/*
 * 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 <stdio.h>
#include <zlib.h>
#include "defs.h"
#include "gzip.h"

#define OPKG_OPK_GZIP_BUFFER_SIZE 8192

struct opkg_opk_gzip_state {
	FILE          *input_file;
	unsigned char  input_buffer[OPKG_OPK_GZIP_BUFFER_SIZE];
	z_stream       stream;
};

static int
_opkg_opk_gzip_init(struct opkg_opk_gzip_state *state)
{
	state->stream.zalloc = Z_NULL;
	state->stream.zfree  = Z_NULL;
	state->stream.opaque = Z_NULL;
	if (inflateInit(&state->stream) != Z_OK) {
		return OPKG_OPK_ERROR;
	}
	return OPKG_OPK_OK;
}

int
opkg_opk_gzip_init_from_file(struct opkg_opk_gzip_state *state,
		const char *file_name)
{
	state->input_file = fopen(file_name, "rb");
	if (state->input_file == NULL) {
		return OPKG_OPK_ERROR;
	}
	state->stream.next_in  = Z_NULL;
	state->stream.avail_in = 0;
	if (_opkg_opk_gzip_init(state) < OPKG_OPK_OK) {
		fclose(state->input_file);
		return OPKG_OPK_ERROR;
	}
	return OPKG_OPK_OK;
}

int
opkg_opk_gzip_init_from_memory(struct opkg_opk_gzip_state *state,
		unsigned char *input, size_t input_size)
{
	state->input_file = NULL;
	state->stream.next_in  = input;
	state->stream.avail_in = input_size;
	return _opkg_opk_gzip_init(state);
}

static int
_opkg_opk_gzip_next_record_from_file(struct opkg_opk_gzip_state *state)
{
	for (;;) {
		if (feof(state->input_file)) {
			fclose(state->input_file);
			state->input_file = NULL;
			inflateEnd(&state->stream);
			return OPKG_OPK_OK;
		}
		if (state->stream.avail_in == 0) {
			state->stream.avail_in = fread(state->input_buffer,
					1, OPKG_OPK_GZIP_BUFFER_SIZE,
					state->input_file);
			if (ferror(state->input_file)) {
				fclose(state->input_file);
				state->input_file = NULL;
				inflateEnd(&state->stream);
				return OPKG_OPK_ERROR;
			}
			state->stream.next_in = state->input_buffer;
		}
		if (state->stream.avail_out == 0) {
			return OPKG_OPK_OK;
		}
		switch (inflate(&state->stream, Z_SYNC_FLUSH)) {
			case Z_OK:
			case Z_STREAM_END:
			case Z_BUF_ERROR:
				break;
			default:
				fclose(state->input_file);
				state->input_file = NULL;
				inflateEnd(&state->stream);
				return OPKG_OPK_ERROR;
		}
	}
}

static int
_opkg_opk_gzip_next_record_from_memory(struct opkg_opk_gzip_state *state)
{
	switch (inflate(&state->stream, Z_SYNC_FLUSH)) {
		case Z_OK:
			return OPKG_OPK_OK;
		case Z_STREAM_END:
			return OPKG_OPK_END;
		default:
			inflateEnd(&state->stream);
			return OPKG_OPK_ERROR;
	}
}

int
opkg_opk_gzip_next_record(struct opkg_opk_gzip_state *state, void *record)
{
	state->stream.next_out  = record;
	state->stream.avail_out = 512;
	if (state->input_file != NULL) {
		return _opkg_opk_gzip_next_record_from_file(state);
	} else {
		return _opkg_opk_gzip_next_record_from_memory(state);
	}
}