package com.example.payments.domain;

import java.math.BigDecimal;
import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.time.Instant;
import java.util.HexFormat;
import java.util.UUID;

public record PaymentCommand(UUID paymentId, String fromAccount, String toAccount, BigDecimal amount,
                             Instant date, String purpose, String notes) {
    public String fingerprint() {
        try {
            var digest=MessageDigest.getInstance("SHA-256");
            for (String value : new String[]{paymentId.toString(),fromAccount,toAccount,amount.toPlainString(),date.toString(),purpose,notes}) {
                // Length framing distinguishes null, empty and embedded delimiters.
                var data=(value==null?"-1:":value.getBytes(StandardCharsets.UTF_8).length+":"+value).getBytes(StandardCharsets.UTF_8);
                digest.update(data);
            }
            return HexFormat.of().formatHex(digest.digest());
        } catch (java.security.NoSuchAlgorithmException impossible) { throw new IllegalStateException(impossible); }
    }
}