package com.example.demo.wykop;

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.http.HttpRequest;
import org.springframework.http.client.ClientHttpRequestExecution;
import org.springframework.http.client.ClientHttpRequestInterceptor;
import org.springframework.http.client.ClientHttpResponse;

import java.io.IOException;
import java.math.BigInteger;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Objects;
import java.util.stream.StreamSupport;

import static java.util.stream.Collectors.joining;

public class WykopApiSigningInterceptor implements ClientHttpRequestInterceptor {

    private static final String API_SIGN_HEADER = "apisign";

    private final ObjectMapper objectMapper;
    private final String secret;

    public WykopApiSigningInterceptor(ObjectMapper objectMapper, String secret) {
        this.objectMapper = objectMapper;
        this.secret = secret;
    }

    @Override
    public ClientHttpResponse intercept(HttpRequest request, byte[] body, ClientHttpRequestExecution execution) throws IOException {
        var url = request.getURI().toASCIIString();
        var paramValues = extractParamValues(objectMapper.readTree(body));
        signRequest(request, secret, url, paramValues);
        return execution.execute(request, body);
    }

    private static void signRequest(HttpRequest request, String secret, String url, String paramValues) {
        try {
            MessageDigest md = MessageDigest.getInstance("MD5");
            md.update((secret + url + paramValues).getBytes());
            System.out.println(secret);
            var md5Sum = String.format("%032x", new BigInteger(1, md.digest()));
            request.getHeaders().add(API_SIGN_HEADER, md5Sum);
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException(e);
        }
    }

    private static String extractParamValues(JsonNode body) {
        return StreamSupport.stream(body.spliterator(), false)
                .map(JsonNode::textValue)
                .filter(Objects::nonNull)
                .collect(joining(","));
    }
}