#include "stdafx.h"
#include "ttd.h"
#include "string.h"
#include "strings.h"
#include "table/strings.h"
#include "namegen.h"
#include "station.h"
#include "town.h"
#include "vehicle.h"
#include "news.h"
#include "screenshot.h"
#include "waypoint.h"

static char *StationGetSpecialString(char *buff);
static char *GetSpecialTownNameString(char *buff, int ind);
static char *GetSpecialPlayerNameString(char *buff, int ind);

static char *DecodeString(char *buff, const char *str);

extern const char _openttd_revision[];

typedef struct LanguagePack {
	uint32 ident;
	uint32 version;			// 32-bits of auto generated version info which is basically a hash of strings.h
	char name[32];			// the international name of this language
	char own_name[32];	// the localized name of this language
	char isocode[16];	// the ISO code for the language (not country code)
	uint16 offsets[32];	// the offsets
	char data[VARARRAY_SIZE];
} LanguagePack;

static char **_langpack_offs;
static LanguagePack *_langpack;
static uint _langtab_num[32]; // Offset into langpack offs
static uint _langtab_start[32]; // Offset into langpack offs

const StringID _currency_string_list[] = {
	STR_CURR_GBP,
	STR_CURR_USD,
	STR_CURR_EUR,
	STR_CURR_YEN,
	STR_CURR_ATS,
	STR_CURR_BEF,
	STR_CURR_CHF,
	STR_CURR_CZK,
	STR_CURR_DEM,
	STR_CURR_DKK,
	STR_CURR_ESP,
	STR_CURR_FIM,
	STR_CURR_FRF,
	STR_CURR_GRD,
	STR_CURR_HUF,
	STR_CURR_ISK,
	STR_CURR_ITL,
	STR_CURR_NLG,
	STR_CURR_NOK,
	STR_CURR_PLN,
	STR_CURR_ROL,
	STR_CURR_RUR,
	STR_CURR_SEK,
	STR_CURR_CUSTOM,
	INVALID_STRING_ID
};

static const StringID _cargo_string_list[NUM_LANDSCAPE][NUM_CARGO] = {
	{ /* LT_NORMAL */
		STR_PASSENGERS,
		STR_TONS,
		STR_BAGS,
		STR_LITERS,
		STR_ITEMS,
		STR_CRATES,
		STR_TONS,
		STR_TONS,
		STR_TONS,
		STR_TONS,
		STR_BAGS,
		STR_RES_OTHER
	},

	{ /* LT_HILLY */
		STR_PASSENGERS,
		STR_TONS,
		STR_BAGS,
		STR_LITERS,
		STR_ITEMS,
		STR_CRATES,
		STR_TONS,
		STR_TONS,
		STR_RES_OTHER,
		STR_TONS,
		STR_BAGS,
		STR_TONS
	},

	{ /* LT_DESERT */
		STR_PASSENGERS,
		STR_LITERS,
		STR_BAGS,
		STR_LITERS,
		STR_TONS,
		STR_CRATES,
		STR_TONS,
		STR_TONS,
		STR_TONS,
		STR_LITERS,
		STR_BAGS,
		STR_TONS
	},

	{ /* LT_CANDY */
		STR_PASSENGERS,
		STR_TONS,
		STR_BAGS,
		STR_NOTHING,
		STR_NOTHING,
		STR_TONS,
		STR_TONS,
		STR_LITERS,
		STR_TONS,
		STR_NOTHING,
		STR_LITERS,
		STR_NOTHING
	}
};

static char *str_cat(char *dst, const char *src)
{
	while ((*dst++ = *src++) != '\0') {}
	return dst - 1;
}

static const char *GetStringPtr(StringID string)
{
	return _langpack_offs[_langtab_start[string >> 11] + (string & 0x7FF)];
}

char *GetString(char *buffr, StringID string)
{
	uint index = string & 0x7FF;
	uint tab = string >> 11;

