#ifndef GPS_NAV_EPOCH_H
#define GPS_NAV_EPOCH_H

#include <stdbool.h>
#include <stdint.h>

/*
 * The current receiver exposes nine tracking channels.  Keep the epoch
 * selector bounded so its exhaustive, allocation-free search has a fixed
 * worst-case cost on the embedded target.
 */
#define GPS_NAV_EPOCH_MAX_CANDIDATES 9u

typedef struct {
	int week;
	double tow_sec;
	uint32_t raw_sample;
} gps_nav_epoch_key_t;

typedef struct {
	uint32_t selected_mask;
	unsigned int selected_count;
	unsigned int reference_index;
} gps_nav_epoch_selection_t;

typedef struct {
	uint64_t epoch_id;
	uint32_t expected_mask;
	uint32_t received_mask;
	bool active;
} gps_nav_epoch_assembly_t;

typedef enum {
	GPS_NAV_EPOCH_EVENT_INVALID = 0,
	GPS_NAV_EPOCH_EVENT_ACCEPTED,
	GPS_NAV_EPOCH_EVENT_DUPLICATE,
	GPS_NAV_EPOCH_EVENT_STALE,
	GPS_NAV_EPOCH_EVENT_FUTURE,
	GPS_NAV_EPOCH_EVENT_COMPLETE
} gps_nav_epoch_event_result_t;

bool gps_nav_epoch_select(
	const gps_nav_epoch_key_t candidates[GPS_NAV_EPOCH_MAX_CANDIDATES],
	unsigned int candidate_count,
	uint32_t sample_window,
	double tow_tolerance_sec,
	gps_nav_epoch_selection_t* selection);

bool gps_nav_epoch_id(
	int week,
	double tow_sec,
	unsigned int period_ms,
	uint64_t* epoch_id);

void gps_nav_epoch_assembly_reset(gps_nav_epoch_assembly_t* assembly);

gps_nav_epoch_event_result_t gps_nav_epoch_assembly_push(
	gps_nav_epoch_assembly_t* assembly,
	uint64_t epoch_id,
	unsigned int channel,
	uint32_t ready_mask);

bool gps_nav_epoch_assembly_remove_channel(
	gps_nav_epoch_assembly_t* assembly,
	unsigned int channel);

bool gps_nav_epoch_assembly_complete(
	const gps_nav_epoch_assembly_t* assembly);

#endif