// Copyright (c) Microsoft Corporation. All rights reserved. // Licensed under the MIT License. package com.azure.core.implementation; import com.azure.core.http.HttpHeaders; import com.azure.core.util.CoreUtils; import com.azure.core.util.DateTimeRfc1123; import java.time.DateTimeException; import java.time.Duration; import java.time.OffsetDateTime; import java.time.temporal.ChronoUnit; import java.util.function.Function; import java.util.function.Supplier; /** * Utility class containing implementation specific methods. */ public final class ImplUtils { private static final String RETRY_AFTER_HEADER = "Retry-After"; private static final String RETRY_AFTER_MS_HEADER = "retry-after-ms"; private static final String X_MS_RETRY_AFTER_MS_HEADER = "x-ms-retry-after-ms"; /** * Attempts to extract a retry after duration from a given set of {@link HttpHeaders}. * <p> * This searches for the well-known retry after headers {@code Retry-After}, {@code retry-after-ms}, and * {@code x-ms-retry-after-ms}. * <p> * If no well-known headers are found null will be returned. * * @param headers The set of headers to search for a well-known retry after header. * @param nowSupplier A supplier for the current time used when {@code Retry-After} is using relative retry after * time. * @return The retry after duration if a well-known retry after header was found, otherwise null. */ public static Duration getRetryAfterFromHeaders(HttpHeaders headers, Supplier<OffsetDateTime> nowSupplier) { // Found 'x-ms-retry-after-ms' header, use a Duration of milliseconds based on the value.  Duration retryDelay = tryGetRetryDelay(headers, X_MS_RETRY_AFTER_MS_HEADER, ImplUtils::tryGetDelayMillis);  if (retryDelay != null) {  return retryDelay; } // Found 'retry-after-ms' header, use a Duration of milliseconds based on the value.  retryDelay = tryGetRetryDelay(headers, RETRY_AFTER_MS_HEADER, ImplUtils::tryGetDelayMillis);  if (retryDelay != null) {  return retryDelay; } // Found 'Retry-After' header. First, attempt to resolve it as a Duration of seconds. If that fails, then // attempt to resolve it as an HTTP date (RFC1123).  retryDelay = tryGetRetryDelay(headers, RETRY_AFTER_HEADER,  headerValue -> tryParseLongOrDateTime(headerValue, nowSupplier));  if (retryDelay != null) {  return retryDelay; } // None of the well-known headers have been found, return null to indicate no retry after.  return null; } private static Duration tryGetRetryDelay(HttpHeaders headers, String headerName, Function<String, Duration> delayParser) {  String headerValue = headers.getValue(headerName);  return CoreUtils.isNullOrEmpty(headerValue) ? null : delayParser.apply(headerValue); } private static Duration tryGetDelayMillis(String value) {  long delayMillis = tryParseLong(value);  return (delayMillis >= 0) ? Duration.ofMillis(delayMillis) : null; } private static Duration tryParseLongOrDateTime(String value, Supplier<OffsetDateTime> nowSupplier) { long delaySeconds; try {  OffsetDateTime retryAfter = new DateTimeRfc1123(value).getDateTime();  delaySeconds = nowSupplier.get().until(retryAfter, ChronoUnit.SECONDS);  } catch (DateTimeException ex) {  delaySeconds = tryParseLong(value);  }  return (delaySeconds >= 0) ? Duration.ofSeconds(delaySeconds) : null; } private static long tryParseLong(String value) { try {  return Long.parseLong(value);  } catch (NumberFormatException ex) {  return -1; } } private ImplUtils() { } } 

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