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>
///     Servo (<c>cnc_rdsvmeter</c>, 0x0056) and spindle (<c>cnc_rdspmeter</c>, 0x0040) meter decode.
///     Both are arrays of 8-byte records carrying the same self-describing envelope as every other
///     value block on this wire — <c>[+0..3] i32 value</c>, <c>[+4..5] u16 base</c> (2 or 10),
///     <c>[+6..7] u16 exponent</c> — so <c>scaled = value / base^exponent</c>.
///     Ported from the sister ignitionoee FOCAS driver v0.17.2 / v0.17.3 (Focas.Wire-019).
/// </summary>
/// <remarks>
///     <para><b>Servo: offset 4 is the BASE, not a decimal count.</b> It holds a steady 10, so the
///     old <c>value / 10^decimal</c> divided every load by 10^10 and published ~0 — on a real
///     Makino cutting at 20,000 rpm the panel read servo 0% on every axis. Servo meters are
///     <b>direct</b> percentages (the live capture shows −57..227).</para>
///     <para><b>Spindle: a fraction of full scale in 1/16384 units.</b> Settled on the real Z-34184
///     by regressing the type-1 meter against the independently read <c>cnc_rddynamic2</c> spindle
///     speed over 596–20,000 rpm: <c>rpm = 1.220749 × meter</c>, and <c>16384 × 1.220749 =
///     20000.75</c> — full scale is the spindle's 20,000 rpm maximum. So the type-1 meter
///     (<c>cnc_rdspmaxrpm</c> by name) is the <b>motor speed as a % of maximum</b>, not a max-rpm
///     constant; the type-0 load meter shares the envelope and the 16384 = 100% scale (its
///     acceleration peaks pin at 32767 — one count short of a 200% overload).</para>
/// </remarks>
[Trait("Category", "Unit")]
public sealed class FocasMeterDecodeTests
{
    private static byte[] Record(int value, int @base, int exponent)
    {
        var b = new byte[8];
        BinaryPrimitives.WriteInt32BigEndian(b.AsSpan(0, 4), value);
        BinaryPrimitives.WriteUInt16BigEndian(b.AsSpan(4, 2), (ushort)@base);
        BinaryPrimitives.WriteUInt16BigEndian(b.AsSpan(6, 2), (ushort)exponent);
        return b;
    }

    // ---- servo ----

    [Fact]
    public void The_live_servo_capture_reads_direct_percentages_not_value_over_ten_to_the_tenth()
    {
        var blocks = WireFixtures.Blocks("svmeter-pair-0x0056-0x0089.bin");
        var meters = FocasWireClient.ParseServoMeters(
            blocks.First(b => b.Command == 0x0056).Payload,
            blocks.First(b => b.Command == 0x0089).Payload,
            maxCount: 32);

        meters[0].Base.ShouldBe(10);
        meters[0].Exponent.ShouldBe(0);
        meters.Take(3).Select(m => m.Scaled).ShouldBe([0.0, 50.0, -3.0]);
    }

    [Fact]
    public void A_servo_record_applies_its_own_exponent()
    {
        var m = FocasWireClient.ParseServoMeters(Record(1234, 10, 1), Array.Empty<byte>(), 32).Single();
        m.Scaled!.Value.ShouldBe(123.4, 1e-9);
    }

    [Theory]
    [InlineData(5, 7, 0)]        // base neither 2 nor 10
    [InlineData(5, 10, 2560)]    // residue past the controlled-axis count
    public void An_undescribable_servo_record_has_no_value_not_zero(int value, int @base, int exponent)
    {
        var m = FocasWireClient.ParseServoMeters(Record(value, @base, exponent), Array.Empty<byte>(), 32).Single();
        m.IsValid.ShouldBeFalse();
        m.Scaled.ShouldBeNull();
    }

    // ---- spindle ----

    [Fact]
    public void The_live_spindle_load_capture_is_a_percentage_of_16384()
    {
        var metrics = FocasWireClient.ParseSpindleMetrics(
            WireFixtures.Payload("live-spmeter-load-0x0040.bin", 0x0040));

        // Slot 1: raw 0x23C3 = 9155, base 10, exponent 0 → 9155 × 100 / 16384 ≈ 55.88 %.
        metrics[0].Value.ShouldBe(9155);
        metrics[0].Percent!.Value.ShouldBe(9155 * 100.0 / 16384, 1e-9);
        // Slot 2 is buffer residue (exponent 0x0A00 = 2560): no value, not a number.
        metrics[1].IsValid.ShouldBeFalse();
        metrics[1].Percent.ShouldBeNull();
    }

    [Fact]
    public void The_live_motor_speed_capture_is_a_percentage_of_maximum_speed()
    {
        var metrics = FocasWireClient.ParseSpindleMetrics(
            WireFixtures.Payload("live-spmeter-maxrpm-0x0040.bin", 0x0040));

        // 0x3FFD = 16381 ≈ 99.98 % — a spindle at (just under) its 20,000 rpm maximum.
        metrics[0].Value.ShouldBe(16381);
        metrics[0].Percent!.Value.ShouldBe(16381 * 100.0 / 16384, 1e-9);
    }

    [Theory]
    [InlineData(16382, 19998)]
    [InlineData(12286, 14998)]
    [InlineData(9830, 12000)]
    [InlineData(695, 850)]
    [InlineData(488, 595)]
    public void Percent_reproduces_the_live_motor_speed_regression(int meter, int rpm)
    {
        var m = FocasWireClient.ParseSpindleMetrics(Record(meter, 10, 0)).Single();
        m.Percent!.Value.ShouldBe(rpm * 100.0 / 20000.0, 0.02);
    }

    [Fact]
    public void Full_scale_is_16384_and_overload_is_not_clamped()
    {
        WireSpindleMetric.FullScale.ShouldBe(16384);
        FocasWireClient.ParseSpindleMetrics(Record(16384, 10, 0)).Single().Percent.ShouldBe(100.0);
        var overload = FocasWireClient.ParseSpindleMetrics(Record(32767, 10, 0)).Single().Percent!.Value;
        overload.ShouldBeInRange(199.9, 200.0);
    }

    [Fact]
    public void The_spindle_envelope_exponent_applies_before_the_full_scale_division()
    {
        // 163840 / 10^1 = 16384 counts = 100 %.
        FocasWireClient.ParseSpindleMetrics(Record(163840, 10, 1)).Single().Percent!.Value.ShouldBe(100.0, 1e-9);
    }
}