import java.util.concurrent.TimeUnit;
import java.util.function.Supplier;

public class RetryUtils {
    private static final long BASE_WAIT_MS = 500;
    private static final int MAX_ATTEMPTS = 5;
    
    public static <T> T executeWithRetry(Supplier<T> supplier) throws NetworkException {
        int attempt = 0;
        while (true) {
            try {
                return supplier.get();
            } catch (Exception e) {
                attempt++;
                if (attempt >= MAX_ATTEMPTS) {
                    throw new NetworkException("重试失败，已达最大重试次数", e);
                }
                
                long waitTime = calculateWaitTime(attempt);
                System.out.println("重试失败，等待 " + waitTime + "ms 后重试... (第 " + attempt + " 次尝试)");
                
                try {
                    TimeUnit.MILLISECONDS.sleep(waitTime);
                } catch (InterruptedException ie) {
                    Thread.currentThread().interrupt();
                    throw new NetworkException("重试被中断", ie);
                }
            }
        }
    }
    
    private static long calculateWaitTime(int attempt) {
        // 指数退避公式：wait = base * 2^attempt
        return BASE_WAIT_MS * (long) Math.pow(2, attempt);
    }
}