/*@Header@*/
/* $Id: shquote.c,v 1.3 2008/09/25 17:33:43 ksb Exp $
 * $Compile: ${cc:-cc} -DTEST -o %F %f
 */
#include <sys/errno.h>
#include <string.h>
#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>

#include "machine.h"

extern char *progname;

/*@Explode out@*/
/* Output a string such that the shell get exactly 1 word		(ksb)
 * that is exactly that string.
 *
 * Compute the shortest quote via:
 * with \ we need 1 for every: " ' \ ~ ` # $ & ; | * ( ) [ ] ? > < {
 *				and $IFS
 *	{ and ~ for csh mostly, ~ is only magic after IFS, really
 *	= is magic under -k in the shell, sigh.
 * with ' we need 2 + 3 for every: '
 * with " we need 2 + 1 for every: $ ` \ "
 *
 * The best could change in the string, so a Human can do better.
 * N.B. nits we don't cost perfectly:
 *	- the last $ in a "word" is not backslashed,
 *	- the ~ is only special as the first character in a word.
 */
void
OutQuote(char *pcOut)
{
	register int fQ, iC, i, fPrefQ;
	register char *pcScan;
	static char *pcIFS = (char *)0;
	auto int aiSum[1<<(8*sizeof(char))];
	auto int iBacks, iDoubles, iSingles;
	static char acMagic[] =
		"\"\'\\`#$&;|*()[?><{~=";
	static char acDoubleDown[] =
		"\"$`\\";

	if ((char *)0 == pcIFS && (char *)0 == (pcIFS = getenv("IFS"))) {
		pcIFS = " \t\n";
	}

	for (i = 0; i < sizeof(aiSum)/sizeof(aiSum[0]); ++i) {
		aiSum[i] = 0;
	}
	iBacks = 0;
	for (pcScan = pcOut; '\000' != (iC = *pcScan); ++pcScan) {
		++aiSum[iC];
		iBacks += (char *)0 != strchr(pcIFS, iC);
	}
	for (i = 0; '\000' != (iC = acMagic[i]); ++i) {
		iBacks += aiSum[iC];
	}
	iDoubles = 2 + (aiSum['$'] + aiSum['`'] + aiSum['\\'] + aiSum['\"']);
	iSingles = 2 + 3*aiSum['\''];

	if (0 == iBacks) {
		printf("%s", pcOut);
		return;
	}
	if (iSingles <= iBacks && 2 == iSingles) {
		printf("\'%s\'", pcOut);
		return;
	}
	if (iDoubles <= iBacks && 2 == iDoubles) {
		printf("\"%s\"", pcOut);
		return;
	}
#if DEBUG_SHQ
	printf("back %d; single %d; double %d\n", iBacks, iSingles, iDoubles);
#endif

	/* No cheap way out, take the (least) hard way
	 */
	if (iBacks <= iDoubles && iBacks <= iSingles) {
		fQ = fPrefQ = '\000';
	} else if (iDoubles < iSingles) {
		fQ = fPrefQ = '\"';
	} else {
		fQ = fPrefQ = '\'';
	}
	if ('\000' != fQ) {
		printf("%c", fQ);
	}
	for (pcScan = pcOut; '\000' != (iC = *pcScan); ++pcScan) {
		switch (fQ) {
		case '\000':
			if ((char *)0 == strchr(acMagic, iC) && (char *)0 == strchr(pcIFS, iC)) {
				break;
			}
			if ('\\' == iC && '\\' == pcScan[1]) {
				printf("\'");
				fQ = '\'';
			} else if ('\000' == fPrefQ || fPrefQ == iC) {
				printf("\\");
			} else {
				printf("%c", fPrefQ);
				fQ = fPrefQ;
			}
			break;
		case '\'':
			if ('\'' != iC) {
				break;
			}
			printf("'\\");
			fQ = '\000';
			break;
		case '\"':
			if ('\"' == iC && '\000' == pcScan[1]) {
				printf("\"\\");
				fQ = '\000';
				break;
			}
			if ((char *)0 == strchr(acDoubleDown, iC)) {
				break;
			}
			/* "...$" preserves the dollar sign, strangely
			 */
			if ('$' == iC && '\000' == pcScan[1]) {
				break;
			}
			printf("\\");
			break;
		default:
			fprintf(stderr, "%s: quote code snark!\n", progname);
			break;
		}
		printf("%c", iC);
	}
	if ('\000' != fQ) {
		printf("%c", fQ);
	}
}

/*@Remove@*/
#if TEST
#include <sysexits.h>

char *progname = "shquote-test";

static char *apcTest[] = {
	"simple",		"white space",
	"doublequote\"",	"singlequote\'",
	"backslash\\",		"dollarsign$",
	"tailspace ",
	"\"\"\"\"", "''''", "\\\\\\\\", "$$$$",
	"ham&eggs", "either|or", "a?b:c;", "-k A=3",
	"\"\'\\`#$&;|*()[?><{~=",
	"\"stuff we want in 'singles' kinda\"",
	(char *)0
};

int
main(int argc, char **argv, char **envp)
{
	register char **ppc;

	for (ppc = 1 == argc ? apcTest : argv+1; (char *)0 != *ppc; ++ppc) {
		printf("%s => ", *ppc);
		OutQuote(*ppc);
		printf("\n");
	}
	exit(EX_OK);
}
/*@Remove@*/
#endif