* Move all physical device initialization logic to main functions

* Move all virtual device initialization to virtualbuffer package.
* Factor out common eventcode helper logic into a new package.

internal/eventcodes/codes.go

@@ -0,0 +1,77 @@
+package eventcodes
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+
+	"github.com/holoplot/go-evdev"
+)
+
+func ParseCodeButton(code string) (evdev.EvCode, error) {
+	prefix := CodePrefixButton
+
+	if strings.HasPrefix(code, CodePrefixKey+"_") {
+		prefix = CodePrefixKey
+	}
+
+	return ParseCode(code, prefix)
+}
+
+func ParseCode(code, prefix string) (evdev.EvCode, error) {
+	code = strings.ToUpper(code)
+
+	var codeLookup map[string]evdev.EvCode
+
+	switch prefix {
+	case CodePrefixButton, CodePrefixKey:
+		codeLookup = evdev.KEYFromString
+	case CodePrefixAxis:
+		codeLookup = evdev.ABSFromString
+	case CodePrefixRelaxis:
+		codeLookup = evdev.RELFromString
+	default:
+		return 0, fmt.Errorf("invalid EvCode prefix '%s'", prefix)
+	}
+
+	switch {
+	case strings.HasPrefix(code, prefix+"_"):
+		eventCode, ok := codeLookup[code]
+		if !ok {
+			return 0, fmt.Errorf("invalid keycode specification '%s'", code)
+		}
+
+		return eventCode, nil
+
+	case strings.HasPrefix(code, "0X"):
+		codeInt, err := strconv.ParseUint(code[2:], 16, 0)
+		if err != nil {
+			return 0, err
+		}
+		return evdev.EvCode(codeInt), nil
+
+	case prefix == CodePrefixButton && !hasError(strconv.Atoi(code)):
+		index, err := strconv.Atoi(code)
+		if err != nil {
+			return 0, err
+		}
+
+		if index >= len(ButtonFromIndex) {
+			return 0, fmt.Errorf("button index '%d' out of bounds", index)
+		}
+
+		return ButtonFromIndex[index], nil
+
+	default:
+		eventCode, ok := codeLookup[prefix+"_"+code]
+		if !ok {
+			return 0, fmt.Errorf("invalid keycode specification '%s'", code)
+		}
+		return eventCode, nil
+	}
+}
+
+// hasError exists solely to switch on errors in conditional and case statements
+func hasError(_ any, err error) bool {
+	return err != nil
+}