int STACK = 0x8000;
#define STDOUT 0xd0580000

__asm(".section .text_init, \"ax\"");
__asm(".global _start");
__asm("_start:");

// Enable Caches in MRAC
__asm("li t0, 0x5f555555");
__asm("csrw 0x7c0, t0");

// Set stack pointer.
__asm("la sp, STACK");

__asm("call main");

// Write 0xff to STDOUT for TB to termiate test.
__asm(".global _finish");
__asm("_finish:");
__asm("li t0, 0xd0580000");
__asm("addi t1, zero, 0xff");
__asm("sb t1, 0(t0)");
__asm("beq x0, x0, _finish");
__asm(".rept 10");
__asm("nop");
__asm(".endr");
__asm(".section .text");

#include <stdarg.h>

static int whisperPutc(char c) {
  *(volatile char*)(STDOUT) = c;
  return c;
}

static int whisperPuts(const char* s) {
  while (*s) whisperPutc(*s++);
  return 1;
}

static int whisperPrintDecimal(int value) {
  char buffer[20];
  int charCount = 0;
  unsigned neg = value < 0;
  if (neg) {
    value = -value;
    whisperPutc('-');
  }
  do {
    char c = '0' + (value % 10);
    value = value / 10;
    buffer[charCount++] = c;
  } while (value);
  char* p = buffer + charCount - 1;
  for (unsigned i = 0; i < charCount; ++i) whisperPutc(*p--);
  if (neg) charCount++;
  return charCount;
}

static int whisperPrintInt(int value, int base) {
  if (base == 10) return whisperPrintDecimal(value);
  char buffer[20];
  int charCount = 0;
  unsigned uu = value;
  if (base == 8) {
    do {
      char c = '0' + (uu & 7);
      buffer[charCount++] = c;
      uu >>= 3;
    } while (uu);
  } else if (base == 16) {
    do {
      int digit = uu & 0xf;
      char c = digit < 10 ? '0' + digit : 'a' + digit - 10;
      buffer[charCount++] = c;
      uu >>= 4;
    } while (uu);
  } else
    return -1;
  char* p = buffer + charCount - 1;
  for (unsigned i = 0; i < charCount; ++i) whisperPutc(*p--);
  return charCount;
}

int whisperPrintfImpl(const char* format, va_list ap) {
  int count = 0;  // Printed character count
  for (const char* fp = format; *fp; fp++) {
    if (*fp != '%') {
      whisperPutc(*fp);
      ++count;
      continue;
    }
    ++fp;  // Skip %
    if (*fp == 0) break;
    if (*fp == '%') {
      whisperPutc('%');
      continue;
    }
    if (*fp == '-') {
      fp++;  // Pad right not yet implemented.
    }
    while (*fp == '0') {
      fp++;  // Pad zero not yet implented.
    }
    if (*fp == '*') {
      int width = va_arg(ap, int);
      fp++;  // Width not yet implemented.
    } else {
      while (*fp >= '0' && *fp <= '9') ++fp;  // Width not yet implemented.
    }
    switch (*fp) {
      case 'd':
        count += whisperPrintDecimal(va_arg(ap, int));
        break;
      case 'u':
        count += whisperPrintDecimal((unsigned)va_arg(ap, unsigned));
        break;
      case 'x':
      case 'X':
        count += whisperPrintInt(va_arg(ap, int), 16);
        break;
      case 'o':
        count += whisperPrintInt(va_arg(ap, int), 8);
        break;
      case 'c':
        whisperPutc(va_arg(ap, int));
        ++count;
        break;
      case 's':
        count += whisperPuts(va_arg(ap, char*));
        break;
    }
  }
  return count;
}

int whisperPrintf(const char* format, ...) {
  va_list ap;
  va_start(ap, format);
  int code = whisperPrintfImpl(format, ap);
  va_end(ap);
  return code;
}

int printf(const char* format, ...) {
  va_list ap;
  va_start(ap, format);
  int code = whisperPrintfImpl(format, ap);
  va_end(ap);
  return code;
}

// #include <stdio.h>

int add(int a, int b) { return (a + b) * (a - b); }

int main() {
  printf("Hello RISCV!\n");
  int a = add(1, 23);
  printf("a:%d\n", a);
  return 0;
}