/* libhw/generic/alarmclock.h - Device-independent alarmclock definitions
 *
 * Copyright (C) 2024  Luke T. Shumaker <lukeshu@lukeshu.com>
 * SPDX-License-Identifier: AGPL-3.0-or-later
 */

#ifndef _LIBHW_GENERIC_ALARMCLOCK_H_
#define _LIBHW_GENERIC_ALARMCLOCK_H_

#include <stdbool.h> /* for bool */
#include <stdint.h>  /* for uint{n}_t and UINT{n}_C */

#include <libmisc/private.h>
#include <libmisc/vcall.h>

/* Useful constants ***********************************************************/

#define NS_PER_S UINT64_C(1000000000) /* needs at least log₂(10⁹) ≈ 29.9 bits */
#define US_PER_S UINT64_C(1000000)    /* needs at least log₂(10⁶) ≈ 19.9 bits */
#define MS_PER_S UINT64_C(1000)       /* needs at least log₂(10³) ≈  9.9 bits */

/* Structs ********************************************************************/

struct alarmclock_trigger;
struct alarmclock_trigger {
	BEGIN_PRIVATE(LIBHW_GENERIC_ALARMCLOCK_H)
	void                            *alarmclock;
	struct alarmclock_trigger       *prev, *next;

	uint64_t                         fire_at_ns;
	void                             (*cb)(void *);
	void                            *cb_arg;
	END_PRIVATE(LIBHW_GENERIC_ALARMCLOCK_H)
};

/* Interface ******************************************************************/

struct alarmclock_vtable;

typedef struct {
	struct alarmclock_vtable     *vtable;
} implements_alarmclock;

struct alarmclock_vtable {
	/**
	 * (2⁶⁴-1 nanoseconds is more than 500 years; there is little
	 * risk of this overflowing)
	 */
	uint64_t (*get_time_ns)(implements_alarmclock *self);

	/**
	 * Returns true on error.
	 *
	 * Implementations may return an error if fire_at_ns is more
	 * than UINT32_MAX µs (72 minutes) in the future.
	 *
	 * If fire_at_ns is in the past, then it will fire
	 * immediately.
	 */
	bool     (*add_trigger)(implements_alarmclock *self, struct alarmclock_trigger *trigger,
	                        uint64_t   fire_at_ns,
	                        void       (*cb)(void *),
	                        void      *cb_arg);

	void     (*del_trigger)(implements_alarmclock *self, struct alarmclock_trigger *trigger);
};

/* Utilities ******************************************************************/

void alarmclock_sleep_until_ns(implements_alarmclock *clock, uint64_t abstime_ns);

static inline void alarmclock_sleep_for_ns(implements_alarmclock *clock, uint64_t delta_ns) {
	alarmclock_sleep_until_ns(clock, VCALL(clock, get_time_ns) + delta_ns);
}

static inline void alarmclock_sleep_for_us(implements_alarmclock *clock, uint64_t delta_us) {
	alarmclock_sleep_for_ns(clock, delta_us * (NS_PER_S/US_PER_S));
}

static inline void alarmclock_sleep_for_ms(implements_alarmclock *clock, uint64_t delta_ms) {
	alarmclock_sleep_for_ns(clock, delta_ms * (NS_PER_S/MS_PER_S));
}

static inline void alarmclock_sleep_for_s(implements_alarmclock *clock, uint64_t delta_s) {
	alarmclock_sleep_for_ns(clock, delta_s * NS_PER_S);
}

/* Globals ********************************************************************/

extern implements_alarmclock *bootclock;

#define sleep_until_ns(t) alarmclock_sleep_until_ns(bootclock, t)
#define sleep_for_ns(t)   alarmclock_sleep_for_ns(bootclock, t)
#define sleep_for_us(t)   alarmclock_sleep_for_us(bootclock, t)
#define sleep_for_ms(t)   alarmclock_sleep_for_ms(bootclock, t)
#define sleep_for_s(t)    alarmclock_sleep_for_s(bootclock, t)

#endif /* _LIBHW_GENERIC_ALARMCLOCK_H_ */