// http://hosted.cjmovie.net/TutMultitask.htm
//
//
#include "kernel.h"
#include "lib/logger/log.h"	// logger facilities
#include "lib/buffer/ringbuffer.h"	
#include "mem.h"
#include "timer.h"
#include "console.h"
#include "x86.h"

#include "syscalls.h"
#include "fs/fs.h"
#include "fs/ext2.h"
#define FOOLOS_MODULE_NAME "task"


#define MAX_TASKS 10

static volatile int current_task=-2;

static volatile struct task_list_struct
{
    bool active;
    uint32_t esp; // stack pointer of the task;
    uint32_t vmem; // number of virtual memory table to switch to
    
}task_list[MAX_TASKS];


void task_create(int pid,void(*thread)())
{
     unsigned int *stack;

    task_list[pid].esp = pmmngr_alloc_block();
    stack = (unsigned int*)task_list[pid].esp+4095; //This makes a pointer to the stack for us

    log(FOOLOS_MODULE_NAME,FOOLOS_LOG_INFO,"new task: stack: 0x%08X  thread: 0x%08X", stack, thread);

 //First, this stuff is pushed by the processor
 *--stack = 0x0202; //This is EFLAGS
 *--stack = 0x08;   //This is CS, our code segment
 *--stack = (uint32_t)thread; //This is EIP
 
 //Next, the stuff pushed by 'pusha'
 *--stack = 0; //EDI
 *--stack = 0; //ESI
 *--stack = 0; //EBP
 *--stack = 0; //Just an offset, no value
 *--stack = 0; //EBX
 *--stack = 0; //EDX
 *--stack = 0; //ECX
 *--stack = 0; //EAX
 
 //Now these are the data segments pushed by the IRQ handler
 /*
 *--stack = 0x10; //DS
 *--stack = 0x10; //ES
 *--stack = 0x10; //FS
 *--stack = 0x10; //GS
 */
 
    task_list[pid].esp = (uint32_t)stack; //Update the stack pointer
    task_list[pid].active=true;

};

// this gets called by our clock interrupt regularly!
uint32_t task_switch_next(uint32_t oldesp)
{
    timer_tick();

    if(current_task==-2)return oldesp;
    if(current_task!=-1)task_list[current_task].esp=oldesp;
    
    for(int i=0;i<MAX_TASKS;i++)
    {
	int pid=(current_task+1+i)%MAX_TASKS; // schedule round robin style

	if(task_list[pid].active)
	{
	    // log(FOOLOS_MODULE_NAME,FOOLOS_LOG_INFO,"switch from %d to pid: %d (0x%08X)", current_task,pid,task_list[pid].esp);
	    current_task=pid;
	    return task_list[pid].esp;
	}

    }

    return oldesp;

}


// task testing //

volatile int c1,c2;

volatile void test1()
{
    while(1)
    {
        c1++;
	syscall_write(1,">",1);
	sleep(1);
    }
}

volatile void test2()
{
    while(1)
    {
        c2++;
	syscall_write(1,"<",1);
	sleep(1);
    }
    
}
void task_init()
{
    task_create(0,test1);
    task_create(1,test2);
    current_task=-1;
}