package natsutil

import (
	"testing"

	"github.com/vmihailenco/msgpack/v5"
)

// ────────────────────────────────────────────────────────────────────────────
// DecodeMsgpackMap tests
// ────────────────────────────────────────────────────────────────────────────

func TestDecodeMsgpackMap_Roundtrip(t *testing.T) {
	orig := map[string]any{
		"request_id": "req-001",
		"user_id":    "user-42",
		"premium":    true,
		"top_k":      int64(10), // msgpack decodes ints as int64
	}
	data, err := msgpack.Marshal(orig)
	if err != nil {
		t.Fatal(err)
	}

	decoded, err := DecodeMsgpackMap(data)
	if err != nil {
		t.Fatal(err)
	}

	if decoded["request_id"] != "req-001" {
		t.Errorf("request_id = %v", decoded["request_id"])
	}
	if decoded["premium"] != true {
		t.Errorf("premium = %v", decoded["premium"])
	}
}

func TestDecodeMsgpackMap_Empty(t *testing.T) {
	data, _ := msgpack.Marshal(map[string]any{})
	m, err := DecodeMsgpackMap(data)
	if err != nil {
		t.Fatal(err)
	}
	if len(m) != 0 {
		t.Errorf("expected empty map, got %v", m)
	}
}

func TestDecodeMsgpackMap_InvalidData(t *testing.T) {
	_, err := DecodeMsgpackMap([]byte{0xFF, 0xFE})
	if err == nil {
		t.Error("expected error for invalid msgpack data")
	}
}

// ────────────────────────────────────────────────────────────────────────────
// DecodeMsgpack (typed struct) tests
// ────────────────────────────────────────────────────────────────────────────

type testMessage struct {
	RequestID string `msgpack:"request_id"`
	UserID    string `msgpack:"user_id"`
	Count     int    `msgpack:"count"`
	Active    bool   `msgpack:"active"`
}

func TestDecodeMsgpackTyped_Roundtrip(t *testing.T) {
	orig := testMessage{
		RequestID: "req-typed-001",
		UserID:    "user-7",
		Count:     42,
		Active:    true,
	}
	data, err := msgpack.Marshal(orig)
	if err != nil {
		t.Fatal(err)
	}

	// Simulate nats.Msg data decoding.
	var decoded testMessage
	if err := msgpack.Unmarshal(data, &decoded); err != nil {
		t.Fatal(err)
	}

	if decoded.RequestID != orig.RequestID {
		t.Errorf("RequestID = %q, want %q", decoded.RequestID, orig.RequestID)
	}
	if decoded.Count != orig.Count {
		t.Errorf("Count = %d, want %d", decoded.Count, orig.Count)
	}
	if decoded.Active != orig.Active {
		t.Errorf("Active = %v, want %v", decoded.Active, orig.Active)
	}
}

// TestTypedStructDecodesMapEncoding verifies that a typed struct can be
// decoded from data that was encoded as map[string]any (backwards compat).
func TestTypedStructDecodesMapEncoding(t *testing.T) {
	// Encode as map (the old way).
	mapData := map[string]any{
		"request_id": "req-compat",
		"user_id":    "user-compat",
		"count":      int64(99),
		"active":     false,
	}
	data, err := msgpack.Marshal(mapData)
	if err != nil {
		t.Fatal(err)
	}

	// Decode into typed struct (the new way).
	var msg testMessage
	if err := msgpack.Unmarshal(data, &msg); err != nil {
		t.Fatal(err)
	}

	if msg.RequestID != "req-compat" {
		t.Errorf("RequestID = %q", msg.RequestID)
	}
	if msg.Count != 99 {
		t.Errorf("Count = %d, want 99", msg.Count)
	}
}

