package service

import (
	"context"
	"fmt"
	"time"

	"carrot_bbs/internal/cache"
	"carrot_bbs/internal/config"
	"carrot_bbs/internal/repository"

	"github.com/casbin/casbin/v2"
)

// CasbinService Casbin 权限服务接口
type CasbinService interface {
	// Enforce 检查权限
	Enforce(ctx context.Context, sub, obj, act string) (bool, error)

	// EnforceForUser 检查用户权限 (自动获取用户角色)
	EnforceForUser(ctx context.Context, userID, obj, act string) (bool, error)

	// AddRoleForUser 为用户添加角色
	AddRoleForUser(ctx context.Context, userID, role string) error

	// DeleteRoleForUser 移除用户角色
	DeleteRoleForUser(ctx context.Context, userID, role string) error

	// GetRolesForUser 获取用户所有角色
	GetRolesForUser(ctx context.Context, userID string) ([]string, error)

	// HasRoleForUser 检查用户是否拥有指定角色
	HasRoleForUser(ctx context.Context, userID, role string) (bool, error)

	// AddPolicy 添加策略
	AddPolicy(ctx context.Context, role, resource, action string) error

	// RemovePolicy 移除策略
	RemovePolicy(ctx context.Context, role, resource, action string) error

	// LoadPolicy 从数据库重新加载策略
	LoadPolicy(ctx context.Context) error

	// ClearCache 清除权限缓存
	ClearCache(ctx context.Context) error
}

type casbinService struct {
	enforcer   *casbin.Enforcer
	cache      cache.Cache
	cacheTTL   time.Duration
	roleRepo   repository.RoleRepository
	skipRoutes map[string]bool
}

func NewCasbinService(
	enforcer *casbin.Enforcer,
	cache cache.Cache,
	roleRepo repository.RoleRepository,
	cfg *config.CasbinConfig,
) CasbinService {
	skipRoutes := make(map[string]bool)
	for _, route := range cfg.SkipRoutes {
		skipRoutes[route] = true
	}

	return &casbinService{
		enforcer:   enforcer,
		cache:      cache,
		cacheTTL:   time.Duration(cfg.CacheTTL) * time.Second,
		roleRepo:   roleRepo,
		skipRoutes: skipRoutes,
	}
}

func (s *casbinService) Enforce(ctx context.Context, sub, obj, act string) (bool, error) {
	// 检查是否跳过权限检查
	if s.skipRoutes[obj] {
		return true, nil
	}

	// 检查缓存
	if s.cache != nil {
		cacheKey := fmt.Sprintf("casbin:check:%s:%s:%s", sub, obj, act)
		if cached, ok := s.cache.Get(cacheKey); ok {
			if allowed, ok := cached.(bool); ok {
				return allowed, nil
			}
		}
	}

	// 执行权限检查
	allowed, err := s.enforcer.Enforce(sub, obj, act)
	if err != nil {
		return false, err
	}

	// 缓存结果
	if s.cache != nil {
		cacheKey := fmt.Sprintf("casbin:check:%s:%s:%s", sub, obj, act)
		s.cache.Set(cacheKey, allowed, s.cacheTTL)
	}

	return allowed, nil
}

func (s *casbinService) EnforceForUser(ctx context.Context, userID, obj, act string) (bool, error) {
	// 获取用户角色
	roles, err := s.GetRolesForUser(ctx, userID)
	if err != nil {
		return false, err
	}

	// 如果用户没有角色，使用默认角色
	if len(roles) == 0 {
		roles = []string{"user"} // 默认角色
	}

	// 检查每个角色的权限
	for _, role := range roles {
		allowed, err := s.Enforce(ctx, role, obj, act)
		if err != nil {
			return false, err
		}
		if allowed {
			return true, nil
		}
	}

	return false, nil
}

func (s *casbinService) AddRoleForUser(ctx context.Context, userID, role string) error {
	// 添加到数据库
	if err := s.roleRepo.AddRoleForUser(ctx, userID, role); err != nil {
		return err
	}

	// 添加到 Casbin
	if _, err := s.enforcer.AddRoleForUser(userID, role); err != nil {
		return err
	}

	// 清除缓存
	return s.clearUserCache(ctx, userID)
}

func (s *casbinService) DeleteRoleForUser(ctx context.Context, userID, role string) error {
	// 从数据库删除
	if err := s.roleRepo.DeleteRoleForUser(ctx, userID, role); err != nil {
		return err
	}

	// 从 Casbin 删除
	if _, err := s.enforcer.DeleteRoleForUser(userID, role); err != nil {
		return err
	}

	// 清除缓存
	return s.clearUserCache(ctx, userID)
}

func (s *casbinService) GetRolesForUser(ctx context.Context, userID string) ([]string, error) {
	// 检查缓存
	if s.cache != nil {
		cacheKey := fmt.Sprintf("casbin:user:roles:%s", userID)
		if cached, ok := s.cache.Get(cacheKey); ok {
			if roles, ok := cached.([]string); ok {
				return roles, nil
			}
		}
	}

	// 从数据库获取
	roles, err := s.roleRepo.GetUserRoles(ctx, userID)
	if err != nil {
		return nil, err
	}

	// 缓存结果
	if s.cache != nil {
		cacheKey := fmt.Sprintf("casbin:user:roles:%s", userID)
		s.cache.Set(cacheKey, roles, s.cacheTTL)
	}

	return roles, nil
}

func (s *casbinService) HasRoleForUser(ctx context.Context, userID, role string) (bool, error) {
	return s.roleRepo.HasRole(ctx, userID, role)
}

func (s *casbinService) AddPolicy(ctx context.Context, role, resource, action string) error {
	if _, err := s.enforcer.AddPolicy(role, resource, action); err != nil {
		return err
	}
	return s.ClearCache(ctx)
}

func (s *casbinService) RemovePolicy(ctx context.Context, role, resource, action string) error {
	if _, err := s.enforcer.RemovePolicy(role, resource, action); err != nil {
		return err
	}
	return s.ClearCache(ctx)
}

func (s *casbinService) LoadPolicy(ctx context.Context) error {
	return s.enforcer.LoadPolicy()
}

func (s *casbinService) ClearCache(ctx context.Context) error {
	if s.cache != nil {
		// 清除所有 casbin 相关缓存
		s.cache.DeleteByPrefix("casbin:")
	}
	return nil
}

func (s *casbinService) clearUserCache(ctx context.Context, userID string) error {
	if s.cache != nil {
		cacheKey := fmt.Sprintf("casbin:user:roles:%s", userID)
		s.cache.Delete(cacheKey)
	}
	return nil
}