Legacy-Characterization-Lab

package com.example.legacy.run7a;

public final class LegacyOrderProcessorDemo {
    public static void main(String[] args) {
        DeterministicLegacyGateway gateway = LegacyTestFixture.gateway();
        LegacyInvoiceResult result = LegacyTestFixture.processor(gateway).process(ScenarioCatalog.platinumHappyPath());
        System.out.println(GoldenMasterSnapshot.from(result));
    }
}

package com.example.legacy.run7a;

import java.math.BigDecimal;
import java.math.RoundingMode;
import java.time.DayOfWeek;
import java.time.ZoneOffset;
import java.util.*;

// Pattern: Legacy Facade (absichtlich) - diese Klasse zeigt eine Monster-Methode als Lernobjekt.
// Sie ist NICHT das Zielbild. Run 7A nutzt sie, um Verhalten abzusichern, bevor Refactoring beginnt.
public final class LegacyOrderProcessor {
    private final LegacyIntegrationGateway gateway;

    public LegacyOrderProcessor(LegacyIntegrationGateway gateway) {
        this.gateway = Objects.requireNonNull(gateway);
    }

    // Anti-Pattern: Long Method + Mixed Responsibilities + Hidden Transaction Script.
    // Zweck in diesem Run: vorhandenes Verhalten sichtbar und testbar machen.
    public LegacyInvoiceResult process(LegacyOrderRequest request) {
        List<String> localEvents = new ArrayList<>();
        List<String> localAudit = new ArrayList<>();
        String orderId = request == null ? "<null>" : request.orderId();

        try {
            localAudit.add("start process order=" + orderId);

            if (request == null) {
                localAudit.add("request is null");
                return LegacyInvoiceResult.failed("<null>", "INVALID_REQUEST", "request must not be null", localEvents, localAudit);
            }
            if (blank(request.orderId())) {
                localAudit.add("orderId missing");
                return LegacyInvoiceResult.failed("<missing>", "INVALID_ORDER_ID", "orderId is required", localEvents, localAudit);
            }
            if (blank(request.customerId())) {
                localAudit.add("customerId missing");
                return LegacyInvoiceResult.failed(request.orderId(), "INVALID_CUSTOMER", "customerId is required", localEvents, localAudit);
            }
            if (request.lines() == null || request.lines().isEmpty()) {
                localAudit.add("no lines");
                return LegacyInvoiceResult.failed(request.orderId(), "EMPTY_ORDER", "at least one line is required", localEvents, localAudit);
            }
            if (request.riskyAccount()) {
                localAudit.add("risky account blocked customer=" + request.customerId());
                localEvents.add("OrderRejected:risky-account");
                gateway.audit("risky account rejected " + request.customerId());
                return LegacyInvoiceResult.failed(request.orderId(), "CUSTOMER_RISK_BLOCK", "customer is blocked by risk checks", localEvents, merge(localAudit, gateway));
            }

            BigDecimal subtotal = BigDecimal.ZERO;
            BigDecimal digitalSubtotal = BigDecimal.ZERO;
            BigDecimal physicalSubtotal = BigDecimal.ZERO;
            int physicalQuantity = 0;
            int totalQuantity = 0;
            Set<String> skusSeen = new LinkedHashSet<>();
            boolean containsTaxReduced = false;
            boolean containsHazardous = false;
            boolean containsGiftEligible = false;

            for (int i = 0; i < request.lines().size(); i++) {
                OrderLineRequest line = request.lines().get(i);
                if (line == null) {
                    return LegacyInvoiceResult.failed(request.orderId(), "INVALID_LINE", "line " + i + " is null", localEvents, localAudit);
                }
                if (blank(line.sku())) {
                    return LegacyInvoiceResult.failed(request.orderId(), "INVALID_SKU", "line " + i + " has no sku", localEvents, localAudit);
                }
                if (line.quantity() <= 0) {
                    return LegacyInvoiceResult.failed(request.orderId(), "INVALID_QUANTITY", "quantity must be positive for " + line.sku(), localEvents, localAudit);
                }
                if (line.unitPrice() == null || line.unitPrice().signum() < 0) {
                    return LegacyInvoiceResult.failed(request.orderId(), "INVALID_PRICE", "price invalid for " + line.sku(), localEvents, localAudit);
                }
                if (!skusSeen.add(line.sku())) {
                    localAudit.add("duplicate sku merged logically=" + line.sku());
                }

