package middleware

import (
	"crypto/rand"
	"crypto/rsa"
	"crypto/x509"
	"encoding/pem"
	"errors"
	"fmt"
	"os"
	"time"

	"github.com/gin-gonic/gin"
	"github.com/golang-jwt/jwt/v5"
	"github.com/joho/godotenv"
	"github.com/oklog/ulid/v2"
	"github.com/timetracker/backend/internal/api/utils"
	"github.com/timetracker/backend/internal/models"
)

var (
	jwtSecret     string
	tokenDuration = 24 * time.Hour
)

func init() {
	// Load .env file
	_ = godotenv.Load()

	// Get JWT secret from environment
	jwtSecret = os.Getenv("JWT_SECRET")

	// Generate a random secret if none is provided
	if jwtSecret == "" {
		randomBytes := make([]byte, 32)
		_, err := rand.Read(randomBytes)
		if err != nil {
			panic("failed to generate JWT secret: " + err.Error())
		}
		jwtSecret = string(randomBytes)
	}

	// Generate and store RSA keys if configured
	if os.Getenv("JWT_KEY_GENERATE") == "true" {
		keyDir := os.Getenv("JWT_KEY_DIR")
		if keyDir == "" {
			keyDir = "./keys"
		}

		// Create directory if it doesn't exist
		if err := os.MkdirAll(keyDir, 0755); err != nil {
			panic("failed to create key directory: " + err.Error())
		}

		// Generate RSA key pair
		privateKey, err := rsa.GenerateKey(rand.Reader, 2048)
		if err != nil {
			panic("failed to generate RSA key pair: " + err.Error())
		}

		// Save private key
		privateKeyFile, err := os.Create(fmt.Sprintf("%s/private.pem", keyDir))
		if err != nil {
			panic("failed to create private key file: " + err.Error())
		}
		defer privateKeyFile.Close()

		privateKeyPEM := &pem.Block{
			Type:  "RSA PRIVATE KEY",
			Bytes: x509.MarshalPKCS1PrivateKey(privateKey),
		}

		if err := pem.Encode(privateKeyFile, privateKeyPEM); err != nil {
			panic("failed to encode private key: " + err.Error())
		}

		// Save public key
		publicKeyFile, err := os.Create(fmt.Sprintf("%s/public.pem", keyDir))
		if err != nil {
			panic("failed to create public key file: " + err.Error())
		}
		defer publicKeyFile.Close()

		publicKeyPEM := &pem.Block{
			Type:  "RSA PUBLIC KEY",
			Bytes: x509.MarshalPKCS1PublicKey(&privateKey.PublicKey),
		}

		if err := pem.Encode(publicKeyFile, publicKeyPEM); err != nil {
			panic("failed to encode public key: " + err.Error())
		}
	}
}

// Claims represents the JWT claims
type Claims struct {
	UserID    string `json:"userId"`
	Email     string `json:"email"`
	Role      string `json:"role"`
	CompanyID string `json:"companyId"`
	jwt.RegisteredClaims
}

// AuthMiddleware checks if the user is authenticated
func AuthMiddleware() gin.HandlerFunc {
	return func(c *gin.Context) {
		// Get the token from cookie
		tokenString, err := c.Cookie("jwt")
		if err != nil {
			utils.UnauthorizedResponse(c, "Authentication cookie is required")
			c.Abort()
			return
		}

		claims, err := validateToken(tokenString)
		if err != nil {
			utils.UnauthorizedResponse(c, "Invalid or expired token")
			c.Abort()
			return
		}

		// Store user information in the context
		c.Set("userID", claims.UserID)
		c.Set("email", claims.Email)
		c.Set("role", claims.Role)
		c.Set("companyID", claims.CompanyID)

		c.Next()
	}
}

// RoleMiddleware checks if the user has the required role
func RoleMiddleware(roles ...string) gin.HandlerFunc {
	return func(c *gin.Context) {
		userRole, exists := c.Get("role")
		if !exists {
			utils.UnauthorizedResponse(c, "User role not found in context")
			c.Abort()
			return
		}

		// Check if the user's role is in the allowed roles
		roleStr, ok := userRole.(string)
		if !ok {
			utils.InternalErrorResponse(c, "Invalid role type in context")
			c.Abort()
			return
		}

		allowed := false
		for _, role := range roles {
			if roleStr == role {
				allowed = true
				break
			}
		}

		if !allowed {
			utils.ForbiddenResponse(c, "Insufficient permissions")
			c.Abort()
			return
		}

		c.Next()
	}
}

// GenerateToken creates a new JWT token for a user
func GenerateToken(user *models.User, c *gin.Context) (string, error) {
	// Create the claims
	claims := Claims{
		UserID:    user.ID.String(),
		Email:     user.Email,
		Role:      user.Role,
		CompanyID: user.CompanyID.String(),
		RegisteredClaims: jwt.RegisteredClaims{
			ExpiresAt: jwt.NewNumericDate(time.Now().Add(tokenDuration)),
			IssuedAt:  jwt.NewNumericDate(time.Now()),
			NotBefore: jwt.NewNumericDate(time.Now()),
		},
	}

	// Create the token
	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)

	// Sign the token
	tokenString, err := token.SignedString([]byte(jwtSecret))
	if err != nil {
		return "", err
	}

	// Set the cookie
	c.SetCookie("jwt", tokenString, int(tokenDuration.Seconds()), "/", "", true, true)

	return tokenString, nil
}

// validateToken validates a JWT token and returns the claims
func validateToken(tokenString string) (*Claims, error) {
	// Parse the token
	token, err := jwt.ParseWithClaims(tokenString, &Claims{}, func(token *jwt.Token) (interface{}, error) {
		// Validate the signing method
		if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, errors.New("unexpected signing method")
		}
		return []byte(jwtSecret), nil
	})

	if err != nil {
		return nil, err
	}

	// Check if the token is valid
	if !token.Valid {
		return nil, errors.New("invalid token")
	}

	// Get the claims
	claims, ok := token.Claims.(*Claims)
	if !ok {
		return nil, errors.New("invalid claims")
	}

	return claims, nil
}

// GetUserIDFromContext extracts the user ID from the context
func GetUserIDFromContext(c *gin.Context) (ulid.ULID, error) {
	userID, exists := c.Get("userID")
	if !exists {
		return ulid.ULID{}, errors.New("user ID not found in context")
	}

	userIDStr, ok := userID.(string)
	if !ok {
		return ulid.ULID{}, errors.New("invalid user ID type in context")
	}

	id, err := ulid.Parse(userIDStr)
	if err != nil {
		return ulid.ULID{}, err
	}

	return id, nil
}

// GetCompanyIDFromContext extracts the company ID from the context
func GetCompanyIDFromContext(c *gin.Context) (ulid.ULID, error) {
	companyID, exists := c.Get("companyID")
	if !exists {
		return ulid.ULID{}, errors.New("company ID not found in context")
	}

	companyIDStr, ok := companyID.(string)
	if !ok {
		return ulid.ULID{}, errors.New("invalid company ID type in context")
	}

	id, err := ulid.Parse(companyIDStr)
	if err != nil {
		return ulid.ULID{}, err
	}

	return id, nil
}