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

int __fp_open(FILE *fp, int fd, bool use_buffering)
{
	/* We initialize fdpos to 0 even in append mode (7.19.3§1) */
	fp->fd = fd;
	fp->fdpos = 0;

	/* We assume all files in the filesystem are non-interactive in order
	   to conform to (7.19.5.3§7)
	   TODO: Vhex might want something more elaborate here */
	if(use_buffering && setvbuf(fp, NULL, _IOFBF, BUFSIZ))
		return -1;

	return 0;
}

void __fp_close(FILE *fp, bool free_fp)
{
	if(!fp)
		return;

	if(fp->fd >= 0) {
		fflush(fp);
		close(fp->fd);
	}
	if(fp->bufowned)
		free(fp->buf);
	if(free_fp)
		free(fp);
}

void __fp_remove_buffer(FILE *fp)
{
	if(fp->bufowned)
		free(fp->buf);

	fp->buf = NULL;
	fp->bufowned = false;
	fp->bufsize = 0;
}

bool __fp_set_buffer(FILE *fp, void *buf, size_t size)
{
	bool owned = false;

	if(!buf) {
		owned = true;
		buf = malloc(size);
		if(!buf)
			return false;
	}

	fp->buf = buf;
	fp->bufowned = owned;
	fp->bufsize = size;
	return true;
}

void __fp_buffer_mode_read(FILE *fp)
{
	if(__fp_hasbuf_write(fp)) {
		fflush(fp);
	}
	if(fp->buf)
		fp->bufdir = __FILE_BUF_READ;
}

void __fp_buffer_mode_write(FILE *fp)
{
	if(__fp_hasbuf_read(fp))
		fflush(fp);
	if(fp->buf)
		fp->bufdir = __FILE_BUF_WRITE;
}

ssize_t __fp_fread2(FILE *fp, void *data, size_t request_size, int stop_char)
{
	if(!fp->readable) {
		fp->error = 1;
		return -1;
	}

	/* If the stream if unbuffered, we might have no buffer for the reads.
	   If it's buffered, we always have one. It's also possible that fp is
	   unbuffered (_IONBF) but has a buffer temporarily because ungetc()
	   has been used, in which case we have to transition from buffered
	   reads into direct reads midway. We use __fp_buffered_read() to
	   handle this. */

	size_t read_size = 0;
	__fp_buffer_mode_read(fp);

	while(read_size < request_size) {
		int remaining = request_size - read_size;
		int chunk = __fp_buffered_read(fp, data+read_size, remaining,
			stop_char);

		/* Stream is not/no longer buffered, finish unbuffered */
		if(chunk < 0 && stop_char >= 0) {
			unsigned char c;

			/* When there is a stop char, we can only read one
			   byte at a time, which is reaaaally slow */
			for(int i = 0; i < remaining; i++) {
				ssize_t rc = __fp_read(fp, &c, 1);
				if(rc != 1)
					break;
				((char *)data)[read_size++] = c;
				if(c == stop_char)
					break;
			}
			return read_size;
		}
		else if(chunk < 0) {
			ssize_t rc = __fp_read(fp, data+read_size, remaining);
			return read_size + (rc == EOF ? 0 : rc);
		}

		read_size += chunk;
		if(read_size >= request_size)
			break;

		/* If a stop char has been read, stop */
		if(stop_char >= 0 && read_size > 0 &&
		   ((char *)data)[read_size-1] == stop_char)
			break;

		/* Get more data from the file descriptor into the buffer */
		if(fp->buf) {
			ssize_t rc = __fp_read(fp, fp->buf, fp->bufsize);
			if(rc <= 0) /* EOF or error */
				break;
			fp->bufread = rc;
		}
	}

	return read_size;
}

ssize_t __fp_buffered_read(FILE *fp, void *data, size_t request_size,
	int stop_char)
{
	if(!fp->buf || __fp_hasbuf_write(fp))
		return -1;

	int read_size = request_size;
	if(read_size > (int)(fp->bufread - fp->bufpos))
		read_size = fp->bufread - fp->bufpos;
	if(read_size <= 0)
		return 0;

	if(stop_char >= 0) {
		char *end = memchr(fp->buf+fp->bufpos, stop_char, read_size);
		if(end != NULL)
			read_size = end - (fp->buf + fp->bufpos) + 1;
	}

	memcpy(data, fp->buf + fp->bufpos, read_size);
	fp->bufpos += read_size;
	fp->bufungetc = fp->bufungetc - read_size;
	if(fp->bufungetc < 0)
		fp->bufungetc = 0;

	/* Rewind the buffer if we read it fully */
	if(fp->bufpos >= fp->bufread) {
		fp->bufread = 0;
		fp->bufpos = 0;

		/* Clear temporary ungetc() buffers of _IONBF streams */
		if(fp->bufmode == _IONBF)
			__fp_remove_buffer(fp);
	}

	return read_size;
}

ssize_t __fp_read(FILE *fp, void *data, size_t size)
{
	size_t read_ = 0;

	while(read_ < size) {
		ssize_t rc = read(fp->fd, data + read_, size - read_);

		if(rc < 0) {
			fp->error = 1;
			return EOF;
		}
		if(rc == 0) {
			fp->eof = 1;
			break;
		}

		fp->fdpos += rc;
		read_ += rc;
	}

	return read_;
}

ssize_t __fp_write(FILE *fp, void const *data, size_t size)
{
	size_t written = 0;

	while(written < size) {
		ssize_t rc = write(fp->fd, data + written, size - written);

		if(rc < 0) {
			fp->error = 1;
			return EOF;
		}
		if(rc == 0)
			break;

		fp->fdpos += rc;
		written += rc;
	}

	return written;
}

int __fp_parse_mode(char const *mode, FILE *fp)
{
	int base = 0;
	bool binary = false;
	bool update = false;

	for(int i = 0; mode[i]; i++) {
		if(mode[i] == 'r' || mode[i] == 'w' || mode[i] == 'a') {
			if(base) goto err;
			base = mode[i];
		}
		else if(mode[i] == 'b')
			binary = true;
		else if(mode[i] == '+')
			update = true;
	}
	if(!base) goto err;

	if(fp) {
		fp->readable = (base == 'r' || update);
		fp->writable = (base == 'w' || base == 'a' || update);
		fp->append = (base == 'a');
		fp->text = !binary;
	}

	if(base == 'r')
		return (update ? O_RDWR : O_RDONLY);
	if(base == 'w')
		return (update ? O_RDWR : O_WRONLY) | O_CREAT | O_TRUNC;
	if(base == 'a')
		return (update ? O_RDWR : O_WRONLY) | O_CREAT;
	/* Fallthrough */

err:
	errno = EINVAL;
	return -1;
}