#ifndef uc_CLOCK_H_
#define uc_CLOCK_H_

#include <sys/time.h>
#include <time.h>
/** @addtogroup Timers
 * @{
 * Clock abstractions
 */
#ifdef __cplusplus
extern "C" {
#endif

/**
 * 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)(const struct UCoreClock *clock, struct timeval *tv);
};

/** Convenience macro for geting the time from a UCoreClock
 * @param uclock pointer to the clock
 * @param tv struct timeval pointer that will be filled in.
 */
#define UCORE_CLOCK_NOW(uclock, tv) (uclock)->now((uclock), (tv))


/** A cached clock where clock.now() returns
 * the cached value. The cache is updated
 * from the real_clock whenever uc_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 uc_settable_clock_set().
 */
struct UCoreSettableClock {
    /** The clock*/
    struct UCoreClock clock;
    /** Current value */
    struct timeval now;
};


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

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

/**
 * Initialize a cached clock whose now() is a cached
 * value of the real_clock.
 *
 * @param uclock clock to initialize
 * @param real_clock underlying clock that updates
 *          the cache.
 *        
 */
void uc_cached_clock_init(struct UCoreCachedClock *uclock, 
                          struct UCoreClock *real_clock);

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


/**
 * Initialize a user settable clock, where now()
 * returns the user set time.
 *
 * @param clock uclock to initialize
 */
void uc_settable_clock_init(struct UCoreSettableClock *uclock);

/**
 * Set the new timeval this clock will return
 *
 * @param tv new timeval to set the clock to
 **/
void uc_settable_clock_set_tv(struct UCoreSettableClock *uclock, 
                              const struct timeval *tv);

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

#ifdef __cplusplus
}
#endif

/** @} (addtogroup) */
#endif