//go:build ignore

// Prints test/vectors/bls12381_vectors.json: the Go reference values for the
// BLS12-381 code of lib/src/bls12381_*.dart, from the libraries that drand
// and tlock use for Quicknet: github.com/kilic/bls12-381 and
// github.com/drand/kyber-bls12381 over it.
//
//   - points: the frozen edge-case encodings of datekeys-ts
//     (src/lib/dkc/testing/bls12381-vectors.json; valid points, sign-bit
//     flips, identity encodings with stray flags or payload, missing
//     compression flag, wrong lengths, uncompressed forms, x + p, points on
//     the curve outside the subgroup, cofactor torsion), each with the
//     verdict of the reference recomputed here: the KeyGroup of the drand
//     crypto schemes (G1 for pedersen-bls-unchained, G2 for
//     bls-unchained-g1-rfc9380), whose UnmarshalBinary is FromCompressed of
//     kilic, and Equal(Null()) for the identity, as profile.Validate uses it.
//   - decode: encodings drawn from a fixed seed: multiples of the generators,
//     their negations, one flipped bit, random x with the compression flag,
//     and random x of points on the curve outside the subgroup; each with the
//     verdict, and for an invalid one the class of the error of kilic
//     ("format", "curve" or "subgroup").
//   - add, multiply: sums and multiples of points drawn from the seed, the
//     special cases included (P + P, P + (-P), the point at infinity, the
//     scalars 0, 1, r - 1, r, r + 1 and 2^256 - 1), computed by kilic.
//   - pairing: e(P, Q) for points drawn from the seed, serialized by
//     kyber-bls12381 (the order of kilic: c1 before c0 at every level).
//   - hash_to_g1: HashToCurve of kilic for the DST of Quicknet and of tlock
//     (BLS_SIG_BLS12381G1_XMD:SHA-256_SSWU_RO_NUL_) on messages drawn from
//     the seed and on the identities of some rounds, and for the DST of the
//     test vectors of RFC 9380, appendix J.9.1, on their messages, with the
//     affine coordinates.
//   - map_to_g1: MapToCurve of kilic (the simplified SWU map, the isogeny and
//     the clearing of the cofactor) on elements u drawn from the seed and on
//     the exceptional ones, u = 0 and Z·u² = -1, which no hash reaches.
//   - signatures: BLS signatures on G1 of kyber's sign/bls (NewSchemeOnG1,
//     the scheme of Quicknet) under keys drawn from the seed, and the verdict
//     of its Verify on each and on edited copies.
//
// The seed is fixed: the output is the same on every run. Run it in the
// module of the reference implementation, which it imports, without changing
// anything there, from the datekeys-go next to this repository: at the tag
// spec-v0.11 or at the draft v0.12, whose packages that it uses are the
// same, and so is the output.
//
//	cd ../datekeys-go && go run ../datekeys-dart/tool/bls12381_go_vectors.go \
//		../datekeys-ts/src/lib/dkc/testing/bls12381-vectors.json \
//		> ../datekeys-dart/test/vectors/bls12381_vectors.json
package main

import (
	"bytes"
	"crypto/sha256"
	"encoding/binary"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"math/big"
	"os"
	"runtime/debug"
	"sort"
	"strings"

	"github.com/drand/drand/v2/common"
	"github.com/drand/drand/v2/crypto"
	"github.com/drand/kyber"
	bls "github.com/drand/kyber-bls12381"
	signbls "github.com/drand/kyber/sign/bls"
	bls12381 "github.com/kilic/bls12-381"
)

const quicknetDST = "BLS_SIG_BLS12381G1_XMD:SHA-256_SSWU_RO_NUL_"

var (
	p, _     = new(big.Int).SetString("1a0111ea397fe69a4b1ba7b6434bacd764774b84f38512bf6730d2a0f6b0f6241eabfffeb153ffffb9feffffffffaaab", 16)
	order, _ = new(big.Int).SetString("73eda753299d7d483339d80809a1d80553bda402fffe5bfeffffffff00000001", 16)
	g1       = bls12381.NewG1()
	g2       = bls12381.NewG2()
)

func must[T any](v T, err error) T {
	if err != nil {
		panic(err)
	}
	return v
}

