local url = "http://justus.l--n.de:3000/JUFS/cc_housebuild/raw/branch/main/src/main.lua"

if not _G["turtle"] then
    error("This program only runs on turtles!")
end

local turtle = _G["turtle"]

print("House building system")
print("JUFS Technologies (c) 2026 (Justus Wolff)")

print("fuel: "..tostring(turtle.getFuelLevel()).."/"..tostring(turtle.getFuelLimit()))
os.sleep(0.1)

function term.setcol(fc, bc)
    term.setTextColor(fc)
    term.setBackgroundColor(bc)
end
local function reset()
    term.setcol(colors.white, colors.black)
    term.clear()
    term.setCursorPos(1,1)
end
local function incline()
    local _,y = term.getCursorPos()
    term.setCursorPos(1,y+1)
end
local function selopt(options, title)
    local selected = 1

    while true do
        reset()
        term.setcol(colors.black, colors.white)
        term.write(title)
        for i,v in pairs(options) do
            incline()
            if i == selected then
                term.setcol(colors.black, colors.blue)
            else
                term.setcol(colors.white, colors.black)
            end
            term.write(v)
        end

        local event,key = os.pullEvent("key")
        if keys.getName(key) == "w" and selected ~= 1 then
            selected = selected - 1
        end
        if keys.getName(key) == "s" and selected ~= #options then
            selected = selected + 1
        end
        if keys.getName(key) == "enter" then
            return selected
        end
    end
end
local function integritycheck()
    if not fs.exists("designs") then
        fs.makeDir("designs")
    end
end
local function posasstring(...)
    local positions = {...}
    local out = ""
    for _,v in pairs(positions) do
        out = out .. tostring(v) .. ":"
    end
    return out
end
local function load(name)
    local file = fs.open("designs/"..name, "r")
    local content = file.readAll()
    file.close()
    content = textutils.unserialiseJSON(content)
    return content["buf"],content["dimensions"]
end
local function bufistype(buf, x,y,z, targettype)
    if buf[posasstring(x,y,z)] == targettype then
        return true
    else
        return targettype == 0 and buf[posasstring(x,y,z)] == nil
    end
end
local function fill_getneighbors(x,y,z, sx,sz, seltype,buf)
    local out = {}
    if x ~= sx and bufistype(buf, x+1,y,z, seltype) then table.insert(out, {x+1,z}) end
    if x ~= 1 and bufistype(buf, x-1,y,z, seltype) then table.insert(out, {x-1,z}) end
    if z ~= sz and bufistype(buf, x,y,z+1, seltype) then table.insert(out, {x,z+1}) end
    if z ~= 1 and bufistype(buf, x,y,z-1, seltype) then table.insert(out, {x,z-1}) end
    return out
end
local function fill(ntype, x,y,z, buf, sx,sz)
    local inittype = buf[posasstring(x,y,z)]
    if inittype == ntype then return end -- no work needs to be done

    local neighbors = fill_getneighbors(x,y,z, sx,sz, inittype,buf)
    buf[posasstring(x,y,z)] = ntype
    local processed = 0
    local totalneighbors = #neighbors
    term.setcol(colors.white, colors.black)
    while #neighbors > 0 do
        term.setCursorPos(1,1)
        term.write(tostring(processed).."/"..tostring(totalneighbors))
        local cn = table.remove(neighbors, 1)
        local cx,cz = cn[1],cn[2]
        local newneigh = fill_getneighbors(cx,y,cz, sx,sz, inittype,buf)
        for _,v in pairs(newneigh) do
            table.insert(neighbors, v)
            buf[posasstring(v[1],y,v[2])] = ntype
            totalneighbors = totalneighbors + 1
        end
        buf[posasstring(cx,y,cz)] = ntype
        processed = processed + 1
    end
end
local function newdesign()
    local buf = {}
    local dimensions = {
        x = 8,
        z = 8,
        y = 1
    }
    local currentfloor = 1
    local camx,camy = 0,0
    local currentblock = 2
    local blockindex = 1
    local blocks = {
        2, -- no ceiling
        3, -- doorway
        4, -- glass
    }
    local function renderblock(index)
        local block = blocks[index]
        if block == 2 then -- no ceiling
            term.blit("C", colors.toBlit(colors.black), colors.toBlit(colors.red))
        end
        if block == 3 then -- doorway
            term.blit("D", colors.toBlit(colors.black), colors.toBlit(colors.brown))
        end
        if block == 4 then -- glass
            term.blit("W", colors.toBlit(colors.black), colors.toBlit(colors.white))
        end
    end
    local shift = false

