identify captures and suicide moves

rules.lua

@@ -41,18 +41,26 @@ function handle_placement(pos)
     end
     our_stone = our_stone:sub(2, -1)
 
-    -- print_r(neighbor_dirs(pos))
-
+    local captured = false
     for i,v in pairs(neighbor_dirs(pos)) do
         local node = check_position(pos + directions[v])
         if node:byte(1) == S then
-
+            if not (node:sub(2, -1) == our_stone) then
+                local captures = check_captures(pos + directions[v])
+                if not (#captures == 0) then
+                    minetest.chat_send_all("You gotcher self a capture right there!  size: "..#captures)
+                    captured = true
+                end
+            end
         end
-
-        --neighbors[i] = pos + v
     end
 
-
+    if not captured then
+        local captures = check_captures(pos)
+        if not (#captures == 0) then
+            minetest.chat_send_all("You gotcher self a suicide move right there!  size: "..#captures)
+        end
+    end
 end
 
 --[[
@@ -140,13 +148,42 @@ function _check_position_uncached(pos)
     end
 end
 
+--[[
+Scans for a connected group, until enumerating the whole group, or
+finding a liberty.  Returns list of captured nodes, or empty list if
+no captures.
+--]]
+function check_captures(pos)
+    local group = {pos}
+    local checked = {[minetest.hash_node_position(pos)] = true}
+    local team = check_position(pos):sub(2,-1)
+
+    local probe = 0
+    while probe < #group do
+        probe = probe + 1
+        pos = group[probe]
 
-function surrounded_group(pos)
-    local group = {}
-    local queue = {}
-end
+        for i,v in pairs(neighbor_dirs(pos)) do
+            local newpos = pos + directions[v]
+            local newhash = minetest.hash_node_position(newpos)
+
+            if not checked[newhash] then
+                checked[newhash] = true
+
+                local newnode = check_position(newpos)
 
+                if newnode:byte(1) == E then
+                    return {}
+                elseif newnode:byte(1) == S and
+                        newnode:sub(2, -1) == team then
+                    group[#group+1] = newpos
+                end
+            end
+        end
+    end
 
+    return group
+end