// 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=-1;

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

int add_task(uint32_t esp, uint32_t vmem)
{

    for(int i=0;i<MAX_TASKS;i++)
    {
	if(task_list[i].active!=true)
	{

	    task_list[i].parent=current_task;
	    task_list[i].vmem=vmem;
	    task_list[i].esp=esp;
	    task_list[i].active=true;
	    task_list[i].waiting=false;
	    task_list[i].skipwait=false;

	    return i;
	}
    }

    panic(FOOLOS_MODULE_NAME,"out of task slots!");
}

uint32_t my_scheduler(uint32_t oldesp)
{
    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 && !task_list[pid].waiting)
	{
	  //  if(current_task!=pid)
	//	    log(FOOLOS_MODULE_NAME,FOOLOS_LOG_INFO,"switch from %d to %d", current_task, pid);

	    current_task=pid;

	    vmem_set_dir(task_list[pid].vmem);
	    return task_list[pid].esp;
	}

    }

    panic(FOOLOS_MODULE_NAME,"nothing to schedule!");
}

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

    // check if multitasking has been started
    if(current_task<0)return oldesp; 

    return my_scheduler(oldesp);

}


//TODO: free vmem too!
//TODO: notify waiting parent when child finished;
uint32_t task_exit(uint32_t oldesp)
{ 
    task_list[current_task].active=false;
    int parent_pid=task_list[current_task].parent;

    log(FOOLOS_MODULE_NAME,FOOLOS_LOG_INFO,"[%d] exit ", current_task);
    if(task_list[parent_pid].active)
    {
	if(task_list[parent_pid].waiting)
	{
    
	   log(FOOLOS_MODULE_NAME,FOOLOS_LOG_INFO,"wakeing up %d ", parent_pid);
	   task_list[parent_pid].waiting=false;
	}
	else
	{
	   log(FOOLOS_MODULE_NAME,FOOLOS_LOG_INFO,"set skipwait on %d ", parent_pid);
	   task_list[parent_pid].skipwait=true;
	}
	
    }

    return my_scheduler(oldesp);

}

uint32_t task_wait(uint32_t oldesp)
{ 
    log(FOOLOS_MODULE_NAME,FOOLOS_LOG_INFO,"[%d] wait", current_task);
    if(task_list[current_task].skipwait)
    {
	task_list[current_task].skipwait=false;
    }
    else
    {
	task_list[current_task].waiting=true;
    }
    return my_scheduler(oldesp);
}

uint32_t task_fork(uint32_t oldesp)
{ 
   int pid=add_task(oldesp,vmem_new_space_dir(task_list[current_task].vmem));
   log(FOOLOS_MODULE_NAME,FOOLOS_LOG_INFO,"[%d] forked -> [%d]", current_task, pid);
   return pid;
}

// init task (root of all other tasks / processes) //
void task_init()
{
    // this is our main task on slot 0 
    task_list[0].parent=0;
    task_list[0].active=true;
    task_list[0].waiting=false;
    task_list[0].vmem=0;
    task_list[0].esp = 0; // will be set by next task_switch_next() call.
    current_task=0;

    static char *argv[]={"/bin/foolshell",NULL};
    static char *env[]={"PATH=/bin","PWD=/home/miguel","PS1=$ ",NULL};
    syscall_execve("/bin/init",argv,env); 
}


int task_get_current_pid()
{
    return current_task;
}