	switch (string) {
		case 0:
			error("!invalid string id 0 in GetString");
			break;

		case 0x30D1:
			return StationGetSpecialString(buffr);

		case STR_SPEC_SCREENSHOT_NAME:
			return DecodeString(buffr, _screenshot_name);
	}

	switch (tab) {
		case 4:
			if (index >= 0xC0) return GetSpecialTownNameString(buffr, index - 0xC0);
			break;

		case 14:
			if (index >= 0xE4) return GetSpecialPlayerNameString(buffr, index - 0xE4);
			break;

		case 15:
			return GetName(index, buffr);

		case 31: // special or dynamic strings
			return DecodeString(buffr, _userstring);

		default:
			break;
	}

	if (index >= _langtab_num[tab])
		error(
			"!String 0x%X is invalid. "
			"Probably because an old version of the .lng file.\n", string
		);

	return DecodeString(buffr, GetStringPtr(string));
}

void InjectDParam(int amount)
{
	memmove(_decode_parameters + amount, _decode_parameters, sizeof(_decode_parameters) - amount * sizeof(uint32));
}


int32 GetParamInt32(void)
{
	int32 result = GetDParam(0);
	memmove(&_decode_parameters[0], &_decode_parameters[1], sizeof(uint32) * (lengthof(_decode_parameters)-1));
	return result;
}

static int64 GetParamInt64(void)
{
	int64 result = GetDParam(0) + ((uint64)GetDParam(1) << 32);
	memmove(&_decode_parameters[0], &_decode_parameters[2], sizeof(uint32) * (lengthof(_decode_parameters)-2));
	return result;
}


int GetParamInt16(void)
{
	int result = (int16)GetDParam(0);
	memmove(&_decode_parameters[0], &_decode_parameters[1], sizeof(uint32) * (lengthof(_decode_parameters)-1));
	return result;
}

int GetParamInt8(void)
{
	int result = (int8)GetDParam(0);
	memmove(&_decode_parameters[0], &_decode_parameters[1], sizeof(uint32) * (lengthof(_decode_parameters)-1));
	return result;
}

int GetParamUint16(void)
{
	int result = GetDParam(0);
	memmove(&_decode_parameters[0], &_decode_parameters[1], sizeof(uint32) * (lengthof(_decode_parameters)-1));
	return result;
}

static const uint32 _divisor_table[] = {
	1000000000,
	100000000,
	10000000,
	1000000,

	100000,
	10000,
	1000,
	100,
	10,
	1
};

static char *FormatCommaNumber(char *buff, int32 number)
{
	uint32 quot,divisor;
	int i;
	uint32 tot;
	uint32 num;

	if (number < 0) {
		*buff++ = '-';
		number = -number;
	}

	num = number;

	tot = 0;
	for (i = 0; i != 10; i++) {
		divisor = _divisor_table[i];
		quot = 0;
		if (num >= divisor) {
			quot = num / _divisor_table[i];
			num = num % _divisor_table[i];
		}
		if (tot |= quot || i == 9) {
			*buff++ = '0' + quot;
			if (i == 0 || i == 3 || i == 6) *buff++ = ',';
		}
	}

	*buff = '\0';

	return buff;
}

static char *FormatNoCommaNumber(char *buff, int32 number)
{
	uint32 quot,divisor;
	int i;
	uint32 tot;
	uint32 num;

	if (number < 0) {
		*buff++ = '-';
		number = -number;
	}

	num = number;

	tot = 0;
	for (i = 0; i != 10; i++) {
		divisor = _divisor_table[i];
		quot = 0;
		if (num >= divisor) {
			quot = num / _divisor_table[i];
			num = num % _divisor_table[i];
		}
		if (tot |= quot || i == 9) {
			*buff++ = '0' + quot;
		}
	}

	*buff = '\0';

	return buff;
}


static char *FormatYmdString(char *buff, uint16 number)
{
	const char *src;
	YearMonthDay ymd;

