From 9a435cdc3e90f6014bc6f670989d715b62c6d7b6 Mon Sep 17 00:00:00 2001
From: hermes <hermes@obahan.xyz>
Date: Wed, 30 Sep 2026 21:59:32 +0200
Subject: [PATCH] add internal/infra/mqtt_test.go

---
 internal/infra/mqtt_test.go | 76 +++++++++++++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)
 create mode 100644 internal/infra/mqtt_test.go

diff --git a/internal/infra/mqtt_test.go b/internal/infra/mqtt_test.go
new file mode 100644
index 0000000..5c01c9d
--- /dev/null
+++ b/internal/infra/mqtt_test.go
@@ -0,0 +1,76 @@
+package infra
+
+import (
+	"bytes"
+	"testing"
+)
+
+func TestMQTTConnectPacket(t *testing.T) {
+	p := mqttConnect("radio-go", "user1", "pass1")
+	// fixed header: 0x10, remaining length
+	if p[0] != 0x10 {
+		t.Fatalf("packet type = 0x%02x, want 0x10", p[0])
+	}
+	rl := int(p[1])
+	if rl != len(p)-2 {
+		t.Fatalf("remaining length %d != %d", rl, len(p)-2)
+	}
+	body := string(p[2:])
+	for _, want := range []string{"MQTT", "user1", "pass1", "radio-go"} {
+		if !bytes.Contains(p, []byte(want)) {
+			t.Fatalf("connect packet missing %q: %q", want, body)
+		}
+	}
+	// protocol level 4 (3.1.1): fixed hdr 2B + name len 2B + "MQTT" 4B => index 8
+	if p[8] != 4 {
+		t.Fatalf("protocol level = %d, want 4", p[8])
+	}
+	// connect flags: clean-session(0x02) | username(0x80) | password(0x40)
+	if p[9] != 0xC2 {
+		t.Fatalf("connect flags = 0x%02x, want 0xC2", p[9])
+	}
+}
+
+func TestMQTTConnectNoAuth(t *testing.T) {
+	p := mqttConnect("c1", "", "")
+	if p[9]&0xC0 != 0 {
+		t.Fatalf("flags should have no user/pass bits: 0x%02x", p[9])
+	}
+}
+
+func TestMQTTPublishPacket(t *testing.T) {
+	topic := "airstudio/nowplaying"
+	payload := `{"title":"Neon Rain"}`
+	p := mqttPublish(topic, []byte(payload))
+	// QoS 0 PUBLISH => 0x30
+	if p[0] != 0x30 {
+		t.Fatalf("packet type = 0x%02x, want 0x30", p[0])
+	}
+	rl := int(p[1])
+	if rl != len(p)-2 {
+		t.Fatalf("remaining length %d != %d", rl, len(p)-2)
+	}
+	// topic is first: 2-byte length + bytes
+	tl := int(p[2])<<8 | int(p[3])
+	if got := string(p[4 : 4+tl]); got != topic {
+		t.Fatalf("topic = %q, want %q", got, topic)
+	}
+	if got := string(p[4+tl:]); got != payload {
+		t.Fatalf("payload = %q, want %q", got, payload)
+	}
+}
+
+func TestMQTTRemainingLengthMultiByte(t *testing.T) {
+	big := bytes.Repeat([]byte("x"), 200)
+	p := mqttPublish("t", big)
+	// 200 + topic overhead > 127 => two-byte remaining length
+	if p[1]&0x80 == 0 {
+		t.Fatalf("expected continuation bit set for >127 remaining, got 0x%02x", p[1])
+	}
+	// MQTT remaining length is base-128 (not bit-shifted): low7 + next*128
+	rl := int(p[1]&0x7F) + int(p[2])*128
+	want := 2 + len("t") + len(big) // topic len + topic + payload (QoS0, no packet id)
+	if rl != want {
+		t.Fatalf("remaining length %d, want %d", rl, want)
+	}
+}