public static String replacePlaceholder()

in dubbo-rpc/dubbo-rpc-triple/src/main/java/org/apache/dubbo/rpc/protocol/tri/rest/util/RestUtils.java [56:187]
131 lines of code
40 McCabe index (conditional complexity)

    public static String replacePlaceholder(String text, Function<String, String> resolver) {
        if (text == null) {
            return null;
        }
        int len = text.length();
        if (len < 2) {
            return text;
        }

        int p = 0, nameStart = 0, nameEnd = 0, valueStart = 0, valueEnd = 0;
        String value;
        StringBuilder buf = null;
        int state = State.START;
        for (int i = 0; i < len; i++) {
            char c = text.charAt(i);
            switch (c) {
                case '$':
                    if (state == State.START) {
                        if (buf == null) {
                            buf = new StringBuilder(len);
                        }
                        buf.append(text, p, i);
                        p = i;
                        state = State.DOLLAR;
                    } else if (state == State.DOLLAR) {
                        if (buf == null) {
                            buf = new StringBuilder(len);
                        }
                        buf.append(text, p, i - 1);
                        p = i;
                        state = State.START;
                    }
                    break;
                case '{':
                    state = state == State.DOLLAR ? State.BRACE_OPEN : State.START;
                    break;
                case ':':
                    state = state == State.NAME_START ? State.COLON : State.START;
                    break;
                case '}':
                    switch (state) {
                        case State.DOLLAR:
                        case State.BRACE_OPEN:
                            state = State.START;
                            break;
                        case State.COLON:
                            state = State.START;
                            valueStart = i;
                            break;
                        case State.DOLLAR_NAME_START:
                        case State.NAME_START:
                        case State.VALUE_START:
                            value = resolver.apply(text.substring(nameStart, nameEnd));
                            if (buf == null) {
                                buf = new StringBuilder(len);
                            }
                            if (value == null) {
                                if (state == State.VALUE_START) {
                                    buf.append(text, valueStart, valueEnd);
                                } else {
                                    buf.append(text, p, i + 1);
                                }
                            } else {
                                buf.append(value);
                            }
                            p = i + 1;
                            state = State.START;
                            break;
                        default:
                    }
                    break;
                case ' ':
                case '\t':
                case '\n':
                case '\r':
                    if (state == State.DOLLAR_NAME_START) {
                        state = State.START;
                        value = resolver.apply(text.substring(nameStart, nameEnd));
                        if (buf == null) {
                            buf = new StringBuilder(len);
                        }
                        if (value == null) {
                            buf.append(text, p, i);
                        } else {
                            buf.append(value);
                        }
                        p = i;
                    }
                    break;
                default:
                    switch (state) {
                        case State.DOLLAR:
                            state = State.DOLLAR_NAME_START;
                            nameStart = i;
                            break;
                        case State.BRACE_OPEN:
                            state = State.NAME_START;
                            nameStart = i;
                            break;
                        case State.COLON:
                            state = State.VALUE_START;
                            valueStart = i;
                            break;
                        case State.DOLLAR_NAME_START:
                        case State.NAME_START:
                            nameEnd = i + 1;
                            break;
                        case State.VALUE_START:
                            valueEnd = i + 1;
                            break;
                        default:
                    }
            }
        }
        if (state == State.DOLLAR_NAME_START) {
            value = resolver.apply(text.substring(nameStart, nameEnd));
            if (buf == null) {
                buf = new StringBuilder(len);
            }
            if (value == null) {
                buf.append(text, p, len);
            } else {
                buf.append(value);
            }
        } else {
            if (buf == null) {
                return text;
            }
            buf.append(text, p, len);
        }
        return buf.toString();
    }