feat(bridge): MQTT bridge with Home Assistant auto-discovery

pkg/bridge/handlers.go

@@ -0,0 +1,35 @@
+package bridge
+
+import (
+	"log/slog"
+	"strings"
+
+	mqtt "github.com/eclipse/paho.mqtt.golang"
+)
+
+func (b *Bridge) onConnect(c mqtt.Client) {
+	c.Publish(b.availTopic(), 1, true, b.availPayload())
+
+	c.Subscribe(b.cfg.DiscoveryPrefix+"/status", 1, func(_ mqtt.Client, msg mqtt.Message) {
+		if string(msg.Payload()) == "online" {
+			b.publishDiscovery()
+			b.OnState(b.dev.GetStatus())
+		}
+	})
+
+	for out := 1; out <= numOutputs; out++ {
+		out := out
+		c.Subscribe(b.cmdTopic(out), 1, func(_ mqtt.Client, msg mqtt.Message) {
+			payload := strings.TrimSpace(string(msg.Payload()))
+			in := inputNumberFromLabel(payload)
+			if in == 0 {
+				slog.Warn("unknown input label", "payload", payload)
+				return
+			}
+			b.dev.SetOutput(out, in)
+			c.Publish(b.stateTopic(out), 1, true, inputLabel(in))
+		})
+	}
+
+	b.publishDiscovery()
+}