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/*
 * Metaphone algorithm for translating a word to
 * a short phonetic equivalent for lookup.
 * char * metaphone(char * word)
 *
 * Original algorithm by Larry Phillips
 * Algorithim is in public domain.
 */
#include <ctype.h>

static char vsvfn[26] = {
     /*  A  B C  D E F G  H I J K L M N O P Q R S T U V W X Y Z */
	 1,16,4,16,9,2,4,16,9,2,0,2,2,2,1,4,0,2,4,4,1,0,0,0,8,0
};

#define FN(x) ((c = (x)) ? vsvfn[c - 'A'] : 0)
#define VOWEL(x)   (FN(x) &  1) /* AEIOU */
#define SAME(x)    (FN(x) &  2) /* FJLMNR */
#define VARSON(x)  (FN(x) &  4) /* CGPST */
#define FRONTV(x)  (FN(x) &  8) /* EIY */
#define NOGHF(x)   (FN(x) & 16) /* BDH */

#define SAY(x)	{ *Metaph++ = (x); continue; }

#define MAXMET 4	/* size of thing created */
#define TRANS 32

char *
metaphone(word)
unsigned char *word;
{
	unsigned char *n, *n_start, *n_end, c;
	unsigned char *Metaph, *metaph_end;
	int KSflag;	/* state flag */
	unsigned char ntrans[TRANS + 2];
	static unsigned char metaph[MAXMET + 1];

	/* clear work areas */
	memset(ntrans, '\0', TRANS + 2);
	memset(metaph, '\0', MAXMET + 1);

	/* Isolate word and make upper case */
	for (n = ntrans + 1, n_end = ntrans + TRANS;
	     (c = *word++) && n < n_end;)
		if (isalpha(c))
			*n++ = toupper(c);
		else
			break;

	n_end = n;
	n = ntrans + 1;
	
	/* process first character */
	switch (*n) {
	case 0:
		return (n);	/* no word found */

	case 'P':
	case 'G':
	case 'K':
		if ('N' == n[1])
			*n++ = '\0';
		break;

	case 'A':
		if ('E' == n[1])
			*n++ = '\0';
		break;

	case 'W':
		switch (n[1]) {
		case 'H':
			n[1] = *n;
			*n++ = 'E';
			break;
		case 'R':
			*n++ = 0;
		}
		break;

	case 'X':
		*n = 'S';
	}

	/* Process rest of word  SAY does continue */
	KSflag = 0;
	metaph_end = (Metaph = metaph) + MAXMET;
	n_start = n;
	for (; Metaph < metaph_end; n++) {
		if (KSflag) {
			KSflag = 0;
			SAY(*n)
		}
		if (n >= n_end)
			break;

		/* Drop double letters except CC */
		if (n[-1] == *n && *n != 'C')
			continue;

		/* check for FJLMNR or first letter vowel */
		if (SAME(*n) || ((n == n_start) && VOWEL(*n)))
			SAY(*n)

		switch (*n) {
		case 'B':
			if (n < n_end || n[-1] != 'M')
				SAY(*n)
			break;

		case 'C':
			if (n[-1] != 'S' || !FRONTV(n[1])) {
				if (n[1] == 'I' && n[2] == 'A')
					SAY('X')
				if (FRONTV(n[1]))
					SAY('S')
				if (n[1] == 'H')
					if ((n == n_start && !VOWEL(n[2])) ||
					      n[-1] == 'S')
						SAY('K')
					else
						SAY('X')
				else
					SAY('K')
			}
			break;

		case 'D':
			SAY((n[1] == 'G' && FRONTV(n[2])) ? 'J' : 'T')

		case 'G':
			if ((n[1] != 'H' || VOWEL(n[2])) &&
			    (n[1] != 'N' || ((n + 1) < n_end &&
			    (n[2] != 'E' || n[3] != 'D'))) &&
			    (n[-1] != 'D' || !FRONTV(n[1])))
				SAY((FRONTV(n[1]) && n[2] != 'G') ? 'J' : 'K')
			break;

		case 'H':
			if (!VARSON(n[-1]) && (!VOWEL(n[-1]) || VOWEL(n[1])))
				SAY('H')
			break;

		case 'K':
			if (n[-1] != 'C')
				SAY('K')
			break;

		case 'P':
			SAY(n[1] == 'H' ? 'F' : 'P')

		case 'Q':
			SAY('K')

		case 'S':
			if (n[1] == 'H' || (n[1] == 'I' && 
			    (n[2] == 'O' || n[2] == 'A')))
				SAY('X')
			else
				SAY('S')

		case 'T':
			if (n[1] == 'I' &&
			    (n[2] == 'O' || n[2] == 'A'))
				SAY('X')
			if (n[1] == 'H')
				SAY('O')
			if (n[1] != 'C' || n[2] == 'H')
				SAY('T')
			break;

		case 'V':
			SAY('F')

		case 'W':
			if(VOWEL(n[-1]))
				SAY(*n)
			break;

		case 'Y':
			if(!VOWEL(n[1]))
				SAY(*n)
			break;

		case 'X':
			if (n == n_start)
				SAY('S')
			KSflag = 1;
			SAY('K')

		case 'Z':
			SAY('S')
		}
	}
	return (metaph);
}

#ifdef TEST
#include <misc.h>
main()
{
	char buf[80];

	while (NULL != ask(buf, "string"))
		printf("%s\n", metaphone(buf));
}
#endif

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