[Freeciv-Dev] Re: (PR#4420) New traderoute rules

["Rafa³ Bursig" <bursig@xxxxxxxxx>]

Dnia 2003.07.17 20:15, Jason Short napisa³(a):

> I think can_enter_marketplace is an unhelpful name.  Perhaps
> can_cities_trade would be better (not to be confused with
> can_establish_trade_route - what you call "entering the marketplace"
> is basically "trade" as opposed to a "trade route")?
> 
Done

> +  if (pcity_homecity->owner == pcity_dest->owner
> +         && map_distance(pcity_homecity->x, pcity_homecity->y,
> +                                 pcity_dest->x, pcity_dest->y) <= 8)
> {
> +    return FALSE;
> +  }
> 
> The above code should just call can_enter_marketplace, right?
> 
fixed

> I also have the problem that the patch doesn't compile; see
> unihand.c:1211.
This is my fault becouse I send wrong version of this patch (trade3 
insted trade4). Here is lastest version with your advices.

I plan commit it tomorow.

Rafal

diff -u -r freeciv/ai/aiunit.c fc/ai/aiunit.c
--- freeciv/ai/aiunit.c Thu Jul 17 20:27:19 2003
+++ fc/ai/aiunit.c      Thu Jul 17 21:37:11 2003
@@ -2477,7 +2477,8 @@
        players_iterate(aplayer) {
          if (pplayers_at_war(pplayer, aplayer)) continue;
          city_list_iterate(pplayer->cities,pdest) {
-           if (pcity && can_establish_trade_route(pcity, pdest)
+           if (pcity && can_cities_trade(pcity, pdest)
+              && can_establish_trade_route(pcity, pdest)
                && map_get_continent(pcity->x, pcity->y) 
                                 == map_get_continent(pdest->x, pdest->y)) {
              tradeval=trade_between_cities(pcity, pdest);
diff -u -r freeciv/client/gui-gtk/dialogs.c fc/client/gui-gtk/dialogs.c
--- freeciv/client/gui-gtk/dialogs.c    Thu Jul 10 13:36:39 2003
+++ fc/client/gui-gtk/dialogs.c Thu Jul 17 21:37:11 2003
@@ -1147,6 +1147,7 @@
                          struct city *phomecity, struct city *pdestcity)
 {
   char buf[128];
+  bool can_establish, can_trade;
   
   my_snprintf(buf, sizeof(buf),
              _("Your caravan from %s reaches the city of %s.\nWhat now?"),
@@ -1155,15 +1156,20 @@
   caravan_city_id=pdestcity->id; /* callbacks need these */
   caravan_unit_id=punit->id;
   
+  can_trade = can_cities_trade(phomecity, pdestcity);
+  can_establish = can_trade
+                && can_establish_trade_route(phomecity, pdestcity);
+  
   caravan_dialog = popup_message_dialog(top_vbox,
                                        _("Your Caravan Has Arrived"), buf,
                                        caravan_close_callback, NULL,
-                          _("Establish 
_Traderoute"),caravan_establish_trade_callback, 0,
+                          (can_establish ? _("Establish _Traderoute") :
+                          _("Enter 
Marketplace")),caravan_establish_trade_callback, 0,
                           _("Help build 
_Wonder"),caravan_help_build_wonder_callback, 0,
                           _("_Keep moving"),NULL, 0,
                           0);
   
-  if (!can_establish_trade_route(phomecity, pdestcity)) {
+  if (!can_trade) {
     message_dialog_button_set_sensitive(caravan_dialog, "button0", FALSE);
   }
   
diff -u -r freeciv/client/gui-gtk-2.0/dialogs.c fc/client/gui-gtk-2.0/dialogs.c
--- freeciv/client/gui-gtk-2.0/dialogs.c        Thu Jul 10 13:36:39 2003
+++ fc/client/gui-gtk-2.0/dialogs.c     Thu Jul 17 21:37:11 2003
@@ -1018,6 +1018,7 @@
                          struct city *phomecity, struct city *pdestcity)
 {
   char buf[128];
+  bool can_establish, can_trade;
   
   my_snprintf(buf, sizeof(buf),
              _("Your caravan from %s reaches the city of %s.\nWhat now?"),
@@ -1026,10 +1027,15 @@
   caravan_city_id=pdestcity->id; /* callbacks need these */
   caravan_unit_id=punit->id;
   
