#ifndef CX_ZIVUOS_KERNEL_H_INCLUDED
#define CX_ZIVUOS_KERNEL_H_INCLUDED

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

#include "zv_types.h"
#include "task.h"
#include "idle.h"

/**
 * @brief That return number of tasks from tasks array (x for zv_task_t [x]).
 * Usefull for zv_kernel_init.
 * 
 * @param X Tasks stack.
 * @return Tasks count on tasks stack.
 */
#define ZV_COUNT_TASKS(X) (sizeof(X) / sizeof(zv_task_t))

/**
 * @brief That is main kernel structure. Do not modify without API.
 * 
 * It store pointer to tasks stack, size of that stack and idle worker.
 */
typedef struct zv_kernel_s {
    
    /** Pointer to tasks stack. */
    zv_task_t *tasks;

    /** Size of tasks stack. */
    zv_tid_t tasks_count;

    /** That is idle worker. By default do nothing. Could be replaced. */
    zv_idle_worker_t idle_worker;

} zv_kernel_t;

/**
 * @brief That initialize kernel structure.
 * 
 * That function initialize kernel structure. It must be called to initialize
 * kernel. 
 * Kernel initialization require tasks stack and kernel structure which is
 * NULL pointers, and tasks stack count which must be greater than 0.
 *
 * @param self Pointer to kernel structure to work on.
 * @param tasks Pointer to tasks stack.
 * @param count Number of tasks slots on stack.
 * @return True when kernel initialize success, false if cannot initialize it.
 */
bool zv_kernel_init(zv_kernel_t *self, zv_task_t *tasks, zv_tid_t count);

/** 
 * @brief That boot OS. It return when task stack is empty.
 * 
 * That is main kernel loop. By default it would not return. 
 * It could be break only when tasks stack is empty, or when any task
 * raise error.
 *
 * @return True when everything is executed, and all tasks had been killed.
 *         False when something went wrong.
 */
bool zv_kernel_boot(zv_kernel_t *self);

/**
 * @brief That function create process.
 * 
 * That function create process, require process worker, process priority
 * and process param. Process param is pointer to any data or number as 
 * intptr_r or uintptr_t. It return task ID or ZV_TID_NULL when can not
 * create process. Process creation fails when worker is NULL pointer or
 * when tasks stack is full.
 *
 * @param self Kernel to work on.
 * @param worker Worker of the process.
 * @param priority Priority of the process. Greater number is bigger priority.
 * @param param Param of the process.
 * @return Task ID on success, ZV_TID_NULL on fail.
 */
zv_tid_t zv_kernel_create_process(
    zv_kernel_t *self,
    zv_worker_t worker,
    zv_priority_t priority,
    void *param
);

/** 
 * @brief That function kill process.
 * 
 * That function kill process. Process can not being killed when not exists.
 * 
 * @param self Kernel to work on.
 * @param target Task ID of task to kill.
 * @return True when task killed successfull, false when failed.
 */
bool zv_kernel_kill_process(
    zv_kernel_t *self,
    zv_tid_t target
);

/**
 * That function return first empty slot TID or ZV_TID_NULL when tasks stack
 * is full.
 * 
 * @param self Kernel to work on.
 * @return First empty task slot TID or ZV_TID_NULL when tasks stack is full.
 */
zv_tid_t __zv_kernel_get_empty_slot(zv_kernel_t *self);

/**
 * That function return pointer to task based on task ID.
 * 
 * @param self Kernel to work on.
 * @param target Task ID to get pointer.
 * @return Pointer to task with given ID or NULL when task slot not exists.
 */
zv_task_t * __zv_kernel_get_task(zv_kernel_t *self, zv_tid_t target);

/**
 * That function return task ID based on pointer to task on task stack.
 * 
 * @param self Kernel to work on.
 * @param target Pointer to task.
 * @return Task ID of that task.
 */
zv_tid_t __zv_kernel_get_tid(zv_kernel_t *self, zv_task_t *target);

#endif