// authServiceServer implements mciasv1.AuthServiceServer.
// All handlers delegate to the same internal packages as the REST server.
package grpcserver

import (
	"context"
	"fmt"
	"net"

	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/peer"
	"google.golang.org/grpc/status"
	"google.golang.org/protobuf/types/known/timestamppb"

	mciasv1 "git.wntrmute.dev/kyle/mcias/gen/mcias/v1"
	"git.wntrmute.dev/kyle/mcias/internal/auth"
	"git.wntrmute.dev/kyle/mcias/internal/crypto"
	"git.wntrmute.dev/kyle/mcias/internal/model"
	"git.wntrmute.dev/kyle/mcias/internal/token"
)

type authServiceServer struct {
	mciasv1.UnimplementedAuthServiceServer
	s *Server
}

// Login authenticates a user and issues a JWT.
// Public RPC — no auth interceptor required.
//
// Security: Identical to the REST handleLogin: always runs Argon2 for unknown
// users to prevent timing-based user enumeration. Generic error returned
// regardless of which step failed.
func (a *authServiceServer) Login(ctx context.Context, req *mciasv1.LoginRequest) (*mciasv1.LoginResponse, error) {
	if req.Username == "" || req.Password == "" {
		return nil, status.Error(codes.InvalidArgument, "username and password are required")
	}

	ip := peerIP(ctx)

	acct, err := a.s.db.GetAccountByUsername(req.Username)
	if err != nil {
		// Security: run dummy Argon2 to equalise timing for unknown users.
		_, _ = auth.VerifyPassword("dummy", auth.DummyHash())
		a.s.db.WriteAuditEvent(model.EventLoginFail, nil, nil, ip, //nolint:errcheck // audit failure is non-fatal
			fmt.Sprintf(`{"username":%q,"reason":"unknown_user"}`, req.Username))
		return nil, status.Error(codes.Unauthenticated, "invalid credentials")
	}

	if acct.Status != model.AccountStatusActive {
		_, _ = auth.VerifyPassword("dummy", auth.DummyHash())
		a.s.db.WriteAuditEvent(model.EventLoginFail, &acct.ID, nil, ip, `{"reason":"account_inactive"}`) //nolint:errcheck
		return nil, status.Error(codes.Unauthenticated, "invalid credentials")
	}

	// Security: check per-account lockout before running Argon2 (F-08).
	locked, lockErr := a.s.db.IsLockedOut(acct.ID)
	if lockErr != nil {
		a.s.logger.Error("lockout check", "error", lockErr)
	}
	if locked {
		_, _ = auth.VerifyPassword("dummy", auth.DummyHash())
		a.s.db.WriteAuditEvent(model.EventLoginFail, &acct.ID, nil, ip, `{"reason":"account_locked"}`) //nolint:errcheck
		return nil, status.Error(codes.ResourceExhausted, "account temporarily locked")
	}

	ok, err := auth.VerifyPassword(req.Password, acct.PasswordHash)
	if err != nil || !ok {
		a.s.db.WriteAuditEvent(model.EventLoginFail, &acct.ID, nil, ip, `{"reason":"wrong_password"}`) //nolint:errcheck
		_ = a.s.db.RecordLoginFailure(acct.ID)
		return nil, status.Error(codes.Unauthenticated, "invalid credentials")
	}

	if acct.TOTPRequired {
		if req.TotpCode == "" {
			a.s.db.WriteAuditEvent(model.EventLoginFail, &acct.ID, nil, ip, `{"reason":"totp_missing"}`) //nolint:errcheck
			_ = a.s.db.RecordLoginFailure(acct.ID)
			return nil, status.Error(codes.Unauthenticated, "TOTP code required")
		}
		secret, err := crypto.OpenAESGCM(a.s.masterKey, acct.TOTPSecretNonce, acct.TOTPSecretEnc)
		if err != nil {
			a.s.logger.Error("decrypt TOTP secret", "error", err, "account_id", acct.ID)
			return nil, status.Error(codes.Internal, "internal error")
		}
		valid, err := auth.ValidateTOTP(secret, req.TotpCode)
		if err != nil || !valid {
			a.s.db.WriteAuditEvent(model.EventLoginTOTPFail, &acct.ID, nil, ip, `{"reason":"wrong_totp"}`) //nolint:errcheck
			_ = a.s.db.RecordLoginFailure(acct.ID)
			return nil, status.Error(codes.Unauthenticated, "invalid credentials")
		}
	}

