package signing

import (
	"crypto/ed25519"
	"encoding/base64"
	"errors"
	"strings"
	"testing"
)

// The signing key, server name and key ID from the spec appendices,
// section "Cryptographic Test Vectors". Every implementation that signs
// JSON should produce the signatures below from them.
const (
	specSeed       = "YJDBA9Xnr2sVqXD9Vj7XVUnmFZcZrlw8Md7kMW+3XA1"
	specServerName = "domain"
	specKeyID      = "1"
)

func specKey(t *testing.T) *KeyPair {
	t.Helper()
	seed, err := base64.RawStdEncoding.DecodeString(specSeed)
	if err != nil {
		t.Fatalf("decode the spec seed: %v", err)
	}
	priv := ed25519.NewKeyFromSeed(seed)
	pub, ok := priv.Public().(ed25519.PublicKey)
	if !ok {
		t.Fatal("unexpected public key type")
	}
	return &KeyPair{ID: specKeyID, Private: priv, Public: pub}
}

// TestSpecJSONSigningVectors signs the two objects from the spec and
// compares the result byte for byte.
func TestSpecJSONSigningVectors(t *testing.T) {
	key := specKey(t)
	cases := []struct {
		name string
		in   string
		want string
	}{
		{
			name: "empty object",
			in:   `{}`,
			want: `{"signatures":{"domain":{"ed25519:1":"K8280/U9SSy9IVtjBuVeLr+HpOB4BQFWbg+UZaADMtTdGYI7Geitb76LTrr5QV/7Xg4ahLwYGYZzuHGZKM5ZAQ"}}}`,
		},
		{
			name: "object with data",
			in:   `{"one":1,"two":"Two"}`,
			want: `{"one":1,"signatures":{"domain":{"ed25519:1":"KqmLSbO39/Bzb0QIYE82zqLwsA+PDzYIpIRA2sRQ4sL53+sN6/fpNSoqE7BP7vBZhG6kYdD13EIMJpvhJI+6Bw"}},"two":"Two"}`,
		},
	}

	for _, tc := range cases {
		t.Run(tc.name, func(t *testing.T) {
			got, err := SignJSON(specServerName, key, []byte(tc.in))
			if err != nil {
				t.Fatalf("SignJSON: %v", err)
			}
			if string(got) != tc.want {
				t.Errorf("SignJSON() =\n %s\nwant\n %s", got, tc.want)
			}
			if err := VerifyJSON(specServerName, "ed25519:"+specKeyID, key.Public, got); err != nil {
				t.Errorf("VerifyJSON on our own signature: %v", err)
			}
		})
	}
}

// TestSignatureIgnoresUnsignedAndSignatures is the property that lets a
// server add a signature, or a timestamp under unsigned, to an object
// without invalidating what is already there.
func TestSignatureIgnoresUnsignedAndSignatures(t *testing.T) {
	key := specKey(t)
	keyID := "ed25519:" + specKeyID

	signed, err := SignJSON(specServerName, key, []byte(`{"a":1,"unsigned":{"age":5}}`))
	if err != nil {
		t.Fatalf("SignJSON: %v", err)
	}
	if !strings.Contains(string(signed), `"unsigned":{"age":5}`) {
		t.Errorf("unsigned was dropped from the signed object: %s", signed)
	}

	// Rewrite unsigned and add another server's signature; ours must
	// still verify.
	tampered := strings.Replace(string(signed), `"age":5`, `"age":9999`, 1)
	if err := VerifyJSON(specServerName, keyID, key.Public, []byte(tampered)); err != nil {
		t.Errorf("changing unsigned broke the signature: %v", err)
	}

	other, err := Generate("other")
	if err != nil {
		t.Fatal(err)
	}
	countersigned, err := SignJSON("second.example", other, signed)
	if err != nil {
		t.Fatalf("SignJSON for a second server: %v", err)
	}
	if err := VerifyJSON(specServerName, keyID, key.Public, countersigned); err != nil {
		t.Errorf("a second signature broke the first: %v", err)
	}
	if err := VerifyJSON("second.example", other.KeyID(), other.Public, countersigned); err != nil {
		t.Errorf("the second signature does not verify: %v", err)
	}
}

// TestSignJSONReplacesOurOwnSignature checks that signing twice with the
// same key leaves one signature, not two entries fighting over the slot.
func TestSignJSONReplacesOurOwnSignature(t *testing.T) {
	key := specKey(t)
	once, err := SignJSON(specServerName, key, []byte(`{"a":1}`))
	if err != nil {
		t.Fatal(err)
	}
	twice, err := SignJSON(specServerName, key, once)
	if err != nil {
		t.Fatal(err)
	}
	if string(once) != string(twice) {
		t.Errorf("signing twice changed the object:\n %s\n %s", once, twice)
	}
}

func TestVerifyJSONRejects(t *testing.T) {
	key := specKey(t)
	keyID := "ed25519:" + specKeyID
	signed, err := SignJSON(specServerName, key, []byte(`{"a":1}`))
	if err != nil {
		t.Fatal(err)
	}