+  can_trade = can_cities_trade(phomecity, pdestcity);
+  can_establish = can_trade
+                 && can_establish_trade_route(phomecity, pdestcity);
+  
   caravan_dialog = popup_message_dialog(GTK_WINDOW(toplevel),
     _("Your Caravan Has Arrived"), 
     buf,
-    _("Establish _Traderoute"),caravan_establish_trade_callback, NULL,
+    (can_establish ? _("Establish _Traderoute") :
+    _("Enter Marketplace")),caravan_establish_trade_callback, NULL,
     _("Help build _Wonder"),caravan_help_build_wonder_callback, NULL,
     _("_Keep moving"), NULL, NULL,
     NULL);
@@ -1037,7 +1043,7 @@
   g_signal_connect(caravan_dialog, "destroy",
                   G_CALLBACK(caravan_destroy_callback), NULL);
   
-  if (!can_establish_trade_route(phomecity, pdestcity)) {
+  if (!can_trade) {
     message_dialog_button_set_sensitive(caravan_dialog, 0, FALSE);
   }
   
diff -u -r freeciv/client/gui-mui/dialogs.c fc/client/gui-mui/dialogs.c
--- freeciv/client/gui-mui/dialogs.c    Thu Jul 10 13:36:39 2003
+++ fc/client/gui-mui/dialogs.c Thu Jul 17 21:37:11 2003
@@ -971,15 +971,19 @@
   my_snprintf(buf, sizeof(buf),_("Your caravan from %s reaches the city of 
%s.\nWhat now?"),
           phomecity->name, pdestcity->name);
 
-  if(can_establish_trade_route(phomecity, pdestcity))
+  if (can_cities_trade(phomecity, pdestcity))
   {
     struct caravan_data *cd = malloc_struct(struct caravan_data);
     if(cd)
     {
       cd->caravan_city_id = pdestcity->id;
       cd->caravan_unit_id = punit->id;
-
-      msg_dlg[i].label = _("_Establish traderoute");
+      if (can_establish_trade_route(phomecity, pdestcity))
+      {
+        msg_dlg[i].label = _("_Establish traderoute");
+      } else {
+        msg_dlg[i].label = _("_Enter Marketplace");
+      }
       msg_dlg[i].function = (APTR)caravan_establish;
       msg_dlg[i].data = (APTR)cd;
       i++;
diff -u -r freeciv/client/gui-sdl/dialogs.c fc/client/gui-sdl/dialogs.c
--- freeciv/client/gui-sdl/dialogs.c    Thu Jul 17 17:56:33 2003
+++ fc/client/gui-sdl/dialogs.c Thu Jul 17 21:37:11 2003
@@ -1506,7 +1506,8 @@
   SDL_String16 *pStr;
   int w = 0, h , canvas_x , canvas_y;
   struct CONTAINER *pCont;
-    
+  char cBuf[128];
+  
   if (pCaravan_Dlg) {
     return;
   }
@@ -1521,8 +1522,11 @@
   
   map_to_canvas_pos(&canvas_x, &canvas_y, pUnit->x, pUnit->y);
   
+  my_snprintf(cBuf, sizeof(cBuf), _("Your Caravan Has Arrived to city %s"),
+                                                         pDestcity->name);
+  
   /* window */
-  pStr = create_str16_from_char(_("Your Caravan Has Arrived") , 12);
+  pStr = create_str16_from_char(cBuf, 12);
   pStr->style |= TTF_STYLE_BOLD;
   
   pWindow = create_window(NULL, pStr , 10 , 10 , WF_DRAW_THEME_TRANSPARENT);
@@ -1535,16 +1539,29 @@
   pCaravan_Dlg->pEndWidgetList = pWindow;
     
   /* ---------- */
-  if (can_establish_trade_route(pHomecity, pDestcity))
+  if (can_cities_trade(pHomecity, pDestcity))
   {
+    int revenue = get_caravan_enter_city_trade_bonus(pHomecity, pDestcity);
+    
+    if (can_establish_trade_route(pHomecity, pDestcity)) {
+      my_snprintf(cBuf, sizeof(cBuf),
+               _("Establish Traderoute with %s ( %d R&G + %d trade )"),
+               pHomecity->name, revenue,
+                       trade_between_cities(pHomecity, pDestcity));
+    } else {
+      revenue = (revenue + 2) / 3;
+      my_snprintf(cBuf, sizeof(cBuf),
+               _("Enter Marketplace ( %d R&G bonus )"), revenue);
+    }
+    
     create_active_iconlabel(pBuf, pWindow->dst, pStr,
-           _("Establish Traderoute"), caravan_establish_trade_callback);
+           cBuf, caravan_establish_trade_callback);
     pBuf->data.cont = pCont;
-    set_wstate(pBuf , FC_WS_NORMAL);
+    set_wstate(pBuf, FC_WS_NORMAL);
   
