protected void updateModifiedServerKey()

in sshd-core/src/main/java/org/apache/sshd/client/keyverifier/KnownHostsServerKeyVerifier.java [349:428]
69 lines of code
13 McCabe index (conditional complexity)

    protected void updateModifiedServerKey(
            ClientSession clientSession, SocketAddress remoteAddress, HostEntryPair match, PublicKey actual,
            Path file, Collection<HostEntryPair> knownHosts)
            throws Exception {
        KnownHostEntry entry = match.getHostEntry();
        String matchLine = ValidateUtils.checkNotNullAndNotEmpty(entry.getConfigLine(), "No entry config line");
        String newLine = prepareModifiedServerKeyLine(
                clientSession, remoteAddress, entry, matchLine, match.getServerKey(), actual);
        if (GenericUtils.isEmpty(newLine)) {
            if (log.isDebugEnabled()) {
                log.debug("updateModifiedServerKey({})[{}] no replacement generated for {}",
                        clientSession, remoteAddress, matchLine);
            }
            return;
        }

        if (matchLine.equals(newLine)) {
            if (log.isDebugEnabled()) {
                log.debug("updateModifiedServerKey({})[{}] unmodified updated line for {}",
                        clientSession, remoteAddress, matchLine);
            }
            return;
        }

        List<String> lines = new ArrayList<>();
        synchronized (updateLock) {
            int matchingIndex = -1; // read all lines but replace the updated one
            try (BufferedReader rdr = Files.newBufferedReader(file, StandardCharsets.UTF_8)) {
                for (String line = rdr.readLine(); line != null; line = rdr.readLine()) {
                    // skip if already replaced the original line
                    if (matchingIndex >= 0) {
                        lines.add(line);
                        continue;
                    }
                    line = GenericUtils.trimToEmpty(line);
                    if (GenericUtils.isEmpty(line)) {
                        lines.add(line);
                        continue;
                    }

                    int pos = line.indexOf(ConfigFileReaderSupport.COMMENT_CHAR);
                    if (pos == 0) {
                        lines.add(line);
                        continue;
                    }

                    if (pos > 0) {
                        line = line.substring(0, pos);
                        line = line.trim();
                    }

                    if (!matchLine.equals(line)) {
                        lines.add(line);
                        continue;
                    }

                    lines.add(newLine);
                    matchingIndex = lines.size();
                }
            }

            ValidateUtils.checkTrue(matchingIndex >= 0, "No match found for line=%s", matchLine);

            try (Writer w = Files.newBufferedWriter(file, StandardCharsets.UTF_8)) {
                for (String l : lines) {
                    w.append(l).append(IoUtils.EOL);
                }
            }

            synchronized (match) {
                match.setServerKey(actual);
                entry.setConfigLine(newLine);
            }
        }

        if (log.isDebugEnabled()) {
            log.debug("updateModifiedServerKey({}) replaced '{}' with '{}'", file, matchLine, newLine);
        }
        resetReloadAttributes(); // force reload on next verification
    }