// Package main provides FX providers for Auth Service.
// This file creates the service inline to avoid importing internal packages.
package main

import (
	"context"
	"crypto/rand"
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"net"
	"time"

	authv1 "git.dcentral.systems/toolz/goplt/api/proto/generated/auth/v1"
	"git.dcentral.systems/toolz/goplt/internal/ent"
	"git.dcentral.systems/toolz/goplt/pkg/config"
	"git.dcentral.systems/toolz/goplt/pkg/logger"
	"git.dcentral.systems/toolz/goplt/pkg/services"
	"github.com/golang-jwt/jwt/v5"
	"go.uber.org/fx"
	"go.uber.org/zap"
	"google.golang.org/grpc"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/health"
	"google.golang.org/grpc/health/grpc_health_v1"
	"google.golang.org/grpc/reflection"
	"google.golang.org/grpc/status"
)

const (
	accessTokenLifetime  = 15 * time.Minute
	refreshTokenLifetime = 7 * 24 * time.Hour
)

// authService provides authentication functionality.
type authService struct {
	client             *ent.Client
	logger             logger.Logger
	identityClient     services.IdentityServiceClient
	jwtSecret          []byte
	accessTokenExpiry  time.Duration
	refreshTokenExpiry time.Duration
}

// hashToken hashes a token using SHA256.
func hashToken(token string) string {
	h := sha256.Sum256([]byte(token))
	return hex.EncodeToString(h[:])
}

// generateRefreshToken generates a random refresh token.
func generateRefreshToken() (string, error) {
	b := make([]byte, 32)
	if _, err := rand.Read(b); err != nil {
		return "", fmt.Errorf("failed to generate token: %w", err)
	}
	return hex.EncodeToString(b), nil
}

// generateAccessToken generates a JWT access token.
func (s *authService) generateAccessToken(userID, email string, roles []string) (string, int64, error) {
	expiresAt := time.Now().Add(s.accessTokenExpiry)
	claims := jwt.MapClaims{
		"sub":        userID,
		"email":      email,
		"roles":      roles,
		"exp":        expiresAt.Unix(),
		"iat":        time.Now().Unix(),
		"token_type": "access",
	}

	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	tokenString, err := token.SignedString(s.jwtSecret)
	if err != nil {
		return "", 0, fmt.Errorf("failed to sign token: %w", err)
	}

	return tokenString, int64(s.accessTokenExpiry.Seconds()), nil
}

// generateRefreshToken generates a refresh token and stores it in the database.
// Note: This is a simplified version - RefreshToken entity needs to be generated first
func (s *authService) generateRefreshToken(ctx context.Context, userID string) (string, error) {
	token, err := generateRefreshToken()
	if err != nil {
		return "", err
	}

	// TODO: Store refresh token in database using RefreshToken entity once generated
	// For now, we'll just return the token
	// tokenHash := hashToken(token)
	// expiresAt := time.Now().Add(s.refreshTokenExpiry)
	// _, err = s.client.RefreshToken.Create()...

	return token, nil
}

// validateAccessToken validates a JWT access token.
func (s *authService) validateAccessToken(tokenString string) (*jwt.Token, jwt.MapClaims, error) {
	token, err := jwt.Parse(tokenString, func(token *jwt.Token) (interface{}, error) {
		if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, fmt.Errorf("unexpected signing method: %v", token.Header["alg"])
		}
		return s.jwtSecret, nil
	})

	if err != nil {
		return nil, nil, fmt.Errorf("failed to parse token: %w", err)
	}

	if !token.Valid {
		return nil, nil, fmt.Errorf("invalid token")
	}

	claims, ok := token.Claims.(jwt.MapClaims)
	if !ok {
		return nil, nil, fmt.Errorf("invalid token claims")
	}

	// Check expiration
	if exp, ok := claims["exp"].(float64); ok {
		if time.Now().Unix() > int64(exp) {
			return nil, nil, fmt.Errorf("token expired")
		}
	}

	return token, claims, nil
}

// validateRefreshToken validates a refresh token.
// Note: This is a simplified version - RefreshToken entity needs to be generated first
func (s *authService) validateRefreshToken(ctx context.Context, tokenString string) (string, error) {
	// TODO: Use RefreshToken entity once generated
	// tokenHash := hashToken(tokenString)
	// rt, err := s.client.RefreshToken.Query()...
	// return rt.UserID, nil

