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typedef struct task {
	int id; //process id
	uint32_t esp; //stack pointer
	uint32_t stack_top; //top of stack
	uint32_t eip; //instruction pointer
	uint32_t cr3; //page directory
	struct task* next; //next task in linked list
	struct task* prev; //previous task
} task_t;

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void tasking_install() {
	printf_info("Initializing tasking...");

	//init first task (kernel task)
	ready_queue = (volatile task_t*)create_process(PRIO_HIGH, (uint32_t)test_1);
	current_task = (task_t*)ready_queue;
	current_task->next = current_task;
	current_task->prev = current_task;

	//add_process(create_process(PRIO_MED, (uint32_t)test_2));
	//add_process(create_process(PRIO_MED, (uint32_t)test_3));

	//create callback to switch tasks
	//add_callback((void*)switch_callback, 1, 1, 0);

	jumpstart_main_thread();
	ASSERT(1, "Failed to start tasking!");
}

static void jumpstart_main_thread() {
	asm volatile("mov %%eax, %%esp": :"a"(current_task->esp));
	asm volatile("pop %gs");
	asm volatile("pop %fs");
	asm volatile("pop %es");
	asm volatile("pop %ds");
	asm volatile("pop %ebp");
	asm volatile("pop %edi");
	asm volatile("pop %esi");
	asm volatile("pop %edx");
	asm volatile("pop %ecx");
	asm volatile("pop %ebx");
	asm volatile("pop %eax");
	asm volatile("iret");
}

task_t* create_process(int priority, uint32_t addr) {
	task_t* task = (task_t*)kmalloc(sizeof(task_t));
	memset(task, 0, sizeof(task_t));
	task->id = next_pid++;
	task->eip = addr;
	task->esp = (uint32_t)kmalloc(KERNEL_STACK_SIZE);
	asm volatile("mov %%cr3, %%eax" : "=a"(task->cr3));
	uint32_t* stack = (uint32_t*)(task->esp + KERNEL_STACK_SIZE);
	task->stack_top = task->esp;
	*--stack = 0x00000202; 		//eflags
	*--stack = 0x8;			//cs
	*--stack = (uint32_t)addr;	//eip
	*--stack = 0;			//eax
	*--stack = 0; 			//ebx
	*--stack = 0;			//ecx
	*--stack = 0;			//edx
	*--stack = 0;			//esi
	*--stack = 0;			//edi
	*--stack = task->esp + KERNEL_STACK_SIZE; //ebp
	*--stack = 0x10;		//ds
	*--stack = 0x10;		//fs
	*--stack = 0x10;		//es
	*--stack = 0x10;		//gs
	task->esp = (uint32_t)stack;
	printf_info("Created process (PID %d) with esp %x eip %x", task->id, task->esp, task->eip);
	return task;

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void task_switch() {
	//if we haven't initialized tasking yet, quit early
	//if (!current_task) return;

	asm volatile("push %eax");
	asm volatile("push %ebx");
	asm volatile("push %ecx");
	asm volatile("push %edx");
	asm volatile("push %esi");
	asm volatile("push %edi");
	asm volatile("push %ebp");
	asm volatile("push %ds");
	asm volatile("push %es");
	asm volatile("push %fs");
	asm volatile("push %gs");
	asm volatile("mov %%esp, %%eax":"=a"(current_task->esp));

	current_task = current_task->next;
	
	asm volatile("mov %%eax, %%cr3": :"a"(current_task->cr3));
	asm volatile("mov %%eax, %%esp": :"a"(current_task->esp));
	asm volatile("pop %gs");
	asm volatile("pop %fs");
	asm volatile("pop %es");
	asm volatile("pop %ds");
	asm volatile("pop %ebp");
	asm volatile("pop %edi");
	asm volatile("pop %esi");
	asm volatile("pop %edx");
	asm volatile("pop %ecx");
	asm volatile("pop %ebx");
	asm volatile("pop %eax");
	asm volatile("iret");
}

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while (1) {
    printf_info("PID: %d", getpid());
    syscall_yield();
}