//
//  LogReg.cpp
//
//  Created by Marc Melikyan on 10/2/20.
//

#include "log_reg_old.h"

#include "../activation/activation_old.h"
#include "../cost/cost_old.h"
#include "../lin_alg/lin_alg_old.h"
#include "../regularization/reg_old.h"
#include "../utilities/utilities.h"

#include <iostream>
#include <random>

MLPPLogRegOld::MLPPLogRegOld(std::vector<std::vector<real_t>> pinputSet, std::vector<real_t> poutputSet, std::string preg, real_t plambda, real_t palpha) {
	inputSet = pinputSet;
	outputSet = poutputSet;
	n = pinputSet.size();
	k = pinputSet[0].size();
	reg = preg;
	lambda = plambda;
	alpha = palpha;

	y_hat.resize(n);
	weights = MLPPUtilities::weightInitialization(k);
	bias = MLPPUtilities::biasInitialization();
}

std::vector<real_t> MLPPLogRegOld::modelSetTest(std::vector<std::vector<real_t>> X) {
	return Evaluate(X);
}

real_t MLPPLogRegOld::modelTest(std::vector<real_t> x) {
	return Evaluate(x);
}

void MLPPLogRegOld::gradientDescent(real_t learning_rate, int max_epoch, bool UI) {
	MLPPLinAlgOld alg;
	MLPPRegOld regularization;
	real_t cost_prev = 0;
	int epoch = 1;
	forwardPass();

	while (true) {
		cost_prev = Cost(y_hat, outputSet);

		std::vector<real_t> error = alg.subtraction(y_hat, outputSet);

		// Calculating the weight gradients
		weights = alg.subtraction(weights, alg.scalarMultiply(learning_rate / n, alg.mat_vec_mult(alg.transpose(inputSet), error)));
		weights = regularization.regWeights(weights, lambda, alpha, reg);

		// Calculating the bias gradients
		bias -= learning_rate * alg.sum_elements(error) / n;
		forwardPass();

		if (UI) {
			MLPPUtilities::CostInfo(epoch, cost_prev, Cost(y_hat, outputSet));
			MLPPUtilities::UI(weights, bias);
		}
		epoch++;

		if (epoch > max_epoch) {
			break;
		}
	}
}

void MLPPLogRegOld::MLE(real_t learning_rate, int max_epoch, bool UI) {
	MLPPLinAlgOld alg;
	MLPPRegOld regularization;
	real_t cost_prev = 0;
	int epoch = 1;
	forwardPass();

	while (true) {
		cost_prev = Cost(y_hat, outputSet);

		std::vector<real_t> error = alg.subtraction(outputSet, y_hat);

		// Calculating the weight gradients
		weights = alg.addition(weights, alg.scalarMultiply(learning_rate / n, alg.mat_vec_mult(alg.transpose(inputSet), error)));
		weights = regularization.regWeights(weights, lambda, alpha, reg);

		// Calculating the bias gradients
		bias += learning_rate * alg.sum_elements(error) / n;
		forwardPass();

		if (UI) {
			MLPPUtilities::CostInfo(epoch, cost_prev, Cost(y_hat, outputSet));
			MLPPUtilities::UI(weights, bias);
		}
		epoch++;
		if (epoch > max_epoch) {
			break;
		}
	}
}

void MLPPLogRegOld::SGD(real_t learning_rate, int max_epoch, bool UI) {
	MLPPLinAlgOld alg;
	MLPPRegOld regularization;
	real_t cost_prev = 0;
	int epoch = 1;

	while (true) {
		std::random_device rd;
		std::default_random_engine generator(rd());
		std::uniform_int_distribution<int> distribution(0, int(n - 1));
		int outputIndex = distribution(generator);

		real_t y_hat = Evaluate(inputSet[outputIndex]);
		cost_prev = Cost({ y_hat }, { outputSet[outputIndex] });

		real_t error = y_hat - outputSet[outputIndex];

		// Weight updation
		weights = alg.subtraction(weights, alg.scalarMultiply(learning_rate * error, inputSet[outputIndex]));
		weights = regularization.regWeights(weights, lambda, alpha, reg);

		// Bias updation
		bias -= learning_rate * error;

		y_hat = Evaluate({ inputSet[outputIndex] });

		if (UI) {
			MLPPUtilities::CostInfo(epoch, cost_prev, Cost({ y_hat }, { outputSet[outputIndex] }));
			MLPPUtilities::UI(weights, bias);
		}
		epoch++;

		if (epoch > max_epoch) {
			break;
		}
	}
	forwardPass();
}

void MLPPLogRegOld::MBGD(real_t learning_rate, int max_epoch, int mini_batch_size, bool UI) {
	MLPPLinAlgOld alg;
	MLPPRegOld regularization;
	real_t cost_prev = 0;
	int epoch = 1;

	// Creating the mini-batches
	int n_mini_batch = n / mini_batch_size;
	auto bacthes = MLPPUtilities::createMiniBatches(inputSet, outputSet, n_mini_batch);
	auto inputMiniBatches = std::get<0>(bacthes);
	auto outputMiniBatches = std::get<1>(bacthes);

	while (true) {
		for (int i = 0; i < n_mini_batch; i++) {
			std::vector<real_t> y_hat = Evaluate(inputMiniBatches[i]);
			cost_prev = Cost(y_hat, outputMiniBatches[i]);

			std::vector<real_t> error = alg.subtraction(y_hat, outputMiniBatches[i]);

			// Calculating the weight gradients
			weights = alg.subtraction(weights, alg.scalarMultiply(learning_rate / outputMiniBatches[i].size(), alg.mat_vec_mult(alg.transpose(inputMiniBatches[i]), error)));
			weights = regularization.regWeights(weights, lambda, alpha, reg);

			// Calculating the bias gradients
			bias -= learning_rate * alg.sum_elements(error) / outputMiniBatches[i].size();
			y_hat = Evaluate(inputMiniBatches[i]);

			if (UI) {
				MLPPUtilities::CostInfo(epoch, cost_prev, Cost(y_hat, outputMiniBatches[i]));
				MLPPUtilities::UI(weights, bias);
			}
		}
		epoch++;
		if (epoch > max_epoch) {
			break;
		}
	}
	forwardPass();
}

real_t MLPPLogRegOld::score() {
	MLPPUtilities util;
	return util.performance(y_hat, outputSet);
}

void MLPPLogRegOld::save(std::string fileName) {
	MLPPUtilities util;
	util.saveParameters(fileName, weights, bias);
}

real_t MLPPLogRegOld::Cost(std::vector<real_t> y_hat, std::vector<real_t> y) {
	MLPPRegOld regularization;
	class MLPPCostOld cost;
	return cost.LogLoss(y_hat, y) + regularization.regTerm(weights, lambda, alpha, reg);
}

std::vector<real_t> MLPPLogRegOld::Evaluate(std::vector<std::vector<real_t>> X) {
	MLPPLinAlgOld alg;
	MLPPActivationOld avn;
	return avn.sigmoid(alg.scalarAdd(bias, alg.mat_vec_mult(X, weights)));
}

real_t MLPPLogRegOld::Evaluate(std::vector<real_t> x) {
	MLPPLinAlgOld alg;
	MLPPActivationOld avn;
	return avn.sigmoid(alg.dot(weights, x) + bias);
}

// sigmoid ( wTx + b )
void MLPPLogRegOld::forwardPass() {
	y_hat = Evaluate(inputSet);
}