package kdbx

import (
	"bytes"
	"encoding/hex"
	"testing"
)

// RFC 8439 section 2.4.2.
func TestChaCha20RFC8439(t *testing.T) {
	key := make([]byte, 32)
	for i := range key {
		key[i] = byte(i)
	}
	nonce, _ := hex.DecodeString("000000000000004a00000000")
	plain := []byte("Ladies and Gentlemen of the class of '99: If I could offer you " +
		"only one tip for the future, sunscreen would be it.")
	want, _ := hex.DecodeString(
		"6e2e359a2568f98041ba0728dd0d6981e97e7aec1d4360c20a27afccfd9fae0b" +
			"f91b65c5524733ab8f593dabcd62b3571639d624e65152ab8f530c359f0861d8" +
			"07ca0dbf500d6a6156a38e088a22b65e52bc514d16ccf806818ce91ab7793736" +
			"5af90bbf74a35be6b40b8eedf2785e42874d")

	got := make([]byte, len(plain))
	newChaCha20(key, nonce, 1).XORKeyStream(got, plain)
	if !bytes.Equal(got, want) {
		t.Fatalf("ciphertext =\n%x\nwant\n%x", got, want)
	}
}

// The keystream must be continuous across calls, because KDBX protects one
// value at a time from a single stream.
func TestChaCha20StreamIsContinuousAcrossCalls(t *testing.T) {
	key := make([]byte, 32)
	nonce := make([]byte, 12)
	src := make([]byte, 200)

	whole := make([]byte, len(src))
	newChaCha20(key, nonce, 0).XORKeyStream(whole, src)

	piecewise := make([]byte, len(src))
	c := newChaCha20(key, nonce, 0)
	for _, n := range []int{1, 7, 56, 64, 72} {
		c.XORKeyStream(piecewise[:n], src[:n])
		piecewise = piecewise[n:]
		src = src[n:]
	}
	piecewise = make([]byte, 200)
	c = newChaCha20(key, nonce, 0)
	off := 0
	for _, n := range []int{1, 7, 56, 64, 72} {
		c.XORKeyStream(piecewise[off:off+n], make([]byte, n))
		off += n
	}
	if !bytes.Equal(whole, piecewise) {
		t.Fatal("keystream differs when produced in pieces")
	}
}