Legacy-Extraktions-Lab

package com.example.legacy.run7b;

public final class ResponsibilityRefactoringDemo {
    public static void main(String[] args) {
        LegacyOrderProcessor legacy = new LegacyOrderProcessor();
        for (OrderRequest request : OrderScenarioCatalog.scenarios()) {
            FakeInvoiceAdapter invoice = new FakeInvoiceAdapter();
            CollectingAuditAdapter audit = new CollectingAuditAdapter();
            RefactoredOrderApplicationService service = RefactoringFactory.create(invoice, audit);
            System.out.println("SCENARIO " + request.orderId());
            System.out.println(" legacy     = " + legacy.process(request));
            System.out.println(" refactored = " + service.process(request).compact());
            System.out.println(" audit      = " + audit.events());
        }
    }
}

package com.example.legacy.run7b;

import java.math.BigDecimal;

// Absichtlich unangenehmer Legacy-Code: mehrere Verantwortungen, Seiteneffekte und fachliche Regeln in einer Methode.
public final class LegacyOrderProcessor {
    public String process(OrderRequest request) {
        if (request.segment() == CustomerSegment.BLOCKED) return "REJECTED|CUSTOMER_BLOCKED";
        if (request.lines().isEmpty()) return "REJECTED|EMPTY_ORDER";
        if (request.segment() == CustomerSegment.B2B && request.shippingCountry() != Country.US && (request.vatId() == null || request.vatId().isBlank())) {
            return "REJECTED|VAT_ID_REQUIRED";
        }
        Money subtotal = Money.eur("0");
        int weight = 0;
        boolean onlyDigital = true;
        for (OrderLine line : request.lines()) {
            if (line.quantity() > 100) return "REJECTED|LINE_QTY_LIMIT";
            subtotal = subtotal.add(line.lineTotal());
            weight += line.totalWeight();
            onlyDigital = onlyDigital && line.digital();
        }
        Money discount = Money.eur("0");
        if (request.segment() == CustomerSegment.VIP) discount = discount.add(subtotal.multiply(new BigDecimal("0.10")));
        if (request.couponCode() != null && request.channel() != OrderChannel.PARTNER_PORTAL) {
            if (request.couponCode().equals("SAVE5")) discount = discount.add(Money.eur("5"));
            if (request.couponCode().equals("WELCOME15")) discount = discount.add(subtotal.multiply(new BigDecimal("0.15")));
        }
        if (request.segment() == CustomerSegment.B2B && subtotal.amount().compareTo(new BigDecimal("1000.00")) >= 0) {
            discount = discount.add(subtotal.multiply(new BigDecimal("0.07")));
        }
        if (discount.greaterThan(subtotal)) discount = subtotal;
        Money afterDiscount = subtotal.subtract(discount);
        Money shipping = Money.eur("0");
        if (!onlyDigital) {
            shipping = switch (request.shippingCountry()) { case AT, DE -> Money.eur("6.90"); case CH -> Money.eur("14.90"); case US -> Money.eur("29.90"); };
            if (afterDiscount.amount().compareTo(new BigDecimal("250.00")) >= 0 && request.shippingCountry() != Country.US) shipping = Money.eur("0");
            if (weight > 10_000) shipping = shipping.add(Money.eur("12.00"));
        }
        Money taxableBase = afterDiscount.add(shipping);
        Money tax;
        if (request.segment() == CustomerSegment.B2B && request.vatId() != null && request.shippingCountry() != Country.AT) tax = Money.eur("0");
        else {
            BigDecimal rate = switch (request.shippingCountry()) { case AT -> new BigDecimal("0.20"); case DE -> new BigDecimal("0.19"); case CH -> new BigDecimal("0.081"); case US -> BigDecimal.ZERO; };
            tax = taxableBase.multiply(rate);
        }
        Money total = taxableBase.add(tax);
        if (total.amount().compareTo(new BigDecimal("2000.00")) > 0) return "REJECTED|LIMIT_EXCEEDED|" + total;
        return "ACCEPTED|" + request.orderId() + "|" + total + "|INV-" + request.orderId();
    }
}

package com.example.legacy.run7b;

