shpsub: Make shp_check_nav() return more useful information

Some callers have to second-guess shp_check_nav() to figure out
whether CN_LANDLOCKED means "too big to fit into the canal" or "can't
go there at all".

Fix that by returning d_navigation.  CN_LANDLOCKED becomes either
NAV_CANAL or NAV_NONE, CN_CONSTRUCTION becomes either NAV_02 or
NAV_60, and CN_NAVIGABLE becomes NAVOK.

The CN_NAVIGABLE, ... codes are now unused.  Drop them.

Signed-off-by: Markus Armbruster <armbru@pond.sub.org>

include/sect.h

@@ -92,14 +92,6 @@ struct sctstr {
     unsigned char sct_defense;	/* Defensive value of a sector */
 };
 
-enum d_navigation {
-    NAV_NONE,	/* ships can't navigate */
-    NAVOK,	/* ships can always navigate */
-    NAV_02,	/* requires 2% effic to navigate */
-    NAV_CANAL,	/* requires 2% effic to navigate and M_CANAL capability */
-    NAV_60	/* requires 60% effic to navigate */
-};
-
 struct dchrstr {
     unsigned char d_uid;
     char d_mnem;		/* map symbol */

include/ship.h

@@ -155,12 +155,6 @@ extern struct mchrstr mchr[SHP_TYPE_MAX + 2];
 /* Work required for building 100% */
 #define SHP_BLD_WORK(lcm, hcm) (20 + (lcm) + 2 * (hcm))
 
- /* return codes from shp_check_nav */
-#define CN_NAVIGABLE	0
-#define CN_LANDLOCKED	1
-#define CN_CONSTRUCTION	2
-#define CN_ERROR	-1
-
 enum {
     SHP_AIROPS_EFF = 50,	/* min. efficiency for air ops */
     SHP_TORP_SHELLS = 3		/* number of shells used by a torpedo */
@@ -191,7 +185,7 @@ extern double shp_torp_hitchance(struct shpstr *, int);
 extern void shp_sel(struct nstr_item *, struct emp_qelem *);
 extern void shp_nav(struct emp_qelem *, double *, double *, int *, natid);
 extern int shp_sweep(struct emp_qelem *, int, int, natid);
-extern int shp_check_nav(struct sctstr *, struct shpstr *);
+extern enum d_navigation shp_check_nav(struct shpstr *, struct sctstr *);
 extern int sect_has_dock(struct sctstr *);
 extern int shp_hardtarget(struct shpstr *);
 extern int shp_nav_one_sector(struct emp_qelem *, int, natid, int);

include/types.h

@@ -36,6 +36,14 @@
 typedef unsigned char natid;	/* NSC_NATID must match this */
 typedef short coord;
 
+enum d_navigation {
+    NAV_NONE,	/* ships can't navigate */
+    NAVOK,	/* ships can always navigate */
+    NAV_02,	/* requires 2% effic to navigate */
+    NAV_CANAL,	/* requires 2% effic to navigate and M_CANAL capability */
+    NAV_60	/* requires 60% effic to navigate */
+};
+
 struct bp;
 struct emp_qelem;
 struct empobj;

src/lib/subs/retreat.c

@@ -172,25 +172,27 @@ retreat_ship1(struct shpstr *sp, char code, int orig)
     }
 
     getsect(sp->shp_x, sp->shp_y, &sect);
-    switch (shp_check_nav(&sect, sp)) {
+    switch (shp_check_nav(sp, &sect)) {
-    case CN_CONSTRUCTION:
+    case NAV_02:
+    case NAV_60:
 	wu(0, sp->shp_own,
 	   "%s %s,\nbut was caught in a construction zone, and couldn't retreat!\n",
 	   prship(sp), conditions[findcondition(code)].desc[orig]);
 	if (!orig)
 	    putship(sp->shp_uid, sp);
 	return 0;
-    case CN_LANDLOCKED:
+    case NAV_NONE:
+    case NAV_CANAL:
 	wu(0, sp->shp_own,
 	   "%s %s,\nbut was landlocked, and couldn't retreat!\n",
 	   prship(sp), conditions[findcondition(code)].desc[orig]);
 	if (!orig)
 	    putship(sp->shp_uid, sp);
 	return 0;
-    case CN_NAVIGABLE:
+    case NAVOK:
 	break;
-    case CN_ERROR:
     default:
+	CANT_REACH();
 	wu(0, sp->shp_own,
 	   "%s %s,\nbut was subject to an empire error, and couldn't retreat!\n",
 	   prship(sp), conditions[findcondition(code)].desc[orig]);
@@ -242,7 +244,7 @@ retreat_ship1(struct shpstr *sp, char code, int orig)
 	mobcost = shp_mobcost(sp);
 
 	getsect(newx, newy, &sect);
-	if (shp_check_nav(&sect, sp) != CN_NAVIGABLE ||
+	if (shp_check_nav(sp, &sect) != NAVOK ||
 	    (sect.sct_own
 	     && relations_with(sect.sct_own, sp->shp_own) < FRIENDLY)) {
 	    wu(0, sp->shp_own, "%s %s,\nbut could not retreat to %s!\n",

