io.datakernel.di.impl.BindingInitializer Maven / Gradle / Ivy

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package io.datakernel.di.impl;

import io.datakernel.di.core.Binding;
import io.datakernel.di.core.Dependency;

import java.util.Collection;
import java.util.Set;
import java.util.stream.Collectors;

import static java.util.Arrays.asList;
import static java.util.Collections.emptySet;

/**
 * This is a {@link Binding} binding modifying function, that can add extra dependencies to it
 * and run initialization code for instance after it was created.
 */
public final class BindingInitializer {
	private static final BindingInitializer NOOP = new BindingInitializer<>(emptySet(),
			compiledBindings -> (instance, instances, synchronizedScope) -> {});

	private final Set dependencies;
	private final BindingInitializerCompiler compiler;

	private BindingInitializer(Set dependencies, BindingInitializerCompiler compiler) {
		this.dependencies = dependencies;
		this.compiler = compiler;
	}

	public Set getDependencies() {
		return dependencies;
	}

	public BindingInitializerCompiler getCompiler() {
		return compiler;
	}

	public static  BindingInitializer of(Set dependencies, BindingInitializerCompiler bindingInitializerCompiler) {
		return new BindingInitializer<>(dependencies, bindingInitializerCompiler);
	}

	@SafeVarargs
	public static  BindingInitializer combine(BindingInitializer... bindingInitializers) {
		return combine(asList(bindingInitializers));
	}

	@SuppressWarnings("unchecked")
	public static  BindingInitializer combine(Collection> bindingInitializers) {
		return new BindingInitializer<>(bindingInitializers.stream().map(BindingInitializer::getDependencies).flatMap(Collection::stream).collect(Collectors.toSet()),
				compiledBindings -> {
					CompiledBindingInitializer[] initializers = bindingInitializers.stream()
							.filter(bindingInitializer -> bindingInitializer != NOOP)
							.map(bindingInitializer -> bindingInitializer.compiler.compile(compiledBindings))
							.toArray(CompiledBindingInitializer[]::new);
					if (initializers.length == 0) return (instance, instances, synchronizedScope) -> {};
					if (initializers.length == 1) return initializers[0];
					if (initializers.length == 2) {
						CompiledBindingInitializer initializer0 = initializers[0];
						CompiledBindingInitializer initializer1 = initializers[1];
						return (instance, instances, synchronizedScope) -> {
							initializer0.initInstance(instance, instances, synchronizedScope);
							initializer1.initInstance(instance, instances, synchronizedScope);
						};
					}
					return (instance, instances, synchronizedScope) -> {
						for (CompiledBindingInitializer initializer : initializers) {
							initializer.initInstance(instance, instances, synchronizedScope);
						}
					};
				});
	}

	@SuppressWarnings("unchecked")
	public static  BindingInitializer noop() {
		return (BindingInitializer) NOOP;
	}
}