// stream is a deterministic byte source: SHA-256 of the label, a counter
// and a block index.
type stream struct {
	label string
	n     uint32
}

func (s *stream) bytes(n int) []byte {
	s.n++
	var out []byte
	for i := uint32(0); len(out) < n; i++ {
		h := sha256.Sum256(binary.BigEndian.AppendUint32(binary.BigEndian.AppendUint32([]byte("DateKeys BLS12-381 vectors "+s.label), s.n), i))
		out = append(out, h[:]...)
	}
	return out[:n]
}

// scalar is a nonzero scalar below r.
func (s *stream) scalar() *big.Int {
	k := new(big.Int).SetBytes(s.bytes(64))
	k.Mod(k, new(big.Int).Sub(order, big.NewInt(1)))
	return k.Add(k, big.NewInt(1))
}

func (s *stream) fp() *big.Int {
	x := new(big.Int).SetBytes(s.bytes(64))
	return x.Mod(x, p)
}

func fp48(x *big.Int) []byte { return x.FillBytes(make([]byte, 48)) }

func hx(b []byte) string { return hex.EncodeToString(b) }

func g1Mul(k *big.Int) *bls12381.PointG1 {
	return g1.MulScalarBig(g1.New(), g1.One(), k)
}

func g2Mul(k *big.Int) *bls12381.PointG2 {
	return g2.MulScalarBig(g2.New(), g2.One(), k)
}

func g1Enc(q *bls12381.PointG1) []byte { return g1.ToCompressed(g1.New().Set(q)) }

func g2Enc(q *bls12381.PointG2) []byte { return g2.ToCompressed(g2.New().Set(q)) }

// errorClass names the check of FromCompressed of kilic that failed.
func errorClass(err error) string {
	switch {
	case strings.Contains(err.Error(), "not on curve"):
		return "curve"
	case strings.Contains(err.Error(), "correct subgroup"):
		return "subgroup"
	default:
		return "format"
	}
}

type decodeVector struct {
	Label string `json:"label"`
	Group string `json:"group"`
	Hex   string `json:"hex"`
	Go    string `json:"go"`
	Class string `json:"class,omitempty"`
}

func verdict(group string, b []byte) decodeVector {
	v := decodeVector{Group: group, Hex: hx(b)}
	var err error
	var zero bool
	if group == "G1" {
		var q *bls12381.PointG1
		if q, err = g1.FromCompressed(b); err == nil {
			zero = g1.IsZero(q)
		}
	} else {
		var q *bls12381.PointG2
		if q, err = g2.FromCompressed(b); err == nil {
			zero = g2.IsZero(q)
		}
	}
	switch {
	case err != nil:
		v.Go, v.Class = "invalid", errorClass(err)
	case zero:
		v.Go = "identity"
	default:
		v.Go = "point"
	}
	return v
}

// schemeVerdict is the verdict of the KeyGroup of the drand scheme, as
// scripts/bls12381-go-verdicts.go of datekeys-ts computes it.
func schemeVerdict(group string, b []byte) string {
	id := crypto.UnchainedSchemeID
	if group == "G2" {
		id = crypto.SigsOnG1ID
	}
	s := must(crypto.SchemeFromName(id))
	k := s.KeyGroup.Point()
	switch {
	case k.UnmarshalBinary(b) != nil:
		return "invalid"
	case k.Equal(k.Null()):
		return "identity"
	default:
		return "point"
	}
}

type addVector struct {
	Label string `json:"label"`
	Group string `json:"group"`
	A     string `json:"a"`
	B     string `json:"b"`
	Sum   string `json:"sum"`
}

type mulVector struct {
	Label   string `json:"label"`
	Group   string `json:"group"`
	Point   string `json:"point"`
	Scalar  string `json:"scalar"`
	Product string `json:"product"`
}

