neighbor search respects both physical walls (solid blocks) and goban-indicated walls

rules.lua

@@ -11,18 +11,90 @@ local modname = minetest.get_current_modname()
 
 local cache = {}
 
-local relative_neighbors = {
+local directions = { [0] =
-    vector.new(1, 0, 0),
+    vector.new(0, 0, -1),
-    vector.new(0, 0, 1),
     vector.new(-1, 0, 0),
-    vector.new(0, 0, -1)
+    vector.new(0, 0, 1),
+    vector.new(1, 0, 0),
 }
 
+local down = vector.new(0, -1, 0)
+
 local solid_drawtypes = {
     normal = true,
     glasslike_framed = true,
 }
 
+local S = ("S"):byte(1)
+local W = ("W"):byte(1)
+local E = ("E"):byte(1)
+local C = ("C"):byte(1)
+
+function handle_placement(pos)
+    cache = {}
+    --minetest.chat_send_all(tostring(pos))
+    --nodecore.node_sound(pos, "dug")
+
+    local our_stone = check_position(pos)
+    if not (our_stone:byte(1) == S) then
+        return
+    end
+    our_stone = our_stone:sub(2, -1)
+
+    -- print_r(neighbor_dirs(pos))
+
+    for i,v in pairs(neighbor_dirs(pos)) do
+        local node = check_position(pos +directions[v])
+        if node:byte(1) == S then
+
+        end
+
+        --neighbors[i] = pos + v
+    end
+
+
+end
+
+--[[
+give valid neighbor directions from a position, excluding solid blocks
+and also respecting borders indicated by goban concrete
+--]]
+function neighbor_dirs(pos)
+    local neighbors = {}
+    for i,v in pairs(directions) do
+        if not edge_check(pos, i) then
+            if not (check_position(pos + directions[i]):byte(1) == W) then
+                neighbors[#neighbors+1] = i
+            end
+        end
+    end
+
+    return neighbors
+end
+
+-- check for walls, physical or implied
+function edge_check(pos, dir, terminate)
+    local under = check_position(pos + down)
+
+    if under:byte(1) == W and under:len() == 3 then
+        local corner = (under:byte(2) == C)
+        local edge_dir = tonumber(under:sub(3, 3))
+
+        if (dir == edge_dir) or (corner and (dir == (edge_dir+1)%4)) then
+            return true
+        end
+    end
+
+    if not terminate then
+        if edge_check(pos+directions[dir], (dir+2)%4, true) then
+            return true
+        end
+    end
+
+    return false
+end
+
+
 --[[
 E: empty
 Stype: a go stone of some type
@@ -61,26 +133,13 @@ function _check_position_uncached(pos)
         end
     end
 
-    if solid_drawtypes[reg_item.drawtype] then
+    if solid_drawtypes[reg_item.drawtype] and not reg_item.groups.falling_node then
         return "W"
     else
         return "E"
     end
 end
 
-function check_captures(pos)
-    minetest.chat_send_all(tostring(pos))
-    nodecore.node_sound(pos, "dug")
-
-    check_position(pos + vector.new(0, -1, 0))
-
-    local neighbors = {}
-
-    for i,v in ipairs(relative_neighbors) do
-        neighbors[i] = pos + v
-    end
-
-end
 
 function surrounded_group(pos)
     local group = {}

stones.lua

@@ -68,7 +68,7 @@ local function reg(name, basename, basedef)
 
         sounds = basedef.sounds,
 
-        on_construct = check_captures
+        on_construct = handle_placement
     })
 
     nodecore.register_craft({