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/*
 * Copyright (C) 2018 2024 gregory higgins.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the Server Side Public License, version 1,
 * as published by MongoDB, Inc.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * Server Side Public License for more details.
 *
 * You should have received a copy of the Server Side Public License
 * along with this program.  If not, see
 * .
 */
package com.fluxtion.compiler.builder.factory;

import com.fluxtion.compiler.generation.GenerationContext;
import com.fluxtion.runtime.annotations.builder.Config;
import com.fluxtion.runtime.annotations.builder.Inject;
import com.fluxtion.runtime.audit.Auditor;

import java.util.Map;
import java.util.ServiceLoader;

/**
 * A factory for creating instances. The SEP will call this method to create
 * nodes.
 *
 * 
Instance re-use
 * To ensure that node instances are re-used there are two approaches:
 * 
 * The factory caches the node, and returns the same instance for the same
 * configuration.
 * 
The factory creates new nodes and the node overrides hashcode and equals.
 * The {@link NodeRegistry} will consult a map for an equivalent node. If an
 * equivalent node is found then the newly created node will be discarded and
 * the existing instance used.
 * 
 * 
 * 
Registering factories
 * Fluxtion employs the {@link ServiceLoader} pattern to register user
 * implemented NodeFactories. Please read the java documentation describing the
 * meta-data a factory implementor must provide to register a factory using the
 * {@link ServiceLoader} pattern.
 *
 * @param 
 * @author Greg Higgins
 */
public interface NodeFactory {

    /**
     * The key in the map passed to the NodeFactory instance that holds the {@link java.lang.reflect.Field} type
     * information for the target field.
     */
    String FIELD_KEY = "NodeFactory.InjectField.TypeInfo";
    /**
     * The key in the map passed to the NodeFactory instance that holds the name of the instance to be injected when
     * using information for the target field.
     */
    String INSTANCE_KEY = "NodeFactory.InjectField.InstanceName";

    /**
     * NodeFactory writer must implement this method to generate instances of
     * nodes. The Fluxtion compiler will call this method when an {@link Inject}
     * instance is created. {@link Config} variables are used to populate the
     * config map.
     *
     * @param config   map configuration
     * @param registry The node registry of the current generation contextß
     * @return The newly created node instance
     */
    T createNode(Map config, NodeRegistry registry);

    /**
     * Callback invoked by Fluxtion generator after the generated SEP has been
     * registered in the{@link GenerationContext}
     *
     * @param config   map configuration
     * @param registry The node registry of the current generation context
     * @param instance the newly created instance
     */
    default void postInstanceRegistration(Map config, NodeRegistry registry, T instance) {
    }

    /**
     * If the node generates a class for this SEP, this callback will indicate
     * the desired target.
     *
     * @param targetLanguage target language for generation
     */
    default void setTargetLanguage(String targetLanguage) {
    }

    /**
     * If the node generates a class for this SEP, this callback gives the node
     * access to the GenerationContext before generation.
     *
     * @param context    The context the Fluxtion SEC compiler uses
     * @param auditorMap auditors map for client to populate, these will be added to the generated EventProcessor
     */
    default void preSepGeneration(GenerationContext context, Map auditorMap) {
    }

    default String factoryName() {
        return "";
    }

    /**
     * Override the injection type inferred by the type variable
     *
     * @return
     */
    default Class injectionType() {
        return null;
    }

}