Add support for Joystick hats.

internal/mappingrules/mapping_rule_hat.go

@@ -0,0 +1,45 @@
+package mappingrules
+
+import (
+	"git.annabunches.net/annabunches/joyful/internal/configparser"
+	"github.com/holoplot/go-evdev"
+)
+
+// A Simple Mapping Rule can map a button to a button or an axis to an axis.
+type MappingRuleHat struct {
+	MappingRuleBase
+	Input  *RuleTargetHat
+	Output *RuleTargetHat
+}
+
+func NewMappingRuleHat(ruleConfig configparser.RuleConfigHat,
+	pDevs map[string]Device,
+	vDevs map[string]Device,
+	base MappingRuleBase) (*MappingRuleHat, error) {
+
+	input, err := NewRuleTargetHatFromConfig(ruleConfig.Input, pDevs)
+	if err != nil {
+		return nil, err
+	}
+
+	output, err := NewRuleTargetHatFromConfig(ruleConfig.Output, vDevs)
+	if err != nil {
+		return nil, err
+	}
+
+	return &MappingRuleHat{
+		MappingRuleBase: base,
+		Input:           input,
+		Output:          output,
+	}, nil
+}
+
+func (rule *MappingRuleHat) MatchEvent(device Device, event *evdev.InputEvent, mode *string) (*evdev.InputDevice, *evdev.InputEvent) {
+	if !rule.MappingRuleBase.modeCheck(mode) ||
+		!rule.Input.MatchEvent(device, event) {
+		return nil, nil
+	}
+
+	// The cast here is safe because the interface is only ever different for unit tests
+	return rule.Output.Device.(*evdev.InputDevice), rule.Output.CreateEvent(rule.Input.NormalizeValue(event.Value), mode)
+}