#include "tasks.h"

#include "kernel.h"
#include "string.h"

void task_init( task_t *task, uint16_t gdt_code_segment_selector, task_func_t entrypoint )
{
	memset( task, 0, sizeof( task_t ) );

	task->nof_switches = 0;
	
	task->cpu_state = (cpu_state_t *)( task->stack + TASK_STACK_SIZE - sizeof( cpu_state_t ) );
	
	task->cpu_state->eax = 0;
	task->cpu_state->ebx = 0;
	task->cpu_state->ecx = 0;
	task->cpu_state->edx = 0;
	task->cpu_state->esi = 0;
	task->cpu_state->edi = 0;
	task->cpu_state->ebp = 0;

	// neded for security spaces and users
	//~ task->cpu_state->esp = 0;
	//~ task->cpu_state->ss = 0;

	task->cpu_state->eip = (uint32_t)entrypoint;
	task->cpu_state->cs = gdt_code_segment_selector;

	// TODO: why?
	task->cpu_state->eflags = 0x202;	
	
	//~ task->cpu_state->error = 0;

	//~ task->cpu_state->gs = 0;
	//~ task->cpu_state->fs = 0;
	//~ task->cpu_state->es = 0;
	//~ task->cpu_state->ds = 0;
}

void task_manager_init( task_manager_t *manager )
{
	memset( manager, 0, sizeof( task_manager_t ) );
	
	manager->nof_tasks = 0;
	manager->current_task = -1;
	memset( manager->task, 0, MAX_NOF_TASKS * sizeof( task_t * ) );
}

void task_manager_add_task( task_manager_t *manager, task_t *task )
{
	if( manager->nof_tasks >= MAX_NOF_TASKS - 1 ) {
		kernel_panic( "Allocating more than %d tasks.. increase kernel constant MAX_NOF_TASKS", MAX_NOF_TASKS );
	}

	manager->task[manager->nof_tasks] = task;
	manager->nof_tasks++;
}

cpu_state_t *task_manager_schedule_task( task_manager_t *manager, cpu_state_t *cpu_state )
{
	// no tasks, no task switch
	if( manager->nof_tasks == 0 ) {
		return cpu_state;
	}
	
	// store state of the current task
	if( manager->current_task >= 0 ) {
		manager->task[manager->current_task]->cpu_state = cpu_state;
	}
		
	// pick next task (simple round robin)
	manager->current_task++;
	if( manager->current_task >= manager->nof_tasks ) {
		manager->current_task = 0;
	}

	manager->task[manager->current_task]->nof_switches++;
	
	return manager->task[manager->current_task]->cpu_state;
}