#include "defs.h"	/*->magic.h (u8,u15x)*/
#include "magic.h"	/*MagicType*/

/* stricter 15-sample mod checking */
static i15x
isMod15(const u8 *p0, i31x size)
{
    i15x ordNum, patNum;
    i15x i;
    const u8 *p;

    if (size < 20+30*15+130+1024) return 0; /* check min length */
    ordNum = p0[20+30*15];
    if (!ordNum || ordNum >= 128) return 0;
    patNum = 0;
    p = p0 + 20+30*15+2; /* pattern table */
    for (i = 0; i < ordNum; i++,p++)
	if (patNum < *p) patNum = *p;
    if (patNum >= 64) return 0;
    if (size < 20+30*15+130+1024+1024*patNum) return 0;
    /* sample length is not checked here */
    return 1;
}

typedef struct {
    const u8 *str;
    i15x off;
    MagicType type;
} MagicInfo;

MagicInfo magicInfo[] = {
    {"SCRM", 0x2c, MAGIC_S3M},
    {"M.K.", 0x438 /*20+30*31+130=1080*/, MAGIC_MOD},
    {"M!K!", 0x438, MAGIC_MOD},
    {"FLT4", 0x438, MAGIC_MOD}, /* FLT8's pattern is different */
    {"#CHN", 0x438, MAGIC_MODX},
    {"##CH", 0x438, MAGIC_MODX}, /* dope.mod */
    {"MTM",  0,     MAGIC_MTM}, /* check after above patterns fail.
				   (A mod songname can be "MTMxxx") */
    {0} };

#define isnum(x) ('0' <= (x) && (x) <= '9')

i15x
magic(const u8 *p, i31x size, MagicType *mtp, i15x *numChp)
{
    MagicInfo *mip;
    i15x ch;

    for (mip = magicInfo; mip->str != 0; mip++) {
	const u8 *ss, *sp;
	if (mip->off + 16 >= size) continue; /* Magicinfo.str must < 16 */
	sp = p + mip->off;
	ch = 0;
	for (ss = mip->str; *ss != 0; ss++,sp++) {
	    if (*ss == '#')
		if (isnum(*sp)) { ch = ch*10 + *sp - '0'; continue; }
		else goto UNMATCH;
	    if (*sp != *ss) goto UNMATCH;
	}
	*mtp = mip->type;
	*numChp = ch;
	return 0;
    UNMATCH:;
    }
    if (isMod15(p, size)) {
	*mtp = MAGIC_MOD15;
	return 0;
    } else return 1;
}