if not digiline then
 print("Digilines not found.")
 return
end
local oldprint=print
local function print(...)
 for k,v in ipairs({...}) do
  oldprint("[Test3D:T400] "..tostring(v))
 end
end
print("Test3D loading.")

local tInstructions = {
"NOP",
"ADD",
"SUB",
"PEEK",
"POKE",
}
local function push(pos,val)
 local meta = minetest.get_meta(pos)
 local sstack = ""
 local stack = string.split(meta:get_string("stack"),"\n")
 if #stack > 15 then
  print("Stack overflow at "..pos.x..","..pos.y..","..pos.z)
  table.remove(stack,1)
 end
 stack[#sstack+1] = tostring(val)
 for k,v in ipairs(stack) do
  sstack = sstack .. v .. "\n"
 end
end
local function pop(pos)
 local meta = minetest.get_meta(pos)
 local sstack = ""
 local stack = string.split(meta:get_string("stack"),"\n")
 local n = table.remove(stack,#stack) or 0
 stack[#sstack+1] = tostring(val)
 for k,v in ipairs(stack) do
  sstack = sstack .. v .. "\n"
 end
 return tonumber(n)
end
local function t400_digiline_receive(pos, node, channel, msg)
 print(pos,node,channel,msg)
 meta = minetest.get_meta(pos)
 if meta:get_string("waitingfor") == channel then
  if meta:get_string("state") == "waitingstack" then
   push(pos,msg)
  if meta:get_string("state") == "waitingins" then
   meta:set_int("ci",tonumber(msg))
  end
 end
end
print("Created T400 digiline function")

local function t400_set_infotext(pos)
 local meta=minetest.get_meta(pos)
 local running="false"
 if meta:get_int("test3d_running") == 1 then running="true" end
 meta:set_string("infotext","Running: "..running.."\nState: "..meta:get_string("state").."\nPC: "..tostring(meta:get_int("pc")).."\nACC: "..tostring(meta:get_int("acc")).."\nBAK: "..tostring(meta:get_int("bak")))
end

local function t400_set_meta(pos)
 local meta = minetest.get_meta(pos)
 local fspec = "size[8,9]\nlabel[0,0;T400 execution node]\nfield[0.25,1;8,1;channel;Channel prefix;${channel}]\n"
 fspec = fspec .. "textarea[0.25,2;8,7.5;program;Program;${program}]\n"
 fspec = fspec .. "button_exit[0,8.5;7.9,1;;Done]\n"
 meta:set_string("formspec",fspec)
 meta:set_string("channel","")
 meta:set_string("state","running") -- can be "running", "waitingstack" or "waitingins"
 meta:set_string("waitingfor","") -- address waiting for
 meta:set_string("stack","") -- internal stack
 meta:set_int("ci",0) -- current instruction
 meta:set_int("pc",0) -- program counter
 t400_set_infotext(pos)
 print("Initialized T400 at "..tostring(pos.x)..","..tostring(pos.y)..","..tostring(pos.z))
end
minetest.register_node("test3d:t400", {
 description = "T400 Execution Node",
 tiles = {
  {
   image="t400.png",
   animation={
    type = "vertical_frames",
    aspect_w=16,
    aspect_h=16,
    length=18,
    length=1.8,
   },
  },
 },
 on_construct = t400_set_meta,
 on_punch = function(pos, _, _, _)
  local meta=minetest.get_meta(pos)
  local cstate = meta:get_int("test3d_running")
  local nstate=1
  if cstate==1 then
   nstate=0
  else
   nstate=1
  end
  print("State: "..tostring(cstate).." -> "..tostring(nstate))
  meta:set_int("test3d_running",nstate)
 end,
 groups = {snappy=1,choppy=2,oddly_breakable_by_hand=2,flammable=3},
 digiline = {
  receptor = {},
  effector = {
   action = t400_digiline_receive
  }
 },
 on_receive_fields = function(pos,_,fields,sender)
  if fields.channel == nil or fields.program == nil then return end
  local meta = minetest.get_meta(pos)
  fields.channel = fields.channel or ""
  meta:set_string("channel",fields.channel)
  print("Channel: "..fields.channel)
  local tProgram = {}
  local lcounter = 0
  for _,line in ipairs(string.split(fields.program,"\n")) do
   if lcounter > 14 then break end -- only 15 real lines will be stored
   local ltab = string.split(line," ")
   local valid=false
   if line:sub(1,1) == "#" then valid=true end
   if line:sub(#line,#line) == ":" then valid=true end
   for _,ins in ipairs(tInstructions) do
    if string.upper(ltab[1]) == ins then 
     valid = true
    end
   end
   if valid then
    lcounter = lcounter + 1
    tProgram[#tProgram+1] = line
    print("Valid: "..line)
   else
    print("Invalid: "..line)
   end
  end
  local sProgram = ""
  for _,l in ipairs(tProgram) do
   sProgram = sProgram .. l .. "\n"
  end
  sProgram = sProgram:sub(1,-1)
  meta:set_string("program",sProgram)
  print("Program:\n"..sProgram)
  meta:set_int("pc",0)
 end
})
print("T400 node registered")

minetest.register_abm({
 nodenames={"test3d:t400"},
 interval=1,
 chance=1,
 action = function(pos)
  function getDigiline(addr)
   digiline:receptor_send(pos,digilines.rules.default,addr,"get")
   minetest.get_meta(pos):set_string("state","waiting")
   minetest.get_meta(pos):set_string("waitingfor",addr)
  end
  local node = minetest.get_node_or_nil(pos)
  local meta = minetest.get_meta(pos)
  if meta:get_string("state") == "running" then
   local state = meta:get_int("test3d_running")
   if state == nil then state=1 end
   if state == 1 then
    local pc = meta:get_int("pc")
    local acc = meta:get_int("acc")
    local bak = meta:get_int("bak")
    print("Running T400 node with instance at position "..tostring(pos.x)..","..tostring(pos.y)..","..tostring(pos.z).." (PC: "..tostring(pc)..", ACC: "..tostring(acc)..", BAK: "..tostring(bak)..")")
    local tProgram = string.split(meta:get_string("program"),"\n")
    local tLine = string.split(tProgram[pc]:upper())
    if pc == #tProgram then pc = 0 end
    meta:set_int("pc",pc+1)
   end
  end
  t400_set_infotext(pos)
 end,
})
print("T400 ABMs registered")

--[[
minetest.register_chatcommand("lua", { -- I'm a terrible person
 params = "<text>",
 description = "Execute some Lua code",
 privs = {talk = true},
 func = function( _ , text)
  e,lstr = pcall(loadstring(text))
  minetest.chat_send_all(tostring(lstr))
 end,
})
]]--