	// For now, return error to indicate this needs proper implementation
	return "", fmt.Errorf("refresh token validation not yet implemented - RefreshToken entity needs to be generated")
}

// revokeRefreshToken revokes a refresh token.
// Note: This is a simplified version - RefreshToken entity needs to be generated first
func (s *authService) revokeRefreshToken(ctx context.Context, tokenString string) error {
	// TODO: Implement once RefreshToken entity is generated
	// tokenHash := hashToken(tokenString)
	// rt, err := s.client.RefreshToken.Query()...
	// return s.client.RefreshToken.DeleteOneID(rt.ID).Exec(ctx)
	return nil // Placeholder
}

// login authenticates a user and returns tokens.
func (s *authService) login(ctx context.Context, email, password string) (*authv1.LoginResponse, error) {
	// Verify credentials with Identity Service
	user, err := s.identityClient.GetUserByEmail(ctx, email)
	if err != nil {
		return nil, fmt.Errorf("invalid credentials")
	}

	// Note: In a real implementation, we'd call VerifyPassword on Identity Service
	// For now, we'll assume Identity Service validates the password
	// This is a simplified version - the Identity Service should expose VerifyPassword

	// Get user roles (simplified - would come from Authz Service)
	roles := []string{} // TODO: Get from Authz Service

	// Generate tokens
	accessToken, expiresIn, err := s.generateAccessToken(user.ID, user.Email, roles)
	if err != nil {
		return nil, fmt.Errorf("failed to generate access token: %w", err)
	}

	refreshToken, err := s.generateRefreshToken(ctx, user.ID)
	if err != nil {
		return nil, fmt.Errorf("failed to generate refresh token: %w", err)
	}

	return &authv1.LoginResponse{
		AccessToken:  accessToken,
		RefreshToken: refreshToken,
		ExpiresIn:    expiresIn,
		TokenType:    "Bearer",
	}, nil
}

// refreshToken refreshes an access token.
func (s *authService) refreshToken(ctx context.Context, refreshTokenString string) (*authv1.RefreshTokenResponse, error) {
	// Validate refresh token
	userID, err := s.validateRefreshToken(ctx, refreshTokenString)
	if err != nil {
		return nil, err
	}

	// Get user from Identity Service
	user, err := s.identityClient.GetUser(ctx, userID)
	if err != nil {
		return nil, fmt.Errorf("user not found")
	}

	// Get user roles (simplified)
	roles := []string{} // TODO: Get from Authz Service

	// Generate new tokens
	accessToken, expiresIn, err := s.generateAccessToken(user.ID, user.Email, roles)
	if err != nil {
		return nil, fmt.Errorf("failed to generate access token: %w", err)
	}

	// Generate new refresh token (rotate)
	newRefreshToken, err := s.generateRefreshToken(ctx, user.ID)
	if err != nil {
		return nil, fmt.Errorf("failed to generate refresh token: %w", err)
	}

	// Revoke old refresh token
	_ = s.revokeRefreshToken(ctx, refreshTokenString)

	return &authv1.RefreshTokenResponse{
		AccessToken:  accessToken,
		RefreshToken: newRefreshToken,
		ExpiresIn:    expiresIn,
		TokenType:    "Bearer",
	}, nil
}

// validateToken validates a JWT token.
func (s *authService) validateToken(tokenString string) (*authv1.ValidateTokenResponse, error) {
	_, claims, err := s.validateAccessToken(tokenString)
	if err != nil {
		return nil, err
	}

	userID, _ := claims["sub"].(string)
	email, _ := claims["email"].(string)
	exp, _ := claims["exp"].(float64)

	roles := []string{}
	if rolesClaim, ok := claims["roles"].([]interface{}); ok {
		for _, r := range rolesClaim {
			if role, ok := r.(string); ok {
				roles = append(roles, role)
			}
		}
	}

	return &authv1.ValidateTokenResponse{
		UserId:    userID,
		Email:     email,
		Roles:     roles,
		ExpiresAt: int64(exp),
	}, nil
}

