#include "file.h"

#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define DEFAULT_BUFFER_SIZE 4096

#define FILE_UNUSABLE(f)    (((f)->f_flags & (FILE_EOF | FILE_ERR)) != 0)

int __libc_file_refill(struct __opaque_file *f)
{
	f->f_buf_datalen = 0;
	f->f_buf_readptr = 0;

	if (f->f_fd < 0) {
		return EBADF;
	}

	if (f->f_flags & FILE_ERR) {
		return EIO;
	}

	if (f->f_flags & FILE_EOF) {
		return SUCCESS;
	}

	if (!f->f_buf) {
		f->f_buf_max = DEFAULT_BUFFER_SIZE;
		f->f_buf = malloc(f->f_buf_max);
		if (!f->f_buf) {
			f->f_buf_max = 0;
			return ENOMEM;
		}
	}

	long r = read(f->f_fd, f->f_buf, f->f_buf_max);
	if (r < 0) {
		return -r;
	}

	f->f_buf_datalen = r;
	return SUCCESS;
}

int __libc_file_read(struct __opaque_file *f, void *out, size_t count)
{
	if (f->f_fd < 0) {
		return EBADF;
	}

	if (f->f_flags & FILE_ERR) {
		return EIO;
	}

	if (f->f_flags & FILE_EOF) {
		return SUCCESS;
	}

	size_t available = f->f_buf_datalen - f->f_buf_readptr;
	if (count > available) {
		count = available;
	}

	memcpy(out, f->f_buf + f->f_buf_readptr, count);

	f->f_buf_readptr += count;

	return count;
}

size_t __libc_file_available(struct __opaque_file *f)
{
	return f->f_buf_datalen - f->f_buf_readptr;
}