// Pattern: Facade/Application Service - orchestriert extrahierte Verantwortungen ohne fachliche Details zu mischen.
public final class RefactoredOrderApplicationService {
    private final OrderValidationService validationService;
    private final PricingEngine pricingEngine;
    private final PaymentPort paymentPort;
    private final InvoicePort invoicePort;
    private final AuditPort auditPort;

    public RefactoredOrderApplicationService(OrderValidationService validationService, PricingEngine pricingEngine, PaymentPort paymentPort, InvoicePort invoicePort, AuditPort auditPort) {
        this.validationService = validationService;
        this.pricingEngine = pricingEngine;
        this.paymentPort = paymentPort;
        this.invoicePort = invoicePort;
        this.auditPort = auditPort;
    }

    public OrderProcessingResult process(OrderRequest request) {
        ValidationResult validation = validationService.validate(request);
        if (!validation.ok()) {
            auditPort.record(request.orderId(), "ORDER_REJECTED", validation.violations().toString());
            return OrderProcessingResult.rejected(request.orderId(), validation.violations());
        }
        PriceBreakdown price = pricingEngine.calculate(request);
        PaymentDecision payment = paymentPort.authorize(request.orderId(), request.customerId(), price.total());
        if (!payment.approved()) {
            auditPort.record(request.orderId(), "PAYMENT_DECLINED", payment.reason());
            return OrderProcessingResult.paymentDeclined(request.orderId(), price, payment.reason());
        }
        String invoiceId = invoicePort.createInvoice(request.orderId(), price);
        auditPort.record(request.orderId(), "ORDER_ACCEPTED", invoiceId + " " + price.compact());
        return OrderProcessingResult.accepted(request.orderId(), price, invoiceId);
    }
}

package com.example.legacy.run7b;

// Pattern: Service Layer - kapselt fachliche Validierung ausserhalb der Monster-Methode.
public final class OrderValidationService {
    public ValidationResult validate(OrderRequest request) {
        ValidationResult result = new ValidationResult();
        if (request.segment() == CustomerSegment.BLOCKED) result.add("CUSTOMER_BLOCKED", "blocked customers cannot order");
        if (request.lines().isEmpty()) result.add("EMPTY_ORDER", "order must contain at least one line");
        if (request.lines().size() > 50) result.add("TOO_MANY_LINES", "manual review required for more than 50 lines");
        if (request.channel() == OrderChannel.PARTNER_PORTAL && request.couponCode() != null) {
            result.add("PARTNER_COUPON_NOT_ALLOWED", "partner orders cannot use retail coupons");
        }
        if (request.segment() == CustomerSegment.B2B && request.shippingCountry() != Country.US && blank(request.vatId())) {
            result.add("VAT_ID_REQUIRED", "B2B orders in EU/CH require a VAT id");
        }
        for (OrderLine line : request.lines()) {
            if (line.quantity() > 100) result.add("LINE_QTY_LIMIT", "line quantity too high for " + line.sku());
            if (!line.unitPrice().isPositive()) result.add("PRICE_NOT_POSITIVE", "unit price must be positive for " + line.sku());
        }
        return result;
    }
    private static boolean blank(String s) { return s == null || s.isBlank(); }
}

package com.example.legacy.run7b;

import java.util.List;

