package middleware

import (
	"context"
	"encoding/json"
	"errors"
	"strconv"
	"strings"
	"time"

	"github.com/go-kratos/kratos/v2/metadata"
	"github.com/go-kratos/kratos/v2/middleware"
	"github.com/go-kratos/kratos/v2/transport"
	"github.com/go-kratos/kratos/v2/transport/http"

	pkgjwt "kra/pkg/jwt"
)

const (
	// metadata keys for claims
	mdKeyUserID      = "x-md-user-id"
	mdKeyUsername    = "x-md-username"
	mdKeyAuthorityID = "x-md-authority-id"
	mdKeyUUID        = "x-md-uuid"
	mdKeyClaims      = "x-md-claims"
)

var (
	ErrMissingToken = errors.New("未登录或非法访问")
	ErrInvalidToken = errors.New("无效的token")
	ErrBlacklistJWT = errors.New("您的帐户异地登陆或令牌失效")
)

// BlacklistChecker JWT黑名单检查接口
type BlacklistChecker interface {
	IsBlacklist(jwt string) bool
}

// JWTAuthConfig JWT认证配置
type JWTAuthConfig struct {
	JWT              *pkgjwt.JWT
	BlacklistChecker BlacklistChecker
	UseMultipoint    bool
	SetRedisJWT      func(token, username string) error
}

// JWTAuth JWT认证中间件
func JWTAuth(cfg JWTAuthConfig) middleware.Middleware {
	return func(handler middleware.Handler) middleware.Handler {
		return func(ctx context.Context, req interface{}) (interface{}, error) {
			if tr, ok := transport.FromServerContext(ctx); ok {
				token := extractToken(tr)
				if token == "" {
					return nil, ErrMissingToken
				}

				// 检查黑名单
				if cfg.BlacklistChecker != nil && cfg.BlacklistChecker.IsBlacklist(token) {
					// 清除token
					if ht, ok := tr.(http.Transporter); ok {
						clearToken(ht)
					}
					return nil, ErrBlacklistJWT
				}

				claims, err := cfg.JWT.ParseToken(token)
				if err != nil {
					if ht, ok := tr.(http.Transporter); ok {
						clearToken(ht)
					}
					if errors.Is(err, pkgjwt.ErrTokenExpired) {
						return nil, errors.New("登录已过期，请重新登录")
					}
					return nil, ErrInvalidToken
				}

				// 将claims存入metadata
				claimsJSON, _ := json.Marshal(claims)
				ctx = metadata.AppendToClientContext(ctx,
					mdKeyUserID, strconv.FormatUint(uint64(claims.BaseClaims.ID), 10),
					mdKeyUsername, claims.Username,
					mdKeyAuthorityID, strconv.FormatUint(uint64(claims.AuthorityID), 10),
					mdKeyUUID, claims.UUID,
					mdKeyClaims, string(claimsJSON),
				)

				// 检查是否需要刷新token
				if cfg.JWT.NeedRefresh(claims) {
					newToken, newClaims, err := cfg.JWT.CreateTokenByOldToken(token, *claims)
					if err == nil {
						if ht, ok := tr.(http.Transporter); ok {
							ht.ReplyHeader().Set("new-token", newToken)
							ht.ReplyHeader().Set("new-expires-at", strconv.FormatInt(newClaims.ExpiresAt.Unix(), 10))
							setToken(ht, newToken, int(time.Until(newClaims.ExpiresAt.Time).Seconds()/60))
						}
						// 多点登录记录新JWT
						if cfg.UseMultipoint && cfg.SetRedisJWT != nil {
							_ = cfg.SetRedisJWT(newToken, newClaims.Username)
						}
					}
				}
			}
			return handler(ctx, req)
		}
	}
}

// JWTAuthSimple 简化版JWT认证中间件（不含黑名单检查）
func JWTAuthSimple(j *pkgjwt.JWT) middleware.Middleware {
	return JWTAuth(JWTAuthConfig{JWT: j})
}

// extractToken 从请求中提取token
func extractToken(tr transport.Transporter) string {
	// 优先从Authorization头获取
	auth := tr.RequestHeader().Get("Authorization")
	if auth != "" {
		if strings.HasPrefix(auth, "Bearer ") {
			return strings.TrimPrefix(auth, "Bearer ")
		}
		return auth
	}

	// 从x-token头获取
	token := tr.RequestHeader().Get("x-token")
	if token != "" {
		return token
	}

	return ""
}

// clearToken 清除token
func clearToken(ht http.Transporter) {
	ht.ReplyHeader().Set("x-token", "")
}

// setToken 设置token到cookie
func setToken(ht http.Transporter, token string, maxAge int) {
	// 通过header设置cookie信息，让前端处理
	ht.ReplyHeader().Set("x-token", token)
}

// GetClaims 从context获取claims
func GetClaims(ctx context.Context) (*pkgjwt.CustomClaims, bool) {
	if md, ok := metadata.FromServerContext(ctx); ok {
		claimsStr := md.Get(mdKeyClaims)
		if claimsStr != "" {
			var claims pkgjwt.CustomClaims
			if err := json.Unmarshal([]byte(claimsStr), &claims); err == nil {
				return &claims, true
			}
		}
	}
	return nil, false
}

// GetUserID 从context获取用户ID
func GetUserID(ctx context.Context) uint {
	if md, ok := metadata.FromServerContext(ctx); ok {
		if idStr := md.Get(mdKeyUserID); idStr != "" {
			if id, err := strconv.ParseUint(idStr, 10, 64); err == nil {
				return uint(id)
			}
		}
	}
	return 0
}

// GetUsername 从context获取用户名
func GetUsername(ctx context.Context) string {
	if md, ok := metadata.FromServerContext(ctx); ok {
		return md.Get(mdKeyUsername)
	}
	return ""
}

// GetAuthorityID 从context获取角色ID
func GetAuthorityID(ctx context.Context) uint {
	if md, ok := metadata.FromServerContext(ctx); ok {
		if idStr := md.Get(mdKeyAuthorityID); idStr != "" {
			if id, err := strconv.ParseUint(idStr, 10, 64); err == nil {
				return uint(id)
			}
		}
	}
	return 0
}

// GetToken 从context获取token
func GetToken(ctx context.Context) string {
	if tr, ok := transport.FromServerContext(ctx); ok {
		return extractToken(tr)
	}
	return ""
}