#ifndef UCORE_CLOCK_H_
#define UCORE_CLOCK_H_

#include <sys/time.h>
#include <time.h>


/**
 * An abstract clock.
 * Instead of hardcoding calls to time()/gettimeofday() and similar,
 * it is useful tp have a level of indirection to better facilitate
 * testing and simulation of code that's dependent on time.
 */
struct UCoreClock {
    /**
     * Name of this clock
     */
    const char *name;
    /**
     * Wrapper for getting the current time.
     * @param tv timeval that will be filled in
     */
    void (*now)(struct UCoreClock *clock, struct timeval *tv);
};


/** A cached clock where clock.now() returns
 * the cached value. The cache is updated
 * from the real_clock whenever ucore_cached_clock_update()
 * is called.
 */
struct UCoreCachedClock {
    /** The clock*/
    struct UCoreClock clock;
    /** The underlying real clock*/
    struct UCoreClock *real_clock;
    /** cached value */
    struct timeval cache;
};

/** A settable clock where clock.now() returns
 * the user settable value. The user updates the clock
 * with ucore_settable_clock_set().
 */
struct UCoreSettableClock {
    /** The clock*/
    struct UCoreClock clock;
    /** The underlying real clock*/
    /** Current value */
    struct timeval now;
};


/** A clock where now() calls gettimeofday()
 */
extern struct UCoreClock ucore_timeofday_clock;

/**
 * A clock where now() calls time().
 * This clock will just have seconds resolution.
 */
extern struct UCoreClock ucore_time_clock;

/**
 * Initialize a cached clock where now() calls time().
 * This clock will this just have seconds resolution.
 * @param clock clock to initialize
 */
void ucore_cached_clock_init(struct UCoreCachedClock *uclock, 
                                struct UCoreClock *real_clock);

/** Update the cached clock from the real_clock
 */
void ucore_cached_clock_update(struct UCoreCachedClock *uclock);


/**
 * Initialize a user settable where now() calls time().
 * This clock will this just have seconds resolution.
 * @param clock clock to initialize
 */
void ucore_settable_clock_init(struct UCoreSettableClock *uclock);

/**
 * Set the new timeval this clock will return
 **/
void ucore_settable_clock_set_tv(struct UCoreSettableClock *uclock, 
                                const struct timeval *tv);

/**
 * Set the new timeval this clock will return
 * Convenience function that takes seconds/microseconds as arguments
 * instead of a struct timeval.
 **/
void ucore_settable_clock_set(struct UCoreSettableClock *uclock, 
                            time_t secs, suseconds_t usecs);

#endif