/*
 * @author  xamidev <xamidev@riseup.net>
 * @brief   Round-robin scheduler
 * @license GPL-3.0-only
 */

#include <kernel.h>
#include <sched/process.h>
#include <mem/paging.h>
#include <stdint.h>
#include <io/serial/serial.h>

extern struct process_t* processes_list;
extern struct process_t* current_process;
extern struct process_t* idle_proc;

/*
 * scheduler_init - Choose the first process
 */
void scheduler_init()
{
    current_process = processes_list;
}

/*
 * scheduler_schedule - Main scheduling routine
 * @context: CPU context of previous process
 *
 * Chooses the next process that we should run.
 * The routine is executed every SCHEDULER_QUANTUM ticks.
 *
 * Return:
 * <context> - CPU context for next process
 */
struct cpu_status_t* scheduler_schedule(struct cpu_status_t* context)
{
    if (context == NULL) {
        panic(NULL, "Scheduler called with NULL context"); 
    }

    if (current_process == NULL) {
        // If no more processes, then set IDLE as the current process, that's it.
        current_process = idle_proc;
    }

    if (current_process == idle_proc && current_process->next == NULL)
    {
        return idle_proc->context;
    }

    current_process->context = context;

    for (;;) {
        struct process_t* prev_process = current_process;
        if (current_process->next != NULL) {
            current_process = current_process->next;
        } else {
            current_process = processes_list;
        }
        
        if (current_process != NULL && current_process->status == DEAD) {
            process_delete(&prev_process, current_process);
            current_process = NULL;
            return idle_proc->context;
        } else {
            current_process->status = RUNNING;
/*             if (prev_process != current_process) {
                DEBUG("Changed from {pid=%u, name=%s} to {pid=%u, name=%s}", prev_process->pid, prev_process->name, current_process->pid, current_process->name);
            } */
            break;
        }
    }

    //DEBUG("current_process={pid=%u, name='%s', root_page_table[virt]=%p}", current_process->pid, current_process->name, current_process->root_page_table);

    load_cr3(VIRT_TO_PHYS((uint64_t)current_process->root_page_table));
    //DEBUG("Loaded process PML4 into CR3");

    return current_process->context;
}