/*
 * fontx2msx.c
 *
 * original code by SASANO Takayoshi
 * --- public domain, no warranty.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/* FONTX2 header */
#define CODETYPE_ASCII	0
#define	CODETYPE_KANJI	1

/* common */
typedef struct {
	unsigned char	identifier[6];
	unsigned char	fontname[8];
	unsigned char	xsize;
	unsigned char	ysize;
	unsigned char	codetype;
} __attribute__((packed)) FONTX2_HEADER;

/* ascii */
typedef struct {
	FONTX2_HEADER	h;

	unsigned char	d[1];
} __attribute__((packed)) FONTX2_ASCII;

/* sjis */
typedef struct {
	FONTX2_HEADER	h;

	unsigned char	tnum;
	unsigned char	d[1];
} __attribute__((packed)) FONTX2_KANJI;

typedef	struct {
	unsigned short	start;
	unsigned short	end;
} __attribute__((packed)) FONTX2_CODETABLE;

/* ROM data buffer */
#define	BUFFERSIZE	262144
static unsigned char	RomData[BUFFERSIZE];

static unsigned char	font_815e[] = {
	0x00, 0x00, 0x00, 0x02, 0x00, 0x04, 0x00, 0x08,
	0x00, 0x10, 0x00, 0x20, 0x00, 0x40, 0x00, 0x80,
	0x01, 0x00, 0x02, 0x00, 0x04, 0x00, 0x08, 0x00,
	0x10, 0x00, 0x20, 0x00, 0x40, 0x00, 0x00, 0x00,
};

static unsigned char	font_815f[] = {
	0x00, 0x00, 0x40, 0x00, 0x20, 0x00, 0x10, 0x00,
	0x08, 0x00, 0x04, 0x00, 0x02, 0x00, 0x01, 0x00,
	0x00, 0x80, 0x00, 0x40, 0x00, 0x20, 0x00, 0x10,
	0x00, 0x08, 0x00, 0x04, 0x00, 0x02, 0x00, 0x00,
};

/* convert a kanji characger */
static	void	convert_kanji_char(unsigned char *in, unsigned char *out)
{
	int	i;

	for (i = 0; i < 8; i++) {
		out[i + 0] = in[i * 2 + 0];
		out[i + 8] = in[i * 2 + 1];
		out[i + 16] = in[i * 2 + 16];
		out[i + 24] = in[i * 2 + 17];
	}

	return;
}

/* convert an ANK character */
static	void	convert_ank_char(unsigned char *in, unsigned char *out, int height, int right)
{
	int	i;
	unsigned char	buf[16];

	memset(buf, 0, sizeof(buf));
	memcpy(buf + sizeof(buf) - height, in, height);

	for (i = 0; i < 8; i++) {
		out[i + 0 + right * 8] = buf[i + 0];
		out[i + 16 + right * 8] = buf[i + 8];
	}

	return;
}

/* SJIS -> JIS */
static	int	_mbcjmstojis(int jms)
{
	int	low, high;

	high = (jms >> 8) & 0xff;
	low  =  jms       & 0xff;

	if (low < 0x9f) {
		if (high < 0xa0) {
			high -= 0x81;
			high *= 2;
			high += 0x21;
		} else {
			high -= 0xe0;
			high *= 2;
			high += 0x5f;
		}
			
		if (low > 0x7f) low--;
		low -= 0x1f;
	} else {
		if (high < 0xa0) {
			high -= 0x81;
			high *= 2;
			high += 0x22;
		} else {
			high -= 0xe0;
			high *= 2;
			high += 0x60;
		}

		low -= 0x7e;
	}

	return (high << 8) | low;
}

/* get kanji font pointer */
static	unsigned char	*get_kanji_pointer(int sjis)
{
	int	kuten, ku, ten, idx, offset;

	kuten = _mbcjmstojis(sjis) - 0x2020;
	ku  = (kuten >> 8) & 0xff;
	ten =  kuten       & 0xff;

	/* invalid */
	if (ku >= 96 || ten >= 96) return NULL;

	/* no convert */
	if (ku == 0 || (ku > 8 && ku < 16)) return NULL;

	if (ku < 48) {
		idx = ku * 96 + ten - (ku >= 16) * 512;
		offset = 0;