                BigDecimal lineTotal = line.unitPrice().multiply(BigDecimal.valueOf(line.quantity())).setScale(2, RoundingMode.HALF_UP);
                subtotal = subtotal.add(lineTotal);
                totalQuantity += line.quantity();
                if (line.digital()) {
                    digitalSubtotal = digitalSubtotal.add(lineTotal);
                } else {
                    physicalSubtotal = physicalSubtotal.add(lineTotal);
                    physicalQuantity += line.quantity();
                    int available = gateway.availableStock(line.sku());
                    localAudit.add("stock check sku=" + line.sku() + " requested=" + line.quantity() + " available=" + available);
                    if (available < line.quantity()) {
                        localEvents.add("OrderRejected:stock-unavailable:" + line.sku());
                        return LegacyInvoiceResult.failed(request.orderId(), "STOCK_UNAVAILABLE", "not enough stock for " + line.sku(), localEvents, merge(localAudit, gateway));
                    }
                }
                if ("REDUCED".equalsIgnoreCase(line.taxCategory())) containsTaxReduced = true;
                if (line.sku().startsWith("HZ-")) containsHazardous = true;
                if (line.giftEligible()) containsGiftEligible = true;
            }

            if (subtotal.compareTo(new BigDecimal("10000.00")) > 0) {
                localEvents.add("OrderRejected:manual-approval-required");
                return LegacyInvoiceResult.failed(request.orderId(), "MANUAL_APPROVAL_REQUIRED", "subtotal exceeds automatic limit", localEvents, localAudit);
            }
            if (containsHazardous && !"DE".equalsIgnoreCase(request.country())) {
                localEvents.add("OrderRejected:hazardous-cross-border");
                return LegacyInvoiceResult.failed(request.orderId(), "HAZARDOUS_CROSS_BORDER", "hazardous goods only domestic", localEvents, localAudit);
            }

            BigDecimal discount = BigDecimal.ZERO;
            String tier = request.customerTier() == null ? "STANDARD" : request.customerTier().toUpperCase(Locale.ROOT);
            if ("PLATINUM".equals(tier)) {
                discount = discount.add(subtotal.multiply(new BigDecimal("0.10")));
                localAudit.add("tier discount platinum 10%");
            } else if ("GOLD".equals(tier)) {
                discount = discount.add(subtotal.multiply(new BigDecimal("0.07")));
                localAudit.add("tier discount gold 7%");
            } else if ("SILVER".equals(tier)) {
                discount = discount.add(subtotal.multiply(new BigDecimal("0.03")));
                localAudit.add("tier discount silver 3%");
            }

            if (!blank(request.couponCode())) {
                String coupon = request.couponCode().trim().toUpperCase(Locale.ROOT);
                if ("WELCOME10".equals(coupon) && subtotal.compareTo(new BigDecimal("50.00")) >= 0) {
                    discount = discount.add(new BigDecimal("10.00"));
                    localAudit.add("coupon WELCOME10 applied");
                } else if ("FREESHIP".equals(coupon)) {
                    localAudit.add("coupon FREESHIP deferred to shipping");
                } else if ("VIP20".equals(coupon) && ("GOLD".equals(tier) || "PLATINUM".equals(tier))) {
                    discount = discount.add(subtotal.multiply(new BigDecimal("0.20")));
                    localAudit.add("coupon VIP20 applied");
                } else {
                    localEvents.add("OrderRejected:invalid-coupon:" + coupon);
                    return LegacyInvoiceResult.failed(request.orderId(), "INVALID_COUPON", "coupon not applicable: " + coupon, localEvents, localAudit);
                }
            }

            discount = discount.setScale(2, RoundingMode.HALF_UP);
            if (discount.compareTo(subtotal.multiply(new BigDecimal("0.40"))) > 0) {
                localAudit.add("discount capped at 40%");
                discount = subtotal.multiply(new BigDecimal("0.40")).setScale(2, RoundingMode.HALF_UP);
            }

