package profile_test

import (
	"bytes"
	"errors"
	"testing"

	"github.com/drand/drand/v2/crypto"

	datekeys "g.activething.com/go/DateKeys"
	"g.activething.com/go/DateKeys/internal/testkit"
	"g.activething.com/go/DateKeys/profile"
)

// Spec §12.2: the decoders of drand, through which the reference reads public
// keys, release signatures and the U of a tlock stanza, accept exactly the
// canonical encodings. The reference relies on them for the rule, so this
// test fails if a dependency update makes them lenient.
func TestDrandPointDecodersAreCanonical(t *testing.T) {
	s, err := crypto.SchemeFromName(crypto.SigsOnG1ID)
	if err != nil {
		t.Fatal(err)
	}
	g1 := func(b []byte) error { return s.SigGroup.Point().UnmarshalBinary(b) }
	g2 := func(b []byte) error { return s.KeyGroup.Point().UnmarshalBinary(b) }
	must := func(b []byte, err error) []byte {
		t.Helper()
		if err != nil {
			t.Fatal(err)
		}
		return b
	}
	cleared := func(b []byte, flags byte) []byte {
		c := bytes.Clone(b)
		c[0] &^= flags
		return c
	}
	key, sig := profile.Quicknet().PublicKey, testkit.Release(1000).Signature
	for _, tc := range []struct {
		name   string
		decode func([]byte) error
		in     []byte
		ok     bool
	}{
		{"G1: a release signature", g1, sig, true},
		{"G1: the point at infinity", g1, testkit.Infinity(48), true},
		{"G2: the Quicknet public key", g2, key, true},
		{"G2: the point at infinity", g2, testkit.Infinity(96), true},
		{"G1: x + p", g1, must(testkit.AddModulus(testkit.Release(testkit.XPlusPRound).Signature, 0)), false},
		{"G2: c1 + p", g2, must(testkit.AddModulus(key, 0)), false},
		{"G2: c0 + p", g2, must(testkit.AddModulus(key, testkit.CoordinateLen)), false},
		{"G1: infinity flag and a payload", g1, testkit.InfinityWithPayload(sig), false},
		{"G2: infinity flag and a payload", g2, testkit.InfinityWithPayload(key), false},
		{"G1: the point at infinity with the sort flag", g1, testkit.Negated(testkit.Infinity(48)), false},
		{"G2: the point at infinity with the sort flag", g2, testkit.Negated(testkit.Infinity(96)), false},
		{"G1: the point at infinity without the compression flag", g1, cleared(testkit.Infinity(48), testkit.FlagCompressed), false},
		{"G1: compression flag cleared", g1, cleared(sig, testkit.FlagCompressed), false},
		{"G2: compression flag cleared", g2, cleared(key, testkit.FlagCompressed), false},
		{"G1: 96 bytes, the length of the uncompressed form", g1, append(bytes.Clone(sig), sig...), false},
		{"G2: 192 bytes, the length of the uncompressed form", g2, append(bytes.Clone(key), key...), false},
		{"G1: 47 bytes", g1, sig[:47], false},
		{"G2: 97 bytes", g2, append(bytes.Clone(key), 0), false},
		{"G1: a point of the curve outside the prime-order subgroup", g1, offSubgroupG1(t), false},
	} {
		if err := tc.decode(tc.in); (err == nil) != tc.ok {
			t.Errorf("%s: decoded %v, want %v (%v)", tc.name, err == nil, tc.ok, err)
		}
	}
}

// Spec §12.1, §12.2: the public key of a profile is the canonical encoding of
// a point of the key group other than the point at infinity. Each profile
// below is otherwise valid, its chain hash computed over the exact bytes of
// its key, and is refused whether it is validated or decoded.
func TestPublicKeyEncodingIsCanonical(t *testing.T) {
	key := profile.Quicknet().PublicKey
	c1PlusP, err := testkit.AddModulus(key, 0)
	if err != nil {
		t.Fatal(err)
	}
	c0PlusP, err := testkit.AddModulus(key, testkit.CoordinateLen)
	if err != nil {
		t.Fatal(err)
	}
	uncompressed := bytes.Clone(key)
	uncompressed[0] &^= testkit.FlagCompressed
	for _, tc := range []struct {
		name string
		key  []byte
	}{
		{"c1 + p", c1PlusP},
		{"c0 + p", c0PlusP},
		{"the point at infinity", testkit.Infinity(96)},
		{"infinity flag and a payload", testkit.InfinityWithPayload(key)},
		{"compression flag cleared", uncompressed},
		{"192 bytes, the length of the uncompressed form", append(bytes.Clone(key), key...)},
	} {
		p := profile.Quicknet()
		p.PublicKey = tc.key
		copy(p.ChainHash[:], chainHashFormula(p))
		if err := p.Validate(); !errors.Is(err, datekeys.ErrUnknownProfile) {
			t.Errorf("%s: Validate: %v", tc.name, err)
		}
		b, err := p.CanonicalCBOR()
		if err != nil {
			t.Fatal(err)
		}
		if _, err := profile.Decode(b); !errors.Is(err, datekeys.ErrUnknownProfile) {
			t.Errorf("%s: Decode: %v", tc.name, err)
		}
	}
}