package link_test

import (
	"crypto/ed25519"
	"crypto/rand"
	"crypto/sha256"
	"encoding/hex"
	"errors"
	"testing"
	"time"

	"github.com/novox/mesh-controller/internal/inventory"
	"github.com/novox/mesh-controller/internal/link"
)

// A token another enrolment holds for the moment is "not now", not a refusal: the node asks again
// with the same request, and nothing is spent (novox/hq issue 083).
func TestAnEnrolmentMetByAHeldTokenIsAskedToTryAgain(t *testing.T) {
	inv := inventory.ForTest(t)
	ctx := t.Context()
	if _, err := inv.AddNode(ctx, "laptop"); err != nil {
		t.Fatal(err)
	}
	issued, err := inv.IssueToken(ctx, "laptop", time.Hour)
	if err != nil {
		t.Fatal(err)
	}
	if _, err := inv.Claim(ctx, issued.Secret, "another enrolment's key", false); err != nil {
		t.Fatal(err)
	}
	public, _, err := ed25519.GenerateKey(rand.Reader)
	if err != nil {
		t.Fatal(err)
	}
	_, err = link.Enrolment{Inventory: inv}.Enrol(ctx, link.EnrolRequest{
		Node: "laptop", Secret: issued.Secret, PublicKey: public})
	if !errors.Is(err, link.ErrTryAgain) {
		t.Fatalf("an enrolment met by a held token was not asked to try again: %v", err)
	}
	// And a token that cannot be used at all is still refused outright.
	_, err = link.Enrolment{Inventory: inv}.Enrol(ctx, link.EnrolRequest{
		Node: "laptop", Secret: "not-a-token", PublicKey: public})
	if err == nil || errors.Is(err, link.ErrTryAgain) {
		t.Fatalf("a token that cannot be used was not refused outright: %v", err)
	}
}

// **A spent token cannot be replayed with a node's public key** (novox/hq issue 083, on review). A
// public key is no secret: finishing an enrolment whose token that key spent takes proof the
// presenter holds its private half, and a proof made with another key — or for another request —
// is refused outright.
func TestASpentTokenCannotBeReplayedWithAPublicKeyAlone(t *testing.T) {
	inv := inventory.ForTest(t)
	ctx := t.Context()
	if _, err := inv.AddNode(ctx, "laptop"); err != nil {
		t.Fatal(err)
	}
	issued, err := inv.IssueToken(ctx, "laptop", time.Hour)
	if err != nil {
		t.Fatal(err)
	}
	victim, victimPrivate, err := ed25519.GenerateKey(rand.Reader)
	if err != nil {
		t.Fatal(err)
	}
	// The victim's enrolment spent the token.
	by := claimantOf(victim)
	if _, err := inv.Claim(ctx, issued.Secret, by, false); err != nil {
		t.Fatal(err)
	}
	if err := inv.Spend(ctx, issued.Secret, by); err != nil {
		t.Fatal(err)
	}

	// Someone with the leaked token and the victim's public key, and no proof.
	_, err = link.Enrolment{Inventory: inv}.Enrol(ctx, link.EnrolRequest{
		Node: "laptop", Secret: issued.Secret, PublicKey: victim, SealingKey: "the attacker's"})
	if err == nil || errors.Is(err, link.ErrTryAgain) {
		t.Fatalf("a spent token was taken again with a public key alone: %v", err)
	}
	// With a proof made by another key.
	_, forger, err := ed25519.GenerateKey(rand.Reader)
	if err != nil {
		t.Fatal(err)
	}
	forged := ed25519.Sign(forger, link.EnrolProof(issued.Secret, victim, "", "the attacker's", ""))
	_, err = link.Enrolment{Inventory: inv}.Enrol(ctx, link.EnrolRequest{
		Node: "laptop", Secret: issued.Secret, PublicKey: victim, SealingKey: "the attacker's", Proof: forged})
	if err == nil {
		t.Fatal("a spent token was taken again with a proof made by another key")
	}
	// With the victim's own proof, but for another request — keys swapped in.
	theirs := ed25519.Sign(victimPrivate, link.EnrolProof(issued.Secret, victim, "", "the victim's", ""))
	_, err = link.Enrolment{Inventory: inv}.Enrol(ctx, link.EnrolRequest{
		Node: "laptop", Secret: issued.Secret, PublicKey: victim, SealingKey: "the attacker's", Proof: theirs})
	if err == nil {
		t.Fatal("a spent token was taken again with a proof made for another request")
	}
	// And the victim's own, proven request is not honoured when the broker redelivered it: the
	// first delivery may already have been answered.
	_, err = link.Enrolment{Inventory: inv}.Enrol(ctx, link.EnrolRequest{
		Node: "laptop", Secret: issued.Secret, PublicKey: victim, SealingKey: "the victim's",
		Proof: theirs, Redelivered: true})
	if err == nil {
		t.Fatal("a redelivered request finished an enrolment already spent")
	}
}

// claimantOf is the claimant the enrolment derives from a key, recomputed here.
func claimantOf(public ed25519.PublicKey) string {
	sum := sha256.Sum256(public)
	return hex.EncodeToString(sum[:])
}