/*
 * cm_heatsink_emulator.c
 *
 *  Created on: 14 Oct 2025
 *      Author: Christian L. V. Madsen (OZ1CM)
 */
#include "cm_heatsink_emulator.h"
#include "math.h"

#define EULER_NUM 2.7182818284590452353602

static int isStructOk(cm_heatsinkEmul_t *inst){
	if(inst == NULL)return 0;
	if(inst->thermalElements == NULL)return 0;
	if(inst->thermalElements_Counts == 0)return 0;

	return 1;

}

static float deltaTempElement(cm_heatsink_thermalElement_t *element, float temperature, float power, float fan_speed){

	if((fan_speed > 0.0) && (fan_speed <= 1.0)){

		float dtemp = element->R_th_MaxFan - element->R_th_MinFan;
		return power * (element->R_th_MinFan + (dtemp * fan_speed));

	}else{
		// Kelvin = Watt * K/W
		return (power * element->R_th);
	}

}

static float updateCthFromFan(cm_heatsink_thermalElement_t *element, float fan_speed){

	if((fan_speed > 0.0) && (fan_speed <= 1.0)){

		float dc = element->C_th_MaxFan - element->C_th_MinFan;
		return (element->C_th_MinFan + (dc * fan_speed));

	}else{
		return element->C_th;
	}

}

int cm_heatsinkEmul_iterate(cm_heatsinkEmul_t *inst, float dtime){
	if(!isStructOk(inst)) return 1;

	float dtemp = inst->ambientTemp;

	// We begin from ambient temperature and move up towards heat source.
	for(int i = (inst->thermalElements_Counts-1); i >= 0; i--){

		// Calculate temperature until we reach requested element!
		dtemp += deltaTempElement(&inst->thermalElements[i], dtemp, inst->power, inst->fan_speed);

		float C_th = updateCthFromFan(&inst->thermalElements[i], inst->fan_speed);

		// Do so the temperature has the responsetime as the heatsink.
		inst->thermalElements[i].temperature = inst->thermalElements[i].temperature + (1.0 / C_th) * (dtemp - inst->thermalElements[i].temperature) * dtime;
	}
	return 0;

}

float cm_heatsinkEmul_getElementTemp(cm_heatsinkEmul_t *inst, int element_idx){
	if(!isStructOk(inst)) return 0.0;
	if(element_idx > (inst->thermalElements_Counts-1)) return 0.0;
	return inst->thermalElements[element_idx].temperature;

}

int cm_heatsinkEmul_setFan(cm_heatsinkEmul_t *inst, float fan_speed){
	if(!isStructOk(inst)) return 1;
	inst->fan_speed = fan_speed;

	return 0;
}


int cm_heatsinkEmul_init(cm_heatsinkEmul_t *inst, cm_heatsink_thermalElement_t *elements, int elements_Count, float C_th, float power, float ambientTemp){

	if(inst == NULL)return 1;
	if(elements == NULL)return 1;
	if(elements_Count == 0)return 1;

	inst->thermalElements = elements;
	inst->thermalElements_Counts = elements_Count;

	inst->power = power;
	inst->ambientTemp = ambientTemp;

	// Dynamic values
	inst->fan_speed = 0;

	// Assume all elements is equal to ambient before we start!
	for(int i = (inst->thermalElements_Counts-1); i >= 0; i--){
		inst->thermalElements[i].temperature = inst->ambientTemp;
	}

	return 0;

}