#include <stdio.h>
#include <stdlib.h>

typedef struct {
	unsigned int d1;	// high to low: d1 = 3
	unsigned int d3;	// low to high: d3 = 3
	unsigned int s1;	// high to off: s1 = 30
	unsigned int s3;	// off to high: s3 = 3
	unsigned int s4;	// high: s4 = 4
				// s3+s4 = time to refetch data from L2;
} PARM;

typedef enum {Active, Drowsy, Sleep} STATE;

typedef struct {
	float opt_drowsy;
	float opt_sleep;
	float opt_hybrid;
} OPT_ENERGY;

float power(STATE s);
float transition_energy(STATE from, STATE to);

OPT_ENERGY * energy_saving(unsigned int *interval, unsigned int len, PARM parm)
{
	OPT_ENERGY * opt_energy;

	unsigned int i, inflection_a, inflection_b;
	float te_active_drowsy, te_active_sleep, te_sleep_active, te_drowsy_active;	// transition energies	
	float saving;

	te_active_drowsy = transition_energy(Active, Drowsy);
	te_active_sleep = transition_energy(Active, Sleep);
	te_drowsy_active = transition_energy(Drowsy, Active);
	te_sleep_active = transition_energy(Sleep, Active);

	opt_energy = (OPT_ENERGY *) malloc(sizeof(OPT_ENERGY));
	if (opt_energy == NULL) {
		printf("no enough memory to allocate\n");
		exit(1);
	}
	opt_energy->opt_drowsy = 0.;
	opt_energy->opt_sleep = 0.;
	opt_energy->opt_hybrid = 0.;

	inflection_a = parm.d1 + parm.d3;
	inflection_b = (unsigned int)((te_active_sleep + te_sleep_active) 
			- (te_active_drowsy + te_drowsy_active))
			/ power(Drowsy) + inflection_a;

	for (i = 0; i < len; i++) {
		if (interval[i] > inflection_b) {
			saving = power(Active) * interval[i] 
				- te_active_sleep - te_sleep_active;
			opt_energy->opt_sleep += saving;
			opt_energy->opt_drowsy += power(Active) * interval[i]
						- te_active_drowsy - te_drowsy_active
						- power(Drowsy) * (interval[i] - inflection_a);
		} else if ( interval[i] > inflection_a ) {
			saving = power(Active) * interval[i] 
				- te_active_drowsy - te_drowsy_active
				- power(Drowsy) * (interval[i] - inflection_a);
			opt_energy->opt_drowsy += saving;
		} else {
			saving = 0.;
		}
		opt_energy->opt_hybrid += saving;
	}
	return opt_energy;
}