package rbac

import (
	"errors"
	"fmt"
	"log/slog"
	"net/http"
	"strings"

	"github.com/golang-jwt/jwt/v5"
	"github.com/labstack/echo/v4"
)

// JWTConfig contains configuration for the JWT middleware
type JWTConfig struct {
	KeyProvider    KeyProvider
	TokenLookup    string   // Format: "header:<name>" or "query:<name>" or "cookie:<name>"
	AuthScheme     string   // Usually "Bearer"
	RequiredGroups []string // Groups that are required for access (any one of these)
	ContextKey     string   // Key to store the claims in the context
	ErrorHandler   func(echo.Context, error) error
	Logger         *slog.Logger // Logger instance for middleware
}

// DefaultJWTConfig is the default JWT auth middleware config
var DefaultJWTConfig = JWTConfig{
	TokenLookup:  "header:Authorization",
	AuthScheme:   "Bearer",
	ContextKey:   "user",
	ErrorHandler: defaultErrorHandler,
}

// defaultErrorHandler returns a 401 Unauthorized error for JWT validation failures
func defaultErrorHandler(c echo.Context, err error) error {
	return echo.NewHTTPError(http.StatusUnauthorized, "invalid or expired jwt")
}

// extractToken determines which token extractor to use based on config
func extractToken(config JWTConfig) func(echo.Context) (string, error) {
	parts := strings.Split(config.TokenLookup, ":")
	extractor := tokenFromHeader(parts[1], config.AuthScheme)
	if parts[0] == "query" {
		extractor = tokenFromQuery(parts[1])
	} else if parts[0] == "cookie" {
		extractor = tokenFromCookie(parts[1])
	}
	return extractor
}

// validateGroups checks if the user belongs to any of the required groups
func validateGroups(claims jwt.MapClaims, requiredGroups []string, logger *slog.Logger) bool {
	if len(requiredGroups) == 0 {
		logger.Debug("no required groups specified, access granted")
		return true
	}

	groups, ok := claims["cognito:groups"].([]interface{})
	if !ok {
		logger.Warn("no groups found in claims", "user", claims["sub"])
		return false
	}

	userGroups := make([]string, 0)
	for _, group := range groups {
		if groupStr, ok := group.(string); ok {
			userGroups = append(userGroups, groupStr)
		}
	}

	for _, reqGroup := range requiredGroups {
		for _, group := range groups {
			if groupStr, ok := group.(string); ok && strings.EqualFold(groupStr, reqGroup) {
				logger.Debug("group validation successful",
					"user", claims["sub"],
					"required_group", reqGroup,
					"user_groups", userGroups)
				return true
			}
		}
	}

	logger.Warn("group validation failed",
		"user", claims["sub"],
		"required_groups", requiredGroups,
		"user_groups", userGroups)
	return false
}

// parseJWT parses and validates the JWT token
func parseJWT(tokenString string, keyProvider KeyProvider, logger *slog.Logger) (*jwt.Token, jwt.MapClaims, error) {
	token, err := jwt.Parse(tokenString, func(token *jwt.Token) (interface{}, error) {
		if _, ok := token.Method.(*jwt.SigningMethodRSA); !ok {
			logger.Error("unexpected signing method", "method", token.Method.Alg())
			return nil, errors.New("unexpected signing method")
		}

		// Get key ID from token header
		kid, ok := token.Header["kid"].(string)
		if !ok {
			logger.Error("no key ID in token header")
			return nil, errors.New("no key ID (kid) in token header")
		}

		// Get public key from provider
		return keyProvider.GetPublicKey(kid)
	})

	if err != nil {
		logger.Error("failed to parse JWT", "error", err)
		return nil, nil, err
	}

	claims, ok := token.Claims.(jwt.MapClaims)
	if !ok || !token.Valid {
		logger.Error("invalid token claims")
		return nil, nil, errors.New("invalid token")
	}

	logger.Debug("JWT parsed successfully",
		"user", claims["sub"],
		"email", claims["email"])
	return token, claims, nil
}

