using System.Runtime.InteropServices;
using System.Text;

namespace Olei.LidarSensor;

/// <summary>
/// Frame header structure for Olei LiDAR sensor (40 bytes)
/// All data is in little-endian format
/// </summary>
[StructLayout(LayoutKind.Sequential, Pack = 1)]
public struct LidarHeader
{
    /// <summary>
    /// Frame ID, always 0xFEF0010F
    /// </summary>
    public const uint FRAME_ID = 0xFEF0010F;

    /// <summary>
    /// Protocol version, current is 0x0200
    /// </summary>
    public const ushort PROTOCOL_VERSION = 0x0200;

    public uint Id;
    public ushort ProtocolVersion;
    public byte DistanceScale;

    // Brand name code (3 bytes)
    public byte BrandName1;
    public byte BrandName2;
    public byte BrandName3;

    // Commercial type code (12 bytes)
    public ulong CommercialType1;
    public uint CommercialType2;

    public ushort InternalTypeCode;
    public ushort HardwareVersion;
    public ushort SoftwareVersion;
    public uint TimeStamp;
    public ushort RotationRateAndDirection;
    public byte SafeZoneStatus;
    public byte ErrorStatus;
    public uint NtpTimestampInteger;

    /// <summary>
    /// Check if the frame ID is valid
    /// </summary>
    public readonly bool IsValidFrame => Id == FRAME_ID;

    /// <summary>
    /// Get rotation rate (Bit[14:0])
    /// </summary>
    public readonly ushort RotationRate => (ushort)(RotationRateAndDirection & 0x7FFF);

    /// <summary>
    /// Get rotation direction (Bit[15]): false = clockwise, true = counter clockwise
    /// </summary>
    public readonly bool IsCounterClockwise => (RotationRateAndDirection & 0x8000) != 0;

    /// <summary>
    /// Check if motor fault occurred (BIT0 of ErrorStatus)
    /// </summary>
    public readonly bool HasMotorFault => (ErrorStatus & 0x01) != 0;

    /// <summary>
    /// Check if abnormal voltage occurred (BIT1 of ErrorStatus)
    /// </summary>
    public readonly bool HasAbnormalVoltage => (ErrorStatus & 0x02) != 0;

    /// <summary>
    /// Check if temperature fault occurred (BIT2 of ErrorStatus)
    /// </summary>
    public readonly bool HasTemperatureFault => (ErrorStatus & 0x04) != 0;

    /// <summary>
    /// Check if any error occurred
    /// </summary>
    public readonly bool HasError => ErrorStatus != 0;

    /// <summary>
    /// Get brand name as string
    /// </summary>
    public readonly string GetBrandName()
    {
        Span<byte> bytes = stackalloc byte[3];
        bytes[0] = BrandName1;
        bytes[1] = BrandName2;
        bytes[2] = BrandName3;
        return Encoding.ASCII.GetString(bytes).TrimEnd('\0');
    }

    /// <summary>
    /// Get OUTPUT bits (BIT[3:0] of SafeZoneStatus)
    /// </summary>
    public readonly byte GetOutputBits => (byte)(SafeZoneStatus & 0x0F);

    /// <summary>
    /// Get INPUT bits (BIT[7:4] of SafeZoneStatus)
    /// </summary>
    public readonly byte GetInputBits => (byte)((SafeZoneStatus >> 4) & 0x0F);
}