From e9a23015203da8bd2d5cf48e518d9e788ba7eee5 Mon Sep 17 00:00:00 2001
From: Sveinung Kvilhaugsvik <sveinung84@users.sourceforge.net>
Date: Thu, 8 Apr 2021 16:33:04 +0200
Subject: [PATCH] A building that allows actions isn't redundant.

Some wonders in sandbox are shown as redundant even if they allow units to
perform an action. Make enabling an action count as a side effect.

Requested by Emmet Hikory in a FIXME comment.

See osdn #41955
---
 common/improvement.c | 55 ++++++++++++++++++++++++++++++++++++++++----
 common/improvement.h |  2 +-
 2 files changed, 52 insertions(+), 5 deletions(-)

diff --git a/common/improvement.c b/common/improvement.c
index f938dd19a0..d1f26dfe66 100644
--- a/common/improvement.c
+++ b/common/improvement.c
@@ -122,6 +122,14 @@ void improvement_feature_cache_init(void)
       }
     } action_enablers_iterate_end;
 
+    pimprove->allows_actions = FALSE;
+    action_enablers_iterate(act) {
+      if (requirement_needs_improvement(pimprove, &act->actor_reqs)) {
+        pimprove->allows_actions = TRUE;
+        break;
+      }
+    } action_enablers_iterate_end;
+
   } improvement_iterate_end;
 }
 
@@ -506,6 +514,48 @@ static bool impr_protects_vs_actions(const struct city *pcity,
   return FALSE;
 }
 
+/**********************************************************************//**
+  Returns TRUE iff improvement allows its owner to perform an action
+**************************************************************************/
+static bool impr_allows_actions(const struct city *pcity,
+                                const struct impr_type *pimprove)
+{
+  /* Fast check */
+  if (!pimprove->allows_actions) {
+    return FALSE;
+  }
+
+  action_enablers_iterate(act) {
+    if (requirement_needs_improvement(pimprove, &act->actor_reqs)) {
+      switch (action_id_get_actor_kind(act->action)) {
+      case AAK_UNIT:
+        unit_type_iterate(ut) {
+          if (!utype_can_do_action(ut, act->action)) {
+            /* Not relevant */
+            continue;
+          }
+
+          if (utype_player_already_has_this(city_owner(pcity), ut)) {
+            /* The player has a unit that may use the buidling */
+            return TRUE;
+          }
+
+          if (can_city_build_unit_now(pcity, ut)) {
+            /* This city can build a unit that uses the building */
+            return TRUE;
+          }
+        } unit_type_iterate_end;
+        break;
+      case AAK_COUNT:
+        fc_assert(action_id_get_actor_kind(act->action) != AAK_COUNT);
+        break;
+      }
+    }
+  } action_enablers_iterate_end;
+
+  return FALSE;
+}
+
 /**********************************************************************//**
   Check if an improvement has side effects for a city.  Side effects
   are any benefits that accrue that are not tracked by the effects
@@ -519,13 +569,10 @@ static bool impr_protects_vs_actions(const struct city *pcity,
 static bool improvement_has_side_effects(const struct city *pcity,
                                          const struct impr_type *pimprove)
 {
-    /* FIXME: There should probably also be a test as to whether
-     *        the improvement *enables* an action (somewhere else),
-     *        but this is hard to determine at city scope. */
-
     return (impr_provides_buildable_units(pcity, pimprove)
             || impr_provides_buildable_extras(pcity, pimprove)
             || impr_prevents_disaster(pcity, pimprove)
+            || impr_allows_actions(pcity, pimprove)
             || impr_protects_vs_actions(pcity, pimprove));
 }
 
diff --git a/common/improvement.h b/common/improvement.h
index 57a2598cc3..375d7158f3 100644
--- a/common/improvement.h
+++ b/common/improvement.h
@@ -87,7 +87,7 @@ struct impr_type {
   bool allows_extras;
   bool prevents_disaster;
   bool protects_vs_actions;
-  
+  bool allows_actions;
 };
 
 
-- 
2.30.2