	// Login succeeded: clear any outstanding failure counter.
	_ = a.s.db.ClearLoginFailures(acct.ID)

	expiry := a.s.cfg.DefaultExpiry()
	roles, err := a.s.db.GetRoles(acct.ID)
	if err != nil {
		return nil, status.Error(codes.Internal, "internal error")
	}
	for _, r := range roles {
		if r == "admin" {
			expiry = a.s.cfg.AdminExpiry()
			break
		}
	}

	tokenStr, claims, err := token.IssueToken(a.s.privKey, a.s.cfg.Tokens.Issuer, acct.UUID, roles, expiry)
	if err != nil {
		a.s.logger.Error("issue token", "error", err)
		return nil, status.Error(codes.Internal, "internal error")
	}
	if err := a.s.db.TrackToken(claims.JTI, acct.ID, claims.IssuedAt, claims.ExpiresAt); err != nil {
		a.s.logger.Error("track token", "error", err)
		return nil, status.Error(codes.Internal, "internal error")
	}

	a.s.db.WriteAuditEvent(model.EventLoginOK, &acct.ID, nil, ip, "") //nolint:errcheck
	a.s.db.WriteAuditEvent(model.EventTokenIssued, &acct.ID, nil, ip, //nolint:errcheck
		fmt.Sprintf(`{"jti":%q}`, claims.JTI))

	return &mciasv1.LoginResponse{
		Token:     tokenStr,
		ExpiresAt: timestamppb.New(claims.ExpiresAt),
	}, nil
}

// Logout revokes the caller's current JWT.
func (a *authServiceServer) Logout(ctx context.Context, _ *mciasv1.LogoutRequest) (*mciasv1.LogoutResponse, error) {
	claims := claimsFromContext(ctx)
	if err := a.s.db.RevokeToken(claims.JTI, "logout"); err != nil {
		a.s.logger.Error("revoke token on logout", "error", err)
		return nil, status.Error(codes.Internal, "internal error")
	}
	a.s.db.WriteAuditEvent(model.EventTokenRevoked, nil, nil, peerIP(ctx), //nolint:errcheck
		fmt.Sprintf(`{"jti":%q,"reason":"logout"}`, claims.JTI))
	return &mciasv1.LogoutResponse{}, nil
}

// RenewToken exchanges the caller's token for a new one.
func (a *authServiceServer) RenewToken(ctx context.Context, _ *mciasv1.RenewTokenRequest) (*mciasv1.RenewTokenResponse, error) {
	claims := claimsFromContext(ctx)

	acct, err := a.s.db.GetAccountByUUID(claims.Subject)
	if err != nil {
		return nil, status.Error(codes.Unauthenticated, "account not found")
	}
	if acct.Status != model.AccountStatusActive {
		return nil, status.Error(codes.Unauthenticated, "account inactive")
	}

	roles, err := a.s.db.GetRoles(acct.ID)
	if err != nil {
		return nil, status.Error(codes.Internal, "internal error")
	}

	expiry := a.s.cfg.DefaultExpiry()
	for _, r := range roles {
		if r == "admin" {
			expiry = a.s.cfg.AdminExpiry()
			break
		}
	}

	newTokenStr, newClaims, err := token.IssueToken(a.s.privKey, a.s.cfg.Tokens.Issuer, acct.UUID, roles, expiry)
	if err != nil {
		return nil, status.Error(codes.Internal, "internal error")
	}

	// Security: revoke old + track new in a single transaction (F-03) so that a
	// failure between the two steps cannot leave the user with no valid token.
	if err := a.s.db.RenewToken(claims.JTI, "renewed", newClaims.JTI, acct.ID, newClaims.IssuedAt, newClaims.ExpiresAt); err != nil {
		return nil, status.Error(codes.Internal, "internal error")
	}

	a.s.db.WriteAuditEvent(model.EventTokenRenewed, &acct.ID, nil, peerIP(ctx), //nolint:errcheck
		fmt.Sprintf(`{"old_jti":%q,"new_jti":%q}`, claims.JTI, newClaims.JTI))

	return &mciasv1.RenewTokenResponse{
		Token:     newTokenStr,
		ExpiresAt: timestamppb.New(newClaims.ExpiresAt),
	}, nil
}

