/* *****************************************************************************
 * decode/std.c -- decode a "standard" CASIO file.
 * Copyright (C) 2017 Thomas "Cakeisalie5" Touhey <thomas@touhey.fr>
 *
 * This file is part of libg1m.
 * libg1m is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 3.0 of the License,
 * or (at your option) any later version.
 *
 * libg1m 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with libg1m; if not, see <http://www.gnu.org/licenses/>.
 * ************************************************************************** */
#include <libg1m/internals.h>
#define FUNC(NAME) g1m_decode_std_##NAME

/* ************************************************************************** */
/*  Getting the parsing function                                              */
/* ************************************************************************** */
/* Correspondance type */
typedef int (*decode_func)(g1m_t*, g1m_buffer_t*, struct standard_header*);
struct corresp {
	unsigned int platform;
	unsigned int type;

	/* result */
	decode_func decode;
};

/* The correspondances */
static struct corresp parsing_functions[] = {
	/* add-ins */
	{g1m_platform_fx, g1m_type_addin,
		FUNC(addin)},
	{g1m_platform_cg, g1m_type_addin,
		FUNC(addin_cg)},

	/* mcs */
	{g1m_platform_fx, g1m_type_mcs,
		FUNC(mcs)},
	{g1m_platform_cg, g1m_type_mcs,
		FUNC(mcs)},

	/* language files */
	{g1m_platform_fx, g1m_type_lang,
		FUNC(lang)},
	{g1m_platform_cg, g1m_type_lang,
		FUNC(lang_cg)},

	/* function keys file */
	{g1m_platform_fx, g1m_type_fkey,
		FUNC(fkey)},
	{g1m_platform_cg, g1m_type_fkey,
		FUNC(lang_cg)},

	/* e-activities */
	{g1m_platform_fx, g1m_type_eact,
		FUNC(eact)},

	/* pictures */
	{g1m_platform_cg, g1m_type_pict,
		FUNC(g3p)},
	{g1m_platform_cp, g1m_type_pict,
		FUNC(c2p)},

	/* storage */
	/*{g1m_platform_none, g1m_type_storage,
		g1m_decode_storage},*/

	{0, 0, NULL}
};

/**
 *	find_decode_function:
 *	Find the parsing function.
 *
 *	@arg	handle		the handle.
 *	@arg	path		the file path.
 *	@arg	std			pointer to the standard header.
 *	@arg	rd			pointer to the decode function.
 *	@return				the error code (0 if ok).
 */

static int find_decode_function(g1m_t *handle, const char *path,
	struct standard_header *std, decode_func *rd)
{
	/* get the type */
	unsigned int platform, type;
	const char *type_string;
	int check_one, check_two;
	if (g1m_get_type_info(path, std->main_id, std->subtype, &type_string,
		&check_one, &check_two, &platform, &type))
		return (g1m_error_magic);
	log_info("Standard Header type is '%s'.", type_string);

	/* check control bytes */
	if (check_one && std->control != ((std->filesize + 0x41) & 0xff)) {
		log_info("First control byte isn't right.");
		return (g1m_error_magic);
	} else if (check_two && std->control2 != ((std->filesize + 0xb8) & 0xff)) {
		log_info("Second control byte isn't right.");
		return (g1m_error_magic);
	}

	/* look for corresponding parsing function */
	struct corresp *c = parsing_functions - 1;
	while ((++c)->decode) {
		if (c->type != type)
			continue;
		if (c->platform != platform)
			continue;

		break;
	}
	if (!c->decode) {
		log_fatal("No parsing function was found for this type.");
		return (g1m_error_magic);
	}

	/* set the vars */
	handle->type = type;
	handle->platform = platform;
	*rd = c->decode;
	return (0);
}

/* ************************************************************************** */
/*  Main standard header decoding function                                    */
/* ************************************************************************** */
/**
 *	g1m_decode_std:
 *	Decode a file with standard header.
 *
 *	@arg	handle			the handle.
 *	@arg	path			the path.
 *	@arg	buffer			the buffer to read from.
 *	@arg	std				the standard header.
 *	@arg	expected_types	the expected types.
 *	@return					the error code (0 if ok).
 */

int g1m_decode_std(g1m_t *handle, const char *path, g1m_buffer_t *buffer,
	struct standard_header *std, g1m_type_t expected_types)
{
	/* reverse the standard header */
	uint8_t *u = (uint8_t*)std;
	for (size_t i = 0; i < sizeof(struct standard_header); i++)
		u[i] = ~u[i];

	/* print header */
	log_info("Raw inverted standard header is:");
	logm_info(std, sizeof(struct standard_header));

	/* correct standard header endianess */
	std->filesize = be32toh(std->filesize);
	std->number = be16toh(std->number);

	/* get type */
	decode_func read_func; int err;
	if ((err = find_decode_function(handle, path, std, &read_func)))
		return (err);

	/* check if the type is alright */
	if (expected_types && handle->type != expected_types)
		return (g1m_error_wrong_type);

	/* log some data */
	log_info("Standard Header filesize is %" PRIu32 "o.", std->filesize);
	log_info("Standard Header num is %" PRIu16 ".", std->number);

	/* subdecode. */
	return ((*read_func)(handle, buffer, std));
}