package auth_test

import (
	"bytes"
	"errors"
	"testing"

	"git.lohmar.co.uk/cclohmar/NextMyDay/internal/core/auth"
)

func TestAEADSealerRoundTrip(t *testing.T) {
	key := bytes.Repeat([]byte{0x42}, auth.KeySize)
	sealer, err := auth.NewAEADSealer(key)
	if err != nil {
		t.Fatalf("NewAEADSealer: %v", err)
	}

	plaintext := []byte("JBSWY3DPEHPK3PXP")
	sealed, err := sealer.Seal(plaintext)
	if err != nil {
		t.Fatalf("Seal: %v", err)
	}
	if bytes.Contains(sealed, plaintext) {
		t.Fatal("ciphertext contains the plaintext")
	}

	opened, err := sealer.Open(sealed)
	if err != nil {
		t.Fatalf("Open: %v", err)
	}
	if !bytes.Equal(opened, plaintext) {
		t.Errorf("Open = %q, want %q", opened, plaintext)
	}

	// A fresh nonce means sealing twice yields different ciphertext.
	sealed2, err := sealer.Seal(plaintext)
	if err != nil {
		t.Fatalf("Seal (2): %v", err)
	}
	if bytes.Equal(sealed, sealed2) {
		t.Error("two seals of the same plaintext are identical (nonce not fresh)")
	}
}

func TestAEADSealerRejectsWrongKeySize(t *testing.T) {
	if _, err := auth.NewAEADSealer(make([]byte, 16)); err == nil {
		t.Error("NewAEADSealer(16 bytes) = nil error, want error")
	}
}

func TestAEADSealerRejectsTamperedCiphertext(t *testing.T) {
	sealer, err := auth.NewAEADSealer(bytes.Repeat([]byte{1}, auth.KeySize))
	if err != nil {
		t.Fatalf("NewAEADSealer: %v", err)
	}
	sealed, err := sealer.Seal([]byte("secret"))
	if err != nil {
		t.Fatalf("Seal: %v", err)
	}
	sealed[len(sealed)-1] ^= 0xff // flip a tag bit
	if _, err := sealer.Open(sealed); !errors.Is(err, auth.ErrInvalidCiphertext) {
		t.Errorf("Open(tampered) = %v, want ErrInvalidCiphertext", err)
	}
}