// EnrollTOTP begins TOTP enrollment for the calling account.
func (a *authServiceServer) EnrollTOTP(ctx context.Context, _ *mciasv1.EnrollTOTPRequest) (*mciasv1.EnrollTOTPResponse, error) {
	claims := claimsFromContext(ctx)
	acct, err := a.s.db.GetAccountByUUID(claims.Subject)
	if err != nil {
		return nil, status.Error(codes.Unauthenticated, "account not found")
	}

	rawSecret, b32Secret, err := auth.GenerateTOTPSecret()
	if err != nil {
		return nil, status.Error(codes.Internal, "internal error")
	}

	secretEnc, secretNonce, err := crypto.SealAESGCM(a.s.masterKey, rawSecret)
	if err != nil {
		return nil, status.Error(codes.Internal, "internal error")
	}

	if err := a.s.db.SetTOTP(acct.ID, secretEnc, secretNonce); err != nil {
		return nil, status.Error(codes.Internal, "internal error")
	}

	otpURI := fmt.Sprintf("otpauth://totp/MCIAS:%s?secret=%s&issuer=MCIAS", acct.Username, b32Secret)

	// Security: secret is shown once here only; the stored form is encrypted.
	return &mciasv1.EnrollTOTPResponse{
		Secret:     b32Secret,
		OtpauthUri: otpURI,
	}, nil
}

// ConfirmTOTP confirms TOTP enrollment.
func (a *authServiceServer) ConfirmTOTP(ctx context.Context, req *mciasv1.ConfirmTOTPRequest) (*mciasv1.ConfirmTOTPResponse, error) {
	if req.Code == "" {
		return nil, status.Error(codes.InvalidArgument, "code is required")
	}

	claims := claimsFromContext(ctx)
	acct, err := a.s.db.GetAccountByUUID(claims.Subject)
	if err != nil {
		return nil, status.Error(codes.Unauthenticated, "account not found")
	}
	if acct.TOTPSecretEnc == nil {
		return nil, status.Error(codes.FailedPrecondition, "TOTP enrollment not started")
	}

	secret, err := crypto.OpenAESGCM(a.s.masterKey, acct.TOTPSecretNonce, acct.TOTPSecretEnc)
	if err != nil {
		return nil, status.Error(codes.Internal, "internal error")
	}

	valid, err := auth.ValidateTOTP(secret, req.Code)
	if err != nil || !valid {
		return nil, status.Error(codes.Unauthenticated, "invalid TOTP code")
	}

	// SetTOTP with existing enc/nonce sets totp_required=1, confirming enrollment.
	if err := a.s.db.SetTOTP(acct.ID, acct.TOTPSecretEnc, acct.TOTPSecretNonce); err != nil {
		return nil, status.Error(codes.Internal, "internal error")
	}

	a.s.db.WriteAuditEvent(model.EventTOTPEnrolled, &acct.ID, nil, peerIP(ctx), "") //nolint:errcheck
	return &mciasv1.ConfirmTOTPResponse{}, nil
}

// RemoveTOTP removes TOTP from an account. Admin only.
func (a *authServiceServer) RemoveTOTP(ctx context.Context, req *mciasv1.RemoveTOTPRequest) (*mciasv1.RemoveTOTPResponse, error) {
	if err := a.s.requireAdmin(ctx); err != nil {
		return nil, err
	}
	if req.AccountId == "" {
		return nil, status.Error(codes.InvalidArgument, "account_id is required")
	}

	acct, err := a.s.db.GetAccountByUUID(req.AccountId)
	if err != nil {
		return nil, status.Error(codes.NotFound, "account not found")
	}

	if err := a.s.db.ClearTOTP(acct.ID); err != nil {
		return nil, status.Error(codes.Internal, "internal error")
	}

	a.s.db.WriteAuditEvent(model.EventTOTPRemoved, nil, &acct.ID, peerIP(ctx), "") //nolint:errcheck
	return &mciasv1.RemoveTOTPResponse{}, nil
}

// peerIP extracts the client IP from gRPC peer context.
func peerIP(ctx context.Context) string {
	p, ok := peer.FromContext(ctx)
	if !ok {
		return ""
	}
	host, _, err := net.SplitHostPort(p.Addr.String())
	if err != nil {
		return p.Addr.String()
	}
	return host
}