快速指南：通过Go语言实现简单权限系统

type User struct {
    ID    int
    Name  string
    Roles []Role
}

type Role struct {
    ID          int
    Name        string
    Permissions []Permission
}

type Permission struct {
    ID   int
    Name string
}

func AuthMiddleware(requiredPermission string) func(http.Handler) http.Handler {
    return func(next http.Handler) http.Handler {
        return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
            // 提取用户信息，例如从JWT中
            user := GetUserFromRequest(r)

            // 检查用户是否拥有权限
            if !HasPermission(user, requiredPermission) {
                http.Error(w, "Unauthorized", http.StatusUnauthorized)
                return
            }

            // 继续处理请求
            next.ServeHTTP(w, r)
        })
    }
}

func HasPermission(user User, permissionName string) bool {
    for _, role := range user.Roles {
        for _, permission := range role.Permissions {
            if permission.Name == permissionName {
                return true
            }
        }
    }
    return false
}

http.Handle("/admin", AuthMiddleware("admin.read")(http.HandlerFunc(AdminHandler)))

const (
    PermissionRead   = 1 << 0 // 1
    PermissionWrite  = 1 << 1 // 2
    PermissionDelete = 1 << 2 // 4
)

type User struct {
    Permissions int
}

func HasPermission(user User, permission int) bool {
    return (user.Permissions & permission) == permission
}

// 使用示例
user := User{Permissions: PermissionRead | PermissionWrite}
if HasPermission(user, PermissionRead) {
    // ...
}

// 假设使用CEL (Common Expression Language)
import "github.com/google/cel-go/cel"

func HasPermission(user User, expression string) (bool, error) {
    env, err := cel.NewEnv(
        cel.Variable("user", cel.ObjectType("User")),
    )
    if err != nil {
        return false, err
    }

    ast, issues := env.Compile(expression)
    if issues != nil && issues.Err() != nil {
        return false, issues.Err()
    }

    prg, err := env.Program(ast)
    if err != nil {
        return false, err
    }

    out, _, err := prg.Eval(map[string]interface{}{
        "user": user,
    })
    if err != nil {
        return false, err
    }

    return out.Value().(bool), nil
}

// 使用示例
user := User{ /* ... */ }
hasPermission, err := HasPermission(user, "user.Role == 'admin' || user.Age > 18")
if err != nil {
    // ...
}