            BigDecimal shipping = BigDecimal.ZERO;
            if (physicalQuantity > 0) {
                shipping = new BigDecimal("4.90");
                if (physicalSubtotal.compareTo(new BigDecimal("100.00")) > 0) shipping = BigDecimal.ZERO;
                if (request.expressShipping()) shipping = shipping.add(new BigDecimal("12.00"));
                if ("FREESHIP".equalsIgnoreCase(String.valueOf(request.couponCode()))) shipping = BigDecimal.ZERO;
                if (!"DE".equalsIgnoreCase(request.country())) shipping = shipping.add(new BigDecimal("9.00"));
            }
            if (request.giftWrap()) {
                if (!containsGiftEligible) {
                    return LegacyInvoiceResult.failed(request.orderId(), "GIFT_WRAP_NOT_ALLOWED", "no gift eligible line", localEvents, localAudit);
                }
                shipping = shipping.add(new BigDecimal("3.50"));
            }
            shipping = shipping.setScale(2, RoundingMode.HALF_UP);

            BigDecimal taxableBase = subtotal.subtract(discount).max(BigDecimal.ZERO);
            BigDecimal taxRate = "DE".equalsIgnoreCase(request.country()) ? new BigDecimal("0.19") : new BigDecimal("0.00");
            if (containsTaxReduced && "DE".equalsIgnoreCase(request.country())) {
                taxRate = new BigDecimal("0.12"); // Legacy bug/behavior: mixed basket gets blended simplified rate.
                localAudit.add("legacy blended reduced tax rate 12%");
            }
            BigDecimal tax = taxableBase.multiply(taxRate).setScale(2, RoundingMode.HALF_UP);
            BigDecimal total = taxableBase.add(shipping).add(tax).setScale(2, RoundingMode.HALF_UP);

            DayOfWeek dow = gateway.now().atZone(ZoneOffset.UTC).getDayOfWeek();
            if (request.expressShipping() && (dow == DayOfWeek.SATURDAY || dow == DayOfWeek.SUNDAY)) {
                localAudit.add("express weekend handling fee");
                total = total.add(new BigDecimal("5.00")).setScale(2, RoundingMode.HALF_UP);
            }

            for (OrderLineRequest line : request.lines()) {
                if (!line.digital()) {
                    boolean reserved = gateway.reserveStock(request.orderId(), line.sku(), line.quantity());
                    if (!reserved) {
                        localEvents.add("OrderRejected:race-stock-unavailable:" + line.sku());
                        return LegacyInvoiceResult.failed(request.orderId(), "STOCK_RACE_LOST", "stock changed for " + line.sku(), localEvents, merge(localAudit, gateway));
                    }
                }
            }

            PaymentDecision payment = gateway.authorizePayment(request.orderId(), request.customerId(), request.paymentMethod(), total);
            if (!payment.approved()) {
                localEvents.add("OrderRejected:payment:" + payment.reason());
                return LegacyInvoiceResult.failed(request.orderId(), "PAYMENT_DECLINED", payment.reason(), localEvents, merge(localAudit, gateway));
            }

            String invoiceId = gateway.nextInvoiceId();
            gateway.saveInvoice(invoiceId, total);
            String invoicePayload = request.orderId() + ":" + invoiceId + ":" + total.toPlainString();
            gateway.publishEvent("InvoiceCreated", invoicePayload);
            gateway.publishEvent("OrderAccepted", request.orderId() + ":" + payment.transactionId());
            localEvents.add("InvoiceCreated:" + invoiceId);
            localEvents.add("OrderAccepted:" + request.orderId());
            localAudit.add("finished success invoice=" + invoiceId + " total=" + total.toPlainString());

            return new LegacyInvoiceResult(true, request.orderId(), invoiceId, subtotal.setScale(2, RoundingMode.HALF_UP), discount,
                    shipping, tax, total, "-", "-", List.copyOf(localEvents), merge(localAudit, gateway));
        } catch (RuntimeException ex) {
            localAudit.add("technical exception " + ex.getClass().getSimpleName() + ":" + ex.getMessage());
            return LegacyInvoiceResult.failed(orderId, "TECHNICAL_FAILURE", ex.getMessage(), localEvents, merge(localAudit, gateway));
        }
    }

    private static boolean blank(String text) { return text == null || text.trim().isEmpty(); }

    private static List<String> merge(List<String> local, LegacyIntegrationGateway gateway) {
        List<String> merged = new ArrayList<>(local);
        if (gateway instanceof DeterministicLegacyGateway d) merged.addAll(d.auditTrail());
        return List.copyOf(merged);
    }
}

package com.example.legacy.run7a;

import java.time.Instant;

public final class LegacyTestFixture {
    private LegacyTestFixture() {}

    public static DeterministicLegacyGateway gateway() {
        return new DeterministicLegacyGateway(Instant.parse("2026-02-02T10:15:30Z"))
                .withStock("BOOK-1", 20)
                .withStock("CHAIR-9", 4)
                .withStock("RARE-1", 1)
                .withStock("HZ-CLEANER", 8)
                .declinePaymentMethod("CARD_DECLINE");
    }

    public static LegacyOrderProcessor processor(DeterministicLegacyGateway gateway) {
        return new LegacyOrderProcessor(gateway);
    }
}

package com.example.legacy.run7a;

import java.math.BigDecimal;
import java.util.List;

