/********************************************************
 *  ██████╗  ██████╗████████╗██╗
 * ██╔════╝ ██╔════╝╚══██╔══╝██║
 * ██║  ███╗██║        ██║   ██║
 * ██║   ██║██║        ██║   ██║
 * ╚██████╔╝╚██████╗   ██║   ███████╗
 *  ╚═════╝  ╚═════╝   ╚═╝   ╚══════╝
 * Geophysical Computational Tools & Library (GCTL)
 *
 * Copyright (c) 2023  Yi Zhang (yizhang-geo@zju.edu.cn)
 *
 * GCTL is distributed under a dual licensing scheme. You can redistribute 
 * it and/or modify it under the terms of the GNU Lesser General Public 
 * License as published by the Free Software Foundation, either version 2 
 * of the License, or (at your option) any later version. You should have 
 * received a copy of the GNU Lesser General Public License along with this 
 * program. If not, see <http://www.gnu.org/licenses/>.
 * 
 * If the terms and conditions of the LGPL v.2. would prevent you from using 
 * the GCTL, please consider the option to obtain a commercial license for a 
 * fee. These licenses are offered by the GCTL's original author. As a rule, 
 * licenses are provided "as-is", unlimited in time for a one time fee. Please 
 * send corresponding requests to: yizhang-geo@zju.edu.cn. Please do not forget 
 * to include some description of your company and the realm of its activities. 
 * Also add information on how to contact you by electronic and paper mail.
 ******************************************************/

#include "loss_func.h"

gctl::loss_func::loss_func()
{
    init_ = false;
    eps_ = 1e-8;
    tnum_ = 0;
    ntype_ = L2;
}

gctl::loss_func::loss_func(const array<double> &tar, norm_type_e n_type, double p, double eps)
{
    init(tar, n_type);
}

gctl::loss_func::~loss_func(){}

void gctl::loss_func::init(const array<double> &tar, norm_type_e n_type, double p, double eps)
{
    if (p < 1) throw std::runtime_error("[gctl::loss_func] Invalid power number.");
    if (eps <= 0) throw std::runtime_error("[gctl::loss_func] Invalid epsilon value.");

    init_ = true;

    tnum_ = tar.size();
    diff_.resize(tnum_);
    us_.resize(tnum_, 1.0);
    tars_ = tar;
    
    ntype_ = n_type;
    eps_ = eps;
    p_ = p;
    return;
}

void gctl::loss_func::set_uncertainty(double uncer)
{
    if (!init_) throw std::runtime_error("[gctl::loss_func] Not initialized.");
    us_.resize(tnum_, uncer);
    return;
}

void gctl::loss_func::set_uncertainty(const array<double> &uncer)
{
    if (!init_) throw std::runtime_error("[gctl::loss_func] Not initialized.");
    if (uncer.size() != tnum_) throw std::runtime_error("[gctl::loss_func] Invalid array size.");
    us_ = uncer;
    return;
}

double gctl::loss_func::evaluate(const array<double> &x, array<double> &g)
{
    if (!init_) throw std::runtime_error("[gctl::loss_func] Not initialized.");
    if (x.size() != tnum_) throw std::runtime_error("[gctl::loss_func] Invalid array size.");

    for (size_t i = 0; i < tnum_; i++)
    {
        diff_[i] = (x[i] - tars_[i])/us_[i];
    }

    double loss = 0.0;
    g.resize(tnum_);

    if (ntype_ == L1)
    {
        for (size_t i = 0; i < tnum_; i++)
        {
            loss += fabs(diff_[i]);
            if (diff_[i] >= 0.0) g[i] = 1.0/(us_[i]*tnum_);
            else g[i] = -1.0/(us_[i]*tnum_);
        }
    }
    else if (ntype_ == L2)
    {
        for (size_t i = 0; i < tnum_; i++)
        {
            loss += diff_[i]*diff_[i];
            g[i] = 2.0*diff_[i]/(us_[i]*tnum_);
        }
    }
    else if (ntype_ == Lp)
    {
        for (size_t i = 0; i < tnum_; i++)
        {
            loss += pow(diff_[i]*diff_[i] + eps_*eps_, 0.5*p_);
            g[i] = p_*pow(diff_[i]*diff_[i] + eps_*eps_, 0.5*p_ - 1)*diff_[i]/(us_[i]*tnum_);
        }
    }
    else throw std::runtime_error("[gctl::loss_func] Invalid measurement type.");

    return loss/tnum_;
}