Prevent building in shielded area

maps/scrap_towny_ffa/building.lua

@@ -4,6 +4,7 @@ local math_floor = math.floor
 local table_insert = table.insert
 local table_size = table.size
 local ScenarioTable = require 'maps.scrap_towny_ffa.table'
+local PvPShield = require 'maps.scrap_towny_ffa.pvp_shield'
 
 local town_zoning_entity_types = { "wall", "gate", "electric-pole", "ammo-turret", "electric-turret", "fluid-turret"}
 
@@ -223,26 +224,19 @@ local function process_built_entities(event)
     local name = entity.name
     local surface = entity.surface
     local position = entity.position
+    local force
     local force_name
     if player_index ~= nil then
         local player = game.players[player_index]
-        if player ~= nil then
-            local force = player.force
-            if force ~= nil then
-                force_name = force.name
-            end
-        end
+        force = player.force
+        force_name = force.name
     else
         local robot = event.robot
-        if robot ~= nil then
-            local force = robot.force
-            if force ~= nil then
-                force_name = force.name
-            end
-        end
+        force = robot.force
+        force_name = force.name
     end
 
-    if Public.near_another_town(force_name, position, surface, 32) == true then
+    if PvPShield.in_other_zones(surface, position, force) or Public.near_another_town(force_name, position, surface, 32) == true then
         if neutral_whitelist[name] then
             entity.force = game.forces['neutral']
         else
@@ -335,6 +329,9 @@ local function on_player_built_tile(event)
     if prevent_landfill_in_restricted_zone(event) then
         return
     end
+    if process_built_entities(event) then
+        return
+    end
     if prevent_tiles_near_towns(event) then
         return
     end

maps/scrap_towny_ffa/info.lua

@@ -37,6 +37,9 @@ Survive as long as you can. Raid other towns. Defend your town.
     Tip: use filter inserters with to get coins/iron/.. out of the market
 - Fishes procreate near towns. The more fishes, the quicker they multiply. Automated fish farm, anyone?
 - Use /rename-town (chat command) to rename your town
+- PvP shields prevent players from entering and building inside, but they can still shoot inside!
+- Your town has a AFK PvP shield that you can use to safely take a quick break
+    without other players killing your town. Deploy it from the market.
 
 # Town members and alliances
 - Once a town is formed, members may invite other players and teams using a coin. To invite another player, drop a coin

maps/scrap_towny_ffa/pvp_shield.lua

@@ -33,7 +33,7 @@ local function remove_drawn_borders(shield)
     end
 end
 
-local function scale_size_and_box(shield)
+local function scale_size_by_lifetime(shield)
     local time_scale = math.min(1, (game.tick - shield.lifetime_start) / shield.time_to_full_size_ticks)
     local scaled_size = time_scale * shield.max_size
 
@@ -63,7 +63,7 @@ function Public.add_shield(surface, force, center, max_size, lifetime_ticks, tim
                 string.format("%.0f", (Public.remaining_lifetime(shield)) / 60 / 60) .. ' minutes')
     end
 
-    scale_size_and_box(shield)
+    scale_size_by_lifetime(shield)
     this.pvp_shields[force.name] = shield
 end
 
@@ -89,7 +89,7 @@ local function update_shield_lifetime()
         if Public.remaining_lifetime(shield) > 0 then
             if shield.size < shield.max_size then
                 remove_drawn_borders(shield)
-                scale_size_and_box(shield)
+                scale_size_by_lifetime(shield)
                 draw_borders(shield)
 
                 -- Push everyone out as we grow (even if they're just standing)
@@ -107,6 +107,18 @@ local function vector_norm(vector)
     return math_sqrt(vector.x ^ 2 + vector.y ^ 2)
 end
 
+function Public.in_other_zones(surface, position, force)
+    local this = ScenarioTable.get_table()
+    for _, shield in pairs(this.pvp_shields) do
+        if not (shield.force == force or surface ~= shield.surface) then
+            if CommonFunctions.point_in_bounding_box(position, shield.box) then
+                return true
+            end
+        end
+    end
+    return false
+end
+
 function Public.push_enemies_out(player)
     local this = ScenarioTable.get_table()
     for _, shield in pairs(this.pvp_shields) do

maps/scrap_towny_ffa/town_center.lua

@@ -419,7 +419,7 @@ local function add_pvp_shield_scaled(position, force, surface)
     force.print("Based on the highest tech on map, your town deploys a PvP shield of "
             .. string.format("%.0f", size) .. " tiles"
             .. " for " .. string.format("%.0f", lifetime_ticks/60/60)  .. " minutes."
-            .. " Enemy players will not be able to enter the shielded area.")
+            .. " Enemy players will not be able to enter and build in the shielded area.")
 end
 
 local function found_town(event)