-- LUALOCALS < ---------------------------------------------------------
local include, nodecore, pairs, string, table
= include, nodecore, pairs, string, table
local string_lower
= string.lower

-- LUALOCALS > ---------------------------------------------------------
local modname = minetest.get_current_modname()

--nodecore.gametime

local cache = {}

local directions = { [0] =
    vector.new(0, 0, -1),
    vector.new(-1, 0, 0),
    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)

    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
    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

--[[
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
W: full block wall
WE0-WE3: edge concrete
WC0-WC3: corner concrete
--]]
function check_position(pos)
    local hash = minetest.hash_node_position(pos)
    if cache[hash] then
        return cache[hash]
    end

    local ret = _check_position_uncached(pos)
    cache[hash] = ret
    return ret
end

function _check_position_uncached(pos)
    local node = minetest.get_node(pos)
    local reg_item = minetest.registered_items[node.name]

    if not reg_item then
        return "W"
    end

    if reg_item.groups and reg_item.groups.go_stone then
        return "S" .. reg_item.go_team
    end

    if reg_item.pattern_def then
        if reg_item.pattern_def.name == "edgy" then
            return "WE" .. node.param2
        elseif reg_item.pattern_def.name == "corny" then
            return "WC" .. node.param2
        end
    end

    if solid_drawtypes[reg_item.drawtype] and not reg_item.groups.falling_node then
        return "W"
    else
        return "E"
    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]

        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



function print_r ( t )
    local print_r_cache={}
    local function sub_print_r(t,indent)
        if (print_r_cache[tostring(t)]) then
            print(indent.."*"..tostring(t))
        else
            print_r_cache[tostring(t)]=true
            if (type(t)=="table") then
                for pos,val in pairs(t) do
                    if (type(val)=="table") then
                        print(indent.."["..pos.."] => "..tostring(t).." {")
                        sub_print_r(val,indent..string.rep(" ",string.len(pos)+8))
                        print(indent..string.rep(" ",string.len(pos)+6).."}")
                    else
                        print(indent.."["..pos.."] => "..tostring(val))
                    end
                end
            else
                print(indent..tostring(t))
            end
        end
    end
    sub_print_r(t,"  ")
end