	} else {
		idx = (ku - 48) * 96 + ten;
		offset = 0x00020000;
	}

	return RomData + offset + 32 * idx;
}

/* convert ank font */
void	convert_ank_font(void *buf, int right)
{
	int	i;
	FONTX2_ASCII	*a = buf;
	unsigned char	*p;

	if (a->h.codetype != CODETYPE_ASCII ||
	    (a->h.xsize + 7) / 8 != 1 || a->h.ysize > 16) {
		printf("invalid font data (ANK)\n");
		return;
	}

	for (i = 0x20; i < 0x80; i++) {
		p = RomData + (i - 0x20) * 32;
		convert_ank_char(&a->d[i * a->h.ysize], p, a->h.ysize, right);
	}

	for (i = 0xa0; i < 0xe0; i++) {
		p = RomData + (i - 0xa0 + 96 * 9) * 32;
		convert_ank_char(&a->d[i * a->h.ysize], p, a->h.ysize, right);
	}

	return;
}

/* convert kanji font */
void	convert_kanji_font(void *buf)
{
	int	i, j;
	FONTX2_KANJI		*k = buf;
	FONTX2_CODETABLE	*c = (FONTX2_CODETABLE *)&k->d[0];
	unsigned char		*d = &k->d[sizeof(FONTX2_CODETABLE) * k->tnum];
	unsigned char		*p;

	if (k->h.codetype != CODETYPE_KANJI ||
	    (k->h.xsize + 7) / 8 != 2 || k->h.ysize != 16) {
		printf("invalid font data (kanji)\n");
		return;
	}

	for (i = 0; i < k->tnum; i++) {
		for (j = c[i].start; j <= c[i].end; j++) {
			p = get_kanji_pointer(j);
			if (p != NULL) {
				convert_kanji_char(d, get_kanji_pointer(j));
			}
			d += 32;
		}
	}

	return;
}

/* fix JIS1 font to recognize MSX kanji ROM */
void	fix_jis1data(void)
{
	unsigned char	*p;

	p = get_kanji_pointer(0x815f);
	convert_kanji_char(font_815f, p);

	/* this is not required, but it should be same style */
	p = get_kanji_pointer(0x815e);
	convert_kanji_char(font_815e, p);

	return;
}

/* load file */
unsigned char *loadfile(char *filename)
{
	FILE	*fp;
	int	size;
	unsigned char *buf = NULL;

	fp = fopen(filename, "r");
	if (fp == NULL) {
		printf("loadfile: file open error (%s)\n", filename);
		goto fin0;
	}

	fseek(fp, 0, SEEK_END);
	size = ftell(fp);
	fseek(fp, 0, SEEK_SET);

	buf = malloc(size);
	if (buf == NULL) {
		printf("loadfile: memory allocation error (%s)\n", filename);
		goto fin0;
	}

	if (fread(buf, size, 1, fp) < 1) {
		printf("loadfile: file read error (%s)\n", filename);
		free(buf);
		buf = NULL;
	}

	fclose(fp);

fin0:
	return buf;
}

/* save file */
void	savefile(char *filename, char *buf, int size)
{
	FILE	*fp;

	fp = fopen(filename, "w");
	if (fp == NULL) {
		printf("savefile: file open error (%s)\n", filename);
		goto fin0;
	}

	if (fwrite(buf, size, 1, fp) < 1) {
		printf("savefile: file write error (%s)\n", filename);
	}

	fclose(fp);

fin0:
	return;
}

/* entry */
int	main(int argc, char *argv[])
{
	int	result;
	unsigned char	*buf;

	if (argc < 5) {
		printf("usage: %s [ank(normal)] [ank(small)] [kanji] [romfile]\n",
		       argv[0]);
		result = EXIT_FAILURE;
		goto fin0;
	}

	memset(RomData, ~0, sizeof(RomData));


	buf = loadfile(argv[1]);
	if (buf != NULL) {
		convert_ank_font(buf, 0);
		free(buf);
	}

	buf = loadfile(argv[2]);
	if (buf != NULL) {
		convert_ank_font(buf, 1);
		free(buf);
	}

	buf = loadfile(argv[3]);
	if (buf != NULL) {
		convert_kanji_font(buf);
		free(buf);
	}

	fix_jis1data();

	savefile(argv[4], RomData, sizeof(RomData));

	result = EXIT_SUCCESS;
fin0:
	return result;
}