package middleware

import (
	"context"
	"fmt"
	"net/http"
	"strings"
	"time"

	"github.com/gin-gonic/gin"
	"golang.org/x/sync/singleflight"

	"github.com/user-management-system/internal/auth"
	"github.com/user-management-system/internal/cache"
	"github.com/user-management-system/internal/domain"
	apierrors "github.com/user-management-system/internal/pkg/errors"
)

// Interfaces for dependency inversion (DIP) — middleware depends on these abstractions, not concrete types.
type authUserRepository interface {
	GetByID(ctx context.Context, id int64) (*domain.User, error)
}

type authUserRoleRepository interface {
	GetUserRolesAndPermissions(ctx context.Context, userID int64) ([]*domain.Role, []*domain.Permission, error)
}

type AuthMiddleware struct {
	jwt          *auth.JWT
	userRepo     authUserRepository
	userRoleRepo authUserRoleRepository
	l1Cache      *cache.L1Cache
	cacheManager *cache.CacheManager
	sfGroup      singleflight.Group
}

func NewAuthMiddleware(
	jwt *auth.JWT,
	userRepo authUserRepository,
	userRoleRepo authUserRoleRepository,
	l1Cache *cache.L1Cache,
) *AuthMiddleware {
	return &AuthMiddleware{
		jwt:          jwt,
		userRepo:     userRepo,
		userRoleRepo: userRoleRepo,
		l1Cache:      l1Cache,
	}
}

func (m *AuthMiddleware) SetCacheManager(cm *cache.CacheManager) {
	m.cacheManager = cm
}

func (m *AuthMiddleware) Required() gin.HandlerFunc {
	return func(c *gin.Context) {
		token := m.extractToken(c)
		if token == "" {
			c.JSON(http.StatusUnauthorized, apierrors.New(http.StatusUnauthorized, "UNAUTHORIZED", "未提供认证令牌"))
			c.Abort()
			return
		}

		claims, err := m.jwt.ValidateAccessToken(token)
		if err != nil {
			c.JSON(http.StatusUnauthorized, apierrors.New(http.StatusUnauthorized, "UNAUTHORIZED", "无效的认证令牌"))
			c.Abort()
			return
		}

		if m.isJTIBlacklisted(c.Request.Context(), claims.JTI) {
			c.JSON(http.StatusUnauthorized, apierrors.New(http.StatusUnauthorized, "UNAUTHORIZED", "令牌已失效，请重新登录"))
			c.Abort()
			return
		}

		if m.isPasswordChangedSinceTokenIssued(c.Request.Context(), claims.UserID, claims.PCE) {
			c.JSON(http.StatusUnauthorized, apierrors.New(http.StatusUnauthorized, "UNAUTHORIZED", "密码已更新，请重新登录"))
			c.Abort()
			return
		}

		if !m.isUserActive(c.Request.Context(), claims.UserID) {
			c.JSON(http.StatusUnauthorized, apierrors.New(http.StatusUnauthorized, "UNAUTHORIZED", "账号不可用，请重新登录"))
			c.Abort()
			return
		}

		c.Set("user_id", claims.UserID)
		c.Set("username", claims.Username)
		c.Set("token_jti", claims.JTI)

		roleCodes, permCodes := m.loadUserRolesAndPerms(c.Request.Context(), claims.UserID)
		c.Set("role_codes", roleCodes)
		c.Set("permission_codes", permCodes)

		c.Next()
	}
}

func (m *AuthMiddleware) Optional() gin.HandlerFunc {
	return func(c *gin.Context) {
		token := m.extractToken(c)
		if token != "" {
			claims, err := m.jwt.ValidateAccessToken(token)
			if err == nil && !m.isJTIBlacklisted(c.Request.Context(), claims.JTI) && !m.isPasswordChangedSinceTokenIssued(c.Request.Context(), claims.UserID, claims.PCE) && m.isUserActive(c.Request.Context(), claims.UserID) {
				c.Set("user_id", claims.UserID)
				c.Set("username", claims.Username)
				c.Set("token_jti", claims.JTI)
				roleCodes, permCodes := m.loadUserRolesAndPerms(c.Request.Context(), claims.UserID)
				c.Set("role_codes", roleCodes)
				c.Set("permission_codes", permCodes)
			}
		}

