#include <avr/io.h>
#include <avr/interrupt.h>
#include <math.h>
#include <stdio.h>
#include <string.h>

#include "controller.h"

#include "bridge.h"
#include "serial.h"

static void adc_init(void)
{
	/* Configure the ADC */
	ADMUX = (1 << REFS1) | (1 << REFS0);
	/* select channel x (0 for now) */
	ADMUX |= 0x0;
	ADCSRA = (1 << ADEN) | (1 << ADIE)
		| (1 << ADPS2) | (1 << ADPS1)
		| (1 << ADPS0);
}

/* Initializes TIMER1 */
static void timer_init(void)
{
	TCCR1B = (1 << WGM12) | (1 << CS12) | (1 << CS10);
	OCR1A = 7200;
	TIMSK|=(1<<OCIE1A);
}

static volatile char controller_in_init;
static volatile char controller_active;
static volatile long controller_target_temp;
static volatile char controller_num_iterations;
static volatile uint16_t controller_measured_temp;

void controller_init(void)
{
	controller_active = 0;
	controller_in_init = 1;

	bridge_init();
	adc_init();
	timer_init();
}

static long celsius_to_adc(double target_temp)
{
	long rv;

	rv = 1203.59290 * exp(-0.0686201496 * target_temp) + 413.59437;
	if (rv > 1017)
		return 1017;
	if (rv < 450)
		return 450;
	return rv;
}

static double adc_to_celsius(long adc)
{
	double rv;

	rv = adc - 413.59437;
	rv /= 1203.59290;
	rv = log(rv);
	rv /= -0.0686201496;
	return rv;
}

int controller_set(double target)
{
	if (target < 8.0 || target > 42.0)
		return 1;

	controller_target_temp = celsius_to_adc(target);
	controller_num_iterations = 1;
	controller_active = 1;
	return 0;
}

double controller_get(void)
{
	return adc_to_celsius(controller_measured_temp);
}

void controller_off(void)
{
	controller_active = 0;
	bridge_off();
}

ISR(TIMER1_COMPA_vect)
{
	/* Start adc measurement */
	ADCSRA |= (1<<ADSC);
}

ISR(ADC_vect) 
{
	if (controller_in_init) {
		controller_measured_temp = ADCW;
		controller_in_init = 0;
	} else {
		controller_measured_temp = (0.8 * controller_measured_temp)
			                 + (0.2 * ADCW);
	}

	if (! controller_active)
		return;

	controller_num_iterations--;
	if (controller_num_iterations) {
#if 0
		char buffer[128];
		snprintf(buffer, sizeof(buffer), "DEBUG adc==%ld adc_target=%ld\r\n",
				(long int)controller_measured_temp,
				controller_target_temp);
		serial_send(buffer, strlen(buffer), 0);
#endif
		return;
	}

	controller_num_iterations = 60;

	if ((long)controller_measured_temp < controller_target_temp - 5) {
		/* Cooling required */
		bridge_on_cool();
		return;
	}

	if ((long)controller_measured_temp > controller_target_temp + 20) {
		/* Heating required */
		bridge_on_heat();
		return;
	}

	/* Temperature is roughly okay, turn bridge off until next
	 * measurement. */
	bridge_off();
}