From d9123b44910d80d7014e4e537b7aa0629dc61b1b Mon Sep 17 00:00:00 2001
From: Enno Rehling <enno@eressea.de>
Date: Tue, 22 Jun 2021 00:36:22 +0200
Subject: [PATCH] additional testing for sea serpent visibility

---
 src/kernel/unit.c |  4 +++-
 src/laws.c        |  9 +++++++--
 src/laws.test.c   | 37 +++++++++++++++++++++++++++++++++++++
 3 files changed, 47 insertions(+), 3 deletions(-)

diff --git a/src/kernel/unit.c b/src/kernel/unit.c
index 64ac33396..d7f14f073 100644
--- a/src/kernel/unit.c
+++ b/src/kernel/unit.c
@@ -1218,7 +1218,9 @@ int invisible(const unit * target, const unit * viewer)
             if (hidden > target->number) hidden = target->number;
             if (viewer) {
                 const resource_type *rtype = get_resourcetype(R_AMULET_OF_TRUE_SEEING);
-                hidden -= i_get(viewer->items, rtype->itype);
+                if (rtype) {
+                    hidden -= i_get(viewer->items, rtype->itype);
+                }
             }
         }
         return hidden;
diff --git a/src/laws.c b/src/laws.c
index 8f30b3416..8ec30f194 100644
--- a/src/laws.c
+++ b/src/laws.c
@@ -4032,8 +4032,13 @@ static enum cansee_t cansee_ex(const unit *u, const region *r, const unit *targe
     enum cansee_t result = CANSEE_HIDDEN;
     if (rings >= target->number) {
         const resource_type *rtype = get_resourcetype(R_AMULET_OF_TRUE_SEEING);
-        int amulet = i_get(u->items, rtype->itype);
-        if (amulet <= 0) {
+        if (rtype) {
+            int amulet = i_get(u->items, rtype->itype);
+            if (amulet <= 0) {
+                return CANSEE_INVISIBLE;
+            }
+        }
+        else {
             return CANSEE_INVISIBLE;
         }
     }
diff --git a/src/laws.test.c b/src/laws.test.c
index 67ea499ce..ed66cc941 100644
--- a/src/laws.test.c
+++ b/src/laws.test.c
@@ -1967,6 +1967,42 @@ static void test_cansee_sphere(CuTest *tc) {
     test_teardown();
 }
 
+/**
+ * Hidden monsters are seen in oceans if they are big enough.
+ */
+static void test_cansee_monsters(CuTest *tc) {
+    unit *u, *u2;
+    race *rc;
+    const item_type *itype;
+
+    test_setup();
+    itype = test_create_itemtype("roi");
+    u = test_create_unit(test_create_faction(), test_create_ocean(0, 0));
+    u2 = test_create_unit(test_create_faction(), u->region);
+    rc = test_create_race("seaserpent");
+    rc->weight = 4999;
+    u_setrace(u2, rc);
+
+    CuAssertTrue(tc, cansee(u->faction, u->region, u2, 0));
+    CuAssertTrue(tc, cansee(u->faction, u->region, u2, 2));
+
+    set_level(u2, SK_STEALTH, 1);
+    CuAssertTrue(tc, !cansee(u->faction, u->region, u2, 0));
+    CuAssertTrue(tc, cansee(u->faction, u->region, u2, 1));
+
+    rc->weight = 5000;
+    /* no stealth for fatties at sea */
+    CuAssertTrue(tc, cansee(u->faction, u->region, u2, 0));
+    CuAssertTrue(tc, cansee(u->faction, u->region, u2, 1));
+
+    /* rings still work */
+    i_change(&u2->items, itype, 1);
+    CuAssertTrue(tc, !cansee(u->faction, u->region, u2, 0));
+    CuAssertTrue(tc, !cansee(u->faction, u->region, u2, 2));
+
+    test_teardown();
+}
+
 static void test_nmr_timeout(CuTest *tc) {
     test_setup();
     CuAssertIntEquals(tc, 0, NMRTimeout());
@@ -2439,6 +2475,7 @@ CuSuite *get_laws_suite(void)
     SUITE_ADD_TEST(suite, test_cansee);
     SUITE_ADD_TEST(suite, test_cansee_ring);
     SUITE_ADD_TEST(suite, test_cansee_sphere);
+    SUITE_ADD_TEST(suite, test_cansee_monsters);
     SUITE_ADD_TEST(suite, test_nmr_timeout);
     SUITE_ADD_TEST(suite, test_long_orders);
     SUITE_ADD_TEST(suite, test_long_order_on_ocean);