-    add_to_gui_list(ID_LABEL , pBuf);
+    add_to_gui_list(ID_LABEL, pBuf);
     
-    w = MAX(w , pBuf->size.w);
+    w = MAX(w, pBuf->size.w);
     h += pBuf->size.h;
   }
   
diff -u -r freeciv/client/gui-win32/dialogs.c fc/client/gui-win32/dialogs.c
--- freeciv/client/gui-win32/dialogs.c  Thu Jul 10 13:36:45 2003
+++ fc/client/gui-win32/dialogs.c       Thu Jul 17 21:37:11 2003
@@ -1035,7 +1035,8 @@
                           struct city *phomecity, struct city *pdestcity)
 {
   char buf[128];
- 
+  bool can_establish, can_trade;
+  
   my_snprintf(buf, sizeof(buf),
               _("Your caravan from %s reaches the city of %s.\nWhat now?"),
               phomecity->name, pdestcity->name);
@@ -1043,15 +1044,20 @@
   caravan_city_id=pdestcity->id; /* callbacks need these */
   caravan_unit_id=punit->id;
  
+  can_trade = can_cities_trade(phomecity, pdestcity);
+  can_establish = can_trade
+                 && can_establish_trade_route(phomecity, pdestcity);
+  
   caravan_dialog=popup_message_dialog(NULL,
                            /*"caravandialog"*/_("Your Caravan Has Arrived"),
                            buf,
-                           _("Establish 
_Traderoute"),caravan_establish_trade_callback, 0,
+                           (can_establish ? _("Establish _Traderoute") :
+                          _("Enter 
Marketplace")),caravan_establish_trade_callback, 0,
                            _("Help build 
_Wonder"),caravan_help_build_wonder_callback, 0,
                            _("_Keep moving"),caravan_keep_moving_callback, 0,
                            0);
  
-  if(!can_establish_trade_route(phomecity, pdestcity))
+  if (!can_enter_marketplace)
     {
       message_dialog_button_set_sensitive(caravan_dialog,0,FALSE);
     }
diff -u -r freeciv/client/gui-xaw/dialogs.c fc/client/gui-xaw/dialogs.c
--- freeciv/client/gui-xaw/dialogs.c    Thu Jul 10 13:36:45 2003
+++ fc/client/gui-xaw/dialogs.c Thu Jul 17 21:37:11 2003
@@ -1228,7 +1228,7 @@
                           caravan_keep_moving_callback, 0, 0,
                           NULL);
   
-  if(!can_establish_trade_route(phomecity, pdestcity))
+  if (!can_cities_trade(phomecity, pdestcity))
     XtSetSensitive(XtNameToWidget(caravan_dialog, "*button0"), FALSE);
   
   if(!unit_can_help_build_wonder(punit, pdestcity))
diff -u -r freeciv/common/city.c fc/common/city.c
--- freeciv/common/city.c       Fri Jul 11 18:15:44 2003
+++ fc/common/city.c    Thu Jul 17 21:37:11 2003
@@ -838,32 +838,64 @@
 /**************************************************************************
 ...
 **************************************************************************/
-bool can_establish_trade_route(struct city *pc1, struct city *pc2)
+bool can_cities_trade(struct city *pc1, struct city *pc2)
 {
-  int i, free1 = 0, free2 = 0;
+  return (pc1 && pc2 && (pc1 != pc2)
+          && (pc1->owner != pc2->owner
+          || map_distance(pc1->x, pc1->y, pc2->x, pc2->y) > 8));
+}
+
 
