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OpenSearch subproject :client:rest
/*
* SPDX-License-Identifier: Apache-2.0
*
* The OpenSearch Contributors require contributions made to
* this file be licensed under the Apache-2.0 license or a
* compatible open source license.
*/
package org.opensearch.client;
import org.apache.http.Header;
import org.apache.http.HttpResponse;
import java.util.ArrayList;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
final class ResponseWarningsExtractor {
/**
* Optimized regular expression to test if a string matches the RFC 1123 date
* format (with quotes and leading space). Start/end of line characters and
* atomic groups are used to prevent backtracking.
*/
private static final Pattern WARNING_HEADER_DATE_PATTERN = Pattern.compile("^ " + // start of line, leading space
// quoted RFC 1123 date format
"\"" + // opening quote
"(?>Mon|Tue|Wed|Thu|Fri|Sat|Sun), " + // day of week, atomic group to prevent backtracking
"\\d{2} " + // 2-digit day
"(?>Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec) " + // month, atomic group to prevent backtracking
"\\d{4} " + // 4-digit year
"\\d{2}:\\d{2}:\\d{2} " + // (two-digit hour):(two-digit minute):(two-digit second)
"GMT" + // GMT
"\"$"); // closing quote (optional, since an older version can still send a warn-date), end of line
/**
* Length of RFC 1123 format (with quotes and leading space), used in
* matchWarningHeaderPatternByPrefix(String).
*/
private static final int WARNING_HEADER_DATE_LENGTH = 0 + 1 + 1 + 3 + 1 + 1 + 2 + 1 + 3 + 1 + 4 + 1 + 2 + 1 + 2 + 1 + 2 + 1 + 3 + 1;
private ResponseWarningsExtractor() {}
/**
* Returns a list of all warning headers returned in the response.
* @param response HTTP response
*/
static List getWarnings(final HttpResponse response) {
List warnings = new ArrayList<>();
for (Header header : response.getHeaders("Warning")) {
String warning = header.getValue();
if (matchWarningHeaderPatternByPrefix(warning)) {
warnings.add(extractWarningValueFromWarningHeader(warning));
} else {
warnings.add(warning);
}
}
return warnings;
}
/**
* Tests if a string matches the RFC 7234 specification for warning headers.
* This assumes that the warn code is always 299 and the warn agent is always
* OpenSearch.
*
* @param s the value of a warning header formatted according to RFC 7234
* @return {@code true} if the input string matches the specification
*/
private static boolean matchWarningHeaderPatternByPrefix(final String s) {
return s.startsWith("299 OpenSearch-");
}
/**
* Refer to org.opensearch.common.logging.DeprecationLogger
*/
private static String extractWarningValueFromWarningHeader(final String s) {
String warningHeader = s;
/*
* The following block tests for the existence of a RFC 1123 date in the warning header. If the date exists, it is removed for
* extractWarningValueFromWarningHeader(String) to work properly (as it does not handle dates).
*/
if (s.length() > WARNING_HEADER_DATE_LENGTH) {
final String possibleDateString = s.substring(s.length() - WARNING_HEADER_DATE_LENGTH);
final Matcher matcher = WARNING_HEADER_DATE_PATTERN.matcher(possibleDateString);
if (matcher.matches()) {
warningHeader = warningHeader.substring(0, s.length() - WARNING_HEADER_DATE_LENGTH);
}
}
final int firstQuote = warningHeader.indexOf('\"');
final int lastQuote = warningHeader.length() - 1;
final String warningValue = warningHeader.substring(firstQuote + 1, lastQuote);
return warningValue;
}
}