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A JSR-330 spec compliant dependency injection framework.
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/*
 * Copyright (C) 2016-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package io.github.pustike.inject.impl;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Objects;
import jakarta.inject.Provider;

import io.github.pustike.inject.BindingKey;
import io.github.pustike.inject.Scope;

/**
 * Binding.
 */
final class Binding {
    private final BindingKey bindingKey;
    private final Provider provider;
    private final Scope scope;
    private final boolean multiBinder;
    private Provider scopedProvider;
    private boolean providerInjected;

    Binding(BindingKey bindingKey, Provider provider, Scope scope) {
        this.bindingKey = Objects.requireNonNull(bindingKey);
        this.provider = Objects.requireNonNull(provider);
        this.scope = Objects.requireNonNull(scope);
        this.multiBinder = provider instanceof MultiBindingProvider;
    }

    Binding(BindingKey bindingKey, Provider provider, Scope scope, DefaultInjector injector) {
        this(bindingKey, provider, scope);
        this.postConfiguration(injector);
    }

    Binding(BindingKey bindingKey, List> bindingList, Scope scope, DefaultInjector injector) {
        this(bindingKey, new MultiBindingProvider<>(bindingKey, bindingList), scope);
        bindingList.forEach(binding -> binding.postConfiguration(injector));
    }

    boolean addBinding(Binding binding) {
        return multiBinder && binding.multiBinder && ((MultiBindingProvider) provider)
                .addBindings((MultiBindingProvider) binding.provider);
    }

    private void postConfiguration(DefaultInjector injector) {
        if (provider instanceof InstanceProvider) {
            ((InstanceProvider) provider).setInjector(injector);
            this.providerInjected = true;// internal instanceProvider doesn't require any dependency injection
        }
        this.scopedProvider = scope.scope(bindingKey, () -> createInstance(injector));
    }

    void createIfEagerSingleton() {
        if (multiBinder) {
            ((MultiBindingProvider) provider).createIfEagerSingleton();
        } else if (scope instanceof SingletonScope && scope.toString().equals(Scopes.EAGER_SINGLETON)) {
            this.scopedProvider.get();
        }
    }

    Object getInstance(BindingKey targetKey) {
        return multiBinder ? ((MultiBindingProvider) provider).getInstance(targetKey) :
                targetKey.isProviderKey() ? this.scopedProvider : this.scopedProvider.get();
    }

    private T createInstance(DefaultInjector injector) {
        // inject dependencies into the provider instance as well!
        if (!providerInjected) {
            injector.injectMembers(provider);
            providerInjected = true;
        }
        // get an instance from the provider
        T newInstance = provider.get();
        if (newInstance != null) {// inject members of the new instance
            injector.injectMembers(bindingKey, newInstance);
        }
        return newInstance;
    }

    private static final class MultiBindingProvider implements Provider {
        private final BindingKey bindingKey;
        private final List> bindingList;

        MultiBindingProvider(BindingKey bindingKey, List> bindingList) {
            this.bindingKey = bindingKey;
            this.bindingList = bindingList;
        }

        boolean addBindings(MultiBindingProvider provider) {
            return bindingList.addAll(provider.bindingList);
        }

        void createIfEagerSingleton() {
            bindingList.forEach(Binding::createIfEagerSingleton);
        }

        Collection getInstance(BindingKey targetKey) {
            List