package seal

import (
	"crypto/ecdh"
	"encoding/base64"
	"encoding/json"
	"os"
	"testing"
)

type fixture struct {
	Recipient KeyPair `json:"recipient"`
	Sealed    []struct {
		Plaintext string `json:"plaintext"`
		Box       Box    `json:"box"`
	} `json:"sealed"`
	Vectors []struct {
		Plaintext  string `json:"plaintext"`
		EphPrivate string `json:"ephPrivate"`
		IV         string `json:"iv"`
		Box        Box    `json:"box"`
	} `json:"vectors"`
}

func readFixture(t *testing.T) fixture {
	t.Helper()
	raw, err := os.ReadFile("testdata/sealed-by-licence-manager.json")
	if err != nil {
		t.Fatal(err)
	}
	var f fixture
	if err := json.Unmarshal(raw, &f); err != nil {
		t.Fatal(err)
	}
	if len(f.Sealed) == 0 || len(f.Vectors) == 0 {
		t.Fatal("the fixture holds no boxes")
	}
	return f
}

// Every box the licence manager's own Seal made opens here to its plaintext.
func TestABoxTheLicenceManagerSealedOpens(t *testing.T) {
	f := readFixture(t)
	for _, s := range f.Sealed {
		got, err := Open(s.Box, f.Recipient.PrivateKey)
		if err != nil || got != s.Plaintext {
			t.Fatalf("opened %q, %v; want %q", got, err, s.Plaintext)
		}
	}
}

// Given the same one-time key and iv, this package seals byte for byte what the licence manager sealed:
// the reverse direction, so whatever opens the licence manager's boxes opens these.
func TestSealIsByteForByteTheLicenceManagersBox(t *testing.T) {
	f := readFixture(t)
	for _, v := range f.Vectors {
		d := base64.StdEncoding.DecodeString
		ephRaw, err1 := d(v.EphPrivate)
		iv, err2 := d(v.IV)
		if err1 != nil || err2 != nil {
			t.Fatal(err1, err2)
		}
		eph, err := ecdh.X25519().NewPrivateKey(ephRaw)
		if err != nil {
			t.Fatal(err)
		}
		got, err := sealWith(v.Plaintext, f.Recipient.PublicKey, eph, iv)
		if err != nil {
			t.Fatal(err)
		}
		if got != v.Box {
			t.Fatalf("sealed %+v\nthe licence manager sealed %+v", got, v.Box)
		}
		if plain, err := Open(got, f.Recipient.PrivateKey); err != nil || plain != v.Plaintext {
			t.Fatalf("reopened %q, %v", plain, err)
		}
	}
}

// A box the agent module's TypeScript sealed (the fixture the licence manager keeps) opens here too.
func TestABoxSealedInTypeScriptOpens(t *testing.T) {
	raw, err := os.ReadFile("testdata/sealed-by-typescript.json")
	if err != nil {
		t.Fatal(err)
	}
	var f struct {
		PrivateKey string `json:"privateKey"`
		Box        Box    `json:"box"`
		Plaintext  string `json:"plaintext"`
	}
	if err := json.Unmarshal(raw, &f); err != nil {
		t.Fatal(err)
	}
	if got, err := Open(f.Box, f.PrivateKey); err != nil || got != f.Plaintext {
		t.Fatalf("opened %q, %v", got, err)
	}
}

// What Seal makes opens with its recipient's key and no other, and a fresh box differs every time.
func TestABoxOpensOnlyForItsRecipient(t *testing.T) {
	a, err := GenerateKeyPair()
	if err != nil {
		t.Fatal(err)
	}
	b, _ := GenerateKeyPair()
	box, err := Seal("a token", a.PublicKey)
	if err != nil {
		t.Fatal(err)
	}
	if got, err := Open(box, a.PrivateKey); err != nil || got != "a token" {
		t.Fatalf("opened %q, %v", got, err)
	}
	if _, err := Open(box, b.PrivateKey); err == nil {
		t.Fatal("a box opened for another key")
	}
	again, _ := Seal("a token", a.PublicKey)
	if again.Eph == box.Eph || again.IV == box.IV {
		t.Fatal("two boxes share a one-time key or iv")
	}
}

// A box changed in any field, or of another version, does not open.
func TestATamperedBoxDoesNotOpen(t *testing.T) {
	f := readFixture(t)
	good := f.Sealed[1].Box
	flip := func(s string) string {
		b, _ := base64.StdEncoding.DecodeString(s)
		b[len(b)-1] ^= 1
		return base64.StdEncoding.EncodeToString(b)
	}
	for name, box := range map[string]Box{
		"ct":      {V: 1, Eph: good.Eph, IV: good.IV, Tag: good.Tag, Ct: flip(good.Ct)},
		"tag":     {V: 1, Eph: good.Eph, IV: good.IV, Tag: flip(good.Tag), Ct: good.Ct},
		"iv":      {V: 1, Eph: good.Eph, IV: flip(good.IV), Tag: good.Tag, Ct: good.Ct},
		"eph":     {V: 1, Eph: flip(good.Eph), IV: good.IV, Tag: good.Tag, Ct: good.Ct},
		"version": {V: 2, Eph: good.Eph, IV: good.IV, Tag: good.Tag, Ct: good.Ct},
	} {
		if _, err := Open(box, f.Recipient.PrivateKey); err == nil {
			t.Fatalf("a box with a changed %s opened", name)
		}
	}
}

// A key that is not X25519 PEM is refused, not misread.
func TestAKeyOfAnotherKindIsRefused(t *testing.T) {
	if _, err := Seal("x", "not a key"); err == nil {
		t.Fatal("sealed to text")
	}
	f := readFixture(t)
	if _, err := Open(f.Sealed[0].Box, f.Recipient.PublicKey); err == nil {
		t.Fatal("opened with a public key")
	}
	if _, err := Seal("x", f.Recipient.PrivateKey); err == nil {
		t.Fatal("sealed to a private key")
	}
}