    while true do
        -- render buf
        reset()
        for x=1+camx,dimensions["x"]+camx,1 do
            for z=1+camy,dimensions["z"]+camy,1 do
                local currentbuf = buf[posasstring(x-camx, currentfloor, z-camy)]
                term.setCursorPos(x, z)
                if currentbuf == 1 then -- wall
                    term.blit(" ", colors.toBlit(colors.white), colors.toBlit(colors.white))
                elseif currentbuf and currentbuf > 1 then -- blocks
                    renderblock(currentbuf-1)
                    --term.blit("C", colors.toBlit(colors.black), colors.toBlit(colors.red))
                elseif currentbuf == 0 or currentbuf == nil then -- nothing
                    if buf[posasstring(x-camx, currentfloor-1, z-camy)] == 2 then
                        term.blit("\127", colors.toBlit(colors.red), colors.toBlit(colors.black))
                    else
                        term.blit("\127", colors.toBlit(colors.gray), colors.toBlit(colors.black))
                    end
                end
            end
        end
        term.setcol(colors.yellow, colors.black)
        local _,y = term.getSize()
        term.setCursorPos(1,y-1)
        term.write("Press Ctrl for menu. ")
        term.setCursorPos(1,y)
        term.write("x: "..tostring(camx))
        term.write(" z: "..tostring(camy))
        term.write(" floor: "..tostring(currentfloor))
        term.write(" Block: ")
        renderblock(blockindex)