// Pattern: Composite Strategy - kombiniert mehrere Rabattstrategien kontrolliert.
public final class PricingEngine {
    private final List<DiscountPolicy> policies;
    private final ShippingCalculator shippingCalculator;
    private final TaxCalculator taxCalculator;

    public PricingEngine(List<DiscountPolicy> policies, ShippingCalculator shippingCalculator, TaxCalculator taxCalculator) {
        this.policies = List.copyOf(policies);
        this.shippingCalculator = shippingCalculator;
        this.taxCalculator = taxCalculator;
    }

    public PriceBreakdown calculate(OrderRequest request) {
        Money subtotal = request.lines().stream().map(OrderLine::lineTotal).reduce(Money.eur("0"), Money::add);
        PricingContext context = new PricingContext(request.segment(), request.channel(), request.shippingCountry(), request.couponCode(), subtotal);
        Money discount = policies.stream().map(p -> p.discountFor(context)).reduce(Money.eur("0"), Money::add);
        if (discount.greaterThan(subtotal)) discount = subtotal;
        Money shipping = shippingCalculator.calculate(request, subtotal.subtract(discount));
        Money taxableBase = subtotal.subtract(discount).add(shipping);
        Money tax = taxCalculator.calculate(request, taxableBase);
        Money total = taxableBase.add(tax);
        return new PriceBreakdown(subtotal, discount, shipping, tax, total);
    }
}

package com.example.legacy.run7b;

import java.math.BigDecimal;

// Pattern: Domain Service - Steuerlogik ist nachvollziehbar und separat testbar.
public final class TaxCalculator {
    public Money calculate(OrderRequest request, Money taxableBase) {
        if (request.segment() == CustomerSegment.B2B && request.vatId() != null && request.shippingCountry() != Country.AT) {
            return Money.eur("0"); // vereinfachtes Reverse-Charge-Beispiel
        }
        BigDecimal rate = switch (request.shippingCountry()) {
            case AT -> new BigDecimal("0.20");
            case DE -> new BigDecimal("0.19");
            case CH -> new BigDecimal("0.081");
            case US -> new BigDecimal("0.00");
        };
        return taxableBase.multiply(rate);
    }
}

package com.example.legacy.run7b;

// Pattern: Domain Service - Versandentscheidung braucht mehrere Daten, gehoert aber nicht in Entity.
public final class ShippingCalculator {
    public Money calculate(OrderRequest request, Money afterDiscount) {
        int weight = request.lines().stream().mapToInt(OrderLine::totalWeight).sum();
        boolean onlyDigital = request.lines().stream().allMatch(OrderLine::digital);
        if (onlyDigital) return Money.eur("0");
        if (afterDiscount.amount().compareTo(new java.math.BigDecimal("250.00")) >= 0 && request.shippingCountry() != Country.US) return Money.eur("0");
        Money base = switch (request.shippingCountry()) {
            case AT, DE -> Money.eur("6.90");
            case CH -> Money.eur("14.90");
            case US -> Money.eur("29.90");
        };
        if (weight > 10_000) return base.add(Money.eur("12.00"));
        return base;
    }
}

package com.example.legacy.run7b;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;

public final class ArchitectureBoundaryCheck {
    public static void main(String[] args) throws IOException {
        Path root = Path.of("src/main/java/com/example/legacy/run7b");
        if (!Files.exists(root)) root = Path.of("code/legacy-refactoring-responsibility-lab/src/main/java/com/example/legacy/run7b");
        long forbidden = Files.walk(root)
                .filter(p -> p.toString().endsWith(".java"))
                .filter(p -> !p.getFileName().toString().contains("LegacyOrderProcessor"))
                .filter(p -> !p.getFileName().toString().contains("TestRunner"))
                .filter(p -> !p.getFileName().toString().contains("Demo"))
                .filter(p -> !p.getFileName().toString().contains("ArchitectureBoundaryCheck"))
                .filter(p -> {
                    try { return Files.readString(p).contains("new LegacyOrderProcessor"); }
                    catch (IOException e) { throw new RuntimeException(e); }
                }).count();
        if (forbidden != 0) throw new AssertionError("new code depends on legacy processor");
        System.out.println("RUN7B_ARCHITECTURE_OK");
    }
}