// Pattern: Test Data Builder / Object Mother - zentrale, lesbare fachliche Szenarien statt kopierter Testdaten.
public final class ScenarioCatalog {
    private ScenarioCatalog() {}

    public static LegacyOrderRequest platinumHappyPath() {
        return new LegacyOrderRequest("ORD-1001", "C-77", "PLATINUM", "DE", "VIP20",
                true, true, false, "CARD_OK", List.of(
                new OrderLineRequest("BOOK-1", 2, new BigDecimal("29.90"), false, true, "REDUCED"),
                new OrderLineRequest("CHAIR-9", 1, new BigDecimal("149.00"), false, true, "STANDARD")));
    }

    public static LegacyOrderRequest insufficientStock() {
        return new LegacyOrderRequest("ORD-1002", "C-88", "STANDARD", "DE", null,
                false, false, false, "CARD_OK", List.of(
                new OrderLineRequest("RARE-1", 5, new BigDecimal("12.00"), false, false, "STANDARD")));
    }

    public static LegacyOrderRequest invalidCoupon() {
        return new LegacyOrderRequest("ORD-1003", "C-99", "SILVER", "DE", "NOPE",
                false, false, false, "CARD_OK", List.of(
                new OrderLineRequest("BOOK-1", 1, new BigDecimal("20.00"), false, true, "REDUCED")));
    }

    public static LegacyOrderRequest digitalOnlyEuCustomer() {
        return new LegacyOrderRequest("ORD-1004", "C-11", "GOLD", "AT", "WELCOME10",
                false, false, false, "CARD_OK", List.of(
                new OrderLineRequest("EBOOK-7", 3, new BigDecimal("19.99"), true, false, "DIGITAL")));
    }

    public static LegacyOrderRequest paymentDeclined() {
        return new LegacyOrderRequest("ORD-1005", "C-55", "STANDARD", "DE", null,
                false, false, false, "CARD_DECLINE", List.of(
                new OrderLineRequest("CHAIR-9", 1, new BigDecimal("149.00"), false, true, "STANDARD")));
    }

    public static LegacyOrderRequest hazardousCrossBorder() {
        return new LegacyOrderRequest("ORD-1006", "C-12", "STANDARD", "AT", null,
                false, false, false, "CARD_OK", List.of(
                new OrderLineRequest("HZ-CLEANER", 1, new BigDecimal("9.99"), false, false, "STANDARD")));
    }
}

package com.example.legacy.run7a;

import java.util.stream.Collectors;

// Pattern: Golden Master - vergleicht beobachtbares Verhalten, nicht interne Struktur.
public final class GoldenMasterSnapshot {
    private GoldenMasterSnapshot() {}

    public static String from(LegacyInvoiceResult result) {
        String events = result.domainEvents().stream().collect(Collectors.joining(","));
        String auditSignal = result.auditTrail().stream()
                .filter(a -> a.contains("stock check") || a.contains("reserved") || a.contains("authorize payment") || a.contains("invoice saved"))
                .collect(Collectors.joining(" | "));
        return "success=" + result.success()
                + ";order=" + result.orderId()
                + ";invoice=" + result.invoiceId()
                + ";subtotal=" + result.subtotal().toPlainString()
                + ";discount=" + result.discount().toPlainString()
                + ";shipping=" + result.shipping().toPlainString()
                + ";tax=" + result.tax().toPlainString()
                + ";total=" + result.total().toPlainString()
                + ";failure=" + result.failureCode()
                + ";events=" + events
                + ";auditSignal=" + auditSignal;
    }
}

package com.example.legacy.run7a;

