protected Object decode()

in dubbo-remoting/dubbo-remoting-api/src/main/java/org/apache/dubbo/remoting/telnet/codec/TelnetCodec.java [170:300]
128 lines of code
43 McCabe index (conditional complexity)

    protected Object decode(Channel channel, ChannelBuffer buffer, int readable, byte[] message) throws IOException {
        if (isClientSide(channel)) {
            return toString(message, getCharset(channel));
        }
        checkPayload(channel, readable);
        if (message == null || message.length == 0) {
            return DecodeResult.NEED_MORE_INPUT;
        }

        if (message[message.length - 1] == '\b') { // Windows backspace echo
            try {
                boolean isDoubleChar = message.length >= 3 && message[message.length - 3] < 0; // double byte char
                channel.send(new String(
                        isDoubleChar ? new byte[] {32, 32, 8, 8} : new byte[] {32, 8},
                        getCharset(channel).name()));
            } catch (RemotingException e) {
                throw new IOException(StringUtils.toString(e));
            }
            return DecodeResult.NEED_MORE_INPUT;
        }

        for (Object command : EXIT) {
            if (isEquals(message, (byte[]) command)) {
                if (logger.isInfoEnabled()) {
                    logger.info(new Exception(
                            "Close channel " + channel + " on exit command: " + Arrays.toString((byte[]) command)));
                }
                channel.close();
                return null;
            }
        }

        boolean up = endsWith(message, UP);
        boolean down = endsWith(message, DOWN);
        if (up || down) {
            LinkedList<String> history = (LinkedList<String>) channel.getAttribute(HISTORY_LIST_KEY);
            if (CollectionUtils.isEmpty(history)) {
                return DecodeResult.NEED_MORE_INPUT;
            }
            Integer index = (Integer) channel.getAttribute(HISTORY_INDEX_KEY);
            Integer old = index;
            if (index == null) {
                index = history.size() - 1;
            } else {
                if (up) {
                    index = index - 1;
                    if (index < 0) {
                        index = history.size() - 1;
                    }
                } else {
                    index = index + 1;
                    if (index > history.size() - 1) {
                        index = 0;
                    }
                }
            }
            if (old == null || !old.equals(index)) {
                channel.setAttribute(HISTORY_INDEX_KEY, index);
                String value = history.get(index);
                if (old != null && old >= 0 && old < history.size()) {
                    String ov = history.get(old);
                    StringBuilder buf = new StringBuilder();
                    for (int i = 0; i < ov.length(); i++) {
                        buf.append('\b');
                    }
                    for (int i = 0; i < ov.length(); i++) {
                        buf.append(' ');
                    }
                    for (int i = 0; i < ov.length(); i++) {
                        buf.append('\b');
                    }
                    value = buf + value;
                }
                try {
                    channel.send(value);
                } catch (RemotingException e) {
                    throw new IOException(StringUtils.toString(e));
                }
            }
            return DecodeResult.NEED_MORE_INPUT;
        }
        for (Object command : EXIT) {
            if (isEquals(message, (byte[]) command)) {
                if (logger.isInfoEnabled()) {
                    logger.info(new Exception("Close channel " + channel + " on exit command " + command));
                }
                channel.close();
                return null;
            }
        }
        byte[] enter = null;
        for (Object command : ENTER) {
            if (endsWith(message, (byte[]) command)) {
                enter = (byte[]) command;
                break;
            }
        }
        if (enter == null) {
            return DecodeResult.NEED_MORE_INPUT;
        }
        LinkedList<String> history = (LinkedList<String>) channel.getAttribute(HISTORY_LIST_KEY);
        Integer index = (Integer) channel.getAttribute(HISTORY_INDEX_KEY);
        channel.removeAttribute(HISTORY_INDEX_KEY);
        if (CollectionUtils.isNotEmpty(history) && index != null && index >= 0 && index < history.size()) {
            String value = history.get(index);
            if (value != null) {
                byte[] b1 = value.getBytes();
                byte[] b2 = new byte[b1.length + message.length];
                System.arraycopy(b1, 0, b2, 0, b1.length);
                System.arraycopy(message, 0, b2, b1.length, message.length);
                message = b2;
            }
        }
        String result = toString(message, getCharset(channel));
        if (result.trim().length() > 0) {
            if (history == null) {
                history = new LinkedList<>();
                channel.setAttribute(HISTORY_LIST_KEY, history);
            }
            if (history.isEmpty()) {
                history.addLast(result);
            } else if (!result.equals(history.getLast())) {
                history.remove(result);
                history.addLast(result);
                if (history.size() > 10) {
                    history.removeFirst();
                }
            }
        }
        return result;
    }