	t.Run("content changed", func(t *testing.T) {
		tampered := strings.Replace(string(signed), `"a":1`, `"a":2`, 1)
		err := VerifyJSON(specServerName, keyID, key.Public, []byte(tampered))
		if !errors.Is(err, ErrBadSignature) {
			t.Errorf("error = %v, want ErrBadSignature", err)
		}
	})

	t.Run("wrong key", func(t *testing.T) {
		other, err := Generate("other")
		if err != nil {
			t.Fatal(err)
		}
		err = VerifyJSON(specServerName, keyID, other.Public, signed)
		if !errors.Is(err, ErrBadSignature) {
			t.Errorf("error = %v, want ErrBadSignature", err)
		}
	})

	t.Run("no signature from that server", func(t *testing.T) {
		err := VerifyJSON("somebody.else", keyID, key.Public, signed)
		if !errors.Is(err, ErrNoSignature) {
			t.Errorf("error = %v, want ErrNoSignature", err)
		}
	})

	t.Run("no signature with that key ID", func(t *testing.T) {
		err := VerifyJSON(specServerName, "ed25519:other", key.Public, signed)
		if !errors.Is(err, ErrNoSignature) {
			t.Errorf("error = %v, want ErrNoSignature", err)
		}
	})

	t.Run("signature is not base64", func(t *testing.T) {
		broken := strings.Replace(string(signed), `"ed25519:1":"`, `"ed25519:1":"!!!`, 1)
		err := VerifyJSON(specServerName, keyID, key.Public, []byte(broken))
		if !errors.Is(err, ErrBadSignature) {
			t.Errorf("error = %v, want ErrBadSignature", err)
		}
	})

	t.Run("signature is the wrong length", func(t *testing.T) {
		short, err := SignJSON(specServerName, key, []byte(`{"a":1}`))
		if err != nil {
			t.Fatal(err)
		}
		broken := strings.Replace(string(short), `"ed25519:1":"`, `"ed25519:1":"AAAA`, 1)
		err = VerifyJSON(specServerName, keyID, key.Public, []byte(broken))
		if !errors.Is(err, ErrBadSignature) {
			t.Errorf("error = %v, want ErrBadSignature", err)
		}
	})
}

func TestSigningBytes(t *testing.T) {
	got, err := SigningBytes([]byte(`{"b":2,"signatures":{"x":{}},"unsigned":{"age":1},"a":1}`))
	if err != nil {
		t.Fatalf("SigningBytes: %v", err)
	}
	if want := `{"a":1,"b":2}`; string(got) != want {
		t.Errorf("SigningBytes() = %s, want %s", got, want)
	}
}

func TestExtractSignatures(t *testing.T) {
	sigs, err := ExtractSignatures([]byte(`{"signatures":{"a.example":{"ed25519:1":"sig"}}}`))
	if err != nil {
		t.Fatalf("ExtractSignatures: %v", err)
	}
	if got, ok := sigs.Get("a.example", "ed25519:1"); !ok || got != "sig" {
		t.Errorf("Get() = %q, %v; want \"sig\", true", got, ok)
	}
	if _, ok := sigs.Get("b.example", "ed25519:1"); ok {
		t.Error("Get found a signature for a server that has none")
	}

	none, err := ExtractSignatures([]byte(`{}`))
	if err != nil {
		t.Fatalf("ExtractSignatures on an unsigned object: %v", err)
	}
	if none != nil {
		t.Errorf("ExtractSignatures() = %v, want nil for an unsigned object", none)
	}
}

func TestSplitKeyID(t *testing.T) {
	cases := []struct {
		in        string
		algorithm string
		id        string
		ok        bool
	}{
		{"ed25519:abc", "ed25519", "abc", true},
		{"ed25519:", "", "", false},
		{":abc", "", "", false},
		{"ed25519", "", "", false},
		{"", "", "", false},
	}
	for _, tc := range cases {
		algorithm, id, ok := SplitKeyID(tc.in)
		if algorithm != tc.algorithm || id != tc.id || ok != tc.ok {
			t.Errorf("SplitKeyID(%q) = %q, %q, %v; want %q, %q, %v",
				tc.in, algorithm, id, ok, tc.algorithm, tc.id, tc.ok)
		}
	}
}

func TestSignJSONRejectsBadInput(t *testing.T) {
	key := specKey(t)
	for _, tc := range []struct{ name, in string }{
		{"not an object", `[1,2]`},
		{"null", `null`},
		{"not JSON", `{`},
		{"a float somewhere", `{"a":1.5}`},
	} {
		if _, err := SignJSON(specServerName, key, []byte(tc.in)); err == nil {
			t.Errorf("SignJSON(%s) succeeded, want an error", tc.name)
		}
	}
	if _, err := SignJSON("", key, []byte(`{}`)); err == nil {
		t.Error("SignJSON with no server name succeeded, want an error")
	}
}