	ConvertDayToYMD(&ymd, number);

	for (src = GetStringPtr(ymd.day + STR_01AC_1ST - 1); (*buff++ = *src++) != '\0';) {}

	buff[-1] = ' ';
	memcpy(buff, GetStringPtr(STR_0162_JAN + ymd.month), 4);
	buff[3] = ' ';

	return FormatNoCommaNumber(buff+4, ymd.year + MAX_YEAR_BEGIN_REAL);
}

static char *FormatMonthAndYear(char *buff, uint16 number)
{
	const char *src;
	YearMonthDay ymd;

	ConvertDayToYMD(&ymd, number);

	for (src = GetStringPtr(STR_MONTH_JAN + ymd.month); (*buff++ = *src++) != '\0';) {}
	buff[-1] = ' ';

	return FormatNoCommaNumber(buff, ymd.year + MAX_YEAR_BEGIN_REAL);
}

static char *FormatTinyDate(char *buff, uint16 number)
{
	YearMonthDay ymd;

	ConvertDayToYMD(&ymd, number);
	buff += sprintf(buff, " %02i-%02i-%04i", ymd.day, ymd.month + 1, ymd.year + MAX_YEAR_BEGIN_REAL);

	return buff;
}

uint GetCurrentCurrencyRate(void)
{
	return _currency_specs[_opt.currency].rate;
}

static char *FormatGenericCurrency(char *buff, const CurrencySpec *spec, int64 number, bool compact)
{
	const char *s;
	char c;
	char buf[40], *p;
	int j;

	// multiply by exchange rate
	number *= spec->rate;

	// convert from negative
	if (number < 0) {
		*buff++ = '-';
		number = -number;
	}

	// add prefix part
	s = spec->prefix;
	while (s != spec->prefix + lengthof(spec->prefix) && (c = *s++) != '\0') *buff++ = c;

	// for huge numbers, compact the number into k or M
	if (compact) {
		compact = 0;
		if (number >= 1000000000) {
			number = (number + 500000) / 1000000;
			compact = 'M';
		} else if (number >= 1000000) {
			number = (number + 500) / 1000;
			compact = 'k';
		}
	}

	// convert to ascii number and add commas
	p = buf;
	j = 4;
	do {
		if (--j == 0) {
			*p++ = spec->separator;
			j = 3;
		}
		*p++ = '0' + number % 10;
	} while (number /= 10);
	do *buff++ = *--p; while (p != buf);

	if (compact) *buff++ = compact;

	// add suffix part
	s = spec->suffix;
	while (s != spec->suffix + lengthof(spec->suffix) && (c = *s++) != '\0') *buff++ = c;

	return buff;
}

static char *DecodeString(char *buff, const char *str)
{
	byte b;

	while ((b = *str++) != '\0') {
		switch (b) {
		case 0x1: // {SETX}
			*buff++ = b;
			*buff++ = *str++;
			break;
		case 0x2: // {SETXY}
			*buff++ = b;
			*buff++ = *str++;
			*buff++ = *str++;
			break;
		case 0x7B: // {COMMA32}
			buff = FormatCommaNumber(buff, GetParamInt32());
			break;
		case 0x7C: // {COMMA16}
			buff = FormatCommaNumber(buff, GetParamInt16());
			break;
		case 0x7D: // {COMMA8}
			buff = FormatCommaNumber(buff, GetParamInt8());
			break;
		case 0x7E: // {NUMU16}
			buff = FormatNoCommaNumber(buff, GetParamInt16());
			break;
		case 0x7F: // {CURRENCY}
			buff = FormatGenericCurrency(buff, &_currency_specs[_opt.currency], GetParamInt32(), false);
			break;
		// 0x80 is reserved for EURO
		case 0x81: // {STRINL}
			str += 2;
			buff = GetString(buff, READ_LE_UINT16(str-2));
			break;
		case 0x82: // {DATE_LONG}
			buff = FormatYmdString(buff, GetParamUint16());
			break;
		case 0x83: // {DATE_SHORT}
			buff = FormatMonthAndYear(buff, GetParamUint16());
			break;
		case 0x84: {// {VELOCITY}
			int value = GetParamInt16();
			if (_opt.kilometers) value = value * 1648 >> 10;
			buff = FormatCommaNumber(buff, value);
			if (_opt.kilometers) {
				memcpy(buff, " km/h", 5);
				buff += 5;
			} else {
				memcpy(buff, " mph", 4);
				buff += 4;
			}
			break;
		}

