#include <limits.h>
#include <stdbool.h>
#include <stdarg.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>

static bool print(const char * str, size_t len) {
  const unsigned char * bytes = (const unsigned char *) str;

  for(size_t i = 0; i < len; i++) {
    if(putchar(bytes[i]) == EOF) {
      return false;
    }
  }

  return true;
}

static bool print_oct(unsigned int strint) {
  int i = strint, j = 10;
  char str[11] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
  
  while(j >= 0 && i > 0) {
    switch(i % 010) {
    case 0: str[j] = '0'; break;
    case 1: str[j] = '1'; break;
    case 2: str[j] = '2'; break;
    case 3: str[j] = '3'; break;
    case 4: str[j] = '4'; break;
    case 5: str[j] = '5'; break;
    case 6: str[j] = '6'; break;
    case 7: str[j] = '7'; break;
    default: return false;
    }
    i /= 010;
    j--;
  }
  for(i = 0; str[i] == '\0'; i++) {}

  return print(str+i, 11-i);
}

static bool print_ptr(void * ptrstr) {
  int i = (int) ptrstr, j = 9;
  char str[10] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
  
  while(j >= 2 && i > 0) {
    switch(i % 0x10) {
    case 0: str[j] = '0'; break;
    case 1: str[j] = '1'; break;
    case 2: str[j] = '2'; break;
    case 3: str[j] = '3'; break;
    case 4: str[j] = '4'; break;
    case 5: str[j] = '5'; break;
    case 6: str[j] = '6'; break;
    case 7: str[j] = '7'; break;
    case 8: str[j] = '8'; break;
    case 9: str[j] = '9'; break;
    case 0xA: str[j] = 'A'; break;
    case 0xB: str[j] = 'B'; break;
    case 0xC: str[j] = 'C'; break;
    case 0xD: str[j] = 'D'; break;
    case 0xE: str[j] = 'E'; break;
    case 0xF: str[j] = 'F'; break;
    default: return false;
    }
    i /= 0x10;
    j--;
  }
  for(i = 0; str[i] == '\0'; i++) {}

  i--;
  str[i] = 'x';
  i--;
  str[i] = '0';

  return print(str+i, 10-i);
}

static bool print_caphex(unsigned int strint) {
  int i = strint, j = 7;
  char str[8] = { 0, 0, 0, 0, 0, 0, 0, 0 };
  
  while(j >= 0 && i > 0) {
    switch(i % 0x10) {
    case 0: str[j] = '0'; break;
    case 1: str[j] = '1'; break;
    case 2: str[j] = '2'; break;
    case 3: str[j] = '3'; break;
    case 4: str[j] = '4'; break;
    case 5: str[j] = '5'; break;
    case 6: str[j] = '6'; break;
    case 7: str[j] = '7'; break;
    case 8: str[j] = '8'; break;
    case 9: str[j] = '9'; break;
    case 0xA: str[j] = 'A'; break;
    case 0xB: str[j] = 'B'; break;
    case 0xC: str[j] = 'C'; break;
    case 0xD: str[j] = 'D'; break;
    case 0xE: str[j] = 'E'; break;
    case 0xF: str[j] = 'F'; break;
    default: return false;
    }
    i /= 0x10;
    j--;
  }
  for(i = 0; str[i] == '\0'; i++) {}

  return print(str+i, 8-i);
}

static bool print_hex(unsigned int strint) {
  int i = strint, j = 7;
  char str[8] = { 0, 0, 0, 0, 0, 0, 0, 0 };
  
  while(j >= 0 && i > 0) {
    switch(i % 0x10) {
    case 0: str[j] = '0'; break;
    case 1: str[j] = '1'; break;
    case 2: str[j] = '2'; break;
    case 3: str[j] = '3'; break;
    case 4: str[j] = '4'; break;
    case 5: str[j] = '5'; break;
    case 6: str[j] = '6'; break;
    case 7: str[j] = '7'; break;
    case 8: str[j] = '8'; break;
    case 9: str[j] = '9'; break;
    case 0xA: str[j] = 'a'; break;
    case 0xB: str[j] = 'b'; break;
    case 0xC: str[j] = 'c'; break;
    case 0xD: str[j] = 'd'; break;
    case 0xE: str[j] = 'e'; break;
    case 0xF: str[j] = 'f'; break;
    default: return false;
    }
    i /= 0x10;
    j--;
  }
  for(i = 0; str[i] == '\0'; i++) {}

  return print(str+i, 8-i);
}

static bool print_int(int strint) {
  int i = strint, j = 10;
  char str[11] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };

