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package com.cookingfox.lapasse.impl.helper;

import com.cookingfox.lapasse.api.facade.Facade;
import com.cookingfox.lapasse.api.state.State;
import com.cookingfox.lapasse.impl.helper.exception.GeneratedConstructorNotFoundException;
import com.cookingfox.lapasse.impl.helper.exception.HandlerMapperInstantiationException;
import com.cookingfox.lapasse.impl.helper.exception.NoGeneratedClassException;
import com.cookingfox.lapasse.impl.internal.HandlerMapper;

import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.util.Objects;

/**
 * Helper class for mapping handlers from annotated class.
 */
public final class LaPasse {

    /**
     * Generated class name suffix.
     */
    public static final String GENERATED_SUFFIX = "$$LaPasseGenerated";

    //----------------------------------------------------------------------------------------------
    // CONSTRUCTOR
    //----------------------------------------------------------------------------------------------

    /**
     * Not meant to be instantiated.
     */
    private LaPasse() {
        throw new UnsupportedOperationException();
    }

    //----------------------------------------------------------------------------------------------
    // PUBLIC METHODS
    //----------------------------------------------------------------------------------------------

    /**
     * Map the handler methods of a facade implementation.
     *
     * @param origin The facade implementation, containing the annotations.
     * @throws NoGeneratedClassException             when no generated class exists for this origin.
     * @throws GeneratedConstructorNotFoundException when the expected generated constructor was not
     *                                               found.
     * @throws HandlerMapperInstantiationException   when an error occurs during the instantiation
     *                                               of the HandlerMapper.
     * @see #mapHandlers(Object, Facade)
     */
    public static void mapHandlers(Facade origin) {
        mapHandlers(origin, origin);
    }

    /**
     * Map the annotated handler methods of a class to its facade.
     *
     * @param origin The class containing the annotations.
     * @param facade The LaPasse facade to map handlers to.
     * @throws NoGeneratedClassException             when no generated class exists for this origin.
     * @throws GeneratedConstructorNotFoundException when the expected generated constructor was not
     *                                               found.
     * @throws HandlerMapperInstantiationException   when an error occurs during the instantiation
     *                                               of the HandlerMapper.
     */
    public static void mapHandlers(Object origin, Facade facade) {
        Objects.requireNonNull(origin, "Origin can not be null");
        Objects.requireNonNull(facade, "Facade can not be null");

        // get generated class name
        Class originClass = origin.getClass();
        String generatedClassName = originClass.getCanonicalName() + GENERATED_SUFFIX;

        // create instance of generated class
        Class handlerMapperClass = getHandlerMapperClass(generatedClassName);
        Constructor constructor = getHandlerMapperConstructor(handlerMapperClass, originClass);
        HandlerMapper handlerMapper = createHandlerMapperInstance(constructor, origin, facade);

        // map handlers
        handlerMapper.mapHandlers();
    }

    //----------------------------------------------------------------------------------------------
    // PROTECTED METHODS
    //----------------------------------------------------------------------------------------------

    /**
     * Creates an instance of the provided HandlerMapper constructor.
     *
     * @param constructor The constructor to create an instance of.
     * @param origin      The annotated class to pass to the constructor.
     * @param facade      The facade to pass to the constructor.
     * @return A HandlerMapper instance.
     * @throws HandlerMapperInstantiationException when an error occurs during the instantiation of
     *                                             the HandlerMapper.
     */
    protected static HandlerMapper createHandlerMapperInstance(
            Constructor constructor, Object origin, Facade facade) {
        try {
            return constructor.newInstance(origin, facade);
        } catch (InstantiationException | IllegalAccessException | InvocationTargetException e) {
            throw new HandlerMapperInstantiationException(constructor, e);
        }
    }

    /**
     * Attempts to load the HandlerMapper class by its Fully-Qualified Class Name.
     *
     * @param fqcn Fully-Qualified Class Name.
     * @return The handler mapper class.
     * @throws NoGeneratedClassException when no generated class exists for this FQCN.
     */
    protected static Class getHandlerMapperClass(String fqcn) {
        try {
            // noinspection unchecked
            return (Class) Class.forName(fqcn);
        } catch (ClassNotFoundException e) {
            throw new NoGeneratedClassException(fqcn);
        }
    }

    /**
     * Attempts to get the default generated HandlerMapper constructor.
     *
     * @param handlerMapperClass HandlerMapper class.
     * @param originClass        The class containing the annotations.
     * @return The generated HandlerMapper constructor.
     * @throws GeneratedConstructorNotFoundException when the expected generated constructor was not
     *                                               found.
     */
    protected static Constructor getHandlerMapperConstructor(
            Class handlerMapperClass, Class originClass) {
        try {
            return handlerMapperClass.getDeclaredConstructor(originClass, Facade.class);
        } catch (NoSuchMethodException e) {
            throw new GeneratedConstructorNotFoundException(handlerMapperClass.getCanonicalName(), e);
        }
    }

}