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

#include "data_manager.h"
#include "barometer.h"

static float pressure[PRESSURE_UNIT_MAX];
static float setting[PRESSURE_UNIT_MAX];
static float altitude[ALTITUDE_UNIT_MAX];

/* utility functions */
static float pressure_to_metres_asl(float real, float setting)
{
	return 44330.f*(1.f-powf(real/setting, 1/5.255));
}


/* exported functions */
#define DATA_MANAGER_GETTER(name, store, bound, enum_type, return_type) \
float name(enum_type unit) \
{ \
	if (unit >= 0 && unit < bound) { \
		return store[unit]; \
	} else { \
		abort(); \
	} \
}

DATA_MANAGER_GETTER(
	data_manager_get_pressure,
	pressure,
	PRESSURE_UNIT_MAX,
	enum pressure_unit,
	float)
DATA_MANAGER_GETTER(
	data_manager_get_setting,
	setting,
	PRESSURE_UNIT_MAX,
	enum pressure_unit,
	float)
DATA_MANAGER_GETTER(
	data_manager_get_altitude,
	altitude,
	ALTITUDE_UNIT_MAX,
	enum altitude_unit,
	float)

void data_manager_init(void)
{
	/* FIXME load initial setting and force a tick synchronously */
}

void data_manager_tick(void)
{
	/* FIXME alt rate */
	/* FIXME calculate on demand? */
	/* FIXME hardcoding the conversion factors here is gross */
	float p = barometer_read();
	pressure[PRESSURE_UNIT_HPA] = p;
	pressure[PRESSURE_UNIT_INHG] = p / 3.38639;

	/* FIXME we need atomic access to alt setting once user can set it. Check
	 * if AVR allows multiple/nested ISRs to run concurrently, pretty sure not
	 */
	float a = pressure_to_metres_asl(p, setting[PRESSURE_UNIT_HPA]);
	altitude[ALTITUDE_UNIT_METRE] = a;
	altitude[ALTITUDE_UNIT_FT] = a * 3.048;
}