		c.Next()
	}
}

func (m *AuthMiddleware) isJTIBlacklisted(ctx context.Context, jti string) bool {
	if jti == "" {
		return false
	}

	key := "jwt_blacklist:" + jti

	// 先检查 L1 缓存
	if _, ok := m.l1Cache.Get(key); ok {
		return true
	}

	// L1 miss 时使用 singleflight 防止缓存击穿
	// 多个并发请求只会触发一次 L2 查询
	if m.cacheManager != nil {
		val, err, _ := m.sfGroup.Do(key, func() (interface{}, error) {
			found, _ := m.cacheManager.Get(ctx, key)
			return found, nil
		})
		if err == nil && val != nil {
			// 回写 L1 缓存
			m.l1Cache.Set(key, true, 5*time.Minute)
			return true
		}
	}

	return false
}

// isPasswordChangedSinceTokenIssued 检查用户密码是否在令牌发放后已更改
// 如果 tokenPCE 为 0（旧令牌），则不检查（向后兼容）
func (m *AuthMiddleware) isPasswordChangedSinceTokenIssued(ctx context.Context, userID int64, tokenPCE int64) bool {
	if tokenPCE == 0 {
		// 旧令牌没有密码变更时间戳，不拦截
		return false
	}

	if m.userRepo == nil {
		return false
	}

	user, err := m.userRepo.GetByID(ctx, userID)
	if err != nil || user.PasswordChangedAt.IsZero() {
		return false
	}

	// 如果令牌的 PCE < 用户密码变更时间，说明密码在令牌发放后已更改
	return tokenPCE < user.PasswordChangedAt.Unix()
}

func (m *AuthMiddleware) loadUserRolesAndPerms(ctx context.Context, userID int64) ([]string, []string) {
	if m.userRoleRepo == nil {
		return nil, nil
	}

	cacheKey := fmt.Sprintf("user_perms:%d", userID)
	if cached, ok := m.l1Cache.Get(cacheKey); ok {
		if entry, ok := cached.(userPermEntry); ok {
			return entry.roles, entry.perms
		}
	}

	// 使用已优化的单次 JOIN 查询获取用户角色和权限
	roles, permissions, err := m.userRoleRepo.GetUserRolesAndPermissions(ctx, userID)
	if err != nil || len(roles) == 0 {
		return nil, nil
	}

	roleCodes := make([]string, 0, len(roles))
	for _, role := range roles {
		roleCodes = append(roleCodes, role.Code)
	}

	permCodes := make([]string, 0, len(permissions))
	for _, perm := range permissions {
		permCodes = append(permCodes, perm.Code)
	}

	m.l1Cache.Set(cacheKey, userPermEntry{roles: roleCodes, perms: permCodes}, 30*time.Minute)
	return roleCodes, permCodes
}

func (m *AuthMiddleware) InvalidateUserPermCache(userID int64) {
	m.l1Cache.Delete(fmt.Sprintf("user_perms:%d", userID))
}

func (m *AuthMiddleware) AddToBlacklist(jti string, ttl time.Duration) {
	if jti != "" && ttl > 0 {
		m.l1Cache.Set("jwt_blacklist:"+jti, true, ttl)
	}
}

func (m *AuthMiddleware) isUserActive(ctx context.Context, userID int64) bool {
	if m.userRepo == nil {
		return true
	}

	user, err := m.userRepo.GetByID(ctx, userID)
	if err != nil {
		return false
	}

	return user.Status == domain.UserStatusActive
}

func (m *AuthMiddleware) extractToken(c *gin.Context) string {
	authHeader := c.GetHeader("Authorization")
	if authHeader == "" {
		return ""
	}

	parts := strings.SplitN(authHeader, " ", 2)
	if len(parts) != 2 || parts[0] != "Bearer" {
		return ""
	}

	return parts[1]
}

type userPermEntry struct {
	roles []string
	perms []string
}