src/lib/subs/shpsub.c

@@ -138,17 +138,19 @@ shp_nav(struct emp_qelem *list, double *minmobp, double *maxmobp,
 	    shp_stays(actor, "was sucked into the sky by a strange looking spaceship", mlp);	/* heh -KHS */
 	    continue;
 	}
-	switch (shp_check_nav(&sect, sp)) {
+	switch (shp_check_nav(sp, &sect)) {
-	case CN_CONSTRUCTION:
+	case NAV_02:
+	case NAV_60:
 	    shp_stays(actor, "is caught in a construction zone", mlp);
 	    continue;
-	case CN_LANDLOCKED:
+	case NAV_NONE:
+	case NAV_CANAL:
 	    shp_stays(actor, "is landlocked", mlp);
 	    continue;
-	case CN_NAVIGABLE:
+	case NAVOK:
 	    break;
-	case CN_ERROR:
 	default:
+	    CANT_REACH();
 	    shp_stays(actor, "was just swallowed by a big green worm", mlp);
 	    continue;
 	}
@@ -292,31 +294,42 @@ shp_stays(natid actor, char *str, struct ulist *mlp)
     free(mlp);
 }
 
-int
+/*
-shp_check_nav(struct sctstr *sect, struct shpstr *shp)
+ * Can SP navigate in SECTP?
+ * Sector ownership is *not* considered!
+ * Return NAVOK when yes.
+ * Return NAV_02 when it could if the sector was at least 2% efficient.
+ * Return NAV_60 when it could if the sector was at least 60% efficient.
+ * Return NAV_CANAL when it lacks capability M_CANAL.
+ * Return NAV_NONE when this sector type isn't navigable at all.
+ */
+enum d_navigation
+shp_check_nav(struct shpstr *sp, struct sctstr *sectp)
 {
-    switch (dchr[sect->sct_type].d_nav) {
+    switch (dchr[sectp->sct_type].d_nav) {
     case NAVOK:
 	break;
     case NAV_CANAL:
-	if (mchr[(int)shp->shp_type].m_flags & M_CANAL) {
+	if (mchr[sp->shp_type].m_flags & M_CANAL) {
-	    if (sect->sct_effic < 2)
+	    if (sectp->sct_effic < 2)
-		return CN_CONSTRUCTION;
+		return NAV_02;
 	} else
-	    return CN_LANDLOCKED;
+	    return NAV_CANAL;
 	break;
     case NAV_02:
-	if (sect->sct_effic < 2)
+	if (sectp->sct_effic < 2)
-	    return CN_CONSTRUCTION;
+	    return NAV_02;
 	break;
     case NAV_60:
-	if (sect->sct_effic < 60)
+	if (sectp->sct_effic < 60)
-	    return CN_CONSTRUCTION;
+	    return NAV_60;
 	break;
     default:
-	return CN_LANDLOCKED;
+	CANT_REACH();
+    case NAV_NONE:
+	return NAV_NONE;
     }
-    return CN_NAVIGABLE;
+    return NAVOK;
 }
 
 int
@@ -748,13 +761,11 @@ shp_nav_one_sector(struct emp_qelem *list, int dir, natid actor,
 	newx = xnorm(mlp->unit.ship.shp_x + dx);
 	newy = ynorm(mlp->unit.ship.shp_y + dy);
 	getsect(newx, newy, &sect);
-	navigate = shp_check_nav(&sect, &mlp->unit.ship);
+	navigate = shp_check_nav(&mlp->unit.ship, &sect);
-	if (navigate != CN_NAVIGABLE ||
+	if (navigate != NAVOK ||
 	    (sect.sct_own
 	     && relations_with(sect.sct_own, actor) < FRIENDLY)) {
-	    if (dchr[sect.sct_type].d_nav == NAV_CANAL &&
+	    if (navigate == NAV_CANAL)
-		!(((struct mchrstr *)mlp->chrp)->m_flags & M_CANAL) &&
-		navigate == CN_LANDLOCKED)
 		sprintf(dp,
 			"is too large to fit into the canal system at %s",
 			xyas(newx, newy, actor));

src/lib/update/sail.c

@@ -247,8 +247,7 @@ sail_nav_fleet(struct fltheadstr *fltp)
 	       fe->num, cname(fe->own));
 	    error = 1;
 	}
-	if ((shp_check_nav(sectp, sp) == CN_LANDLOCKED) &&
+	if (shp_check_nav(sp, sectp) == NAV_CANAL) {
-	    (dchr[sectp->sct_type].d_nav == NAV_CANAL)) {
 	    wu(0, fltp->own,
 	       "Your ship #%d (%s) is too big to fit through the canal.\n",
 	       fe->num, cname(fe->own));
@@ -259,7 +258,7 @@ sail_nav_fleet(struct fltheadstr *fltp)
 	return 0;
     sp = getshipp(fltp->leader);
     sectp = getsectp(fltp->x, fltp->y);
-    if (shp_check_nav(sectp, sp) != CN_NAVIGABLE)
+    if (shp_check_nav(sp, sectp) != NAVOK)
 	wu(0, fltp->own, "Your fleet lead by %d is trapped by land.\n",
 	   fltp->leader);
     sp = getshipp(fltp->leader);