java-design-patterns/step-builder/src/main/java/com/iluwatar/stepbuilder/CharacterStepBuilder.java

package com.iluwatar.stepbuilder;

import java.util.ArrayList;
import java.util.List;

/**
 * The Step Builder class.
 */
public class CharacterStepBuilder {

	private CharacterStepBuilder() {
	}

	public static NameStep newBuilder() {
		return new CharacterSteps();
	}

	/**
	 * First Builder Step in charge of the Character name.
	 * Next Step available : ClassStep
	 */
	public interface NameStep {
		ClassStep name(String name);
	}

	/**
	 * This step is in charge of setting the Character class (fighter or wizard).
	 * Fighter choice : Next Step available : WeaponStep
	 * Wizard choice : Next Step available : SpellStep
	 */
	public interface ClassStep {
		WeaponStep fighterClass(String fighterClass);
		SpellStep wizardClass(String wizardClass);
	}

	/**
	 * This step is in charge of the weapon.
	 * Weapon choice : Next Step available : AbilityStep
	 * No weapon choice : Next Step available : BuildStep
	 */
	public interface WeaponStep {
		AbilityStep withWeapon(String weapon);
		BuildStep noWeapon();
	}

	/**
	 * This step is in charge of the spell.
	 * Spell choice : Next Step available : AbilityStep
	 * No spell choice : Next Step available : BuildStep
	 */
	public interface SpellStep {
		AbilityStep withSpell(String spell);
		BuildStep noSpell();
	}

	/**
	 * This step is in charge of abilities.
	 * Next Step available : BuildStep
	 */
	public interface AbilityStep {
		AbilityStep withAbility(String ability);
		BuildStep noMoreAbilities();
		BuildStep noAbilities();
	}

	/**
	 * This is the final step in charge of building the Character Object.
	 * Validation should be here.
	 */
	public interface BuildStep {
		Character build();
	}


	/**
	 * Step Builder implementation.
	 */
	private static class CharacterSteps
	    implements NameStep, ClassStep, WeaponStep, SpellStep, AbilityStep, BuildStep {

		private String name;
		private String fighterClass;
		private String wizardClass;
		private String weapon;
		private String spell;
		private List<String> abilities = new ArrayList<>();

		@Override
		public ClassStep name(String name) {
			this.name = name;
			return this;
		}

		@Override
		public WeaponStep fighterClass(String fighterClass) {
			this.fighterClass = fighterClass;
			return this;
		}

		@Override
		public SpellStep wizardClass(String wizardClass) {
			this.wizardClass = wizardClass;
			return this;
		}

		@Override
		public AbilityStep withWeapon(String weapon) {
			this.weapon = weapon;
			return this;
		}

		@Override
		public BuildStep noWeapon() {
			return this;
		}

		@Override
		public AbilityStep withSpell(String spell) {
			this.spell = spell;
			return this;
		}

		@Override
		public BuildStep noSpell() {
			return this;
		}

		@Override
		public AbilityStep withAbility(String ability) {
			this.abilities.add(ability);
			return this;
		}

		@Override
		public BuildStep noMoreAbilities() {
			return this;
		}

		@Override
		public BuildStep noAbilities() {
			return this;
		}

		@Override
		public Character build() {
			Character character = new Character(name);

			if (fighterClass != null) {
				character.setFighterClass(fighterClass);
			} else {
				character.setWizardClass(wizardClass);
			}

			if (weapon != null) {
				character.setWeapon(weapon);
			} else {
				character.setSpell(spell);
			}

			if (!abilities.isEmpty()) {
				character.setAbilities(abilities);
			}

			return character;
		}
	}
}