  if(i < 0) {
    i = -i;
  }
  
  while(j > 0 && i > 0) {
    switch(i % 10) {
    case 0: str[j] = '0'; break;
    case 1: str[j] = '1'; break;
    case 2: str[j] = '2'; break;
    case 3: str[j] = '3'; break;
    case 4: str[j] = '4'; break;
    case 5: str[j] = '5'; break;
    case 6: str[j] = '6'; break;
    case 7: str[j] = '7'; break;
    case 8: str[j] = '8'; break;
    case 9: str[j] = '9'; break;
    default: return false;
    }
    i /= 10;
    j--;
  }
  for(i = 0; str[i] == '\0'; i++) {}

  if(strint < 0) {
    i--;
    str[i] = '-';
  }

  return print(str+i, 11-i);
}

static bool print_uint(unsigned int strint) {
  int i = strint;
  if(i < 0) {
    i = -i;
  }
  return print_int(i);
}

int printf(const char * restrict format, ...) {
  int errno;
  va_list parameters;
  va_start(parameters, format);

  int written = 0;

  while(*format != '\0') {
    size_t maxrem = INT_MAX - written;

    if(format[0] != '%' || format[1] == '%') {
      if(format[0] == '%') {
	format++;
      }

      size_t amount = 1;

      while(format[amount] && format[amount] != '%') {
	amount++;
      }

      if(maxrem < amount) {
	errno = EOVERFLOW;
	return -1;
      }

      if(!print(format, amount)) {
	return -1;
      }

      format += amount;
      written += amount;
      continue;
    }

    const char * format_begun_at = format++;

    /* TODO: Implement all format specifiers (%g, %o, &c.) */
    if(*format == 'c') {
      format++;
      char c = (char) va_arg(parameters, int);

      if(!maxrem) {
        errno = EOVERFLOW;
	return -1;
      }

      if(!print(&c, sizeof(c))) {
	return -1;
      }

      written++;
    }
    else if(*format == 's') {
      format++;
      const char * str = va_arg(parameters, const char *);
      size_t len = strlen(str);

      if(maxrem < len) {
        errno = EOVERFLOW;
	return -1;
      }

      if(!print(str, len)) {
	return -1;
      }

      written += len;
    }
    else if(*format == 'd' || *format == 'i') {
      format++;
      int i = (int) va_arg(parameters, int);

      if(!maxrem) {
	errno = EOVERFLOW;
	return -1;
      }

      if(!print_int(i)) {
	return -1;
      }

      written += 11;
    }
    else if(*format == 'u') {
      format++;
      int i = (int) va_arg(parameters, int);

      if(!maxrem) {
	errno = EOVERFLOW;
	return -1;
      }

      if(!print_uint(i)) {
	return -1;
      }

      written += 10;
    }
    else if(*format == 'o') {
      format++;
      int i = (int) va_arg(parameters, int);

      if(!maxrem) {
	errno = EOVERFLOW;
	return -1;
      }

      if(!print_oct(i)) {
	return -1;
      }

      written += 11;
    }
    else if(*format == 'x') {
      format++;
      int i = (int) va_arg(parameters, int);

      if(!maxrem) {
	errno = EOVERFLOW;
	return -1;
      }

      if(!print_hex(i)) {
	return -1;
      }

      written += 10;
    }
    else if(*format == 'X') {
      format++;
      int i = (int) va_arg(parameters, int);

      if(!maxrem) {
	errno = EOVERFLOW;
	return -1;
      }

      if(!print_caphex(i)) {
	return -1;
      }

      written += 8;
    }
    else if(*format == 'p') {
      format++;
      void * ptr = (void *) va_arg(parameters, void *);

      if(!maxrem) {
	errno = EOVERFLOW;
	return -1;
      }

      if(!print_ptr(ptr)) {
	return -1;
      }

      /* This is gonna need a change on 64-bit systems. */
      written += 10;
    }else if(*format == 'n') {
      format++;

      if(!maxrem) {
	errno = EOVERFLOW;
	return -1;
      }

      if(!print_int(written)) {
	return -1;
      }

      written += 11;
    }
    else if(*format == '%') {
      format++;
      
      if(!maxrem) {
	errno = EOVERFLOW;
	return -1;
      }

      if(!print("%", 1)) {
	return -1;
      }

      written++;
    }
    else {
      format = format_begun_at;
      size_t len = strlen(format);

      if(maxrem < len) {
        errno = EOVERFLOW;
	return -1;
      }

      if(!print(format, len)) {
	return -1;
      }

      format += len;
    } 
  }

  va_end(parameters);

  return(written);
}