// 
// Utility
//

#include <math.h>
#include <stdlib.h>
#include <stdbool.h>

#include "utility.h"

typedef float(*utility_function_prototype)(float _x, float _eta, float _sig);
float util_func_tanh(float _x, float _eta, float _sig);
float util_func_gauss(float _x, float _eta, float _sig);

struct utility_s {
    float target;
    int goal;
    int scale;
    bool flip;
    utility_function_prototype f;
    float eta;
    float sig;
};

utility utility_create(float _target, int _goal, int _scale)
{
    utility u = (utility) malloc(sizeof(struct utility_s));
    u->target = _target;
    u->goal = _goal;
    u->scale = _scale;

    switch (u->goal) {
    case UTIL_GOAL_MIN:
        u->f = &util_func_tanh;
        u->eta = u->target;
        u->sig = 1.0f;
        u->flip = true;
        break;
    case UTIL_GOAL_MAX:
        u->f = &util_func_tanh;
        u->eta = u->target;
        u->sig = 1.0f;
        u->flip = false;
        break;
    case UTIL_GOAL_MEET:
        u->f = &util_func_gauss;
        u->eta = u->target;
        u->sig = 1.0f;
        u->flip = false;
        break;
    case UTIL_GOAL_AVOID:
        u->f = &util_func_gauss;
        u->eta = u->target;
        u->sig = 1.0f;
        u->flip = true;
        break;
    default:;
    }

    return u;
}

void utility_free(utility _u)
{
    free(_u);
}

float utility_evaluate(utility _u, float _x)
{
    float y = _x;
    if (_u->scale==UTIL_SCALE_LOG)
        y = logf(y);
    float v = _u->f( y, _u->eta, _u->sig);
    return (_u->flip) ? 1-v : v;

}

float util_func_tanh(float _x, float _eta, float _sig) {
    return tanhf((_x-_eta)/_sig);
}

float util_func_gauss(float _x, float _eta, float _sig) {
    return expf( -powf((_x-_eta),2)/(2*_sig*_sig) );
}