-  if (!pc1 || !pc2 || pc1 == pc2
-      || (pc1->owner == pc2->owner
-         && map_distance(pc1->x, pc1->y, pc2->x, pc2->y) <= 8)) {
+/**************************************************************************
+  Function don't check min cities distance then should be call with
+  connection of can_cities_trade(...) function.
+**************************************************************************/
+bool can_establish_trade_route(struct city *pc1, struct city *pc2)
+{
+  int i, trade = -1;
+  bool can_establish = TRUE;
+  
+  if (!pc1 || !pc2 || pc1 == pc2 || have_cities_trade_route(pc1, pc2)) {
     return FALSE;
   }
-
-  for (i = 0; i < NUM_TRADEROUTES; i++) {
-    if (pc1->trade[i] == pc2->id || pc2->trade[i] == pc1->id) {
-      /* cities already have a traderoute */
-      return FALSE;
+    
+  if (city_num_trade_routes(pc1) == NUM_TRADEROUTES) {
+    int slot = 0, value = pc1->trade_value[0];
+    
+    trade = trade_between_cities(pc1, pc2);
+    /* find min */
+    for (i = 1; i < NUM_TRADEROUTES; i++) {
+      if (value > pc1->trade_value[i]) {
+       slot = i;
+       value = pc1->trade_value[i];
+      }
     }
-
-    if (pc1->trade[i] == 0) {
-      free1++;
-    }
-    if (pc2->trade[i] == 0) {
-      free2++;
+    /* can we replace traderoute */
+    if (value >= trade) {
+      can_establish = FALSE;
     }
   }
+  
+  if (can_establish && city_num_trade_routes(pc2) == NUM_TRADEROUTES) {
+    int slot = 0, value = pc2->trade_value[0];
+    
+    if (trade == -1) {
+      trade = trade_between_cities(pc1, pc2);
+    }
+    /* find min */
+    for (i = 1; i < NUM_TRADEROUTES; i++) {
+      if (value > pc2->trade_value[i]) {
+       slot = i;
+       value = pc2->trade_value[i];
+      }
+    }
+    /* can we replace traderoute */
+    if (value >= trade) {
+      can_establish = FALSE;
+    }
+  }  
 
-  /* both cities need a free slot */
-  return (free1 > 0 && free2 > 0);
+  return can_establish;
 }
 
 /**************************************************************************
@@ -902,6 +934,56 @@
   return n;
 }
 
+/**************************************************************************
+  Returns the revenue trade route bonus.
+**************************************************************************/
+int get_caravan_enter_city_trade_bonus(struct city *pc1, struct city *pc2)
+{
+  int i, tb;
+
+  tb=(map_distance(pc1->x, pc1->y, pc2->x, pc2->y)+10);
+  /* should this be real_map_distance?  Leaving for now -- Syela */
+  tb=(tb*(pc1->trade_prod+pc2->trade_prod))/24;
+  /* 
+   * fudge factor to more closely approximate Civ2 behavior (Civ2 is
+   * really very different -- this just fakes it a little better) 
+   */
+  tb *= 3;
+
+  /* 
+   * one time bonus is not affected by factors in
+   * trade_between_cities() 
+   */
+  for (i = 0; i < num_known_tech_with_flag(city_owner(pc1),
+                                          TF_TRADE_REVENUE_REDUCE); i++) {
+    tb = (tb * 2) / 3;
+  }
+  /* was: A_RAILROAD, A_FLIGHT */
+  
+  /*
+   * this value will be reduced when both cities have established
+   * traderoute togeder -> tb = (tb + 2) / 3;
+   */
+  
+  return tb;
+}
+
+/**************************************************************************
+  Check if cities have established trade route.
+**************************************************************************/
+bool have_cities_trade_route(struct city *pc1, struct city *pc2)
+{
+  int i;
+  
+  for (i = 0; i < NUM_TRADEROUTES; i++) {
+    if (pc1->trade[i] == pc2->id || pc2->trade[i] == pc1->id) {
+      /* cities already have a traderoute */
+      return TRUE;
+    }
+  }
+  return FALSE;
+}
+
 /*************************************************************************
   Calculate amount of gold remaining in city after paying for buildings 
   and units.
diff -u -r freeciv/common/city.h fc/common/city.h
--- freeciv/common/city.h       Tue May 13 16:23:03 2003
+++ fc/common/city.h    Thu Jul 17 21:37:11 2003
@@ -396,10 +396,13 @@
 bool city_can_be_built_here(int x, int y);
 