		// 0x85 is used as escape character..
		case 0x85:
			switch (*str++) {
			case 0: /* {CURRCOMPACT} */
				buff = FormatGenericCurrency(buff, &_currency_specs[_opt.currency], GetParamInt32(), true);
				break;
			case 1: /* {INT32} */
				buff = FormatNoCommaNumber(buff, GetParamInt32());
				break;
			case 2: /* {REV} */
				buff = str_cat(buff, _openttd_revision);
				break;
			case 3: { /* {SHORTCARGO} */
				// Short description of cargotypes. Layout:
				// 8-bit = cargo type
				// 16-bit = cargo count
				const char *s;
				StringID cargo_str = _cargo_string_list[_opt.landscape][(byte)GetParamInt8()];
				uint16 multiplier = (cargo_str == STR_LITERS) ? 1000 : 1;
				// liquid type of cargo is multiplied by 100 to get correct amount
				buff = FormatCommaNumber(buff, GetParamInt16() * multiplier);
				s = GetStringPtr(cargo_str);

				memcpy(buff++, " ", 1);
				while (*s) *buff++ = *s++;
			} break;
			case 4: /* {CURRCOMPACT64} */
				// 64 bit compact currency-unit
				buff = FormatGenericCurrency(buff, &_currency_specs[_opt.currency], GetParamInt64(), true);
				break;

			default:
				error("!invalid escape sequence in string");
			}
			break;

		case 0x86: // {SKIP}
			GetParamInt16();
			//assert(0);
			break;
		case 0x87: { // {VOLUME}
			const char *s;
			buff = FormatCommaNumber(buff, GetParamInt16() * 1000);
			memcpy(buff++, " ", 1);
			s = GetStringPtr(STR_LITERS);
			while (*s) *buff++ = *s++;
			break;
		}

		case 0x88: // {STRING}
			buff = GetString(buff, (uint16)GetParamUint16());
			break;

		case 0x99: { // {CARGO}
			// Layout now is:
			//   8bit   - cargo type
			//   16-bit - cargo count
			int cargo_str = _cargoc.names_long_s[GetParamInt8()];
			// Now check if the cargo count is 1, if it is, increase string by 32.
			if (GetDParam(0) != 1) cargo_str += 32;
			buff = GetString(buff, cargo_str);
			break;
		}

		case 0x9A: { // {STATION}
			Station *st;
			InjectDParam(1);
			st = GetStation(GetDParam(1));
			if (st->xy == 0) { // station doesn't exist anymore
				buff = GetString(buff, STR_UNKNOWN_DESTINATION);
				break;
			}
			SetDParam(0, st->town->townnametype);
			SetDParam(1, st->town->townnameparts);
			buff = GetString(buff, st->string_id);
			break;
		}
		case 0x9B: { // {TOWN}
			Town *t;
			t = GetTown(GetDParam(0));
			assert(t->xy);
			SetDParam(0, t->townnameparts);
			buff = GetString(buff, t->townnametype);
			break;
		}

		case 0x9C: { // {CURRENCY64}
			buff = FormatGenericCurrency(buff, &_currency_specs[_opt.currency], GetParamInt64(), false);
			break;
		}