        -- user input
        local event = table.pack(os.pullEvent())
        if event[1] == "mouse_click" or event[1] == "mouse_drag" then
            event[3] = event[3]-camx
            event[4] = event[4]-camy
            if event[3] <= dimensions["x"] and event[4] <= dimensions["z"] then
                if event[2] == 1 then -- left button, set
                    if shift then
                        fill(1, event[3],currentfloor,event[4], buf,dimensions["x"],dimensions["z"])
                    end
                    buf[posasstring(event[3], currentfloor, event[4])] = 1
                end
                if event[2] == 3 then -- middle button, set special block
                    if shift then
                        fill(currentblock, event[3],currentfloor,event[4], buf,dimensions["x"],dimensions["z"])
                    end
                    buf[posasstring(event[3], currentfloor, event[4])] = currentblock
                end
                if event[2] == 2 then -- right button, erase
                    if shift then
                        fill(0, event[3],currentfloor,event[4], buf,dimensions["x"],dimensions["z"])
                    end
                    buf[posasstring(event[3], currentfloor, event[4])] = 0
                end
            end
        end
        if event[1] == "mouse_scroll" then
            if event[2] == 1 then -- down
                if blockindex == #blocks then blockindex = 1 else blockindex = blockindex + 1 end
            end
            if event[2] == -1 then -- up
                if blockindex == 1 then blockindex = #blocks else blockindex = blockindex - 1 end
            end
            currentblock = blocks[blockindex]
        end
        if event[1] == "key" then
            if keys.getName(event[2]) == "leftShift" then
                shift = true
            end
            if keys.getName(event[2]) == "leftCtrl" then -- menu
                local action = selopt({
                    "Save",
                    "Load",
                    "Exit",
                    "Change X size",
                    "Change floor amount",
                    "Change Z size"
                }, "menu")
                if action == 3 then return end -- exit
                if action == 1 then -- save
                    reset()
                    for _,v in pairs(fs.list("designs")) do
                        term.write(v)
                        incline()
                    end
                    write("Enter name: ")
                    local name = read()
                    local file = fs.open("designs/"..name, "w")
                    file.write(textutils.serialiseJSON({
                        ["dimensions"] = dimensions,
                        ["buf"] = buf
                    }))
                    file.close()
                end
                if action == 2 then -- load
                    reset()
                    for _,v in pairs(fs.list("designs")) do
                        term.write(v)
                        incline()
                    end
                    write("Enter name: ")
                    local name = read()
                    if not fs.exists("designs/"..name) or name == "" then
                        printError("Design not found!")
                    else
                        buf,dimensions = load(name)
                        camx,camy,currentfloor = 0,0,1
                    end
                end
                if action == 4 then -- change X size
                    reset()
                    write("Enter new X size: ")
                    local xsize = tonumber(read())
                    dimensions["x"] = xsize
                end
                if action == 5 then -- change floor amount
                    reset()
                    write("Enter new floor amount: ")
                    local ysize = tonumber(read())
                    dimensions["y"] = ysize
                end
                if action == 6 then -- change Z size
                    reset()
                    write("Enter new Z size: ")
                    local zsize = tonumber(read())
                    dimensions["z"] = zsize
                end
            end
            if keys.getName(event[2]) == "q" and currentfloor < dimensions["y"] then -- go up
                currentfloor = currentfloor + 1
            end
            if keys.getName(event[2]) == "e" and currentfloor > 1 then -- go down
                currentfloor = currentfloor - 1
            end
            if keys.getName(event[2]) == "w" and camy < dimensions["z"] then -- pan up
                camy = camy + 1
            end
            if keys.getName(event[2]) == "s" and camy > -dimensions["z"] then -- pan down
                camy = camy - 1
            end
            if keys.getName(event[2]) == "a" and camx < dimensions["x"] then -- pan left
                camx = camx + 1
            end
            if keys.getName(event[2]) == "d" and camx > -dimensions["z"] then -- pan right
                camx = camx - 1
            end
        end
        if event[1] == "key_up" then
            if keys.getName(event[2]) == "leftShift" then shift = false end
        end
    end
end
local function move(direction, continousattempt)
    if direction == "left" then
        turtle.turnLeft()
        return
    end
    if direction == "right" then
        turtle.turnRight()
        return
    end
    while true do
        if turtle.getFuelLevel() == 0 then
            reset()
            print("Out of fuel! Trying to refuel.")
            while true do
                local suc = turtle.refuel(64)
                if suc then
                    break
                end
                local current = turtle.getSelectedSlot()
                if current == 16 then
                    turtle.select(1)
                else
                    turtle.select(current+1)
                end
                os.sleep(1)
            end 
        end
        local suc,reason = turtle[direction]()
        if not suc and not continousattempt then
            printError(reason)
            print("Resolve the error and press enter to continue.")
            read("")
        elseif not suc and continousattempt then
            reset()
            printError("Failure moving "..direction.." Continous attempt true.")
        elseif suc then
            break
        end
    end
end
local function place(direction)
    local func = turtle.place
    local cfunc = turtle.compare
    if direction == "down" then
        func = turtle.placeDown
        cfunc = turtle.compareDown
    end
    if direction == "up" then
        func = turtle.placeUp
        cfunc = turtle.compareUp
    end

    while true do
        local suc = func()
        if not suc then -- next slot
            if cfunc() and turtle.getItemDetail(turtle.getSelectedSlot()) ~= nil then return end
            local current = turtle.getSelectedSlot()
            if current == 16 then
                turtle.select(1)
            else
                turtle.select(current+1)
            end
        else break end
        os.sleep(0) -- yield
    end
end
local function placebuf(buf, x, y, z)
    if buf[posasstring(x,y,z)] == 1 then
        place("down")
    end
end
local function directiondist(direction, wanted)
    if direction == 0 then return 1 end
    if direction == 1 and wanted == -1 then return 2 end
    if direction == -1 and wanted == 1 then return 2 end

