package jwt

import (
	"errors"
	"time"

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

// Kind 区分令牌主体：小程序用户 / 后台管理员
type Kind string

const (
	KindUser  Kind = "user"
	KindAdmin Kind = "admin"
)

// Claims 自定义声明，user 与 admin 复用同一结构，用 Kind 区分
type Claims struct {
	ID   string `json:"id"`
	Kind Kind   `json:"kind"`
	Name string `json:"name"`
	Role string `json:"role,omitempty"`
	jwt.RegisteredClaims
}

// Manager 签发/校验令牌
type Manager struct {
	secret      []byte
	expireHours int
}

func NewManager(secret string, expireHours int) *Manager {
	if expireHours <= 0 {
		expireHours = 168
	}
	return &Manager{secret: []byte(secret), expireHours: expireHours}
}

// Generate 签发令牌
func (m *Manager) Generate(id string, kind Kind, name, role string) (string, error) {
	now := time.Now()
	claims := Claims{
		ID:   id,
		Kind: kind,
		Name: name,
		Role: role,
		RegisteredClaims: jwt.RegisteredClaims{
			IssuedAt:  jwt.NewNumericDate(now),
			ExpiresAt: jwt.NewNumericDate(now.Add(time.Duration(m.expireHours) * time.Hour)),
			Issuer:    "pets-be",
		},
	}
	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	return token.SignedString(m.secret)
}

// Parse 校验并解析令牌
func (m *Manager) Parse(tokenStr string) (*Claims, error) {
	token, err := jwt.ParseWithClaims(tokenStr, &Claims{}, func(t *jwt.Token) (any, error) {
		if _, ok := t.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, errors.New("unexpected signing method")
		}
		return m.secret, nil
	})
	if err != nil {
		return nil, err
	}
	claims, ok := token.Claims.(*Claims)
	if !ok || !token.Valid {
		return nil, errors.New("invalid token")
	}
	return claims, nil
}