World eater master

-- Mocking the APIs for editor support
-- Remove before running in minecraft
--[[
local rednet = {
  open = function(_) end,
  close = function(_) end,
  receive = function(_)
    return 0, "ok"
  end,
}
local os = {
  sleep = function(_) end,
}
local gps = {
  locate = function(_)
    return 0, 0, 0
  end,
}
local fs = {
  exists = function(_)
    return false
  end,
  open = function(_, _)
    return {
      writeLine = function(_) end,
      close = function(_) end,
    }
  end,
}
--]]

local function getSide(x, z)
  if (x <= 0) and (z <= 0) then
    return "NW"
  end
  if (x > 0) and (z > 0) then
    return "SE"
  end
  if (x <= 0) and (z > 0) then
    return "SW"
  end
  if (x > 0) and (z <= 0) then
    return "NE"
  end
end

local function nextCoordsEvery(x, z, limit)
  local side = getSide(x, z)
  if side == "NW" then
    if z == 0 then
      return x, z + 1, false
    end
    return x - 1, z + 1, false
  end
  if side == "SE" then
    if z == 1 then
      return x, z - 1, false
    end
    return x + 1, z - 1, false
  end
  if side == "SW" then
    if x == 0 then
      return x + 1, z, false
    end
    return x + 1, z + 1, false
  end
  if side == "NE" then
    if x == 1 then
      if math.abs(z) == limit then
        return x, z, true
      end
      return x - 1, z - 1, false
    end
    return x - 1, z - 1, false
  end
end

local function nextCoords(x, z, limits)
  local x1, z1, limitReached = nextCoordsEvery(x, z, limits)
  if limitReached then
    return x1, z1, true
  elseif math.fmod(x1, 2) == 0 then
    return nextCoordsEvery(x1, z1, limits)
  else
    return x1, z1, false
  end
end

local function locate()
  print("Getting the current location via GPS...")
  local x, y, z = gps.locate(1)
  if x == nil then
    print("Waiting for GPS signal")
    while x == nil do
      os.sleep(10)
      x, y, z = gps.locate(1)
    end
  end
  print("Got the current location via GPS!")
  return x, y, z
end

local NEXT_COORDS_FILE_NAME = ".eater_next_coords"
local LIMIT = 10

-- Init
rednet.open("back")

local x0, y0, z0 = locate()
y0 = y0 - 1

if not fs.exists(NEXT_COORDS_FILE_NAME) then
  local f = fs.open(NEXT_COORDS_FILE_NAME, "w")
  f.writeLine("0")
  f.writeLine("0")
  f.writeLine("false")
  f.close()
end

local f = fs.open(NEXT_COORDS_FILE_NAME, "r")
local x, z = tonumber(f.readLine()), tonumber(f.readLine())
local limitReached = f.readLine() == "true"

-- Main loop
while true do
  print("Waiting for a signal from a turtle...")
  local id, msg = rednet.receive()
  if msg == "eater_turtle ready" then
    print("Received ready signal from #" .. id .. " turtle")
    if limitReached then
      print("Nothing to order!")
      rednet.send(id, "eater_master done")
    else
      print("Ordering the turtle #" .. id .. " to go to " .. x .. ", " .. z)
      rednet.send(id, "eater_master go " .. x .. " " .. z)
      x, z, limitReached = nextCoords(x, z, LIMIT)
      local saveF = fs.open(NEXT_COORDS_FILE_NAME, "w")
      saveF.writeLine(tostring(x))
      saveF.writeLine(tostring(z))
      saveF.writeLine(tostring(limitReached))
      saveF.close()
    end
  elseif msg == "eater_turtle search" then
    print("Received search signal from #" .. id .. " turtle")
    print("Sending zero coordinates to the turtle #" .. id)
    rednet.send(id, "eater_master zero " .. x0 .. " " .. y0 .. " " .. z0)
  else
    print("Received unknown signal from #" .. id .. ", not sure what to do")
  end
end