package vn.sis.appointment;

import java.util.Collection;
import java.util.Map;

final class Json {
    private Json() {
    }

    static String stringify(Object value) {
        if (value == null) {
            return "null";
        }
        if (value instanceof String text) {
            return quote(text);
        }
        if (value instanceof Number || value instanceof Boolean) {
            return value.toString();
        }
        if (value instanceof Map<?, ?> map) {
            StringBuilder builder = new StringBuilder("{");
            boolean first = true;
            for (Map.Entry<?, ?> entry : map.entrySet()) {
                if (!first) {
                    builder.append(',');
                }
                first = false;
                builder.append(quote(String.valueOf(entry.getKey())))
                        .append(':')
                        .append(stringify(entry.getValue()));
            }
            return builder.append('}').toString();
        }
        if (value instanceof Collection<?> collection) {
            StringBuilder builder = new StringBuilder("[");
            boolean first = true;
            for (Object item : collection) {
                if (!first) {
                    builder.append(',');
                }
                first = false;
                builder.append(stringify(item));
            }
            return builder.append(']').toString();
        }
        return quote(value.toString());
    }

    static String quote(String value) {
        StringBuilder builder = new StringBuilder(value.length() + 16).append('"');
        for (int i = 0; i < value.length(); i++) {
            char ch = value.charAt(i);
            switch (ch) {
                case '"' -> builder.append("\\\"");
                case '\\' -> builder.append("\\\\");
                case '\b' -> builder.append("\\b");
                case '\f' -> builder.append("\\f");
                case '\n' -> builder.append("\\n");
                case '\r' -> builder.append("\\r");
                case '\t' -> builder.append("\\t");
                default -> {
                    if (ch < 0x20) {
                        builder.append(String.format("\\u%04x", (int) ch));
                    } else {
                        builder.append(ch);
                    }
                }
            }
        }
        return builder.append('"').toString();
    }
}