package authn

import (
	"context"
	"crypto/ed25519"
	"encoding/base64"
	"encoding/json"
	"os"
	"testing"
	"time"

	"sourcecraft.dev/bigbes/sr-ht-core/auth"
	"sourcecraft.dev/bigbes/sr-ht-core/config"
	"sourcecraft.dev/bigbes/sr-ht-core/crypto"
	"github.com/dolthub/dolt/go/libraries/doltcore/creds"
	"github.com/fernet/fernet-go"
	"github.com/vaughan0/go-ini"
	jose "gopkg.in/go-jose/go-jose.v2"
	"gopkg.in/go-jose/go-jose.v2/jwt"
)

// TestMain synthesizes an in-memory instance config (random fernet network key +
// random ed25519 webhooks seed) and runs crypto.InitCrypto once, so that cookie
// encryption (crypto.Encrypt / DecryptWithoutExpiration) and bearer-token HMAC
// (auth.BearerToken.Encode / auth.DecodeBearerToken) share a keyset across the
// whole package's tests. No network, no Postgres.
func TestMain(m *testing.M) {
	var fk fernet.Key
	if err := fk.Generate(); err != nil {
		panic(err)
	}

	seed := make([]byte, ed25519.SeedSize)
	// Deterministic non-zero seed is fine; these keys never leave the test.
	for i := range seed {
		seed[i] = byte(i + 1)
	}

	conf := ini.File{
		"sr.ht":    ini.Section{"network-key": fk.Encode()},
		"webhooks": ini.Section{"private-key": base64.StdEncoding.EncodeToString(seed)},
	}
	crypto.InitCrypto(conf)

	os.Exit(m.Run())
}

// testCtx returns a context carrying the config/service so that
// auth.DecodeGrants (which reads config.ServiceName) works in tests.
func testCtx() context.Context {
	return config.Context(context.Background(), ini.File{}, "dolt.sr.ht")
}

// stubBackend is an in-memory MetaBackend: LookupUser fills from a fixed table,
// IsRevoked consults a set of revoked hashes. Both can be told to fail
// (transient error) to exercise the temporary-error path.
type stubBackend struct {
	users     map[string]auth.AuthContext // keyed by lowercased username (no "~")
	revoked   map[[64]byte]bool
	lookupErr error
	revokeErr error
}

func (s *stubBackend) LookupUser(ctx context.Context, username string, out *auth.AuthContext) error {
	if s.lookupErr != nil {
		return s.lookupErr
	}
	u, ok := s.users[normalize(username)]
	if !ok {
		return errUnknownUser
	}
	*out = u
	return nil
}

func (s *stubBackend) IsRevoked(ctx context.Context, username string, hash [64]byte, clientID string) (bool, error) {
	if s.revokeErr != nil {
		return false, s.revokeErr
	}
	return s.revoked[hash], nil
}

func normalize(username string) string {
	if len(username) > 0 && username[0] == '~' {
		username = username[1:]
	}
	return toLower(username)
}

func toLower(s string) string {
	b := []byte(s)
	for i, c := range b {
		if c >= 'A' && c <= 'Z' {
			b[i] = c + ('a' - 'A')
		}
	}
	return string(b)
}

var errUnknownUser = errTest("unknown user")
var errBackendDown = errTest("backend down")

type errTest string

func (e errTest) Error() string { return string(e) }

// withStubBackend installs a stub MetaBackend for the duration of a test and
// resets the token cache and clock, restoring everything afterwards.
func withStubBackend(t *testing.T, s MetaBackend) {
	t.Helper()
	prev := meta
	meta = s
	resetTokenCache()
	prevNow := nowFn
	t.Cleanup(func() {
		meta = prev
		nowFn = prevNow
		resetTokenCache()
	})
}

func resetTokenCache() {
	tokenCacheMu.Lock()
	tokenCache = map[[64]byte]cacheEntry{}
	tokenCacheMu.Unlock()
}

func sampleUser(id int, username, userType string) auth.AuthContext {
	notice := "suspended for testing"
	ac := auth.AuthContext{
		UserID:   id,
		Username: username,
		Email:    username + "@example.com",
		UserType: userType,
	}
	if userType == auth.USER_TYPE_SUSPENDED {
		ac.SuspensionNotice = &notice
	}
	return ac
}

// forgeCookie fernet-encrypts a unified-login cookie payload for username.
func forgeCookie(t *testing.T, username string) string {
	t.Helper()
	payload, err := json.Marshal(auth.AuthCookie{Name: username})
	if err != nil {
		t.Fatal(err)
	}
	return string(crypto.Encrypt(payload))
}

// forgePAT builds a valid meta personal access token for username with the
// given grants and expiry, HMAC-signed with the test keyset.
func forgePAT(username, grants string, expires time.Time) string {
	bt := auth.BearerToken{
		Version:  auth.TokenVersion,
		Expires:  auth.ToTimestamp(expires),
		Grants:   grants,
		Username: username,
	}
	return bt.Encode()
}

// mintDoltJWT builds an EdDSA JWS exactly as dolt's creds.RPCCreds does: kid +
// dolt_token_version headers, and aud/iss/sub/exp claims.
func mintDoltJWT(t *testing.T, priv ed25519.PrivateKey, kid, aud, iss, sub string, expiry time.Time) string {
	t.Helper()
	signingKey := jose.SigningKey{Algorithm: jose.EdDSA, Key: priv}
	opts := &jose.SignerOptions{ExtraHeaders: map[jose.HeaderKey]interface{}{
		jose.HeaderKey(creds.JWTKIDHeader):           kid,
		jose.HeaderKey(creds.DoltTokenVersionHeader): "2023.01",
	}}
	signer, err := jose.NewSigner(signingKey, opts)
	if err != nil {
		t.Fatal(err)
	}
	raw, err := jwt.Signed(signer).Claims(jwt.Claims{
		Audience: jwt.Audience{aud},
		Issuer:   iss,
		Subject:  sub,
		Expiry:   jwt.NewNumericDate(expiry),
	}).CompactSerialize()
	if err != nil {
		t.Fatal(err)
	}
	return raw
}