/*
 * 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)

enum _opkg_opk_gzip_dir {
	_OPKG_OPK_GZIP_DIR_READ,
	_OPKG_OPK_GZIP_DIR_WRITE,
};

struct opkg_opk_gzip {
	enum _opkg_opk_gzip_dir   dir;
	char                     *buffer;
	size_t                    buffer_size;
	opkg_opk_gzip_read_func  *read_func;
	opkg_opk_gzip_write_func *write_func;
	void                     *user_data;
	z_stream                  stream;
};

static struct opkg_opk_gzip *
_opkg_opk_gzip_init(enum _opkg_opk_gzip_dir dir, char *buffer, size_t size,
		opkg_opk_gzip_read_func *read_func,
		opkg_opk_gzip_write_func *write_func, void *user_data)
{
	struct opkg_opk_gzip *gzip;
	gz_header             gz_header;

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

	gzip->dir         = dir;
	gzip->buffer      = buffer;
	gzip->buffer_size = size;
	gzip->read_func   = read_func;
	gzip->write_func  = write_func;
	gzip->user_data   = user_data;

	gzip->stream.zalloc   = Z_NULL;
	gzip->stream.zfree    = Z_NULL;
	gzip->stream.opaque   = Z_NULL;

	if (dir == _OPKG_OPK_GZIP_DIR_READ) {
		gzip->stream.next_in  = Z_NULL;
		gzip->stream.avail_in = 0;
		if (inflateInit2(&gzip->stream, OPKG_OPK_GZIP_WINDOW_BITS_) !=
				Z_OK) {
			free(gzip);
			return NULL;
		}
	} else {
		gzip->stream.next_out  = buffer;
		gzip->stream.avail_out = size;
		if (deflateInit2(&gzip->stream, 9, Z_DEFLATED,
					OPKG_OPK_GZIP_WINDOW_BITS_, 9,
					Z_DEFAULT_STRATEGY) != Z_OK) {
			free(gzip);
			return NULL;
		}
		gz_header.text    = 0;
		gz_header.time    = 0;       /* Stored as 32-bit unsigned int */
		gz_header.os      = 3;       /* Unix, per RFC 1952 */
		gz_header.extra   = Z_NULL;
		gz_header.name    = Z_NULL;
		gz_header.comment = Z_NULL;
		gz_header.hcrc    = 0;
		if (deflateSetHeader(&gzip->stream, &gz_header) != Z_OK) {
			deflateEnd(&gzip->stream);
			free(gzip);
			return NULL;
		}
	}

	return gzip;
}

struct opkg_opk_gzip *
opkg_opk_gzip_init_read(opkg_opk_gzip_read_func *read, void *user_data)
{
	return _opkg_opk_gzip_init(_OPKG_OPK_GZIP_DIR_READ, NULL, 0,
			read, NULL, user_data);
}

struct opkg_opk_gzip *
opkg_opk_gzip_init_write(char *buffer, size_t size,
		opkg_opk_gzip_write_func *write, void *user_data)
{
	return _opkg_opk_gzip_init(_OPKG_OPK_GZIP_DIR_WRITE, buffer, size,
			NULL, write, user_data);
}

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

	/* Sanity check */
	if (gzip->dir != _OPKG_OPK_GZIP_DIR_READ) {
		return OPKG_OPK_ERROR;
	}

	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_func(gzip->user_data,
						(char **) &gzip->stream.next_in,
						(size_t *) &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;
		}
	}
}

int
opkg_opk_gzip_write(struct opkg_opk_gzip *gzip, void *record, size_t size,
		int last)
{
	/* Sanity check */
	if (gzip->dir != _OPKG_OPK_GZIP_DIR_WRITE) {
		return OPKG_OPK_ERROR;
	}

	gzip->stream.next_in  = record;
	gzip->stream.avail_in = size;

	do {
		switch (deflate(&gzip->stream,
					(last > 0 ? Z_FINISH : Z_NO_FLUSH))) {
			case Z_OK:
			case Z_BUF_ERROR:
			case Z_STREAM_END:
				break;
			default:
				return OPKG_OPK_ERROR;
		}
		/* Process output buffer. */
		switch (gzip->write_func(gzip->user_data,
					gzip->buffer_size
					- gzip->stream.avail_out)) {
			case OPKG_OPK_OK:
				gzip->stream.next_out  = gzip->buffer;
				gzip->stream.avail_out = gzip->buffer_size;
				break;
			case OPKG_OPK_END:
			case OPKG_OPK_ERROR:
			default:
				return OPKG_OPK_ERROR;
		}
	} while (gzip->stream.avail_out == 0);

	if (gzip->stream.avail_in != 0) {
		return OPKG_OPK_ERROR;
	}
	if (last == 0) {
		/* Input buffer is empty and needs refilled. */
		return OPKG_OPK_OK;
	} else {
		return OPKG_OPK_END;
	}
}

int
opkg_opk_gzip_free(struct opkg_opk_gzip *gzip)
{
	int ret;

	ret = OPKG_OPK_OK;
	if (gzip->dir == _OPKG_OPK_GZIP_DIR_READ) {
		if (inflateEnd(&gzip->stream) != Z_OK) {
			ret = OPKG_OPK_ERROR;
		}
	} else {
		if (deflateEnd(&gzip->stream) != Z_OK) {
			ret = OPKG_OPK_ERROR;
		}
	}
	free(gzip);
	return ret;
}