type pairingVector struct {
	Label string `json:"label"`
	G1    string `json:"g1"`
	G2    string `json:"g2"`
	GT    string `json:"gt"`
}

type hashVector struct {
	Label string `json:"label"`
	DST   string `json:"dst"`
	Msg   string `json:"msg"`
	Point string `json:"point"`
	X     string `json:"x"`
	Y     string `json:"y"`
}

type mapVector struct {
	Label string `json:"label"`
	U     string `json:"u"`
	Point string `json:"point"`
}

type signatureVector struct {
	Label     string `json:"label"`
	PublicKey string `json:"public_key"`
	Msg       string `json:"msg"`
	Signature string `json:"signature"`
	Go        bool   `json:"go"`
}

func main() {
	out := struct {
		Description string            `json:"description"`
		Generator   string            `json:"generator"`
		Libraries   string            `json:"libraries"`
		PointsFrom  string            `json:"points_from"`
		Points      []decodeVector    `json:"points"`
		Decode      []decodeVector    `json:"decode"`
		Add         []addVector       `json:"add"`
		Multiply    []mulVector       `json:"multiply"`
		Pairing     []pairingVector   `json:"pairing"`
		HashToG1    []hashVector      `json:"hash_to_g1"`
		MapToG1     []mapVector       `json:"map_to_g1"`
		Signatures  []signatureVector `json:"signatures"`
	}{
		Description: "Go reference values for the BLS12-381 code of lib/src/bls12381_*.dart: decoding verdicts, " +
			"sums, multiples, pairings, hashes to G1 and BLS signatures on G1; see tool/bls12381_go_vectors.go.",
		Generator: "tool/bls12381_go_vectors.go",
		Libraries: libraries(),
		PointsFrom: "the encodings of src/lib/dkc/testing/bls12381-vectors.json of datekeys-ts at 289fe71, " +
			"with the verdicts recomputed by this generator",
	}

	// The frozen edge cases of datekeys-ts.
	var frozen struct {
		Vectors []struct{ Label, Group, Hex, Go string }
	}
	if err := json.Unmarshal(must(os.ReadFile(os.Args[1])), &frozen); err != nil {
		panic(err)
	}
	for _, f := range frozen.Vectors {
		b := must(hex.DecodeString(f.Hex))
		v := verdict(f.Group, b)
		if (len(b) == 48 && f.Group == "G1") || (len(b) == 96 && f.Group == "G2") {
			if s := schemeVerdict(f.Group, b); s != v.Go {
				panic(f.Label + ": kilic and the drand scheme disagree")
			}
		} else {
			v.Go, v.Class = schemeVerdict(f.Group, b), "format"
		}
		if v.Go != f.Go {
			panic(f.Label + ": the verdict of datekeys-ts is not the one of Go")
		}
		v.Label = f.Label
		out.Points = append(out.Points, v)
	}

