#include <errno.h>
#include <stdint.h>
#include <stddef.h>
#include <sys/stat.h>
#include <sys/types.h>

#include "bsp/uart.h"

extern char __heap_start[];
extern char __heap_end[];

static char *heap_cur;

void *_sbrk(ptrdiff_t incr)
{
  if (heap_cur == NULL) {
    heap_cur = __heap_start;
  }

  char *prev = heap_cur;
  char *next = heap_cur + incr;
  if (next < __heap_start || next > __heap_end) {
    errno = ENOMEM;
    return (void *)-1;
  }

  heap_cur = next;
  return prev;
}

int _write(int fd, const void *buf, size_t count)
{
  if (fd != 1 && fd != 2) {
    errno = EBADF;
    return -1;
  }

  const char *s = (const char *)buf;
  for (size_t i = 0; i < count; ++i) {
    bsp_uart_putc(s[i]);
  }
  return (int)count;
}

int _read(int fd, void *buf, size_t count)
{
  if (fd != 0) {
    errno = EBADF;
    return -1;
  }

  char *s = (char *)buf;
  size_t n = 0;
  while (n < count) {
    int ch = bsp_uart_getc_nonblocking();
    if (ch < 0) {
      break;
    }
    s[n++] = (char)ch;
  }
  return (int)n;
}

int _close(int fd)
{
  (void)fd;
  return -1;
}

int _fstat(int fd, struct stat *st)
{
  if (fd < 0 || st == NULL) {
    errno = EBADF;
    return -1;
  }
  st->st_mode = S_IFCHR;
  return 0;
}

int _isatty(int fd)
{
  return (fd == 0 || fd == 1 || fd == 2) ? 1 : 0;
}

off_t _lseek(int fd, off_t offset, int whence)
{
  (void)fd;
  (void)offset;
  (void)whence;
  errno = ESPIPE;
  return (off_t)-1;
}

int _getpid(void)
{
  return 1;
}

int _kill(int pid, int sig)
{
  (void)pid;
  (void)sig;
  errno = EINVAL;
  return -1;
}

void _exit(int status)
{
  uint32_t code = 0x5a5a0000U | ((uint32_t)status & 0xffffU);
  asm volatile ("csrw mscratch, %0" :: "r"(code) : "memory");
  asm volatile ("fence" ::: "memory");
  for (;;) {
    asm volatile ("wfi");
  }
}