namespace Nonemm.Keying;

/// Reads the bytes a WinKeyer sends back in host mode and works out when it has
/// stopped sending.
///
/// A byte from 0xC0 to 0xDF is a status byte; the low six bits are the flags,
/// and 0x04 is set while the keyer is sending. Bytes from 0x80 to 0xBF are the
/// speed pot, and printable bytes are the keyer echoing what it has sent.
/// Neither says anything about the buffer, so both are passed over.
///
/// Where the bit meanings come from: `docs/keying.md`.
public sealed class WinkeyerStatus
{
    private const byte StatusLow = 0xC0;
    private const byte StatusHigh = 0xDF;
    private const byte BusyFlag = 0x04;

    public bool IsSending { get; private set; }

    /// True on the byte that says the keyer has finished: it was sending and
    /// now is not. Every other byte returns false, including a second status
    /// byte that repeats what the last one said.
    public bool Read(byte value)
    {
        if (value is < StatusLow or > StatusHigh)
        {
            return false;
        }
        bool wasSending = IsSending;
        IsSending = (value & BusyFlag) != 0;
        return wasSending && !IsSending;
    }
}