package siphash

import "testing"

// Reference test vectors from the SipHash paper (Aumasson & Bernstein 2012).
// Key: 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
// Input: 00 01 02 ... (incremental bytes)
var testKey = Key{0x0706050403020100, 0x0f0e0d0c0b0a0908}

// 64-bit test vector: SipHash-2-4("", key) from the reference appendix.
func TestSum64Empty(t *testing.T) {
	got := Sum64(testKey, []byte{})
	// Reference vector for empty input.
	want := uint64(0x726fdb47dd0e0e31)
	if got != want {
		t.Fatalf("Sum64(\"\") = %016x, want %016x", got, want)
	}
}

// 64-bit test vector: input = [0x00] (single zero byte).
func TestSum64OneByte(t *testing.T) {
	got := Sum64(testKey, []byte{0x00})
	want := uint64(0x74f839c593dc67fd)
	if got != want {
		t.Fatalf("Sum64([0x00]) = %016x, want %016x", got, want)
	}
}

// 64-bit test vectors for n=8 and n=16.
func TestSum64Eight(t *testing.T) {
	p := []byte{0, 1, 2, 3, 4, 5, 6, 7}
	got := Sum64(testKey, p)
	want := uint64(0x93f5f5799a932462) // reference vector n=8
	if got != want {
		t.Fatalf("Sum64(0..7) = %016x, want %016x", got, want)
	}
}

func TestSum64Sixteen(t *testing.T) {
	p := []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15}
	got := Sum64(testKey, p)
	want := uint64(0x3f2acc7f57c29bdb) // reference vector n=16
	if got != want {
		t.Fatalf("Sum64(0..15) = %016x, want %016x", got, want)
	}
}

// Verify Sum128 produces distinct lo/hi values.
func TestSum128Distinct(t *testing.T) {
	p := []byte("hello world")
	r := Sum128(testKey, p)
	if r[0] == r[1] {
		t.Fatal("Sum128 lo == hi, suspicious")
	}
	if r[0] == 0 || r[1] == 0 {
		t.Fatal("Sum128 has zero half")
	}
}

// Verify domain separation: different prefixes produce different keys.
func TestSum128DomainSep(t *testing.T) {
	word := []byte("cat")
	en := append([]byte{0x01}, word...)
	ja := append([]byte{0x02}, word...)
	rEN := Sum128(testKey, en)
	rJA := Sum128(testKey, ja)
	if rEN == rJA {
		t.Fatal("domain separation failed: EN and JA keys identical")
	}
}

// Verify determinism.
func TestSum128Deterministic(t *testing.T) {
	p := []byte("東京")
	a := Sum128(testKey, p)
	b := Sum128(testKey, p)
	if a != b {
		t.Fatal("Sum128 not deterministic")
	}
}