/*
 * Copyright (C) 2023  Patrick McDermott
 *
 * This file is part of opkg-opkg.
 *
 * opkg-opkg is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * opkg-opkg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with opkg-opkg.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <stdlib.h>
#include <zlib.h>
#include "defs.h"
#include "gzip.h"
#include "ustar.h"

#define OPKG_OPK_GZIP_WINDOW_BITS_ (15 + 16)

struct opkg_opk_gzip {
	int      (*read)(void *, char **, size_t *);
	void      *user_data;
	z_stream   stream;
};

struct opkg_opk_gzip *
opkg_opk_gzip_init(opkg_opk_gzip_read_func *read, void *user_data)
{
	struct opkg_opk_gzip *gzip;

	gzip = malloc(sizeof(*gzip));
	if (gzip == NULL) {
		return NULL;
	}

	gzip->read      = read;
	gzip->user_data = user_data;

	gzip->stream.next_in  = Z_NULL;
	gzip->stream.avail_in = 0;
	gzip->stream.zalloc   = Z_NULL;
	gzip->stream.zfree    = Z_NULL;
	gzip->stream.opaque   = Z_NULL;
	if (inflateInit2(&gzip->stream, OPKG_OPK_GZIP_WINDOW_BITS_) != Z_OK) {
		free(gzip);
		return NULL;
	}

	return gzip;
}

int
opkg_opk_gzip_read(struct opkg_opk_gzip *gzip, void *record)
{
	int end;

	gzip->stream.next_out  = record;
	gzip->stream.avail_out = OPKG_OPK_USTAR_RECORD_SIZE;

	for (;;) {
		end = 0;
		if (gzip->stream.avail_in == 0) {
			/* Input buffer is empty and needs refilled. */
			switch (gzip->read(gzip->user_data,
						&gzip->stream.next_in,
						&gzip->stream.avail_in)) {
				case OPKG_OPK_OK:
					break;
				case OPKG_OPK_END:
					end = 1;
					break;
				case OPKG_OPK_ERROR:
				default:
					return OPKG_OPK_ERROR;
			}
		}
		switch (inflate(&gzip->stream, Z_SYNC_FLUSH)) {
			case Z_OK:
				break;
			case Z_BUF_ERROR:
				if (end == 1) {
					return OPKG_OPK_ERROR;
				}
				break;
			case Z_STREAM_END:
				if (gzip->stream.avail_out != 0) {
					/* Premature end */
					return OPKG_OPK_ERROR;
				}
				return OPKG_OPK_END;
			default:
				return OPKG_OPK_ERROR;
		}
		if (gzip->stream.avail_out == 0) {
			/* Output buffer is filled and ready for use. */
			return OPKG_OPK_OK;
		}
	}
}

void
opkg_opk_gzip_free(struct opkg_opk_gzip *gzip)
{
	inflateEnd(&gzip->stream);
	free(gzip);
}