package jnpf.audit.sdk.aspect;

import jnpf.util.JsonUtil;
import org.springframework.web.context.request.RequestAttributes;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;

import java.nio.charset.StandardCharsets;
import java.util.Base64;
import java.util.List;
import java.util.Map;

/** Resolves the display-only audit title supplied by the scoped online form request wrapper. */
final class AuditRequestTitleResolver {

    static final String HEADER_NAME = "X-Audit-Display-Fields";
    private static final int MAX_HEADER_LENGTH = 8192;
    private static final int MAX_FIELDS = 50;
    private static final int MAX_TITLE_LENGTH = 400;

    private AuditRequestTitleResolver() {
    }

    static String resolveCurrentRequest() {
        RequestAttributes attributes = RequestContextHolder.getRequestAttributes();
        if (!(attributes instanceof ServletRequestAttributes)) {
            return null;
        }
        String encoded = ((ServletRequestAttributes) attributes).getRequest().getHeader(HEADER_NAME);
        return resolveEncoded(encoded);
    }

    static String resolveEncoded(String encoded) {
        if (encoded == null || encoded.isEmpty() || encoded.length() > MAX_HEADER_LENGTH) {
            return null;
        }
        try {
            String json = new String(Base64.getDecoder().decode(encoded), StandardCharsets.UTF_8);
            List<Map> fields = JsonUtil.getJsonToList(json, Map.class);
            StringBuilder title = new StringBuilder();
            int count = 0;
            for (Map field : fields) {
                if (field == null || count++ >= MAX_FIELDS) {
                    break;
                }
                String value = clean(field.get("displayValue"));
                if (value.isEmpty()) {
                    continue;
                }
                int separatorLength = title.length() > 0 ? 1 : 0;
                int remaining = MAX_TITLE_LENGTH - title.length() - separatorLength;
                if (remaining <= 0) {
                    break;
                }
                if (separatorLength > 0) {
                    title.append('/');
                }
                title.append(value, 0, Math.min(value.length(), remaining));
            }
            return title.length() == 0 ? null : title.toString();
        } catch (Throwable ignored) {
            return null;
        }
    }

    private static String clean(Object value) {
        if (value == null) {
            return "";
        }
        return String.valueOf(value).replace('\r', ' ').replace('\n', ' ').trim();
    }
}