	// Decoding.
	s := &stream{label: "decode"}
	for i := 0; i < 24; i++ {
		b := g1Enc(g1Mul(s.scalar()))
		neg := bytes.Clone(b)
		neg[0] ^= 0x20
		flip := bytes.Clone(b)
		bit := 3 + int(binary.BigEndian.Uint16(s.bytes(2)))%(48*8-3)
		flip[bit/8] ^= 0x80 >> (bit % 8)
		for j, c := range [][]byte{b, neg, flip} {
			v := verdict("G1", c)
			v.Label = fmt.Sprintf("G1 multiple %d, %s", i, []string{"as encoded", "negated", fmt.Sprintf("bit %d flipped", bit)}[j])
			out.Decode = append(out.Decode, v)
		}
	}
	for i := 0; i < 8; i++ {
		b := g2Enc(g2Mul(s.scalar()))
		neg := bytes.Clone(b)
		neg[0] ^= 0x20
		flip := bytes.Clone(b)
		bit := 3 + int(binary.BigEndian.Uint16(s.bytes(2)))%(96*8-3)
		flip[bit/8] ^= 0x80 >> (bit % 8)
		for j, c := range [][]byte{b, neg, flip} {
			v := verdict("G2", c)
			v.Label = fmt.Sprintf("G2 multiple %d, %s", i, []string{"as encoded", "negated", fmt.Sprintf("bit %d flipped", bit)}[j])
			out.Decode = append(out.Decode, v)
		}
	}
	// Random x, with the compression flag and either sign: on the curve or
	// not, and then outside the subgroup.
	classes := map[string]int{}
	for i := 0; classes["G1 subgroup"] < 16 || classes["G1 curve"] < 8; i++ {
		b := fp48(s.fp())
		b[0] |= 0x80 | s.bytes(1)[0]&0x20
		v := verdict("G1", b)
		key := "G1 " + v.Class
		if classes[key] >= 16 {
			continue
		}
		classes[key]++
		v.Label = fmt.Sprintf("G1 random x %d", i)
		out.Decode = append(out.Decode, v)
	}
	for i := 0; classes["G2 subgroup"] < 8 || classes["G2 curve"] < 4; i++ {
		b := append(fp48(s.fp()), fp48(s.fp())...)
		b[0] |= 0x80 | s.bytes(1)[0]&0x20
		v := verdict("G2", b)
		key := "G2 " + v.Class
		if classes[key] >= 8 {
			continue
		}
		classes[key]++
		v.Label = fmt.Sprintf("G2 random x %d", i)
		out.Decode = append(out.Decode, v)
	}

	// Sums.
	s = &stream{label: "add"}
	inf1, inf2 := g1.Zero(), g2.Zero()
	for i := 0; i < 16; i++ {
		a, b := g1Mul(s.scalar()), g1Mul(s.scalar())
		out.Add = append(out.Add, addVector{fmt.Sprintf("G1 sum %d", i), "G1", hx(g1Enc(a)), hx(g1Enc(b)), hx(g1Enc(g1.Add(g1.New(), a, b)))})
	}
	a1 := g1Mul(s.scalar())
	for _, c := range []struct {
		label string
		a, b  *bls12381.PointG1
	}{
		{"G1 P + P", a1, a1},
		{"G1 P + (-P)", a1, g1.Neg(g1.New(), a1)},
		{"G1 P + infinity", a1, inf1},
		{"G1 infinity + P", inf1, a1},
		{"G1 infinity + infinity", inf1, inf1},
	} {
		out.Add = append(out.Add, addVector{c.label, "G1", hx(g1Enc(c.a)), hx(g1Enc(c.b)), hx(g1Enc(g1.Add(g1.New(), c.a, c.b)))})
	}
	for i := 0; i < 8; i++ {
		a, b := g2Mul(s.scalar()), g2Mul(s.scalar())
		out.Add = append(out.Add, addVector{fmt.Sprintf("G2 sum %d", i), "G2", hx(g2Enc(a)), hx(g2Enc(b)), hx(g2Enc(g2.Add(g2.New(), a, b)))})
	}
	a2 := g2Mul(s.scalar())
	for _, c := range []struct {
		label string
		a, b  *bls12381.PointG2
	}{
		{"G2 P + P", a2, a2},
		{"G2 P + (-P)", a2, g2.Neg(g2.New(), a2)},
		{"G2 P + infinity", a2, inf2},
		{"G2 infinity + P", inf2, a2},
	} {
		out.Add = append(out.Add, addVector{c.label, "G2", hx(g2Enc(c.a)), hx(g2Enc(c.b)), hx(g2Enc(g2.Add(g2.New(), c.a, c.b)))})
	}

