package jwt

import (
	"errors"
	"time"

	"github.com/golang-jwt/jwt/v5"
)

// Claims JWT声明
type Claims struct {
	UserID   uint   `json:"user_id"`
	TenantID uint   `json:"tenant_id"`
	Role     string `json:"role"`
	jwt.RegisteredClaims
}

// JWTManager JWT管理器
type JWTManager struct {
	secretKey []byte
}

// NewJWTManager 创建JWT管理器
func NewJWTManager(secretKey string) *JWTManager {
	return &JWTManager{
		secretKey: []byte(secretKey),
	}
}

// GenerateAccessToken 生成访问令牌
func (m *JWTManager) GenerateAccessToken(userID, tenantID uint, role string) (string, time.Time, error) {
	expiresAt := time.Now().Add(24 * time.Hour) // 24小时有效

	claims := &Claims{
		UserID:   userID,
		TenantID: tenantID,
		Role:     role,
		RegisteredClaims: jwt.RegisteredClaims{
			ExpiresAt: jwt.NewNumericDate(expiresAt),
			IssuedAt:  jwt.NewNumericDate(time.Now()),
			Issuer:    "smart-customer-service",
			Subject:   "access_token",
		},
	}

	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	tokenString, err := token.SignedString(m.secretKey)
	if err != nil {
		return "", time.Time{}, err
	}

	return tokenString, expiresAt, nil
}

// GenerateRefreshToken 生成刷新令牌
func (m *JWTManager) GenerateRefreshToken(userID, tenantID uint) (string, time.Time, error) {
	expiresAt := time.Now().Add(7 * 24 * time.Hour) // 7天有效

	claims := &Claims{
		UserID:   userID,
		TenantID: tenantID,
		RegisteredClaims: jwt.RegisteredClaims{
			ExpiresAt: jwt.NewNumericDate(expiresAt),
			IssuedAt:  jwt.NewNumericDate(time.Now()),
			Issuer:    "smart-customer-service",
			Subject:   "refresh_token",
		},
	}

	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	tokenString, err := token.SignedString(m.secretKey)
	if err != nil {
		return "", time.Time{}, err
	}

	return tokenString, expiresAt, nil
}

// ValidateToken 验证令牌
func (m *JWTManager) ValidateToken(tokenString string) (*Claims, error) {
	token, err := jwt.ParseWithClaims(tokenString, &Claims{}, func(token *jwt.Token) (interface{}, error) {
		// 验证签名方法
		if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, errors.New("无效的签名方法")
		}
		return m.secretKey, nil
	})

	if err != nil {
		return nil, err
	}

	if claims, ok := token.Claims.(*Claims); ok && token.Valid {
		return claims, nil
	}

	return nil, errors.New("无效的令牌")
}

// ParseToken 解析令牌（不验证过期）
func (m *JWTManager) ParseToken(tokenString string) (*Claims, error) {
	parser := jwt.NewParser(jwt.WithoutClaimsValidation())
	token, _, err := parser.ParseUnverified(tokenString, &Claims{})
	if err != nil {
		return nil, err
	}

	if claims, ok := token.Claims.(*Claims); ok {
		return claims, nil
	}

	return nil, errors.New("无法解析令牌声明")
}

// GetTokenExpiration 获取令牌过期时间
func (m *JWTManager) GetTokenExpiration(tokenString string) (time.Time, error) {
	claims, err := m.ParseToken(tokenString)
	if err != nil {
		return time.Time{}, err
	}

	return claims.ExpiresAt.Time, nil
}

// IsTokenExpired 检查令牌是否过期
func (m *JWTManager) IsTokenExpired(tokenString string) (bool, error) {
	expiresAt, err := m.GetTokenExpiration(tokenString)
	if err != nil {
		return true, err
	}

	return time.Now().After(expiresAt), nil
}

// GeneratePasswordResetToken 生成密码重置令牌
func (m *JWTManager) GeneratePasswordResetToken(userID, tenantID uint) (string, time.Time, error) {
	expiresAt := time.Now().Add(1 * time.Hour) // 1小时有效

	claims := &Claims{
		UserID:   userID,
		TenantID: tenantID,
		RegisteredClaims: jwt.RegisteredClaims{
			ExpiresAt: jwt.NewNumericDate(expiresAt),
			IssuedAt:  jwt.NewNumericDate(time.Now()),
			Issuer:    "smart-customer-service",
			Subject:   "password_reset",
		},
	}

	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	tokenString, err := token.SignedString(m.secretKey)
	if err != nil {
		return "", time.Time{}, err
	}

	return tokenString, expiresAt, nil
}

// GenerateEmailVerificationToken 生成邮箱验证令牌
func (m *JWTManager) GenerateEmailVerificationToken(userID, tenantID uint) (string, time.Time, error) {
	expiresAt := time.Now().Add(24 * time.Hour) // 24小时有效

	claims := &Claims{
		UserID:   userID,
		TenantID: tenantID,
		RegisteredClaims: jwt.RegisteredClaims{
			ExpiresAt: jwt.NewNumericDate(expiresAt),
			IssuedAt:  jwt.NewNumericDate(time.Now()),
			Issuer:    "smart-customer-service",
			Subject:   "email_verification",
		},
	}

	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	tokenString, err := token.SignedString(m.secretKey)
	if err != nil {
		return "", time.Time{}, err
	}

	return tokenString, expiresAt, nil
}

// GenerateAPIToken 生成API令牌
func (m *JWTManager) GenerateAPIToken(tenantID uint, permissions []string) (string, time.Time, error) {
	expiresAt := time.Now().Add(30 * 24 * time.Hour) // 30天有效

	claims := &Claims{
		TenantID: tenantID,
		Role:     "api",
		RegisteredClaims: jwt.RegisteredClaims{
			ExpiresAt: jwt.NewNumericDate(expiresAt),
			IssuedAt:  jwt.NewNumericDate(time.Now()),
			Issuer:    "smart-customer-service",
			Subject:   "api_token",
		},
	}

	// 添加自定义声明
	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	
	// 添加权限声明
	token.Claims.(jwt.MapClaims)["permissions"] = permissions

	tokenString, err := token.SignedString(m.secretKey)
	if err != nil {
		return "", time.Time{}, err
	}

	return tokenString, expiresAt, nil
}

// GetTokenClaims 获取令牌声明（安全版本）
func (m *JWTManager) GetTokenClaims(tokenString string) (map[string]interface{}, error) {
	claims, err := m.ValidateToken(tokenString)
	if err != nil {
		return nil, err
	}

	return map[string]interface{}{
		"user_id":   claims.UserID,
		"tenant_id": claims.TenantID,
		"role":      claims.Role,
		"exp":       claims.ExpiresAt.Time.Unix(),
		"iat":       claims.IssuedAt.Time.Unix(),
		"iss":       claims.Issuer,
		"sub":       claims.Subject,
	}, nil
}

// RenewToken 续期令牌
func (m *JWTManager) RenewToken(tokenString string) (string, time.Time, error) {
	claims, err := m.ValidateToken(tokenString)
	if err != nil {
		return "", time.Time{}, err
	}

	// 根据令牌类型续期
	switch claims.Subject {
	case "access_token":
		return m.GenerateAccessToken(claims.UserID, claims.TenantID, claims.Role)
	case "refresh_token":
		return m.GenerateRefreshToken(claims.UserID, claims.TenantID)
	case "api_token":
		// API令牌不自动续期
		return "", time.Time{}, errors.New("API令牌不支持自动续期")
	default:
		return "", time.Time{}, errors.New("未知的令牌类型")
	}
}