io.datakernel.di.core.BindingTransformer Maven / Gradle / Ivy

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package io.datakernel.di.core;

import io.datakernel.di.impl.BindingLocator;
import org.jetbrains.annotations.NotNull;

import java.util.Comparator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

import static java.util.stream.Collectors.toList;

/**
 * This is a transformation function that is applied by the {@link Injector injector} to each binding once.
 */
@FunctionalInterface
public interface BindingTransformer {
	BindingTransformer IDENTITY = (bindings, scope, key, binding) -> binding;

	@NotNull Binding transform(BindingLocator bindings, Scope[] scope, Key key, Binding binding);

	@SuppressWarnings("unchecked")
	static  BindingTransformer identity() {
		return (BindingTransformer) IDENTITY;
	}

	/**
	 * Modules export a priority multimap of transformers.
	 * 
	 * This transformer aggregates such map into one big generator to be used by {@link Injector#compile} method.
	 * The map is converted to a sorted list of sets.
	 * Then for each of those sets, similar to {@link BindingGenerator#combinedGenerator generators},
	 * only zero or one transformer from that set are allowed to return anything but the binding is was given (being an identity transformer).
	 * 

	 * So if two transformers differ in priority then they can be applied both in order of their priority.
	 */
	@SuppressWarnings("unchecked")
	static BindingTransformer combinedTransformer(Map>> transformers) {

		List>> transformerList = transformers.entrySet().stream()
				.sorted(Comparator.comparing(Entry::getKey))
				.map(Entry::getValue)
				.collect(toList());

		return (bindings, scope, key, binding) -> {
			Binding