// Pattern: Refactoring Seam - Zielbild für späteren Run 7B, ohne Verhalten in Run 7A zu verändern.
public interface RefactoringSeamInventory {
    boolean canReserve(String sku, int quantity);
    void reserve(String orderId, String sku, int quantity);
}

package com.example.legacy.run7a;

import java.util.LinkedHashMap;
import java.util.Map;

public final class LegacyCharacterizationTestRunner {
    public static void main(String[] args) {
        Map<String, String> expected = new LinkedHashMap<>();
        expected.put("platinumHappyPath", "success=true;order=ORD-1001;invoice=INV-1001;subtotal=208.80;discount=62.64;shipping=15.50;tax=17.54;total=179.20;failure=-;events=InvoiceCreated:INV-1001,OrderAccepted:ORD-1001;auditSignal=stock check sku=BOOK-1 requested=2 available=20 | stock check sku=CHAIR-9 requested=1 available=4 | 2026-02-02T10:15:30Z reserved 2 of BOOK-1 for ORD-1001 | 2026-02-02T10:15:30Z reserved 1 of CHAIR-9 for ORD-1001 | 2026-02-02T10:15:30Z authorize payment CARD_OK total=179.20 | 2026-02-02T10:15:30Z invoice saved INV-1001 total=179.20");
        expected.put("insufficientStock", "success=false;order=ORD-1002;invoice=-;subtotal=0;discount=0;shipping=0;tax=0;total=0;failure=STOCK_UNAVAILABLE;events=OrderRejected:stock-unavailable:RARE-1;auditSignal=stock check sku=RARE-1 requested=5 available=1");
        expected.put("invalidCoupon", "success=false;order=ORD-1003;invoice=-;subtotal=0;discount=0;shipping=0;tax=0;total=0;failure=INVALID_COUPON;events=OrderRejected:invalid-coupon:NOPE;auditSignal=stock check sku=BOOK-1 requested=1 available=20");
        expected.put("digitalOnlyEuCustomer", "success=true;order=ORD-1004;invoice=INV-1001;subtotal=59.97;discount=14.20;shipping=0.00;tax=0.00;total=45.77;failure=-;events=InvoiceCreated:INV-1001,OrderAccepted:ORD-1004;auditSignal=2026-02-02T10:15:30Z authorize payment CARD_OK total=45.77 | 2026-02-02T10:15:30Z invoice saved INV-1001 total=45.77");
        expected.put("paymentDeclined", "success=false;order=ORD-1005;invoice=-;subtotal=0;discount=0;shipping=0;tax=0;total=0;failure=PAYMENT_DECLINED;events=OrderRejected:payment:PAYMENT_PROVIDER_DECLINED;auditSignal=stock check sku=CHAIR-9 requested=1 available=4 | 2026-02-02T10:15:30Z reserved 1 of CHAIR-9 for ORD-1005 | 2026-02-02T10:15:30Z authorize payment CARD_DECLINE total=177.31");
        expected.put("hazardousCrossBorder", "success=false;order=ORD-1006;invoice=-;subtotal=0;discount=0;shipping=0;tax=0;total=0;failure=HAZARDOUS_CROSS_BORDER;events=OrderRejected:hazardous-cross-border;auditSignal=stock check sku=HZ-CLEANER requested=1 available=8");

        assertSnapshot("platinumHappyPath", expected, ScenarioCatalog.platinumHappyPath());
        assertSnapshot("insufficientStock", expected, ScenarioCatalog.insufficientStock());
        assertSnapshot("invalidCoupon", expected, ScenarioCatalog.invalidCoupon());
        assertSnapshot("digitalOnlyEuCustomer", expected, ScenarioCatalog.digitalOnlyEuCustomer());
        assertSnapshot("paymentDeclined", expected, ScenarioCatalog.paymentDeclined());
        assertSnapshot("hazardousCrossBorder", expected, ScenarioCatalog.hazardousCrossBorder());
        System.out.println("RUN7A_TESTS_OK");
    }

    private static void assertSnapshot(String name, Map<String, String> expected, LegacyOrderRequest request) {
        DeterministicLegacyGateway gateway = LegacyTestFixture.gateway();
        LegacyOrderProcessor processor = LegacyTestFixture.processor(gateway);
        String actual = GoldenMasterSnapshot.from(processor.process(request));
        String wanted = expected.get(name);
        if (!wanted.equals(actual)) {
            throw new AssertionError("Snapshot mismatch for " + name + "\nExpected:\n" + wanted + "\nActual:\n" + actual);
        }
    }
}