Sandi_Metz_Gilded_Rose_Approach.java

package com.gildedrose;

import com.google.common.collect.ImmutableMap;

import java.lang.reflect.InvocationTargetException;
import java.util.List;
import java.util.stream.Collectors;

public class GildedRose {

    private static final Class<Item> DEFAULT_CLASS = Item.class;

    private static final ImmutableMap<String, String> SPECIALIZED_CLASSES =
            ImmutableMap.of("normal", Normal.class.getName(),
                    "Aged Brie", Brie.class.getName(),
                    "Backstage passes..", Backstage.class.getName());

    private List<Item> items;

    GildedRose(final List<Item> items) {
        this.items = items;
    }

    public void updateQuality() {
        this.items = items.stream().map(this::qualityUpdater).collect(Collectors.toList());
    }

    private Item qualityUpdater(final Item item) {
        Class<?> clazz;

        try {
            clazz = Class.forName(SPECIALIZED_CLASSES.get(item.getName()));
        } catch (final ClassNotFoundException e) {
            clazz = DEFAULT_CLASS;
        }

        try {
            return (Item) clazz.getConstructor(String.class, int.class, int.class)
                    .newInstance(item.getName(), item.getQuality(), item.getDaysRemaining());
        } catch (final InstantiationException | InvocationTargetException | NoSuchMethodException | IllegalAccessException e) {
            // log failure for the item here
            e.printStackTrace();
        }

        // null item means it is unknown at the moment
        return null;
    }


}


class Item {
    private final String name;
    protected int quality;
    protected int daysRemaining;

    Item(final String name, final int quality, final int daysRemaining) {
        this.name = name;
        this.quality = quality;
        this.daysRemaining = daysRemaining;
    }

    protected void tick() {
    }

    public String getName() {
        return name;
    }

    public int getDaysRemaining() {
        return daysRemaining;
    }

    public int getQuality() {
        return quality;
    }
}

class Normal extends Item {


    Normal(final String name, final int quality, final int daysRemaining) {
        super(name, quality, daysRemaining);
    }

    @Override
    protected void tick() {
        daysRemaining--;

        if (quality == 0) {
            return;
        }

        quality--;

        if (daysRemaining <= 0) {
            quality--;
        }
    }
}

class Brie extends Item {


    Brie(final String name, final int quality, final int daysRemaining) {
        super(name, quality, daysRemaining);
    }

    @Override
    protected void tick() {
        daysRemaining--;

        if (quality >= 50) {
            return;
        }

        quality++;

        if (daysRemaining <= 0) {
            quality++;
        }
    }
}

class Backstage extends Item {


    Backstage(final String name, final int quality, final int daysRemaining) {
        super(name, quality, daysRemaining);
    }

    @Override
    protected void tick() {
        daysRemaining--;

        if (quality >= 50) {
            return;
        }

        if (daysRemaining < 0) {
            quality = 0;
        }

        quality++;

        if (daysRemaining < 10) {
            quality++;
        }

        if (daysRemaining < 5) {
            quality++;
        }
    }
}