();
    }
}