如何使用Golang实现装饰器功能叠加_使用Decorator Pattern增强操作

func FetchData() error {
    fmt.Println("Fetching data...")
    return nil
}

func LogDecorator(f func() error) func() error {
    return func() error {
        fmt.Println("[LOG] Start")
        err := f()
        fmt.Println("[LOG] Done")
        return err
    }
}

func RetryDecorator(f func() error, maxRetries int) func() error {
    return func() error {
        var err error
        for i := 0; i <= maxRetries; i++ {
            err = f()
            if err == nil {
                return nil
            }
            if i < maxRetries {
                fmt.Printf("[RETRY] Attempt %d failed: %v\n", i+1, err)
                time.Sleep(time.Second)
            }
        }
        return err
    }
}

enhanced := RetryDecorator(LogDecorator(FetchData), 2)
enhanced() // 先 log，再 retry 控制

call := CircuitBreakerDecorator(
    MetricsDecorator(
        TimeoutDecorator(httpGet, 5*time.Second),
        "api_fetch"
    ),
    cb
)

type DecoratorOption struct {
    WithTimeout time.Duration
    WithRetries int
    WithLogger  *log.Logger
}

func WithTimeout(d time.Duration) func(*DecoratorOption) {
    return func(o *DecoratorOption) { o.WithTimeout = d }
}

func WithRetries(n int) func(*DecoratorOption) {
    return func(o *DecoratorOption) { o.WithRetries = n }
}

func BuildDecorator(opts ...func(*DecoratorOption)) func(func() error) func() error {
    opt := &DecoratorOption{WithRetries: 1}
    for _, apply := range opts {
        apply(opt)
    }
    return func(f func() error) func() error {
        return RetryDecorator(TimeoutDecorator(f, opt.WithTimeout), opt.WithRetries)
    }
}

decorator := BuildDecorator(WithTimeout(3*time.Second), WithRetries(3))
wrapped := decorator(FetchData)