// JWTWithConfig returns a JWT auth middleware with config
func JWTWithConfig(config JWTConfig) echo.MiddlewareFunc {
	// Set defaults
	if config.TokenLookup == "" {
		config.TokenLookup = DefaultJWTConfig.TokenLookup
	}
	if config.AuthScheme == "" {
		config.AuthScheme = DefaultJWTConfig.AuthScheme
	}
	if config.ContextKey == "" {
		config.ContextKey = DefaultJWTConfig.ContextKey
	}
	if config.ErrorHandler == nil {
		config.ErrorHandler = DefaultJWTConfig.ErrorHandler
	}
	if config.KeyProvider == nil {
		panic("JWT middleware requires a KeyProvider")
	}
	if config.Logger == nil {
		config.Logger = slog.Default()
	}

	extractor := extractToken(config)

	return func(next echo.HandlerFunc) echo.HandlerFunc {
		return func(c echo.Context) error {
			tokenString, err := extractor(c)
			if err != nil {
				config.Logger.Error("failed to extract token",
					"error", err,
					"path", c.Request().URL.Path,
					"method", c.Request().Method)
				return config.ErrorHandler(c, err)
			}

			_, claims, err := parseJWT(tokenString, config.KeyProvider, config.Logger)
			if err != nil {
				config.Logger.Error("failed to validate JWT",
					"error", err,
					"path", c.Request().URL.Path,
					"method", c.Request().Method)
				return config.ErrorHandler(c, err)
			}

			// Check required groups if specified
			if !validateGroups(claims, config.RequiredGroups, config.Logger) {
				config.Logger.Warn("insufficient permissions",
					"user", claims["sub"],
					"path", c.Request().URL.Path,
					"method", c.Request().Method)
				return echo.NewHTTPError(http.StatusForbidden, "insufficient permissions")
			}

			// Store user information in context
			c.Set(config.ContextKey, claims)

			config.Logger.Info("authenticated request",
				"user", claims["sub"],
				"path", c.Request().URL.Path,
				"method", c.Request().Method)

			return next(c)
		}
	}
}

// JWT returns a JWT auth middleware with default configuration
func JWT(keyProvider KeyProvider) echo.MiddlewareFunc {
	config := DefaultJWTConfig
	config.KeyProvider = keyProvider
	return JWTWithConfig(config)
}

// tokenFromHeader extracts token from Authorization header
func tokenFromHeader(header string, authScheme string) func(echo.Context) (string, error) {
	return func(c echo.Context) (string, error) {
		auth := c.Request().Header.Get(header)
		if auth == "" {
			return "", fmt.Errorf("missing auth header: %s", header)
		}

		l := len(authScheme)
		if len(auth) > l+1 && auth[:l] == authScheme {
			return auth[l+1:], nil
		}
		return "", fmt.Errorf("invalid auth header format for scheme: %s", authScheme)
	}
}

// tokenFromQuery extracts token from query parameter
func tokenFromQuery(param string) func(echo.Context) (string, error) {
	return func(c echo.Context) (string, error) {
		token := c.QueryParam(param)
		if token == "" {
			return "", errors.New("missing auth query parameter")
		}
		return token, nil
	}
}

// tokenFromCookie extracts token from cookie
func tokenFromCookie(name string) func(echo.Context) (string, error) {
	return func(c echo.Context) (string, error) {
		cookie, err := c.Cookie(name)
		if err != nil {
			return "", err
		}
		return cookie.Value, nil
	}
}

//// GroupGuard middleware ensures a user has at least one of the required groups
//func GroupGuard(requiredGroups ...string) echo.MiddlewareFunc {
//	return func(next echo.HandlerFunc) echo.HandlerFunc {
//		return func(c echo.Context) error {
//			userClaims, ok := c.Get("user").(jwt.MapClaims)
//			if !ok {
//				return echo.NewHTTPError(http.StatusUnauthorized, "user not authenticated")
//			}
//
//			groups, ok := userClaims["cognito:groups"].([]interface{})
//			if !ok {
//				return echo.NewHTTPError(http.StatusForbidden, "no groups found for user")
//			}
//
//			for _, requiredGroup := range requiredGroups {
//				for _, group := range groups {
//					if groupStr, ok := group.(string); ok && strings.EqualFold(groupStr, requiredGroup) {
//						return next(c)
//					}
//				}
//			}
//
//			return echo.NewHTTPError(http.StatusForbidden, "insufficient permissions")
//		}
//	}
//}