dsaCalc/src/de/banananetwork/dsa/requirements/Requirement.java

package de.banananetwork.dsa.requirements;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.function.Supplier;

public abstract class Requirement {

	public abstract RequirementCheckResult checkOn(Character character);

	private static class SingleRequirement extends Requirement {


	}

	private static class CombinedRequirement extends Requirement {

		private final RequirementLink requirementLink;
		private final Requirement[] requirements;

		private CombinedRequirement(RequirementLink requirementLink, Requirement[] requirements) {
			this.requirementLink = requirementLink;
			this.requirements = requirements;
		}

		@Override
		public RequirementCheckResult checkOn(Character character) {
			return null;
		}

	}

	public static class Builder {

		private final List<Supplier<Requirement>> requirements = new ArrayList<>();
		private RequirementLink requirementLink;

		public Builder(RequirementLink requirementLink) {
			this.requirementLink = requirementLink;
		}

		Builder add(Supplier<Requirement> requirementSupplier) {
			this.requirements.add(requirementSupplier);
			return this;
		}

		public Builder add(Requirement requirement) {
			return this.add(() -> requirement);
		}

		public Builder add(Builder requirement) {
			return this.add(requirement::create);
		}

		private Builder addAll(Collection<Supplier<Requirement>> requirements) {
			this.requirements.addAll(requirements);
			return this;
		}

		public Builder addAll(Builder requirements) {
			return this.addAll(requirements.requirements);
		}

		private Requirement create() {
			switch (this.requirements.size()) {
				case 0:
					throw new IllegalStateException();
				case 1:
					return this.requirements.get(0).get();
				default:
					return new CombinedRequirement(this.requirementLink, this.requirements.stream().map(Supplier::get).toArray(Requirement[]::new));
			}
		}

	}

}