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)
	}
}