Patterns und Refactoring

<?xml version="1.0" encoding="UTF-8"?>
        <project xmlns="http://maven.apache.org/POM/4.0.0"
                 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
            <modelVersion>4.0.0</modelVersion>
            <parent>
                <groupId>at.aydin.academy</groupId>
                <artifactId>34patternsrefactoring-pair</artifactId>
                <version>1.0.0</version>
                <relativePath>../pom.xml</relativePath>
            </parent>
            <artifactId>patterns-modern</artifactId>
            <packaging>jar</packaging>
            <name>Patterns Modern</name>

            <dependencies>

<dependency>
    <groupId>org.junit.jupiter</groupId>
    <artifactId>junit-jupiter</artifactId>
    <scope>test</scope>
</dependency>

            </dependencies>
            <build>
                <plugins>
                    <plugin>
                        <groupId>org.apache.maven.plugins</groupId>
                        <artifactId>maven-compiler-plugin</artifactId>
                    </plugin>

                </plugins>
            </build>
        </project>

package at.aydin.lab.patterns.modern;

public enum CustomerType {
    STANDARD, PREMIUM, EMPLOYEE
}

package at.aydin.lab.patterns.modern;

// Design Pattern: Strategy
// Zweck: Rabattalgorithmus ist austauschbar und ohne zentrale Switch-Anweisung erweiterbar.
@FunctionalInterface
public interface PricingStrategy {
    double apply(double basePrice);
}

package at.aydin.lab.patterns.modern;

import java.util.*;

// Design Pattern: Factory
// Zweck: Auswahl konkreter Strategies wird an einer Stelle konfiguriert.
public final class PricingStrategyFactory {
    private final Map<CustomerType, PricingStrategy> strategies = Map.of(CustomerType.STANDARD, p -> p, CustomerType.PREMIUM,
        p -> p * 0.9, CustomerType.EMPLOYEE, p -> p * 0.7);
    public PricingStrategy forType(CustomerType type) {
        return Optional.ofNullable(strategies.get(type)).orElseThrow();
    }
}

package at.aydin.lab.patterns.modern;

public final class PriceService {
    private final PricingStrategyFactory factory;
    public PriceService(PricingStrategyFactory factory) {
        this.factory = factory;
    }

    public double price(CustomerType type, double base) {
        return factory.forType(type).apply(base);
    }
}

package at.aydin.lab.patterns.modern;

import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.assertEquals;

class PriceServiceTest {
    @Test
    void delegatesToStrategy() {
        assertEquals(90, new PriceService(new PricingStrategyFactory()).price(CustomerType.PREMIUM, 100));
    }
}