package crypto

import (
	"bytes"
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"encoding/hex"
	"testing"
)

func TestDeriveConsistency(t *testing.T) {
	k1 := make([]byte, 32)
	if _, err := rand.Read(k1); err != nil {
		t.Fatal(err)
	}
	salt := make([]byte, KdfSaltLength)
	if _, err := rand.Read(salt); err != nil {
		t.Fatal(err)
	}
	k2a, na, err := DeriveKeyAndGcmNonce(k1, salt)
	if err != nil {
		t.Fatal(err)
	}
	k2b, nb, err := DeriveKeyAndGcmNonce(k1, salt)
	if err != nil {
		t.Fatal(err)
	}
	if !bytes.Equal(k2a, k2b) || !bytes.Equal(na, nb) {
		t.Fatalf("inconsistent derivation")
	}
}

func TestDecryptWithClientEncrypt(t *testing.T) {
	// Mirror the client derivation implicitly by using same Derive function and Decrypt call.
	k1 := make([]byte, 32)
	if _, err := rand.Read(k1); err != nil {
		t.Fatal(err)
	}
	salt := make([]byte, KdfSaltLength)
	if _, err := rand.Read(salt); err != nil {
		t.Fatal(err)
	}
	pt := []byte("hello world")

	// Perform a local encrypt with same Derive to simulate client behavior
	k2, nonce, err := DeriveKeyAndGcmNonce(k1, salt)
	if err != nil {
		t.Fatal(err)
	}
	blk, err := aes.NewCipher(k2)
	if err != nil {
		t.Fatal(err)
	}
	a, err := cipher.NewGCMWithNonceSize(blk, GcmNonceLength)
	if err != nil {
		t.Fatal(err)
	}
	ct := a.Seal(nil, nonce, pt, nil)

	got, err := DecryptGCM(k1, salt, ct, nil)
	if err != nil {
		t.Fatal(err)
	}
	if !bytes.Equal(pt, got) {
		t.Fatalf("mismatch: want %s got %s", hex.EncodeToString(pt), hex.EncodeToString(got))
	}
}