	// Multiples.
	s = &stream{label: "multiply"}
	max256 := new(big.Int).Sub(new(big.Int).Lsh(big.NewInt(1), 256), big.NewInt(1))
	special := []struct {
		label string
		k     *big.Int
	}{
		{"0", big.NewInt(0)},
		{"1", big.NewInt(1)},
		{"2", big.NewInt(2)},
		{"r - 1", new(big.Int).Sub(order, big.NewInt(1))},
		{"r", new(big.Int).Set(order)},
		{"r + 1", new(big.Int).Add(order, big.NewInt(1))},
		{"2^256 - 1", max256},
	}
	for i := 0; i < 12; i++ {
		q, k := g1Mul(s.scalar()), new(big.Int).SetBytes(s.bytes(32))
		out.Multiply = append(out.Multiply, mulVector{fmt.Sprintf("G1 multiple %d", i), "G1", hx(g1Enc(q)), k.Text(16), hx(g1Enc(g1.MulScalarBig(g1.New(), q, k)))})
	}
	q1 := g1Mul(s.scalar())
	for _, c := range special {
		out.Multiply = append(out.Multiply, mulVector{"G1 by " + c.label, "G1", hx(g1Enc(q1)), c.k.Text(16), hx(g1Enc(g1.MulScalarBig(g1.New(), q1, c.k)))})
	}
	for i := 0; i < 6; i++ {
		q, k := g2Mul(s.scalar()), new(big.Int).SetBytes(s.bytes(32))
		out.Multiply = append(out.Multiply, mulVector{fmt.Sprintf("G2 multiple %d", i), "G2", hx(g2Enc(q)), k.Text(16), hx(g2Enc(g2.MulScalarBig(g2.New(), q, k)))})
	}
	q2 := g2Mul(s.scalar())
	for _, c := range special {
		out.Multiply = append(out.Multiply, mulVector{"G2 by " + c.label, "G2", hx(g2Enc(q2)), c.k.Text(16), hx(g2Enc(g2.MulScalarBig(g2.New(), q2, c.k)))})
	}

	// Pairings, through kyber-bls12381.
	s = &stream{label: "pairing"}
	suite := bls.NewBLS12381Suite()
	for i := 0; i < 6; i++ {
		a := suite.G1().Point().Mul(scalarOf(s.scalar()), nil)
		b := suite.G2().Point().Mul(scalarOf(s.scalar()), nil)
		out.Pairing = append(out.Pairing, pairingVector{fmt.Sprintf("e(P, Q) %d", i), marshal(a), marshal(b), marshal(suite.Pair(a, b))})
	}
	{
		a := suite.G1().Point().Mul(scalarOf(s.scalar()), nil)
		b := suite.G2().Point().Mul(scalarOf(s.scalar()), nil)
		out.Pairing = append(out.Pairing,
			pairingVector{"e(infinity, Q)", marshal(suite.G1().Point().Null()), marshal(b), marshal(suite.Pair(suite.G1().Point().Null(), b))},
			pairingVector{"e(P, infinity)", marshal(a), marshal(suite.G2().Point().Null()), marshal(suite.Pair(a, suite.G2().Point().Null()))})
	}

	// Hashes to G1.
	s = &stream{label: "hash"}
	hashOne := func(label, dst string, msg []byte) hashVector {
		q := must(g1.HashToCurve(msg, []byte(dst)))
		u := g1.ToUncompressed(g1.New().Set(q))
		return hashVector{label, dst, hx(msg), hx(g1Enc(q)), hx(u[:48]), hx(u[48:])}
	}
	for i := 0; i < 24; i++ {
		n := int(s.bytes(1)[0]) % 80
		out.HashToG1 = append(out.HashToG1, hashOne(fmt.Sprintf("a message of %d bytes", n), quicknetDST, s.bytes(n)))
	}
	sch := must(crypto.SchemeFromName(crypto.SigsOnG1ID))
	for _, round := range []uint64{1, 1000, 1001, 1004, 2000, 83903165811, 1<<53 - 1} {
		id := sch.DigestBeacon(&common.Beacon{Round: round})
		out.HashToG1 = append(out.HashToG1, hashOne(fmt.Sprintf("the identity of round %d", round), quicknetDST, id))
	}
	const rfcDST = "QUUX-V01-CS02-with-BLS12381G1_XMD:SHA-256_SSWU_RO_"
	for _, m := range []string{"", "abc", "abcdef0123456789", "q128_" + strings.Repeat("q", 128), "a512_" + strings.Repeat("a", 512)} {
		out.HashToG1 = append(out.HashToG1, hashOne(fmt.Sprintf("RFC 9380 J.9.1, msg %q", shorten(m)), rfcDST, []byte(m)))
	}