// logout invalidates a refresh token.
func (s *authService) logout(ctx context.Context, refreshTokenString string) error {
	return s.revokeRefreshToken(ctx, refreshTokenString)
}

// authServerImpl implements the AuthService gRPC server.
type authServerImpl struct {
	authv1.UnimplementedAuthServiceServer
	service *authService
	logger  *zap.Logger
}

// Login authenticates a user and returns tokens.
func (s *authServerImpl) Login(ctx context.Context, req *authv1.LoginRequest) (*authv1.LoginResponse, error) {
	resp, err := s.service.login(ctx, req.Email, req.Password)
	if err != nil {
		return nil, status.Errorf(codes.Unauthenticated, "login failed: %v", err)
	}
	return resp, nil
}

// RefreshToken refreshes an access token.
func (s *authServerImpl) RefreshToken(ctx context.Context, req *authv1.RefreshTokenRequest) (*authv1.RefreshTokenResponse, error) {
	resp, err := s.service.refreshToken(ctx, req.RefreshToken)
	if err != nil {
		return nil, status.Errorf(codes.Unauthenticated, "refresh failed: %v", err)
	}
	return resp, nil
}

// ValidateToken validates a JWT token.
func (s *authServerImpl) ValidateToken(ctx context.Context, req *authv1.ValidateTokenRequest) (*authv1.ValidateTokenResponse, error) {
	resp, err := s.service.validateToken(req.Token)
	if err != nil {
		return nil, status.Errorf(codes.Unauthenticated, "validation failed: %v", err)
	}
	return resp, nil
}

// Logout invalidates a refresh token.
func (s *authServerImpl) Logout(ctx context.Context, req *authv1.LogoutRequest) (*authv1.LogoutResponse, error) {
	if err := s.service.logout(ctx, req.RefreshToken); err != nil {
		return nil, status.Errorf(codes.Internal, "logout failed: %v", err)
	}
	return &authv1.LogoutResponse{Success: true}, nil
}

// provideAuthService creates the auth service and gRPC server.
func provideAuthService() fx.Option {
	return fx.Options(
		// Auth service
		fx.Provide(func(
			client *ent.Client,
			log logger.Logger,
			identityClient services.IdentityServiceClient,
			cfg config.ConfigProvider,
		) (*authService, error) {
			jwtSecret := cfg.GetString("auth.jwt_secret")
			if jwtSecret == "" {
				jwtSecret = "default-secret-change-in-production" // TODO: Generate or require
			}

			return &authService{
				client:             client,
				logger:             log,
				identityClient:     identityClient,
				jwtSecret:          []byte(jwtSecret),
				accessTokenExpiry:  accessTokenLifetime,
				refreshTokenExpiry: refreshTokenLifetime,
			}, nil
		}),

		// gRPC server implementation
		fx.Provide(func(authService *authService, log logger.Logger) (*authServerImpl, error) {
			zapLogger, _ := zap.NewProduction()
			return &authServerImpl{
				service: authService,
				logger:  zapLogger,
			}, nil
		}),

		// gRPC server wrapper
		fx.Provide(func(
			serverImpl *authServerImpl,
			cfg config.ConfigProvider,
			log logger.Logger,
		) (*grpcServerWrapper, error) {
			port := cfg.GetInt("services.auth.port")
			if port == 0 {
				port = 8081
			}

			addr := fmt.Sprintf("0.0.0.0:%d", port)
			listener, err := net.Listen("tcp", addr)
			if err != nil {
				return nil, fmt.Errorf("failed to listen on %s: %w", addr, err)
			}

			grpcServer := grpc.NewServer()
			authv1.RegisterAuthServiceServer(grpcServer, serverImpl)

			// Register health service
			healthServer := health.NewServer()
			grpc_health_v1.RegisterHealthServer(grpcServer, healthServer)
			healthServer.SetServingStatus("auth.v1.AuthService", grpc_health_v1.HealthCheckResponse_SERVING)

			// Register reflection for grpcurl
			reflection.Register(grpcServer)

			return &grpcServerWrapper{
				server:   grpcServer,
				listener: listener,
				port:     port,
				logger:   log,
			}, nil
		}),
	)
}