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

static	unsigned char	buf[1048576];
static	int	sjis2offset[0x8000];

/* FONTX2 header: this font is kanji only */
#define	CODETYPE_KANJI	1

/* common */
typedef struct {
	uint8_t	identifier[6];
	uint8_t	fontname[8];
	uint8_t	xsize;
	uint8_t	ysize;
	uint8_t	codetype;
} __attribute__((packed)) FONTX2_HEADER;

/* sjis */
typedef struct {
	FONTX2_HEADER	h;

	uint8_t	tnum;
} __attribute__((packed)) FONTX2_KANJI;

typedef	struct {
	uint16_t	start;
	uint16_t	end;
} __attribute__((packed)) FONTX2_CODETABLE;

static	FONTX2_CODETABLE	region[256];
static	int	region_entry;

#if 0
static	unsigned char	Data[] = {

	// uint8_t	length;		// sizeof(bitmap) + sizeof(data)
	// uint8_t	pad;
	// uint16_t	sjis_code;	// big-endian
	// uint8_t	bitmap[36];
	// uint8_t	data[];

};
#endif

static	void	decode(unsigned char *out, unsigned char *in)
{
	int	i;
	int	bmp_index, bmp_bit, tmp_index, data_index;
	unsigned char	*bmp, *data;
	unsigned char	tmp[6];

	bmp = in;
	data = in + 0x24;	

	/* initial state: all zero */
	memset(tmp, 0, sizeof(tmp));

	data_index = 0;
	for (i = 0; i < 288; i++) {
		bmp_index = i / 8;
		bmp_bit = 7 - (i % 8);
		tmp_index = i % sizeof(tmp);

		if (bmp[bmp_index] & (1 << bmp_bit)) {
			tmp[tmp_index] = data[data_index++];
		}

		if (!((tmp_index + 1) % sizeof(tmp))) {
			memcpy(out, tmp, sizeof(tmp));
			out += sizeof(tmp);
		}
	}

	return;
}

static	void	dump_font(FILE *fp)
{
	unsigned char	b[288];
	int	i;

	for (i = 0; i < 0x7fff; i++) {
		if (!sjis2offset[i]) continue;

		decode(b, &buf[sjis2offset[i] + 4]);
		fwrite(b, sizeof(b), 1, fp);
	}

	return;
}

static	void	dump_header(FILE *fp)
{
	FONTX2_KANJI	k;

	strncpy(k.h.identifier, "FONTX2", sizeof(k.h.identifier));
	strncpy(k.h.fontname, "FSSR023 ", sizeof(k.h.fontname));
	k.h.xsize = k.h.ysize = 48;
	k.h.codetype = CODETYPE_KANJI;
	k.tnum = region_entry;

	fwrite(&k, sizeof(k), 1, fp);
	fwrite(region, sizeof(FONTX2_CODETABLE), region_entry, fp);

	return;
}

static	void	create_table(void)
{
	int	i, j;

	region_entry = 0;

	for (i = 0; i < 0x7fff; ) {
		if (!sjis2offset[i]) {
			i++;
			continue;
		}

		region[region_entry].start = i | 0x8000;
		for (j = i + 1; sjis2offset[j]; j++);
		region[region_entry].end = (j - 1) | 0x8000;

		i = j;
		printf("region #%d: %4x - %4x\n", region_entry, region[region_entry].start, region[region_entry].end);

		region_entry++;

	}

	return;
}  

static	void	create_offset(void)
{
	int	i, offset, sjis;

	memset(sjis2offset, 0, sizeof(sjis2offset));

	for (i = 0x8000; i < 0xf200; i += 4) {
		offset = (buf[i + 1] << 24) | (buf[i + 0] << 16) | 
			(buf[i + 3] << 8) | buf[i + 2];

		if (!offset) continue;
		sjis = (buf[offset + 2] << 8) | buf[offset + 3];

		printf("sjis %x offset %x\n", sjis, offset);
		sjis2offset[sjis & 0x7fff] = offset;
	}

	return;
}

static	void	load(void)
{
	int	i;
	FILE	*fp;

	memset(buf, 0, sizeof(buf));

	fp = fopen("fssr023a.bin", "rb");
	if (fp != NULL) {
		for (i = 0; i < sizeof(buf) / 2; i++) {
			buf[i] = fgetc(fp);
		}

		fclose(fp);
	}

	fp = fopen("fssr023b.bin", "rb");
	if (fp != NULL) {
		for (i = sizeof(buf) / 2; i < sizeof(buf); i++) {
			buf[i] = fgetc(fp);
		}

		fclose(fp);
	}

	return;
}

int	main(int argc, char *argv[])
{
	FILE	*fp;

	load();
	create_offset();
	create_table();

	fp = fopen("fssr023.fnt", "wb");
	if (fp != NULL) {
		dump_header(fp);
		dump_font(fp);
		fclose(fp);
	}

	return 0;
}