Refactor logging and start adding rule matching code.

internal/logger/logger.go

@@ -0,0 +1,27 @@
+package logger
+
+import (
+	"fmt"
+	"os"
+)
+
+func Log(msg string) {
+	fmt.Println(msg)
+}
+
+func LogIfError(err error, msg string) {
+	if err == nil {
+		return
+	}
+
+	fmt.Printf("%s: %s\n", msg, err.Error())
+}
+
+func FatalIfError(err error, msg string) {
+	if err == nil {
+		return
+	}
+
+	LogIfError(err, msg)
+	os.Exit(1)
+}

internal/rules/keymapping.go

@@ -0,0 +1,50 @@
+package rules
+
+import (
+	"git.annabunches.net/annabunches/joyful/internal/logger"
+	"github.com/holoplot/go-evdev"
+)
+
+type KeyMappingRule interface {
+	MatchEvent(*evdev.InputDevice, *evdev.InputEvent)
+}
+
+type SimpleMappingRule struct {
+	Input  RuleTarget
+	Output RuleTarget
+}
+
+type ComboMappingRule struct {
+	Input  []RuleTarget
+	Output RuleTarget
+}
+
+func (rule *SimpleMappingRule) MatchEvent(device *evdev.InputDevice, event *evdev.InputEvent) *evdev.InputEvent {
+	if event.Type != evdev.EV_KEY ||
+		device != rule.Input.Device ||
+		event.Code != rule.Input.Code {
+		return nil
+	}
+
+	// how we process inverted rules depends on the event type
+	value := event.Value
+	if rule.Input.Inverted {
+		switch rule.Input.Type {
+		case evdev.EV_KEY:
+			if value == 0 {
+				value = 1
+			} else {
+				value = 0
+			}
+		default:
+			logger.Log("Tried to handle inverted rule for unknown event type. Skipping rule.")
+			return nil
+		}
+	}
+
+	return &evdev.InputEvent{
+		Type:  rule.Output.Type,
+		Code:  rule.Output.Code,
+		Value: value,
+	}
+}

internal/rules/types.go

@@ -0,0 +1,10 @@
+package rules
+
+import "github.com/holoplot/go-evdev"
+
+type RuleTarget struct {
+	Device   *evdev.InputDevice
+	Type     evdev.EvType
+	Code     evdev.EvCode
+	Inverted bool
+}