// ────────────────────────────────────────────────────────────────────────────
// Binary data tests (audio []byte in msgpack)
// ────────────────────────────────────────────────────────────────────────────

type audioMessage struct {
	SessionID string `msgpack:"session_id"`
	Audio     []byte `msgpack:"audio"`
	SampleRate int   `msgpack:"sample_rate"`
}

func TestBinaryDataRoundtrip(t *testing.T) {
	audio := make([]byte, 32768)
	for i := range audio {
		audio[i] = byte(i % 256)
	}

	orig := audioMessage{
		SessionID:  "sess-audio-001",
		Audio:      audio,
		SampleRate: 24000,
	}
	data, err := msgpack.Marshal(orig)
	if err != nil {
		t.Fatal(err)
	}

	var decoded audioMessage
	if err := msgpack.Unmarshal(data, &decoded); err != nil {
		t.Fatal(err)
	}

	if len(decoded.Audio) != len(orig.Audio) {
		t.Fatalf("audio len = %d, want %d", len(decoded.Audio), len(orig.Audio))
	}
	for i := range decoded.Audio {
		if decoded.Audio[i] != orig.Audio[i] {
			t.Fatalf("audio[%d] = %d, want %d", i, decoded.Audio[i], orig.Audio[i])
		}
	}
}

// TestBinaryVsBase64Size shows the wire-size win of raw bytes vs base64 string.
func TestBinaryVsBase64Size(t *testing.T) {
	audio := make([]byte, 16384)

	// Old approach: base64 string in map.
	import_b64 := make([]byte, (len(audio)*4+2)/3) // approximate base64 size
	mapMsg := map[string]any{
		"session_id": "sess-1",
		"audio_b64":  string(import_b64),
	}
	mapData, _ := msgpack.Marshal(mapMsg)

	// New approach: raw bytes in struct.
	structMsg := audioMessage{
		SessionID: "sess-1",
		Audio:     audio,
	}
	structData, _ := msgpack.Marshal(structMsg)

	t.Logf("base64-in-map: %d bytes, raw-bytes-in-struct: %d bytes (%.0f%% smaller)",
		len(mapData), len(structData),
		100*(1-float64(len(structData))/float64(len(mapData))))
}

// ────────────────────────────────────────────────────────────────────────────
// Benchmarks
// ────────────────────────────────────────────────────────────────────────────

func BenchmarkEncodeMap(b *testing.B) {
	data := map[string]any{
		"request_id": "req-bench",
		"user_id":    "user-bench",
		"message":    "What is the weather today?",
		"premium":    true,
		"top_k":      10,
	}
	for b.Loop() {
		_, _ = msgpack.Marshal(data)
	}
}

func BenchmarkEncodeStruct(b *testing.B) {
	data := testMessage{
		RequestID: "req-bench",
		UserID:    "user-bench",
		Count:     10,
		Active:    true,
	}
	for b.Loop() {
		_, _ = msgpack.Marshal(data)
	}
}

func BenchmarkDecodeMap(b *testing.B) {
	raw, _ := msgpack.Marshal(map[string]any{
		"request_id": "req-bench",
		"user_id":    "user-bench",
		"message":    "What is the weather today?",
		"premium":    true,
		"top_k":      10,
	})
	for b.Loop() {
		var m map[string]any
		_ = msgpack.Unmarshal(raw, &m)
	}
}

func BenchmarkDecodeStruct(b *testing.B) {
	raw, _ := msgpack.Marshal(testMessage{
		RequestID: "req-bench",
		UserID:    "user-bench",
		Count:     10,
		Active:    true,
	})
	for b.Loop() {
		var m testMessage
		_ = msgpack.Unmarshal(raw, &m)
	}
}

func BenchmarkDecodeAudio32KB(b *testing.B) {
	raw, _ := msgpack.Marshal(audioMessage{
		SessionID:  "s1",
		Audio:      make([]byte, 32768),
		SampleRate: 24000,
	})
	for b.Loop() {
		var m audioMessage
		_ = msgpack.Unmarshal(raw, &m)
	}
}