 /* trade functions */
+bool can_cities_trade(struct city *pc1, struct city *pc2);
 bool can_establish_trade_route(struct city *pc1, struct city *pc2);
+bool have_cities_trade_route(struct city *pc1, struct city *pc2);
 int trade_between_cities(struct city *pc1, struct city *pc2);
 int city_num_trade_routes(struct city *pcity);
-
+int get_caravan_enter_city_trade_bonus(struct city *pc1, struct city *pc2);
+  
 /* list functions */
 struct city *city_list_find_id(struct city_list *This, int id);
 struct city *city_list_find_name(struct city_list *This, const char *name);
diff -u -r freeciv/common/unit.c fc/common/unit.c
--- freeciv/common/unit.c       Thu Jul 17 20:27:19 2003
+++ fc/common/unit.c    Thu Jul 17 21:37:11 2003
@@ -243,8 +243,7 @@
   pdestcity = map_get_city(punit->x, punit->y);
   if (!pdestcity) return FALSE;
   phomecity = find_city_by_id(punit->homecity);
-  if (!phomecity) return FALSE;
-  return can_establish_trade_route(phomecity, pdestcity);
+  return (phomecity && can_cities_trade(phomecity, pdestcity));
 }
 
 /**************************************************************************
diff -u -r freeciv/server/citytools.c fc/server/citytools.c
--- freeciv/server/citytools.c  Thu Jul 17 19:19:28 2003
+++ fc/server/citytools.c       Thu Jul 17 22:15:27 2003
@@ -59,7 +59,6 @@
                                  struct player *pplayer);
 static void server_set_tile_city(struct city *pcity, int city_x, int city_y,
                                 enum city_tile_type type);
-static void remove_trade_route(struct city *pc1, struct city *pc2);
 static bool update_city_tile_status(struct city *pcity, int city_x,
                                    int city_y);
 
@@ -1695,7 +1694,7 @@
 /**************************************************************************
 ...
 **************************************************************************/
-static void remove_trade_route(struct city *pc1, struct city *pc2)
+void remove_trade_route(struct city *pc1, struct city *pc2)
 {
   int i;
 
@@ -1710,46 +1709,67 @@
 }
 
 /**************************************************************************
+...
+**************************************************************************/
+static void remove_smallest_trade_route(struct city *pcity)
+{
+  int i, slot, value;
+  struct city *pdest;
+    
+  assert(pcity);
+  
+  slot = 0;
+  value = pcity->trade_value[0];
+  for (i = 1; i < NUM_TRADEROUTES; i++) {
+    if (value > pcity->trade_value[i]) {
+      slot = i;
+      value = pcity->trade_value[i];
+    }
+  }
+    
+  if ((pdest = find_city_by_id(pcity->trade[slot]))) {
+    for (i = 1; i < NUM_TRADEROUTES; i++) {
+      if (pdest->trade[i] == pcity->id) {
+        pdest->trade[i] = 0;
+        break;
+      }
+    }
+  }
+  
+  pcity->trade[slot] = 0;
+}
+
+/**************************************************************************
 Establish a trade route, notice that there has to be space for them, 
-So use can_establish_Trade_route first.
-returns the revenue aswell.
+So you must use can_establish_trade_route first.
 **************************************************************************/
-int establish_trade_route(struct city *pc1, struct city *pc2)
+void establish_trade_route(struct city *pc1, struct city *pc2)
 {
-  int i, tb;
+  int i;
 
+  if (city_num_trade_routes(pc1) == NUM_TRADEROUTES) {
+    remove_smallest_trade_route(pc1);
+  }
+  
+  if (city_num_trade_routes(pc2) == NUM_TRADEROUTES) {
+    remove_smallest_trade_route(pc2);
+  }
+  
   for (i = 0; i < NUM_TRADEROUTES; i++) {
     if (pc1->trade[i] == 0) {
       pc1->trade[i]=pc2->id;
       break;
     }
   }
+  
   for (i = 0; i < NUM_TRADEROUTES; i++) {
     if (pc2->trade[i] == 0) {
       pc2->trade[i]=pc1->id;
       break;
     }
   }
-
-  tb=(map_distance(pc1->x, pc1->y, pc2->x, pc2->y)+10);
-/* should this be real_map_distance?  Leaving for now -- Syela */
-  tb=(tb*(pc1->trade_prod+pc2->trade_prod))/24;
-  /* 
-   * fudge factor to more closely approximate Civ2 behavior (Civ2 is
-   * really very different -- this just fakes it a little better) 
-   */
-  tb *= 3;
-
-  /* 
-   * one time bonus is not affected by factors in
-   * trade_between_cities() 
-   */
-  for (i = 0; i < num_known_tech_with_flag(city_owner(pc1),
-                                          TF_TRADE_REVENUE_REDUCE); i++) {
-    tb = (tb * 2) / 3;
-  }
-  /* was: A_RAILROAD, A_FLIGHT */
-  return tb;
+  
+  return;
 }
 
