package com.mydreamjob.salarycalculator;

import com.mydreamjob.salarycalculator.dto.SalaryCalculationOverrideRequest;
import com.mydreamjob.salarycalculator.dto.SalaryCalculationRequest;
import org.springframework.stereotype.Component;

import java.math.BigDecimal;
import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.HexFormat;

@Component
public class SalaryRequestFingerprint {

    public String fingerprint(SalaryCalculationRequest request) {
        StringBuilder canonical = new StringBuilder();
        append(canonical, normalize(request.getCityCode()));
        append(canonical, normalize(request.getExpectedPolicyVersion()));
        append(canonical, decimal(request.getGrossMonthlySalary()));
        append(canonical, String.valueOf(request.getMonthIndex() == null ? 1 : request.getMonthIndex()));
        append(canonical, decimal(request.getSpecialAdditionalDeduction() == null
                ? BigDecimal.ZERO : request.getSpecialAdditionalDeduction()));
        SalaryCalculationOverrideRequest overrides = request.getOverrides();
        if (overrides == null) {
            for (int i = 0; i < 7; i++) {
                append(canonical, "");
            }
        } else {
            append(canonical, decimal(overrides.getSocialSecurityBase()));
            append(canonical, decimal(overrides.getHousingFundBase()));
            append(canonical, decimal(overrides.getPensionRate()));
            append(canonical, decimal(overrides.getMedicalRate()));
            append(canonical, decimal(overrides.getUnemploymentRate()));
            append(canonical, decimal(overrides.getHousingFundRate()));
            append(canonical, decimal(overrides.getSeriousIllnessMonthlyFee()));
        }
        return sha256(canonical.toString());
    }

    private void append(StringBuilder builder, String value) {
        builder.append(value.length()).append(':').append(value).append('|');
    }

    private String normalize(String value) {
        return value == null ? "" : value.trim();
    }

    private String decimal(BigDecimal value) {
        if (value == null) {
            return "";
        }
        BigDecimal normalized = value.stripTrailingZeros();
        if (normalized.scale() < 0) {
            normalized = normalized.setScale(0);
        }
        return normalized.toPlainString();
    }

    private String sha256(String value) {
        try {
            MessageDigest digest = MessageDigest.getInstance("SHA-256");
            return HexFormat.of().formatHex(digest.digest(value.getBytes(StandardCharsets.UTF_8)));
        } catch (NoSuchAlgorithmException ex) {
            throw new IllegalStateException("SHA-256 is unavailable", ex);
        }
    }
}