		case 0x9D: { // {WAYPOINT}
			Waypoint *wp = GetWaypoint(GetDParam(0));
			StringID str;
			int idx;
			if (wp->string != STR_NULL) {
				GetParamInt32(); // skip it
				str = wp->string;
			} else {
				idx = wp->town_cn;
				if (idx == 0) {
					str = STR_WAYPOINTNAME_CITY;
				} else {
					InjectDParam(1);
					SetDParam(1, idx + 1);
					str = STR_WAYPOINTNAME_CITY_SERIAL;
				}
				SetDParam(0, wp->town_index);
			}

			buff = GetString(buff, str);
		} break;

		case 0x9E: { // {DATE_TINY}
			buff = FormatTinyDate(buff, GetParamUint16());
			break;
		}

		// case 0x88..0x98: // {COLORS}
		// case 0xE: // {TINYFONT}
		// case 0xF: // {BIGFONT}
		// 0x9E is the highest number that is available.
		default:
			*buff++ = b;
		}
	}
	*buff = '\0';
	return buff;
}


static char *StationGetSpecialString(char *buff)
{
	int x = GetParamInt8();
	if (x & 0x01) *buff++ = '\xB4';
	if (x & 0x02) *buff++ = '\xB5';
	if (x & 0x04) *buff++ = '\xB6';
	if (x & 0x08) *buff++ = '\xB7';
	if (x & 0x10) *buff++ = '\xB8';
	*buff = '\0';
	return buff;
}

static char *GetSpecialTownNameString(char *buff, int ind)
{
	uint32 x = GetParamInt32();

	_town_name_generators[ind](buff, x);

	while (*buff != '\0') buff++;
	return buff;
}

static const char * const _silly_company_names[] = {
	"Bloggs Brothers",
	"Tiny Transport Ltd.",
	"Express Travel",
	"Comfy-Coach & Co.",
	"Crush & Bump Ltd.",
	"Broken & Late Ltd.",
	"Sam Speedy & Son",
	"Supersonic Travel",
	"Mike's Motors",
	"Lightning International",
	"Pannik & Loozit Ltd.",
	"Inter-City Transport",
	"Getout & Pushit Ltd.",
};

static const char * const _surname_list[] = {
	"Adams",
	"Allan",
	"Baker",
	"Bigwig",
	"Black",
	"Bloggs",
	"Brown",
	"Campbell",
	"Gordon",
	"Hamilton",
	"Hawthorn",
	"Higgins",
	"Green",
	"Gribble",
	"Jones",
	"McAlpine",
	"MacDonald",
	"McIntosh",
	"Muir",
	"Murphy",
	"Nelson",
	"O'Donnell",
	"Parker",
	"Phillips",
	"Pilkington",
	"Quigley",
	"Sharkey",
	"Thomson",
	"Watkins",
	"Grumpy",
	"Dozy",
	"Speedy",
	"Nosey",
	"Dribble",
	"Mushroom",
	"Cabbage",
	"Sniffle",
	"Fishy",
	"Swindle",
	"Sneaky",
	"Nutkins",
};

static const char _initial_name_letters[] = {
	'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',
	'K', 'L', 'M', 'N', 'P', 'R', 'S', 'T', 'W',
};

static char *GenAndCoName(char *buff)
{
	uint32 x = GetParamInt32();
	uint base,num;

	base = 0;
	num = 29;
	if (_opt.landscape == LT_CANDY) {
		base = num;
		num = 12;
	}

	buff = str_cat(buff, _surname_list[base + ((num * (byte)(x >> 16)) >> 8)]);
	buff = str_cat(buff, " & Co.");

	return buff;
}

static char *GenPlayerName_4(char *buff)
{
	uint32 x = GetParamInt32();
	uint i, base, num;

	buff[0] = _initial_name_letters[(sizeof(_initial_name_letters) * (byte)x) >> 8];
	buff[1] = '.';
	buff[2] = ' '; // Insert a space after initial and period "I. Firstname" instead of "I.Firstname"
	buff += 3;