 /**************************************************************************
diff -u -r freeciv/server/citytools.h fc/server/citytools.h
--- freeciv/server/citytools.h  Thu Jul 17 19:19:28 2003
+++ fc/server/citytools.h       Thu Jul 17 23:02:30 2003
@@ -74,8 +74,9 @@
                 const char *name);
 void remove_city(struct city *pcity);
 
-int establish_trade_route(struct city *pc1, struct city *pc2);
-
+void establish_trade_route(struct city *pc1, struct city *pc2);
+void remove_trade_route(struct city *pc1, struct city *pc2);
+  
 void do_sell_building(struct player *pplayer, struct city *pcity, int id);
 void building_lost(struct city *pcity, int id);
 void change_build_target(struct player *pplayer, struct city *pcity, 
diff -u -r freeciv/server/unithand.c fc/server/unithand.c
--- freeciv/server/unithand.c   Thu Jul 17 20:27:21 2003
+++ fc/server/unithand.c        Thu Jul 17 22:03:50 2003
@@ -1152,58 +1152,143 @@
                                 struct packet_unit_request *req)
 {
   struct unit *punit = player_find_unit_by_id(pplayer, req->unit_id);
+  struct city *pcity_out_of_home = NULL, *pcity_out_of_dest = NULL;
   struct city *pcity_homecity, *pcity_dest = find_city_by_id(req->city_id);
-  int revenue;
+  int revenue, i;
+  bool home_full = FALSE, dest_full = FALSE, can_establish;
   
-  if (!punit || !unit_flag(punit, F_TRADE_ROUTE) || !pcity_dest) {
+  if (!punit || !pcity_dest || !unit_flag(punit, F_TRADE_ROUTE)) {
     return FALSE;
   }
 
   pcity_homecity = player_find_city_by_id(pplayer, punit->homecity);
-  if (!pcity_homecity) {
+  if (!pcity_homecity || pcity_homecity == pcity_dest) {
     return FALSE;
   }
     
   if (!is_tiles_adjacent(punit->x, punit->y, pcity_dest->x, pcity_dest->y)
-      && !same_pos(punit->x, punit->y, pcity_dest->x, pcity_dest->y))
+      && !same_pos(punit->x, punit->y, pcity_dest->x, pcity_dest->y)) {
     return FALSE;
+  }
 
   if (!(same_pos(punit->x, punit->y, pcity_dest->x, pcity_dest->y)
-       || try_move_unit(punit, pcity_dest->x, pcity_dest->y)))
+       || try_move_unit(punit, pcity_dest->x, pcity_dest->y))) {
     return FALSE;
+  }
 
