#include <os_sched.h>
#include "os_port.h"
#include "os_critical.h"
#include "os_rdy_list.h"
#include "os_yield_list.h"
#include "os_idle.h"
#include "os_isr.h"

volatile os_task_t* g_os_sched_current_task_p;
volatile os_size_t g_os_sched_pending_cnt;
static volatile os_task_t* p_curr_task;
static volatile os_task_t* p_next_task;
static os_bool_t s_os_sched_wip_flag;

/* ------------------------------------------------------------------------------------------------------------------ */
/*  */


void os_sched_init(void){
    g_os_sched_current_task_p = 0;
    g_os_sched_pending_cnt = 0;
    s_os_sched_wip_flag = OS_FALSE;
}

void os_sched_in_isr(void){
    os_critical_enter_in_isr();

    if(s_os_sched_wip_flag == OS_TRUE){
        // 调度正在进行中，返回
        os_critical_leave_in_isr();
        return;
    }
    s_os_sched_wip_flag = OS_TRUE;

    if(g_os_isr_nesting_cnt>0){
        // 中断嵌套
        g_os_sched_pending_cnt++;
        s_os_sched_wip_flag = OS_FALSE;
        os_critical_leave_in_isr();
        return;
    }

    if(g_os_sched_current_task_p && g_os_sched_current_task_p->state == kOsTaskState_Running){
        // 当前任务还在运行，返回
        s_os_sched_wip_flag = OS_FALSE;
        os_critical_leave_in_isr();
        return;
    }

    p_curr_task = g_os_sched_current_task_p;

    // 获取下一个任务
    os_priority_t priority = os_priority_get_highest();
    os_rdy_list_t* p_rdy_list = os_rdy_list_get(priority);
    os_list_node_t* p_node = p_rdy_list->head.next;
    p_next_task = os_list_member_of(p_node, os_task_t, node);
    if(!os_idle_is_idle_task((os_task_t*)p_next_task)){
        os_rdy_list_remove((os_task_t*)p_next_task);
    }

    // yield 的任务加入就绪表
    for(p_node = g_os_yield_list.next; p_node!=&g_os_yield_list; ){
        os_task_t* p_task = os_list_member_of(p_node, os_task_t, node);
        p_node = p_node->next;
        os_yield_list_remove(p_task);
        if(!os_idle_is_idle_task(p_task)) {
            os_rdy_list_insert(p_task);
        }
    }

    // 下个任务就是当前任务, 获得一次运行的机会
    if(p_next_task==p_curr_task){
        p_next_task->state = kOsTaskState_Running;
        p_next_task->remain_ticks = p_next_task->init_ticks;
        s_os_sched_wip_flag = OS_FALSE;
        os_critical_leave_in_isr();
        return;
    }

    s_os_sched_wip_flag = OS_FALSE;
    os_critical_leave_in_isr();

    // 执行上下文切换
    os_port_context_switch((void*)(p_curr_task?&p_curr_task->stack.sp:0), (void*)&p_next_task->stack.sp);
}