/*
 * @author  xamidev <xamidev@riseup.net>
 * @brief   System call handling
 * @license GPL-3.0-only
 */

#include "sched/scheduler.h"
#include <arch/x86.h>
#include <kernel.h>
#include <stddef.h>
#include <io/term/term.h>
#include <sched/process.h>

extern struct process* current_process;

void sys_write(unsigned int fd, const char* buf, size_t count)
{
    switch (fd) {
        case 1: //stdout
            for (size_t i=0; i<count; i++) {
                internal_putc(buf[i], NULL);
            }
            break;

        case 2: //stderr
            for (size_t i=0; i<count; i++) {
                internal_putc(buf[i], NULL);
            }
            break;
    }
}

void sys_exit(int error_code)
{
    current_process->status = DEAD;
    DEBUG("exiting process PID=%u name=%s", current_process->pid, current_process->name);
}

/*
 * syscall_handler - System call dispatcher
 * @regs: CPU state
 *
 * This function is called from the interrupt dispatcher,
 * when an interrupt 0x80 is emitted from userland.
 *
 * It switches control to the syscall number provided
 * in %rax. 
 *
 * We try to follow the System V convention here:
 * - syscall number in %rax
 * - args in %rdi, %rsi, %rdx, %r10, %r8, %r9
 * - return value (if any) in %rax
 *
 * Return:
 * <regs> - CPU state after system call
 */
struct cpu_status* syscall_handler(struct cpu_status* regs)
{
    DEBUG("Syscall %lx with (arg0=%lx arg1=%lx)", regs->rax, regs->rdi, regs->rsi);

    switch (regs->rax)
    {
        case 0: //sys_read
            break;
        case 1: //sys_write
            sys_write(regs->rdi, (char*)regs->rsi, regs->rdx);
            break;
        case 60: //sys_exit
            sys_exit(regs->rdi);
            break;
        default:
            regs->rax = 0xbad515ca11;
            break;
    }

    return regs;
}