	i = ((sizeof(_initial_name_letters) + 35) * (byte)(x >> 8)) >> 8;
	if (i < sizeof(_initial_name_letters)) {
		buff[0] = _initial_name_letters[i];
		buff[1] = '.';
		buff[2] = ' '; // Insert a space after initial and period "I. J. Firstname" instead of "I.J.Firstname"
		buff += 3;
	}

	base = 0;
	num = 29;
	if (_opt.landscape == LT_CANDY) {
		base = num;
		num = 12;
	}

	buff = str_cat(buff, _surname_list[base + ((num * (byte)(x >> 16)) >> 8)]);

	return buff;
}

static const char * const _song_names[] = {
	"Tycoon DELUXE Theme",
	"Easy Driver",
	"Little Red Diesel",
	"Cruise Control",
	"Don't Walk!",
	"Fell Apart On Me",
	"City Groove",
	"Funk Central",
	"Stoke It",
	"Road Hog",
	"Aliens Ate My Railway",
	"Snarl Up",
	"Stroll On",
	"Can't Get There From Here",
	"Sawyer's Tune",
	"Hold That Train!",
	"Movin' On",
	"Goss Groove",
	"Small Town",
	"Broomer's Oil Rag",
	"Jammit",
	"Hard Drivin'"
};

static char *GetSpecialPlayerNameString(char *buff, int ind)
{
	switch (ind) {
		case 1: // not used
			return str_cat(buff, _silly_company_names[GetParamInt32() & 0xFFFF]);

		case 2: // used for Foobar & Co company names
			return GenAndCoName(buff);

		case 3: // President name
			return GenPlayerName_4(buff);

		case 4: // song names
			return str_cat(buff, _song_names[GetParamUint16() - 1]);
	}

	// town name?
	if (IS_INT_INSIDE(ind - 6, 0, SPECSTR_TOWNNAME_LAST-SPECSTR_TOWNNAME_START + 1)) {
		buff = GetSpecialTownNameString(buff, ind - 6);
		return str_cat(buff, " Transport");
	}

	// language name?
	if (IS_INT_INSIDE(ind, (SPECSTR_LANGUAGE_START - 0x70E4), (SPECSTR_LANGUAGE_END - 0x70E4) + 1)) {
		int i = ind - (SPECSTR_LANGUAGE_START - 0x70E4);
		return str_cat(buff, i == _dynlang.curr ? _langpack->own_name : _dynlang.ent[i].name);
	}

	// resolution size?
	if (IS_INT_INSIDE(ind, (SPECSTR_RESOLUTION_START - 0x70E4), (SPECSTR_RESOLUTION_END - 0x70E4) + 1)) {
		int i = ind - (SPECSTR_RESOLUTION_START - 0x70E4);
		return buff + sprintf(buff, "%dx%d", _resolutions[i][0], _resolutions[i][1]);
	}

	// screenshot format name?
	if (IS_INT_INSIDE(ind, (SPECSTR_SCREENSHOT_START - 0x70E4), (SPECSTR_SCREENSHOT_END - 0x70E4) + 1)) {
		int i = ind - (SPECSTR_SCREENSHOT_START - 0x70E4);
		return str_cat(buff, GetScreenshotFormatDesc(i));
	}

	assert(0);
	return NULL;
}

// remap a string ID from the old format to the new format
StringID RemapOldStringID(StringID s)
{
	switch (s) {
		case 0x0006: return STR_SV_EMPTY;
		case 0x7000: return STR_SV_UNNAMED;
		case 0x70E4: return SPECSTR_PLAYERNAME_ENGLISH;
		case 0x70E9: return SPECSTR_PLAYERNAME_ENGLISH;
		case 0x8864: return STR_SV_TRAIN_NAME;
		case 0x902B: return STR_SV_ROADVEH_NAME;
		case 0x9830: return STR_SV_SHIP_NAME;
		case 0xA02F: return STR_SV_AIRCRAFT_NAME;

		default:
			if (IS_INT_INSIDE(s, 0x300F, 0x3030))
				return s - 0x300F + STR_SV_STNAME;
			else
				return s;
	}
}

bool ReadLanguagePack(int lang_index)
{
	int tot_count, i;
	LanguagePack *lang_pack;
	size_t len;
	char **langpack_offs;
	char *s;

