package middleware

import (
	"context"
	"errors"
	"net/http"
	"server/internal/config"
	"server/internal/pkg/errs"
	"server/internal/pkg/httputil"
	"strings"
	"time"

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

type JWTMiddleware struct {
	cfg *config.JWTConfig
}

type contextKey string

const UserContextKey contextKey = "user"

const RefreshTokenType = "refresh"

type Claims struct {
	UserID int32 `json:"user_id"`
	jwt.RegisteredClaims
}

type RefreshClaims struct {
	UserID int32  `json:"user_id"`
	Type   string `json:"type"`
	jwt.RegisteredClaims
}

func NewJWTMiddleware(cfg *config.Config) *JWTMiddleware {
	jwtCfg := cfg.JWTConfig

	return &JWTMiddleware{cfg: &jwtCfg}
}

func GetClaims(ctx context.Context) (*Claims, bool) {
	claims, ok := ctx.Value(UserContextKey).(*Claims)
	return claims, ok
}

// ParseToken 解析accessToken
func (m *JWTMiddleware) ParseToken(tokenStr string) (*Claims, error) {
	token, err := jwt.ParseWithClaims(
		tokenStr,
		&Claims{},
		func(token *jwt.Token) (interface{}, error) {
			return []byte(m.cfg.Secret), nil
		},
	)

	if err != nil || !token.Valid {
		return nil, errs.ErrInvalidToken
	}

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

	if claims.UserID == 0 {
		return nil, errs.ErrInvalidTokenClaims
	}

	return claims, nil
}

// ParseRefreshToken 解析RefreshToken
func (m *JWTMiddleware) ParseRefreshToken(tokenStr string) (*RefreshClaims, error) {
	token, err := jwt.ParseWithClaims(
		tokenStr,
		&RefreshClaims{},
		func(token *jwt.Token) (interface{}, error) {
			return []byte(m.cfg.Secret), nil
		},
	)

	if err != nil {
		// Token 已过期
		if errors.Is(err, jwt.ErrTokenExpired) {
			return nil, errs.ErrExpiredRefreshToken
		}

		// 签名错误、格式错误、非法 Token
		return nil, errs.ErrInvalidRefreshToken
	}

	if !token.Valid {
		return nil, errs.ErrInvalidRefreshToken
	}

	claims, ok := token.Claims.(*RefreshClaims)
	if !ok {
		return nil, errs.ErrInvalidRefreshToken
	}

	if claims.UserID == 0 {
		return nil, errs.ErrInvalidRefreshToken
	}

	if claims.Type != RefreshTokenType {
		return nil, errs.ErrInvalidRefreshToken
	}

	return claims, nil
}

func (m *JWTMiddleware) Middleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		auth := r.Header.Get("Authorization")

		if auth == "" {
			httputil.Fail(w, errs.ErrUnauthenticated)
			return
		}

		parts := strings.SplitN(auth, " ", 2)
		if len(parts) != 2 || parts[0] != "Bearer" {
			httputil.Fail(w, errs.ErrUnauthenticated)
			return
		}

		tokenStr := parts[1]

		claims, err := m.ParseToken(tokenStr)
		if err != nil {
			httputil.Fail(w, errs.ErrInvalidToken)
			return
		}

		ctx := context.WithValue(r.Context(), UserContextKey, claims)

		next.ServeHTTP(w, r.WithContext(ctx))
	})
}

func (m *JWTMiddleware) GenerateAccessToken(userID int32) (string, time.Time, error) {
	now := time.Now()
	expiresAt := now.Add(m.cfg.Expire)

	accessClaims := Claims{
		UserID: userID,
		RegisteredClaims: jwt.RegisteredClaims{
			ExpiresAt: jwt.NewNumericDate(expiresAt),
			IssuedAt:  jwt.NewNumericDate(now),
		},
	}

	accessToken := jwt.NewWithClaims(jwt.SigningMethodHS256, accessClaims)
	token, err := accessToken.SignedString([]byte(m.cfg.Secret))
	if err != nil {
		return "", time.Time{}, err
	}

	return token, expiresAt, nil
}

func (m *JWTMiddleware) GenerateRefreshToken(userID int32) (string, time.Time, error) {
	now := time.Now()
	expiresAt := now.Add(m.cfg.RefreshExpire)

	refreshClaims := RefreshClaims{
		UserID: userID,
		Type:   RefreshTokenType,
		RegisteredClaims: jwt.RegisteredClaims{
			ExpiresAt: jwt.NewNumericDate(expiresAt),
			IssuedAt:  jwt.NewNumericDate(now),
		},
	}

	refreshToken := jwt.NewWithClaims(jwt.SigningMethodHS256, refreshClaims)
	token, err := refreshToken.SignedString([]byte(m.cfg.Secret))
	if err != nil {
		return "", time.Time{}, err
	}

	return token, expiresAt, nil
}