/**++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 *
 *                                              PANIC
 *                              Portable Algorithms and Numerics In C++
 *
 *                       Scientific computing from scratch, with feeling.
 *
 * Copyright (c) 2026 Michelle Bausager
 *
 * This file is part of PANIC.
 *
 * PANIC is free software licensed under the GNU General Public License v3.0 or later.
 * You may redistribute and/or modify it under the terms of the GPL.
 *
 * PANIC 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 LICENSE file for the full license text.
 *
 * SPDX-License-Identifier: GPL-3.0-or-later
 *
 *++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 *
 * Project Name:      PANIC
 * Module Name:       neural_network
 * File Name:         layer.hpp
 * Revision:          0.1.0
 * Date:              23-06-2026
 * Author:            Michelle Bausager
 *
 * Description:
 * Defines the base layers struct used in other layers in neural network
 *
 *++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++*/
#pragma once
//---------------------------------------------------------------------------------------------------------------------------
// INCLUDE DESCRIPTION
//---------------------------------------------------------------------------------------------------------------------------
#include <config/types.hpp> // panic::uint_t, panic::int_t, and panic::real_t
#include <tensor/matrix.hpp> // panic::tensor::real_matrix (uint_matrix, int_matrix)


namespace panic{
	namespace neural_network{



/**
 * @brief Base layer for the rest of the neural network library to use
 *
 *    	This base layer should be used in all layers/activations that have a forward and backward function
 * 		This is done so it's easy to make a list of layers in the model to loop over.
 * 		The virtual means it should use derived object's version when called with a pointer.
 * 		The =0 means the derivative object NEEDS to have these functions to work.
 * 
 * The struct is used for PANIC neural_network library.
 */
struct layer{

     /**
     * @brief Emphty output matrix to store layer input
     *
     * Output shape:
     * samples x neuron_count
     */
    panic::tensor::real_matrix inputs;

	 /**
     * @brief Emphty output matrix to store layer output
     *
     * Output shape:
     * samples x neuron_count
     */
	panic::tensor::real_matrix outputs;

     /**
     * @brief Emphty matrix to store output for backward pass
     *
     */
    panic::tensor::real_matrix dinputs;

    /**
     * @brief Default de-constructor
     *
     */
	virtual ~layer() = default;


    /**
     * @brief Virtual forward function for derivative layers
     *
     * @param inputs Data matrix input for forward function.
     * 
     * @Note It's equal to 0 because it make the derivative 
     * 		object NEEDS to have these function to work.
     */
	virtual bool forward(const panic::tensor::real_matrix& inputs) = 0;

    /**
     * @brief Virtual backward function for derivative layers
     *
     * @param dinputs Data matrix input for backward function.
     * 
     * @Note It's equal to 0 because it make the derivative 
     * 		object NEEDS to have these function to work.
     */
	virtual bool backward(const panic::tensor::real_matrix& dinputs) = 0;

};



	} // namespace tensor
} // namespace panic