	{
		char *lang = str_fmt("%s%s", _path.lang_dir, _dynlang.ent[lang_index].file);
		lang_pack = ReadFileToMem(lang, &len, 100000);
		free(lang);
	}
	if (lang_pack == NULL) return false;
	if (len < sizeof(LanguagePack) ||
			lang_pack->ident != TO_LE32(LANGUAGE_PACK_IDENT) ||
			lang_pack->version != TO_LE32(LANGUAGE_PACK_VERSION)) {
		free(lang_pack);
		return false;
	}

#if defined(TTD_BIG_ENDIAN)
	for (i = 0; i != 32; i++) {
		lang_pack->offsets[i] = READ_LE_UINT16(&lang_pack->offsets[i]);
	}
#endif

	tot_count = 0;
	for (i = 0; i != 32; i++) {
		uint num = lang_pack->offsets[i];
		_langtab_start[i] = tot_count;
		_langtab_num[i] = num;
		tot_count += num;
	}

	// Allocate offsets
	langpack_offs = malloc(tot_count * sizeof(*langpack_offs));

	// Fill offsets
	s = lang_pack->data;
	for (i = 0; i != tot_count; i++) {
		len = (byte)*s;
		*s++ = '\0'; // zero terminate the string before.
		if (len >= 0xC0) len = ((len & 0x3F) << 8) + (byte)*s++;
		langpack_offs[i] = s;
		s += len;
	}

	free(_langpack);
	_langpack = lang_pack;

	free(_langpack_offs);
	_langpack_offs = langpack_offs;

	ttd_strlcpy(_dynlang.curr_file, _dynlang.ent[lang_index].file, sizeof(_dynlang.curr_file));


	_dynlang.curr = lang_index;
	return true;
}

// make a list of the available language packs. put the data in _dynlang struct.
void InitializeLanguagePacks(void)
{
	DynamicLanguages *dl = &_dynlang;
	int i;
	int n;
	int m;
	int def;
	LanguagePack hdr;
	FILE *in;
	char *files[32];

	n = GetLanguageList(files, lengthof(files));

	def = 0; // default language file

	// go through the language files and make sure that they are valid.
	for (i = m = 0; i != n; i++) {
		int j;

		char *s = str_fmt("%s%s", _path.lang_dir, files[i]);
		in = fopen(s, "rb");
		free(s);
		if (in == NULL ||
				(j = fread(&hdr, sizeof(hdr), 1, in), fclose(in), j) != 1 ||
				hdr.ident != TO_LE32(LANGUAGE_PACK_IDENT) ||
				hdr.version != TO_LE32(LANGUAGE_PACK_VERSION)) {
			free(files[i]);
			continue;
		}

		dl->ent[m].file = files[i];
		dl->ent[m].name = strdup(hdr.name);

		if (strcmp(hdr.name, "English") == 0) def = m;

		m++;
	}

	if (m == 0)
		error(n == 0 ? "No available language packs" : "Invalid version of language packs");

	dl->num = m;
	for (i = 0; i != dl->num; i++)
		dl->dropdown[i] = SPECSTR_LANGUAGE_START + i;
	dl->dropdown[i] = INVALID_STRING_ID;

	for (i = 0; i != dl->num; i++)
		if (strcmp(dl->ent[i].file, dl->curr_file) == 0) {
			def = i;
			break;
		}

	if (!ReadLanguagePack(def))
		error("can't read language pack '%s'", dl->ent[def].file);
}
