/*
 * fontx2xm7.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	131072
static unsigned char	RomData[BUFFERSIZE];

/* 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, n, ix;

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

	ix = ten / 32;

	if (ku < 8) {		/* 0区〜7区 */
		switch (ix) {
		case	1:	ix = 2; break;
		case	2:	ix = 1; break;
		}
		n = (ku + ix * 8) * 32 + (ten % 32);

	} else if (ku < 16) {	/* 8区〜15区 (未定義) */
		n = -1;

	} else if (ku < 32) {	/* 16区〜31区 */
		n = (ku + 16 + ix * 16) * 32 + (ten % 32);

	} else if (ku < 48) {	/* 32区〜47区 */
		n = (ku + 48 + ix * 16) * 32 + (ten % 32);

	} else {		/* 48区以降 (未定義) */
		n = -1;

	}

	return (n < 0) ? NULL : (RomData + n * 32);
}

/* 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) memcpy(p, d, 32);
			d += 32;
		}
	}

	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	i, result;
	unsigned char	*buf;

	if (argc < 3) {
		printf("usage: %s [kanji] [romfile]\n",
		       argv[0]);
		result = EXIT_FAILURE;
		goto fin0;
	}

	for (i = 0; i < sizeof(RomData); i++) RomData[i] = i & 1;

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

	savefile(argv[2], RomData, sizeof(RomData));

	result = EXIT_SUCCESS;
fin0:
	return result;
}