using System.Buffers.Binary;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Driver.FOCAS.Wire;

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

/// <summary>
///     <c>cnc_rddynamic2</c> position blocks (0x0026) are self-describing: <c>[0..3] i32 raw</c>,
///     <c>[4..5] u16 base</c> (2 or 10), <c>[6..7] u16 exponent</c> (<c>0xFFFF</c> = vacant slot);
///     <c>value = raw / base^exponent</c>. Ported from the sister ignitionoee FOCAS driver v0.17.0
///     (which also deleted the fabricated <c>cnc_getfigure</c> 0x00D3 — the real 31i-B refuses it
///     with <c>rc=1</c>) and Focas.Wire-014 (absurd exponents are refused, not divided by).
/// </summary>
[Trait("Category", "Unit")]
public sealed class FocasPositionDecodeTests
{
    private static byte[] Block(int raw, int @base, int exponent)
    {
        var b = new byte[8];
        BinaryPrimitives.WriteInt32BigEndian(b.AsSpan(0, 4), raw);
        BinaryPrimitives.WriteUInt16BigEndian(b.AsSpan(4, 2), (ushort)@base);
        BinaryPrimitives.WriteUInt16BigEndian(b.AsSpan(6, 2), (ushort)exponent);
        return b;
    }

    [Fact]
    public void The_live_dynamic2_capture_scales_every_position_from_its_own_block()
    {
        // ref-dynamic2-axis1.bin: four 0x0026 blocks (absolute / machine / relative / distance of
        // axis 1), every one base 10, exponent 4. Undecoded they read 2801574 / 2801200 / 32 / 0.
        var dynamic = FocasWireClient.ParseDynamic2(WireFixtures.Blocks("ref-dynamic2-axis1.bin"));

        dynamic.Axis.Absolute.ToEngineering(0)!.Value.ShouldBe(280.1574, 1e-9);
        dynamic.Axis.Machine.ToEngineering(0)!.Value.ShouldBe(280.1200, 1e-9);
        dynamic.Axis.Relative.ToEngineering(0)!.Value.ShouldBe(0.0032, 1e-9);
        dynamic.Axis.Distance.ToEngineering(0)!.Value.ShouldBe(0.0, 1e-9);
        dynamic.FeedRate.ShouldBe(0);
        dynamic.SpindleSpeed.ShouldBe(0);
    }

    [Fact]
    public void The_block_scale_wins_over_the_configured_decimal_places()
    {
        var p = FocasWireClient.ParsePositionBlock(Block(123456, 10, 3));
        p.ToEngineering(fallbackDecimalPlaces: 1)!.Value.ShouldBe(123.456, 1e-9);
    }

    [Theory]
    [InlineData("live-dynamic2-axis1-0x0026.bin", 0.0374)]   // Z-34184 X
    [InlineData("live-dynamic2-axis2-0x0026.bin", 370.177)]  // Z-34184 Y
    public void Axis_scoped_live_requests_return_that_axis_scaled(string fixture, double expected)
    {
        var blocks = WireFixtures.Blocks(fixture).Where(b => b.Command == 0x0026).ToList();
        blocks.Count.ShouldBe(1, "an axis-scoped request returns exactly one 0x0026 block");

        FocasWireClient.ParsePositionBlock(blocks[0].Payload).ToEngineering(0)!.Value.ShouldBe(expected, 1e-9);
    }

    [Theory]
    [InlineData(40, 2, 3, 5.0)]           // inch-mode binary base
    [InlineData(-22000, 10, 3, -22.0)]
    [InlineData(42, 10, 0, 42.0)]
    public void Positions_scale_by_base_to_the_exponent(int raw, int @base, int exponent, double expected)
    {
        FocasWireClient.ParsePositionBlock(Block(raw, @base, exponent)).ToEngineering(0)!.Value.ShouldBe(expected, 1e-9);
    }

    [Theory]
    [InlineData(1, 10, 0xFFFF)]   // vacant-slot marker
    [InlineData(1234, 7, 2)]      // base neither 2 nor 10
    [InlineData(1234, 0, 2)]
    [InlineData(123456, 10, 400)] // would divide by Infinity → a Good 0.0 at the origin
    [InlineData(123456, 10, 40)]
    public void An_undescribable_block_has_no_value(int raw, int @base, int exponent)
    {
        var p = FocasWireClient.ParsePositionBlock(Block(raw, @base, exponent));
        p.IsValid.ShouldBeFalse();
        p.ToEngineering(3).ShouldBeNull();
    }

    [Fact]
    public void Every_plausible_exponent_still_decodes()
    {
        for (var exp = 0; exp <= 18; exp++)
            FocasWireClient.ParsePositionBlock(Block(1, 10, exp)).IsValid.ShouldBeTrue($"exponent {exp}");
    }

    [Fact]
    public void A_block_without_a_scale_falls_back_to_the_configured_decimal_places()
    {
        // A 4-byte block carries no envelope (older simulators); only then does
        // PositionDecimalPlaces apply.
        var p = FocasWireClient.ParsePositionBlock([0x00, 0x00, 0x30, 0x39]); // 12345
        p.HasScale.ShouldBeFalse();
        p.ToEngineering(2)!.Value.ShouldBe(123.45, 1e-9);
        p.ToEngineering(0)!.Value.ShouldBe(12345.0);
    }

    [Fact]
    public void A_raw_integer_position_converts_implicitly_as_a_scale_less_value()
    {
        FocasPosition p = 12345;
        p.HasScale.ShouldBeFalse();
        p.Raw.ShouldBe(12345);
    }
}