subs: Clean up convoluted logic in shp_nav_one_sector()

Handle "no movement" before the movement loop instead of relying on
the first iteration of the loop.

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

diff --git a/src/lib/subs/shpsub.c b/src/lib/subs/shpsub.c
index cabe59d13c22999ca743718b48a9761b793c1a79..8291c46dadf7e75905527516e841cf665a4c2731 100644 (file)
--- a/src/lib/subs/shpsub.c
+++ b/src/lib/subs/shpsub.c
@@ -775,39 +775,50 @@ shp_nav_one_sector(struct emp_qelem *list, int dir, natid actor)
     newy = ynorm(mlp->unit.ship.shp_y + dy);
     getsect(newx, newy, &sect);
 
+    if (sect.sct_own && relations_with(sect.sct_own, actor) < FRIENDLY) {
+       mpr(actor, "can't go to %s\n", xyas(newx, newy, actor));
+       return 1;
+    }
+
     move = 0;
     for (qp = list->q_back; qp != list; qp = next) {
        next = qp->q_back;
        mlp = (struct ulist *)qp;
-       stuck = shp_check_nav(&mlp->unit.ship, &sect);
-       if (stuck == SHP_STUCK_NOT &&
-           (!sect.sct_own
-            || relations_with(sect.sct_own, actor) >= FRIENDLY))
+       switch (shp_check_nav(&mlp->unit.ship, &sect)) {
+       case SHP_STUCK_NOT:
            move = 1;
+           break;
+       case SHP_STUCK_CANAL:
+           break;
+       default:
+           CANT_REACH();
+           /* fall through */
+       case SHP_STUCK_CONSTRUCTION:
+       case SHP_STUCK_IMPASSABLE:
+           mpr(actor, "can't go to %s\n", xyas(newx, newy, actor));
+           return 1;
+       }
+    }
+    if (!move) {
+       mpr(actor, "is too large to fit into the canal system at %s\n",
+           xyas(newx, newy, actor));
+       return 1;
     }
 
     for (qp = list->q_back; qp != list; qp = next) {
        next = qp->q_back;
        mlp = (struct ulist *)qp;
        stuck = shp_check_nav(&mlp->unit.ship, &sect);
-       if (stuck != SHP_STUCK_NOT ||
-           (sect.sct_own
-            && relations_with(sect.sct_own, actor) < FRIENDLY)) {
-           if (stuck == SHP_STUCK_CANAL &&
-               (!sect.sct_own
-                || relations_with(sect.sct_own, actor) >= FRIENDLY))
-               sprintf(dp,
-                       "is too large to fit into the canal system at %s",
-                       xyas(newx, newy, actor));
-           else
-               sprintf(dp, "can't go to %s", xyas(newx, newy, actor));
-           if (!move) {
-               mpr(actor, "%s\n", dp);
-               return 1;
-           } else {
-               shp_stays(actor, dp, mlp);
-               continue;
-           }
+       if (stuck == SHP_STUCK_CANAL) {
+           sprintf(dp,
+                   "is too large to fit into the canal system at %s",
+                   xyas(newx, newy, actor));
+           shp_stays(actor, dp, mlp);
+           continue;
+       } else if (CANT_HAPPEN(stuck != SHP_STUCK_NOT)) {
+           sprintf(dp, "can't go to %s", xyas(newx, newy, actor));
+           shp_stays(actor, dp, mlp);
+           continue;
        }
 
        if (mlp->mobil <= 0.0) {