qmk-rgb/internal/via/protocol.go

package via

import (
	"fmt"

	"github.com/wobkey/rgb/internal/device"
	"github.com/wobkey/rgb/internal/hid"
)

// Protocol implements the VIA protocol for communication with a keyboard.
type Protocol struct {
	handle *hid.Device
	kb     device.Keyboard
}

// New creates a new VIA protocol handler for a connected device.
func New(dev device.Device) (*Protocol, error) {
	h, err := hid.OpenPath(dev.Path)
	if err != nil {
		return nil, fmt.Errorf("open device %s: %w", dev.Path, err)
	}

	return &Protocol{
		handle: h,
		kb:     dev.Keyboard,
	}, nil
}

// Close releases the device handle.
func (p *Protocol) Close() error {
	if p.handle != nil {
		return p.handle.Close()
	}
	return nil
}

// ReportID is the VIA report ID.
const ReportID = 0x52

// Message defines VIA message types.
type Message uint8

const (
	Enable Message = 0x01
	Set    Message = 0x02
	Get    Message = 0x03
)

// LEDType defines QMK LED subsystem types.
type LEDType uint8

const (
	RGBLight LEDType = 0x01
)

// EnableHandshake sends the enable message to initialize the VIA connection.
func (p *Protocol) EnableHandshake() error {
	report := []byte{0x00, byte(Enable), 0x00, 0x00, 0x00}
	_, err := p.handle.SendReport(report[0], report[1:])
	return err
}

// SetValue sends a set value command for the given LED type and parameter.
func (p *Protocol) SetValue(ledType LEDType, param uint8, value uint8) error {
	report := []byte{0x00, byte(Set), byte(ledType), param, value}
	_, err := p.handle.SendReport(report[0], report[1:])
	return err
}

// GetValue sends a get value request and reads the response.
func (p *Protocol) GetValue(ledType LEDType, param uint8) ([]byte, error) {
	report := []byte{0x00, byte(Get), byte(ledType), param, 0x00}
	_, err := p.handle.SendReport(report[0], report[1:])
	if err != nil {
		return nil, fmt.Errorf("send get request: %w", err)
	}

	buf := make([]byte, 64)
	n, err := p.handle.Read(buf)
	if err != nil {
		return nil, fmt.Errorf("read response: %w", err)
	}

	return buf[:n], nil
}