-  if (!can_establish_trade_route(pcity_homecity, pcity_dest)) {
-    int i;
-    notify_player_ex(pplayer, pcity_dest->x, pcity_dest->y, E_NOEVENT,
-                    _("Game: Sorry, your %s cannot establish"
-                      " a trade route here!"),
-                    unit_name(punit->type));
-    for (i = 0; i < NUM_TRADEROUTES; i++) {
-      if (pcity_homecity->trade[i]==pcity_dest->id) {
-       notify_player_ex(pplayer, pcity_dest->x, pcity_dest->y, E_NOEVENT,
-                     _("      A traderoute already exists between %s and %s!"),
-                     pcity_homecity->name, pcity_dest->name);
-       return FALSE;
+  if (!can_cities_trade(pcity_homecity, pcity_dest)) {
+    return FALSE;
+  }
+  
+  can_establish = !(have_cities_trade_route(pcity_homecity, pcity_dest));
+    
+  revenue = get_caravan_enter_city_trade_bonus(pcity_homecity, pcity_dest);
+  
+  if (can_establish) {
+    home_full = (city_num_trade_routes(pcity_homecity) == NUM_TRADEROUTES);
+    dest_full = (city_num_trade_routes(pcity_dest) == NUM_TRADEROUTES);
+  }
+  
+  if (home_full || dest_full) {
+    int trade = trade_between_cities(pcity_homecity, pcity_dest);
+    
+    if (home_full) {
+      int slot = 0, value = pcity_homecity->trade_value[0];
+      
+      /* find min */
+      for (i = 1; i < NUM_TRADEROUTES; i++) {
+       if (value > pcity_homecity->trade_value[i]) {
+         slot = i;
+         value = pcity_homecity->trade_value[i];
+       }
       }
-    }
-    if (city_num_trade_routes(pcity_homecity) == NUM_TRADEROUTES) {
-      notify_player_ex(pplayer, pcity_dest->x, pcity_dest->y, E_NOEVENT,
+      
+      if (value < trade) {
+       pcity_out_of_home = find_city_by_id(pcity_homecity->trade[slot]);
+      } else {
+        notify_player_ex(pplayer, pcity_dest->x, pcity_dest->y, E_NOEVENT,
+                    _("Game: Sorry, your %s cannot establish"
+                      " a trade route here!"), unit_name(punit->type));
+        notify_player_ex(pplayer, pcity_dest->x, pcity_dest->y, E_NOEVENT,
                       _("      The city of %s already has %d "
-                        "trade routes!"), pcity_homecity->name,
+                        "better trade routes!"), pcity_homecity->name,
                       NUM_TRADEROUTES);
-      return FALSE;
+        can_establish = FALSE;
+      }
     }
-    if (city_num_trade_routes(pcity_dest) == NUM_TRADEROUTES) {
-      notify_player_ex(pplayer, pcity_dest->x, pcity_dest->y, E_NOEVENT,
+    
+    if (dest_full && can_establish) {
+      int slot = 0, value = pcity_dest->trade_value[0];
+      
+      /* find min */
+      for (i = 1; i < NUM_TRADEROUTES; i++) {
+       if (value > pcity_dest->trade_value[i]) {
+         slot = i;
+         value = pcity_dest->trade_value[i];
+       }
+      }
+      
+      if ((value < trade)
+         && (pcity_out_of_dest = find_city_by_id(pcity_dest->trade[slot]))) {
+       remove_trade_route(pcity_dest, pcity_out_of_dest);
+       notify_player_ex(city_owner(pcity_out_of_dest),
+                         pcity_out_of_dest->x, pcity_out_of_dest->y, E_NOEVENT,
+                    _("Game: Sorry, Your city %s cannot hold"
+                      " a trade route from %s!"), pcity_out_of_dest->name,
+                         pcity_dest->name);
+         
+       if (pcity_out_of_home) {
+         remove_trade_route(pcity_homecity, pcity_out_of_home);
+         notify_player_ex(city_owner(pcity_out_of_home),
+                         pcity_out_of_home->x, pcity_out_of_home->y, E_NOEVENT,
+                    _("Game: Sorry, Your city %s cannot hold"
+                      " a trade route from %s!"), pcity_out_of_home->name,
+                         pcity_homecity->name);
+       }
+       
+      } else {
+       notify_player_ex(pplayer, pcity_dest->x, pcity_dest->y, E_NOEVENT,
+                    _("Game: Sorry, your %s cannot establish"
+                      " a trade route here!"), unit_name(punit->type));
+        notify_player_ex(pplayer, pcity_dest->x, pcity_dest->y, E_NOEVENT,
                       _("      The city of %s already has %d "
-                        "trade routes!"), pcity_dest->name,
+                        "better trade routes!"), pcity_dest->name,
                       NUM_TRADEROUTES);
-      return FALSE;
+       can_establish = FALSE;
+      }  
+    } else {
+      if (can_establish && pcity_out_of_home) {
+         remove_trade_route(pcity_homecity, pcity_out_of_home);
+         notify_player_ex(city_owner(pcity_out_of_home),
+                         pcity_out_of_home->x, pcity_out_of_home->y, E_NOEVENT,
+                    _("Game: Sorry, Your city %s cannot hold"
+                      " a trade route from %s!"), pcity_out_of_home->name,
+                         pcity_homecity->name);
+      }
     }
-    return FALSE;
+    
+  }
+  
+  if (can_establish) {
+   /*  establish traderoute */
+    for (i = 0; i < NUM_TRADEROUTES; i++) {
+      if (pcity_homecity->trade[i] == 0) {
+        pcity_homecity->trade[i]=pcity_dest->id;
+        break;
+      }
+    }
+  
+    for (i = 0; i < NUM_TRADEROUTES; i++) {
+      if (pcity_dest->trade[i] == 0) {
+        pcity_dest->trade[i]=pcity_homecity->id;
+        break;
+      }
+    }
+  } else {
+    /* enter marketplace */
+    revenue = (revenue + 2) / 3;
   }
   