	// The map to G1 of one element.
	s = &stream{label: "map"}
	z := big.NewInt(11)
	// Z·u² = -1: u² = -1/Z, a square since -Z is one.
	minusInvZ := new(big.Int).Sub(p, new(big.Int).ModInverse(z, p))
	root := new(big.Int).ModSqrt(minusInvZ, p)
	if root == nil {
		panic("-1/Z is not a square")
	}
	us := []struct {
		label string
		u     *big.Int
	}{
		{"u = 0, exceptional", big.NewInt(0)},
		{"Z·u² = -1, exceptional", root},
		{"Z·u² = -1, the other root, exceptional", new(big.Int).Sub(p, root)},
		{"u = 1", big.NewInt(1)},
		{"u = p - 1", new(big.Int).Sub(p, big.NewInt(1))},
	}
	for i := 0; i < 8; i++ {
		us = append(us, struct {
			label string
			u     *big.Int
		}{fmt.Sprintf("u drawn from the seed %d", i), s.fp()})
	}
	for _, c := range us {
		q := must(g1.MapToCurve(fp48(c.u)))
		out.MapToG1 = append(out.MapToG1, mapVector{c.label, hx(fp48(c.u)), hx(g1Enc(q))})
	}

	// BLS signatures on G1, the scheme of Quicknet.
	s = &stream{label: "signatures"}
	scheme := signbls.NewSchemeOnG1(suite)
	for i := 0; i < 6; i++ {
		sk := scalarOf(s.scalar())
		pk := suite.G2().Point().Mul(sk, nil)
		msg := s.bytes(32)
		sig := must(scheme.Sign(sk, msg))
		other := s.bytes(32)
		for _, c := range []struct {
			label    string
			msg, sig []byte
		}{
			{fmt.Sprintf("signature %d", i), msg, sig},
			{fmt.Sprintf("signature %d of another message", i), other, sig},
			{fmt.Sprintf("signature %d negated", i), msg, negate(sig)},
		} {
			out.Signatures = append(out.Signatures, signatureVector{c.label, marshal(pk), hx(c.msg), hx(c.sig), scheme.Verify(pk, c.msg, c.sig) == nil})
		}
	}

	enc := json.NewEncoder(os.Stdout)
	enc.SetIndent("", " ")
	enc.SetEscapeHTML(false)
	if err := enc.Encode(out); err != nil {
		panic(err)
	}
}

func scalarOf(k *big.Int) kyber.Scalar {
	return bls.NewKyberScalar().SetBytes(k.FillBytes(make([]byte, 32)))
}

func marshal(m interface{ MarshalBinary() ([]byte, error) }) string {
	return hex.EncodeToString(must(m.MarshalBinary()))
}

func negate(sig []byte) []byte {
	c := bytes.Clone(sig)
	c[0] ^= 0x20
	return c
}

func shorten(m string) string {
	if len(m) > 20 {
		return m[:20] + "…"
	}
	return m
}

// libraries names the versions of the libraries this program ran with.
func libraries() string {
	info, ok := debug.ReadBuildInfo()
	if !ok {
		panic("no build info")
	}
	var out []string
	for _, d := range info.Deps {
		switch d.Path {
		case "github.com/kilic/bls12-381", "github.com/drand/kyber", "github.com/drand/kyber-bls12381", "github.com/drand/drand/v2":
			out = append(out, d.Path+" "+d.Version)
		}
	}
	sort.Strings(out)
	return strings.Join(out, ", ")
}