Java Client

Code example for Java

import com.fasterxml.jackson.databind.ObjectMapper;

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.time.Instant;
import java.util.HexFormat;
import java.util.Map;

public class PaymentEngineClient {
    private final String apiKey;
    private final String secretKey;
    private final String baseUrl;
    private final HttpClient httpClient;
    private final ObjectMapper mapper;

    public PaymentEngineClient(String apiKey, String secretKey) {
        this(apiKey, secretKey, "https://api.2settle.io");
    }

    public PaymentEngineClient(String apiKey, String secretKey, String baseUrl) {
        this.apiKey = apiKey;
        this.secretKey = secretKey;
        this.baseUrl = baseUrl;
        this.httpClient = HttpClient.newHttpClient();
        this.mapper = new ObjectMapper();
    }

    private SignedRequest sign(String method, String path, Object body) throws Exception {
        String timestamp = String.valueOf(Instant.now().toEpochMilli());
        String bodyStr = mapper.writeValueAsString(body == null ? Map.of() : body);
        String bodyHash = sha256(bodyStr);
        String payload = timestamp + "|" + method + "|" + path + "|" + bodyHash;
        String hmacKey = sha256(secretKey);
        String signature = hmacSha256(hmacKey, payload);

        return new SignedRequest(timestamp, signature, bodyStr);
    }

    private Map<String, Object> request(String method, String path, Object body) throws Exception {
        SignedRequest signed = sign(method, path, body);

        HttpRequest.Builder builder = HttpRequest.newBuilder()
                .uri(URI.create(baseUrl + path))
                .header("Content-Type", "application/json")
                .header("X-API-Key", apiKey)
                .header("X-Timestamp", signed.timestamp())
                .header("X-Signature", signed.signature());

        if ("GET".equals(method)) {
            builder.GET();
        } else {
            builder.method(method, HttpRequest.BodyPublishers.ofString(signed.body()));
        }

        HttpResponse<String> response = httpClient.send(
                builder.build(),
                HttpResponse.BodyHandlers.ofString()
        );

        return mapper.readValue(response.body(), Map.class);
    }

    public Map<String, Object> createPayment(Map<String, Object> options) throws Exception {
        return request("POST", "/v1/payments", options);
    }

    public Map<String, Object> getPayment(String reference) throws Exception {
        return request("GET", "/v1/payments/" + reference, Map.of());
    }

    public Map<String, Object> claimGift(String reference, Map<String, Object> receiver) throws Exception {
        return request(
                "POST",
                "/v1/payments/gifts/" + reference + "/claim/confirm",
                Map.of("receiver", receiver)
        );
    }

    public Map<String, Object> fulfillRequest(
            String reference,
            Map<String, Object> payer,
            String crypto,
            String network
    ) throws Exception {
        return request(
                "POST",
                "/v1/payments/requests/" + reference + "/fulfill",
                Map.of(
                        "payer", payer,
                        "crypto", crypto,
                        "network", network
                )
        );
    }

    private static String sha256(String value) throws Exception {
        MessageDigest digest = MessageDigest.getInstance("SHA-256");
        byte[] hash = digest.digest(value.getBytes(StandardCharsets.UTF_8));
        return HexFormat.of().formatHex(hash);
    }

    private static String hmacSha256(String key, String payload) throws Exception {
        Mac mac = Mac.getInstance("HmacSHA256");
        mac.init(new SecretKeySpec(key.getBytes(StandardCharsets.UTF_8), "HmacSHA256"));
        byte[] hash = mac.doFinal(payload.getBytes(StandardCharsets.UTF_8));
        return HexFormat.of().formatHex(hash);
    }

    private record SignedRequest(String timestamp, String signature, String body) {}

    public static void main(String[] args) throws Exception {
        PaymentEngineClient client = new PaymentEngineClient("pk_xxx", "sk_xxx");

        Map<String, Object> transfer = client.createPayment(Map.of(
                "type", "transfer",
                "fiatAmount", 10000,
                "fiatCurrency", "NGN",
                "crypto", "USDT",
                "network", "trc20",
                "chargeFrom", "fiat",
                "payer", Map.of("chatId", "7389201648"),
                "receiver", Map.of(
                        "bankCode", "090405",
                        "accountNumber", "8012345678"
                )
        ));

        Map<String, Object> payment = (Map<String, Object>) transfer.get("payment");

        System.out.println("Deposit " + payment.get("cryptoAmount") + " USDT to:");
        System.out.println(payment.get("depositAddress"));
    }
}