package signing

import (
	"crypto/ed25519"
	"errors"
	"testing"
)

type doc struct {
	Revision struct {
		ID        string     `json:"id"`
		State     string     `json:"state"`
		Upstream  string     `json:"upstream"`
		Signature *Signature `json:"signature,omitempty"`
	} `json:"revision"`
}

func newDoc(id, state string) doc {
	var d doc
	d.Revision.ID = id
	d.Revision.State = state
	d.Revision.Upstream = "http://adapter:8080"
	return d
}

func TestSignAndVerify(t *testing.T) {
	signer, pub, err := GenerateKey("key-1")
	if err != nil {
		t.Fatal(err)
	}
	v := NewVerifier(map[string]ed25519.PublicKey{"key-1": pub})

	d := newDoc("R-1", "stable")
	sig, err := signer.Sign(d)
	if err != nil {
		t.Fatal(err)
	}
	if err := v.Verify(d, &sig); err != nil {
		t.Fatalf("freshly signed document does not verify: %v", err)
	}
}

// TestSignatureCoversContent is the property the whole barrier depends on: a
// tampered descriptor must not verify.
func TestSignatureCoversContent(t *testing.T) {
	signer, pub, _ := GenerateKey("key-1")
	v := NewVerifier(map[string]ed25519.PublicKey{"key-1": pub})

	d := newDoc("R-1", "experiment")
	sig, _ := signer.Sign(d)

	// Promoting a signed experiment to stable by editing the descriptor is
	// exactly the attack the signature exists to stop.
	tampered := d
	tampered.Revision.State = "stable"
	if err := v.Verify(tampered, &sig); !errors.Is(err, ErrBadSignature) {
		t.Errorf("a tampered descriptor verified: %v", err)
	}

	redirected := d
	redirected.Revision.Upstream = "http://attacker:8080"
	if err := v.Verify(redirected, &sig); !errors.Is(err, ErrBadSignature) {
		t.Errorf("a redirected upstream verified: %v", err)
	}
}

// TestSignatureMemberIsExcluded checks that a document signs its content and
// not its own signature, so a signed document round-trips.
func TestSignatureMemberIsExcluded(t *testing.T) {
	signer, pub, _ := GenerateKey("key-1")
	v := NewVerifier(map[string]ed25519.PublicKey{"key-1": pub})

	d := newDoc("R-1", "stable")
	sig, _ := signer.Sign(d)

	attached := d
	attached.Revision.Signature = &sig
	if err := v.Verify(attached, &sig); err != nil {
		t.Fatalf("a document carrying its own signature does not verify: %v", err)
	}
}

func TestUnsignedIsRefused(t *testing.T) {
	_, pub, _ := GenerateKey("key-1")
	v := NewVerifier(map[string]ed25519.PublicKey{"key-1": pub})

	// A verifier that passes unsigned input is worse than no verifier, because
	// it reports success.
	if err := v.Verify(newDoc("R-1", "stable"), nil); !errors.Is(err, ErrUnsigned) {
		t.Errorf("unsigned document returned %v, want ErrUnsigned", err)
	}
}

func TestUntrustedKeyIsRefused(t *testing.T) {
	rogue, _, _ := GenerateKey("rogue-key")
	_, trustedPub, _ := GenerateKey("key-1")
	v := NewVerifier(map[string]ed25519.PublicKey{"key-1": trustedPub})

	d := newDoc("R-1", "stable")
	sig, _ := rogue.Sign(d)

	if err := v.Verify(d, &sig); !errors.Is(err, ErrUnknownKey) {
		t.Errorf("a signature from an untrusted key returned %v, want ErrUnknownKey", err)
	}
}

func TestAlgorithmCannotBeDowngraded(t *testing.T) {
	signer, pub, _ := GenerateKey("key-1")
	v := NewVerifier(map[string]ed25519.PublicKey{"key-1": pub})

	d := newDoc("R-1", "stable")
	sig, _ := signer.Sign(d)
	sig.Algorithm = "none"

	if err := v.Verify(d, &sig); !errors.Is(err, ErrUnsupportedAlgorithm) {
		t.Errorf("an algorithm downgrade returned %v, want ErrUnsupportedAlgorithm", err)
	}
}

// TestCanonicalizationIsStable matters because an adapter or Daimon in another
// language must be able to produce a signature this verifier accepts.
func TestCanonicalizationIsStable(t *testing.T) {
	d := newDoc("R-1", "stable")

	first, err := Canonicalize(d)
	if err != nil {
		t.Fatal(err)
	}
	for i := 0; i < 100; i++ {
		again, err := Canonicalize(d)
		if err != nil {
			t.Fatal(err)
		}
		if string(again) != string(first) {
			t.Fatalf("canonical form varied between runs:\n%s\n%s", first, again)
		}
	}

	// Key order in the source must not change the canonical bytes.
	fromMap := map[string]any{
		"revision": map[string]any{
			"upstream": "http://adapter:8080",
			"state":    "stable",
			"id":       "R-1",
		},
	}
	mapForm, err := Canonicalize(fromMap)
	if err != nil {
		t.Fatal(err)
	}
	if string(mapForm) != string(first) {
		t.Errorf("canonical form depends on key order:\n%s\n%s", first, mapForm)
	}
}

func TestNewSignerRejectsBadInput(t *testing.T) {
	_, priv, _ := ed25519.GenerateKey(nil)
	if _, err := NewSigner("", priv); err == nil {
		t.Error("a signer with no key id was accepted")
	}
	if _, err := NewSigner("key-1", ed25519.PrivateKey("short")); err == nil {
		t.Error("a malformed private key was accepted")
	}
}