//
// formatted console output -- printf, panic.
//

// TODO Printf to not use mul/div/mod and all that and send stuff to hw-implemented UART

#include <stdarg.h>

#include "types.h"
#include "param.h"
#include "spinlock.h"
#include "sleeplock.h"
#include "fs.h"
#include "file.h"
#include "memlayout.h"
#include "riscv.h"
#include "defs.h"
#include "proc.h"

volatile int panicked = 0;

// lock to avoid interleaving concurrent printf's.
static struct {
  struct spinlock lock;
  int locking;
} pr;

static char digits[] = "0123456789abcdef";

int mul(int x, int y)
{
  int ret = x;
  for (int tmp = y-1; tmp > 0; tmp--) {
    // Add higher and lower 16 bits seperately
    // apparently gcc uses muldi3 builtin while adding long long ints    
    int rettmp = ret;    
    ret = (((uint16)(x>>16))+((uint16)(rettmp>>16)));
    ret += (((uint16)(x&0xffff))+((uint16)(rettmp&0xffff)));
  }
  return ret;
}

int mod(int x, int y)
{
  int idx = 0;
  for (idx = 0; mul(idx, y) <= x; idx++);
  idx = x-mul((idx-1), y);
  return idx;
}

int div(int x, int y)
{
  if (y >= x)
    return 0;
  int ret = 1;
  for (; (x=x-y) >= y; ret++);  
  return ret;
}

static void
printint(int xx, int base, int sign)
{
  char buf[16];
  int i;
  uint x;
  
  if(sign && (sign = xx < 0))
    x = -xx;
  else
    x = xx;

  i = 0;
  do {
    buf[i++] = digits[mod(x, base)];
    x = div(x, base);
  } while(x != 0);

  if(sign)
    buf[i++] = '-';

  while(--i >= 0)
    consputc(buf[i]);
}

static void
printptr(uint64 x)
{
  int i;
  consputc('0');
  consputc('x');
  for (i = 0; i < (mul(sizeof(uint64), 2)); i++, x <<= 4)
    consputc(digits[x >> (mul(sizeof(uint64), 8) - 4)]);
}

// Print to the console. only understands %d, %x, %p, %s.
void
printf(char *fmt, ...)
{
  va_list ap;
  int i, c, locking;
  char *s;

  locking = pr.locking;
  if(locking)
    acquire(&pr.lock);

  if (fmt == 0)
    panic("null fmt");

  va_start(ap, fmt);
  for(i = 0; (c = fmt[i] & 0xff) != 0; i++){
    if(c != '%'){
      consputc(c);
      continue;
    }
    c = fmt[++i] & 0xff;
    if(c == 0)
      break;
    switch(c){
    case 'd':
      printint(va_arg(ap, int), 10, 1);
      break;
    case 'x':
      printint(va_arg(ap, int), 16, 1);
      break;
    case 'p':
      printptr(va_arg(ap, uint64));
      break;
    case 's':
      if((s = va_arg(ap, char*)) == 0)
        s = "(null)";
      for(; *s; s++)
        consputc(*s);
      break;
    case '%':
      consputc('%');
      break;
    default:
      // Print unknown % sequence to draw attention.
      consputc('%');
      consputc(c);
      break;
    }
  }

  if(locking)
    release(&pr.lock);
}

void
panic(char *s)
{
  pr.locking = 0;
  printf("panic: ");
  printf(s);
  printf("\n");
  panicked = 1; // freeze uart output from other CPUs
  for(;;)
    ;
}

void
printfinit(void)
{
  initlock(&pr.lock, "pr");
  pr.locking = 1;
}