/**
 * @ingroup kernel
 * @{
 * @file        sched.h
 * @author      Freie Universität Berlin, Computer Systems & Telematics
 * @author      Kaspar Schleiser <kaspar@schleiser.de>
 */

#ifndef _SCHEDULER_H
#define _SCHEDULER_H

#include <stddef.h>
#include <bitarithm.h>
#include "tcb.h"

#define MAXTHREADS 32

#if ARCH_32_BIT
#define SCHED_PRIO_LEVELS 32
#else
#define SCHED_PRIO_LEVELS 16
#endif

/**
 * @brief   Initializes thread table, active thread information, and runqueues
 */
void sched_init(void);

/**
 * @brief   Triggers the scheduler to select schedule the next task
 */
void sched_run(void);

/**
 * @brief   Set the status of the specified process
 *
 * @param[in]   process     Pointer to the thread control block of the 
 *                          targeted process
 * @param[in]   status      The new status of this thread
 */
void sched_set_status(tcb_t *process, unsigned int status);

/**
 * @brief   Switch to thread of higher priority
 *
 * @param[in]   current_prio    The priority of the current thread
 * @param[in]   other_prio      The priority of the target thread
 * @param[in]   in_isr          1 if currently in interrupt context, 0 otherwise */
void sched_switch(uint16_t current_prio, uint16_t other_prio, int in_isr);

/**
 * @brief   Call context switching at task exit
 */
void cpu_switch_context_exit(void);

/**
 *  Request a context switch for the next scheduler run (useful during 
 *  interrupt handling)
 */
extern volatile unsigned int sched_context_switch_request;

/**
 *  Thread table
 */
extern volatile tcb_t *sched_threads[MAXTHREADS];

/**
 *  Currently active thread
 */
extern volatile tcb_t *active_thread;

/**
 *  Number of running (non-terminated) threads
 */
extern volatile int num_tasks;

/**
 *  Process ID of active thread
 */
extern volatile int thread_pid;

#if SCHEDSTATISTICS
/**
 *  Scheduler statistics
 */
typedef struct {
    unsigned int laststart; /*< Time stamp of the last time this thread was
                                scheduled to run */
    unsigned int schedules; /*< How often the thread was scheduled to run */
    unsigned int runtime;   /*< The total runtime of this thread */
} schedstat;

/**
 *  Thread statistics table
 */
extern schedstat pidlist[MAXTHREADS];

/**
 *  Register a callback for every scheduler run
 */
void sched_register_cb(void (*callback)(uint32_t, uint32_t));
#endif

/** @} */
#endif // _SCHEDULER_H