/* ScummVM - Graphic Adventure Engine
 *
 * ScummVM is the legal property of its developers, whose names
 * are too numerous to list here. Please refer to the COPYRIGHT
 * file distributed with this source distribution.
 *
 * This program 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 2
 * of the License, or (at your option) any later version.
 *
 * This program 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 this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 */

#include "glk/tads/tads2/tads2.h"
#include "glk/tads/tads2/types.h"

namespace Glk {
namespace TADS {
namespace TADS2 {

/**
 * Signatures for character map files.  The signature is stored at the
 * beginning of the file.
 */
// single-byte character map version 1.0.0
#define CMAP_SIG_S100  "TADS2 charmap S100\n\r\01a"

void TADS2::cmap_init_default() {
	size_t i;

	// initialize the input table
	for (i = 0 ; i < sizeof(G_cmap_input)/sizeof(G_cmap_input[0]) ; ++i)
		G_cmap_input[i] = (unsigned char)i;

	// initialize the output table
	for (i = 0 ; i < sizeof(G_cmap_output)/sizeof(G_cmap_output[0]) ; ++i)
		G_cmap_output[i] = (unsigned char)i;

	// we have a null ID
	memset(G_cmap_id, 0, sizeof(G_cmap_id));

	// indicate that it's the default
	strcpy(G_cmap_ldesc, "(native/no mapping)");

	// note that we have no character set loaded
	S_cmap_loaded = false;
}

int TADS2::cmap_load_internal(const char *filename) {
	osfildef *fp;
	static char sig1[] = CMAP_SIG_S100;
	char buf[256];
	uchar lenbuf[2];
	size_t len;
	int sysblk;

	// if there's no mapping file, use the default mapping
	if (filename == 0) {
		// initialize with the default mapping
		cmap_init_default();

		// return success
		return 0;
	}

	// open the file
	fp = osfoprb(filename, OSFTCMAP);
	if (fp == 0)
		return 1;

	// check the signature
	if (osfrb(fp, buf, sizeof(sig1))
		|| memcmp(buf, sig1, sizeof(sig1)) != 0) {
		osfcls(fp);
		return 2;
	}

	// load the ID
	G_cmap_id[4] = '\0';
	if (osfrb(fp, G_cmap_id, 4)) {
		osfcls(fp);
		return 3;
	}

	// load the long description
	if (osfrb(fp, lenbuf, 2)
		|| (len = osrp2(lenbuf)) > sizeof(G_cmap_ldesc)
		|| osfrb(fp, G_cmap_ldesc, len)) {
		osfcls(fp);
		return 4;
	}

	// load the two tables - input, then output
	if (osfrb(fp, G_cmap_input, sizeof(G_cmap_input))
		|| osfrb(fp, G_cmap_output, sizeof(G_cmap_output))) {
		osfcls(fp);
		return 5;
	}

	// read the next section header
	if (osfrb(fp, buf, 4)) {
		osfcls(fp);
		return 6;
	}

	// if it's "SYSI", read the system information string
	if (!memcmp(buf, "SYSI", 4)) {
		// read the length prefix, then the string
		if (osfrb(fp, lenbuf, 2)
			|| (len = osrp2(lenbuf)) > sizeof(buf)
			|| osfrb(fp, buf, len)) {
			osfcls(fp);
			return 7;
		}

		// we have a system information block
		sysblk = true;
	} else {
		// there's no system information block
		sysblk = false;
	}

	/*
	 * call the OS code, so that it can do any system-dependent
	 * initialization for the new character mapping
	 */
	os_advise_load_charmap(G_cmap_id, G_cmap_ldesc, sysblk ? buf : "");

	// read the next section header
	if (sysblk && osfrb(fp, buf, 4)) {
		osfcls(fp);
		return 8;
	}

	// see if we have an entity list
	if (!memcmp(buf, "ENTY", 4)) {
		// read the entities
		for (;;) {
			unsigned int cval;
			char expansion[CMAP_MAX_ENTITY_EXPANSION];

			// read the next item's length and character value
			if (osfrb(fp, buf, 4)) {
				osfcls(fp);
				return 9;
			}

			// decode the values
			len = osrp2(buf);
			cval = osrp2(buf+2);

			// if we've reached the zero marker, we're done
			if (len == 0 && cval == 0)
				break;

			// read the string
			if (len > CMAP_MAX_ENTITY_EXPANSION
				|| osfrb(fp, expansion, len)) {
				osfcls(fp);
				return 10;
			}

			// tell the output code about the expansion
			tio_set_html_expansion(cval, expansion, len);
		}
	}

	/*
	 * ignore anything else we find - if the file format is updated to
	 * include extra information in the future, and this old code tries
	 * to load an updated file, we'll just ignore the new information,
	 * which should always be placed after the "SYSI" block (if present)
	 * to ensure compatibility with past versions (such as this code)
	 */
	// no problems - close the file and return success
	osfcls(fp);
	return 0;
}

int TADS2::cmap_load(const char *filename) {
	int err;

	// try loading the file
	if ((err = cmap_load_internal(filename)) != 0)
		return err;

	/*
	 * note that we've explicitly loaded a character set, if they named
	 * a character set (if not, this simply establishes the default
	 * setting, so we haven't explicitly loaded anything)
	 */
	if (filename != nullptr)
		S_cmap_loaded = true;

	// success
	return 0;
}

void TADS2::cmap_override() {
	// apply the default mapping
	cmap_init_default();

	/*
	 * pretend we have a character map loaded, so that we don't try to
	 * load another one if the game specifies a character set
	 */
	S_cmap_loaded = true;
}

void TADS2::cmap_set_game_charset(errcxdef *ec, const char *internal_id,
		const char *internal_ldesc, const char *argv0) {
	char filename[OSFNMAX];

	/*
	 * If a character set is already explicitly loaded, ignore the
	 * game's character set - the player asked us to use a particular
	 * mapping, so ignore what the game wants.  (This will probably
	 * result in incorrect display of non-ASCII character values, but
	 * the player is most likely to use this to avoid errors when an
	 * appropriate mapping file for the game is not available.  In this
	 * case, the player informs us by setting the option that he or she
	 * knows and accepts that the game will not look exactly right.)
	 */
	if (S_cmap_loaded)
		return;

	/*
	 * ask the operating system to name the mapping file -- this routine
	 * will determine, if possible, the current native character set,
	 * and apply a system-specific naming convention to tell us what
	 * mapping file we should open
	 */
	os_gen_charmap_filename(filename, internal_id, argv0);

	// try loading the mapping file
	if (cmap_load_internal(filename))
		errsig2(ec, ERR_CHRNOFILE,
				ERRTSTR, errstr(ec, filename, strlen(filename)),
				ERRTSTR, errstr(ec, internal_ldesc, strlen(internal_ldesc)));

	/**
	 * We were successful - the game's internal character set is now
	 * mapped to the current native character set.  Even though we
	 * loaded an ldesc from the mapping file, forget that and store the
	 * internal ldesc that the game specified.  The reason we do this is
	 * that it's possible that the player will dynamically switch native
	 * character sets in the future, at which point we'll need to
	 * re-load the mapping table, which could raise an error if a
	 * mapping file for the new character set isn't available.  So, we
	 * may need to provide the same explanation later that we needed to
	 * provide here.  Save the game's character set ldesc for that
	 * eventuality, since it describes exactly what the *game* wanted.
	 */
	strcpy(G_cmap_ldesc, internal_ldesc);
}

} // End of namespace TADS2
} // End of namespace TADS
} // End of namespace Glk