package auth

import (
	"fmt"
	"time"
	"github.com/golang-jwt/jwt/v5"
	"photography-backend/internal/config"
)

// JWTService JWT服务
type JWTService struct {
	secretKey            []byte
	accessTokenDuration  time.Duration
	refreshTokenDuration time.Duration
}

// JWTClaims JWT声明
type JWTClaims struct {
	UserID   uint   `json:"user_id"`
	Username string `json:"username"`
	Role     string `json:"role"`
	jwt.RegisteredClaims
}

// TokenPair 令牌对
type TokenPair struct {
	AccessToken  string `json:"access_token"`
	RefreshToken string `json:"refresh_token"`
	TokenType    string `json:"token_type"`
	ExpiresIn    int64  `json:"expires_in"`
}

// NewJWTService 创建JWT服务
func NewJWTService(cfg *config.JWTConfig) *JWTService {
	accessDuration, _ := time.ParseDuration(cfg.ExpiresIn)
	refreshDuration, _ := time.ParseDuration(cfg.RefreshExpiresIn)
	
	return &JWTService{
		secretKey:            []byte(cfg.Secret),
		accessTokenDuration:  accessDuration,
		refreshTokenDuration: refreshDuration,
	}
}

// GenerateTokenPair 生成令牌对
func (s *JWTService) GenerateTokenPair(userID uint, username, role string) (*TokenPair, error) {
	// 生成访问令牌
	accessToken, err := s.generateToken(userID, username, role, s.accessTokenDuration)
	if err != nil {
		return nil, fmt.Errorf("failed to generate access token: %w", err)
	}
	
	// 生成刷新令牌
	refreshToken, err := s.generateToken(userID, username, role, s.refreshTokenDuration)
	if err != nil {
		return nil, fmt.Errorf("failed to generate refresh token: %w", err)
	}
	
	return &TokenPair{
		AccessToken:  accessToken,
		RefreshToken: refreshToken,
		TokenType:    "Bearer",
		ExpiresIn:    int64(s.accessTokenDuration.Seconds()),
	}, nil
}

// generateToken 生成令牌
func (s *JWTService) generateToken(userID uint, username, role string, duration time.Duration) (string, error) {
	now := time.Now()
	claims := &JWTClaims{
		UserID:   userID,
		Username: username,
		Role:     role,
		RegisteredClaims: jwt.RegisteredClaims{
			ExpiresAt: jwt.NewNumericDate(now.Add(duration)),
			IssuedAt:  jwt.NewNumericDate(now),
			NotBefore: jwt.NewNumericDate(now),
			Issuer:    "photography-backend",
		},
	}
	
	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	return token.SignedString(s.secretKey)
}

// ValidateToken 验证令牌
func (s *JWTService) ValidateToken(tokenString string) (*JWTClaims, error) {
	token, err := jwt.ParseWithClaims(tokenString, &JWTClaims{}, 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.secretKey, nil
	})
	
	if err != nil {
		return nil, fmt.Errorf("failed to parse token: %w", err)
	}
	
	if claims, ok := token.Claims.(*JWTClaims); ok && token.Valid {
		return claims, nil
	}
	
	return nil, fmt.Errorf("invalid token")
}

// RefreshToken 刷新令牌
func (s *JWTService) RefreshToken(refreshToken string) (*TokenPair, error) {
	claims, err := s.ValidateToken(refreshToken)
	if err != nil {
		return nil, fmt.Errorf("invalid refresh token: %w", err)
	}
	
	// 生成新的令牌对
	return s.GenerateTokenPair(claims.UserID, claims.Username, claims.Role)
}

// GetClaimsFromToken 从令牌中获取声明
func (s *JWTService) GetClaimsFromToken(tokenString string) (*JWTClaims, error) {
	token, err := jwt.ParseWithClaims(tokenString, &JWTClaims{}, func(token *jwt.Token) (interface{}, error) {
		return s.secretKey, nil
	})
	
	if err != nil {
		return nil, err
	}
	
	if claims, ok := token.Claims.(*JWTClaims); ok {
		return claims, nil
	}
	
	return nil, fmt.Errorf("invalid claims")
}