package omemo

import (
	"bytes"
	"reflect"
	"testing"

	"dev.narayana.im/narayana/telegabber/e2ee/omemo/libsignal"
)

func TestEncryptOuterRoundTrip(t *testing.T) {
	for _, tc := range []struct {
		name    string
		version int
	}{
		{"legacy", libsignal.ProtocolVersionLegacy},
		{"modern", libsignal.ProtocolVersionModern},
	} {
		t.Run(tc.name, func(t *testing.T) {
			plaintext := []byte("hello from telegram")

			payload, err := EncryptOuter(tc.version, plaintext, "gateway@example.com")
			if err != nil {
				t.Fatalf("EncryptOuter: %v", err)
			}
			if len(payload.Ciphertext) == 0 {
				t.Fatalf("expected non-empty ciphertext")
			}
			if tc.version == libsignal.ProtocolVersionLegacy && len(payload.IV) != legacyIVLen {
				t.Fatalf("expected a %d-byte IV for legacy, got %d", legacyIVLen, len(payload.IV))
			}
			if tc.version == libsignal.ProtocolVersionModern && payload.IV != nil {
				t.Fatalf("expected no IV for modern (receiver re-derives it), got %d bytes", len(payload.IV))
			}

			got, err := DecryptOuter(tc.version, payload)
			if err != nil {
				t.Fatalf("DecryptOuter: %v", err)
			}
			if !bytes.Equal(got, plaintext) {
				t.Fatalf("round trip mismatch: got %q, want %q", got, plaintext)
			}
		})
	}
}

func TestEncryptOuterTamperDetection(t *testing.T) {
	for _, tc := range []struct {
		name    string
		version int
	}{
		{"legacy", libsignal.ProtocolVersionLegacy},
		{"modern", libsignal.ProtocolVersionModern},
	} {
		t.Run(tc.name, func(t *testing.T) {
			payload, err := EncryptOuter(tc.version, []byte("secret"), "gateway@example.com")
			if err != nil {
				t.Fatalf("EncryptOuter: %v", err)
			}

			tampered := *payload
			tampered.Ciphertext = append([]byte{}, payload.Ciphertext...)
			tampered.Ciphertext[0] ^= 0xFF

			if _, err := DecryptOuter(tc.version, &tampered); err == nil {
				t.Fatalf("expected DecryptOuter to reject tampered ciphertext")
			}
		})
	}
}

func TestSCERoundTrip(t *testing.T) {
	plaintext := []byte("hello sce")
	xmlBytes, err := sceEncode(plaintext, "alice@example.com")
	if err != nil {
		t.Fatalf("sceEncode: %v", err)
	}
	got, err := sceDecode(xmlBytes)
	if err != nil {
		t.Fatalf("sceDecode: %v", err)
	}
	if !bytes.Equal(got, plaintext) {
		t.Fatalf("got %q, want %q", got, plaintext)
	}
}

func TestWireEnvelopeEncodeDecode(t *testing.T) {
	env := &WireEnvelope{
		Version:   libsignal.ProtocolVersionModern,
		SenderSID: 12345,
		Payload:   []byte("ciphertext-bytes"),
		Keys: []WireKey{
			{RecipientJID: "bob@example.com", DeviceID: 1, IsPreKey: true, Ciphertext: []byte("key-ciphertext-1")},
			{RecipientJID: "bob@example.com", DeviceID: 2, IsPreKey: false, Ciphertext: []byte("key-ciphertext-2")},
		},
	}

	raw, err := env.Encode()
	if err != nil {
		t.Fatalf("Encode: %v", err)
	}

	got, err := DecodeWireEnvelope(raw)
	if err != nil {
		t.Fatalf("DecodeWireEnvelope: %v", err)
	}

	if got.Version != env.Version || got.SenderSID != env.SenderSID || !bytes.Equal(got.Payload, env.Payload) {
		t.Fatalf("round trip mismatch: got %+v", got)
	}
	if len(got.Keys) != len(env.Keys) {
		t.Fatalf("expected %d keys, got %d", len(env.Keys), len(got.Keys))
	}
	for i := range env.Keys {
		if !reflect.DeepEqual(got.Keys[i], env.Keys[i]) {
			t.Fatalf("key %d mismatch: got %+v, want %+v", i, got.Keys[i], env.Keys[i])
		}
	}
}