package secp256k1

import (
	"encoding/hex"
	"testing"
)

func TestECDHSymmetry(t *testing.T) {
	var a, b [32]byte
	a[31] = 1
	b[31] = 2
	pubA, ok := PubKey(a)
	if !ok {
		t.Fatal("pub a")
	}
	pubB, ok := PubKey(b)
	if !ok {
		t.Fatal("pub b")
	}
	x1, ok := ECDH(a, pubB)
	if !ok {
		t.Fatal("ecdh a,b")
	}
	x2, ok := ECDH(b, pubA)
	if !ok {
		t.Fatal("ecdh b,a")
	}
	if x1 != x2 {
		t.Fatalf("shared secrets differ: %x %x", x1, x2)
	}
	// 2*G has this x coordinate.
	const want = "c6047f9441ed7d6d3045406e95c07cd85c778e4b8cef3ca7abac09b95c709ee5"
	if got := hex.EncodeToString(x1[:]); got != want {
		t.Fatalf("x = %s, want %s", got, want)
	}
}

func TestECDHRejectsBadInput(t *testing.T) {
	var zero, one [32]byte
	one[31] = 1
	if _, ok := ECDH(zero, one); ok {
		t.Fatal("accepted zero secret")
	}
	badPub := [32]byte{0xff}
	if _, ok := ECDH(one, badPub); ok {
		t.Fatal("accepted off-curve public key")
	}
}

func TestValidatePubKey(t *testing.T) {
	var one [32]byte
	one[31] = 1
	pub, _ := PubKey(one)
	if !ValidatePubKey(pub) {
		t.Fatal("rejected a real public key")
	}
	if ValidatePubKey([32]byte{0xff}) {
		t.Fatal("accepted an off-curve key")
	}
}