-  revenue = establish_trade_route(pcity_homecity, pcity_dest);
   conn_list_do_buffer(&pplayer->connections);
   notify_player_ex(pplayer, pcity_dest->x, pcity_dest->y, E_NOEVENT,
                   _("Game: Your %s from %s has arrived in %s,"
@@ -1213,21 +1298,70 @@
   wipe_unit(punit);
   pplayer->economic.gold+=revenue;
   update_tech(pplayer, revenue);
-  send_player_info(pplayer, pplayer);
-  city_refresh(pcity_homecity);
-  city_refresh(pcity_dest);
-
-  /* Notify the owners of the city. */
-  send_city_info(pplayer, pcity_homecity);
-  send_city_info(city_owner(pcity_dest), pcity_dest);
-
-  /* 
-   * Notify the players about the other city so that they get the
-   * tile_trade value.
-   */
-  send_city_info(city_owner(pcity_dest), pcity_homecity);
-  send_city_info(pplayer, pcity_dest);
+  
+  if (can_establish) {
+    city_refresh(pcity_homecity);
+    city_refresh(pcity_dest);
+    if (pcity_out_of_home) {
+      city_refresh(pcity_out_of_home);
+    }
+    if (pcity_out_of_dest) {
+      city_refresh(pcity_out_of_dest);
+    }
+  
+    /* Notify the owners of the city. */
+    send_city_info(pplayer, pcity_homecity);
+    send_city_info(city_owner(pcity_dest), pcity_dest);
 
+    if (pcity_out_of_home) {
+      send_city_info(city_owner(pcity_out_of_home), pcity_out_of_home);
+    }
+    if (pcity_out_of_dest) {
+      send_city_info(city_owner(pcity_out_of_dest), pcity_out_of_dest);
+    }
+  
+    /* 
+     * Notify the players about the other city so that they get the
+     * tile_trade value.
+     */
+    if (pplayer != city_owner(pcity_dest)) {
+      send_city_info(city_owner(pcity_dest), pcity_homecity);
+      send_city_info(pplayer, pcity_dest);
+    }
+    
+    if (pcity_out_of_home) {
+      if (city_owner(pcity_dest) != city_owner(pcity_out_of_home)) {
+        send_city_info(city_owner(pcity_dest), pcity_out_of_home);
+        send_city_info(city_owner(pcity_out_of_home), pcity_dest);
+      }
+      if (pplayer != city_owner(pcity_out_of_home)) {
+        send_city_info(pplayer, pcity_out_of_home);
+        send_city_info(city_owner(pcity_out_of_home), pcity_homecity);
+      }
+      if (pcity_out_of_dest && city_owner(pcity_out_of_home) !=
+                                       city_owner(pcity_out_of_dest)) {
+        send_city_info(city_owner(pcity_out_of_home), pcity_out_of_dest);
+      }
+    }
+    
+    if (pcity_out_of_dest) {
+      if (city_owner(pcity_dest) != city_owner(pcity_out_of_dest)) {
+        send_city_info(city_owner(pcity_dest), pcity_out_of_dest);
+        send_city_info(city_owner(pcity_out_of_dest), pcity_dest);
+      }
+      if (pplayer != city_owner(pcity_out_of_dest)) {
+        send_city_info(pplayer, pcity_out_of_dest);
+        send_city_info(city_owner(pcity_out_of_dest), pcity_homecity);
+      }
+      if (pcity_out_of_home && city_owner(pcity_out_of_home) !=
+                                       city_owner(pcity_out_of_dest)) {
+        send_city_info(city_owner(pcity_out_of_dest), pcity_out_of_home);
+      }
+    }
+    
+    send_player_info(pplayer, pplayer);
+    
+  }
   conn_list_do_unbuffer(&pplayer->connections);
   return TRUE;
 }