    if direction ~= wanted then return 1 end -- failsafes
    if direction == wanted then return 0 end
end
local function needstobeplaced(placecode, clayer)
    if clayer == 0 or clayer == 2 then
        return placecode == 1
    end
    if clayer == 1 then
        return placecode == 1 or placecode == 4
    end
    if clayer == 3 then
        return placecode == 1 or placecode == 4 or placecode == 3
    end
end
local function getnearestunplaced(buf, pbuf, cx,cy,cz,clayer, sx,sz, direction)
    local distance = math.huge
    local selected = nil

    for x=1,sx,1 do
        for y=1,sz,1 do
            local extracost = 0
            if x ~= cx and direction ~= 0 then
                extracost = extracost + 1
            end
            if y > cz and direction ~= 1 then
                extracost = extracost + directiondist(direction, 1)
            end
            if y < cz and direction ~= -1 then
                extracost = extracost + directiondist(direction, -1)
            end

            local needplace = buf[posasstring(x,cy,y)]
            if pbuf[posasstring(x,cy,y)] then needplace = 0 end -- already placed
            needplace = needstobeplaced(needplace, clayer)
            if needplace then -- needs to be placed, calculate distance
                local cd = math.abs(y-cz)+math.abs(x-cx) -- raw distance (amount of blocks between)
                cd = cd + extracost
                if cd < distance then
                    distance = cd
                    selected = {x,y}
                end
            end
        end
    end
    return selected
end
local function center(direction, wanted)
    if direction == 1 and wanted ~= 1 then
        move("left")
        return true
    end
    if direction == -1 and wanted ~= -1 then
        move("right")
        return true
    end
    if direction == 0 then return true end
    return false
end
local function moveto(x,y,cx,cz,direction)
    while x ~= cx do
        if cx < x then -- x
            center(direction)
            direction = 0
            cx = cx + 1
            move("forward")
        end
        if cx > x then
            center(direction)
            direction = 0
            cx = cx - 1
            move("back")
        end
    end
    while y ~= cz do
        if y > cz then -- z
            if center(direction, 1) then move("right") end
            cz = cz + 1
            move("forward")
            direction = 1
        end
        if y < cz then
            if center(direction, -1) then move("left") end
            cz = cz - 1
            move("forward")
            direction = -1
        end
    end
    return cx,cz,direction
end
local function tcontains(x, y)
    for _,v in pairs(x) do
        if v == y then return true end
    end
    return false
end
local function render(buf, pbuf, cx,cy,cz, tx,tz, sx,sz, shouldsetlist,invertslist)
    shouldsetlist = shouldsetlist or {
        1,
    }

    local tsx,tsy = term.getSize()
    local camx,camy = cx-(tsx/2),cz-(tsy/2)

    reset()
    for x=1,sx,1 do
        for z=1,sz,1 do
            local currentbuf = pbuf[posasstring(x, cy, z)]
            term.setCursorPos(x-camx, z-camy)
            if currentbuf then -- wall
                term.blit(" ", colors.toBlit(colors.white), colors.toBlit(colors.white))
            elseif (currentbuf == false or currentbuf == nil) and (invertslist and not tcontains(shouldsetlist, buf[posasstring(x, cy, z)]) or tcontains(shouldsetlist, buf[posasstring(x, cy, z)])) then -- nothing
                term.blit("\127", colors.toBlit(colors.gray), colors.toBlit(colors.black))
            end
        end
    end
    term.setCursorPos(cx-camx,cz-camy)
    term.blit(" ", colors.toBlit(colors.red), colors.toBlit(colors.red))
    term.setCursorPos(tx-camx,tz-camy)
    term.blit(" ", colors.toBlit(colors.lime), colors.toBlit(colors.lime))
end
local function printdes(buf, dimensions)
    move("up")
    move("forward")

    local cx = 1
    local cz = 1
    local direction = 0
    for cy=1,dimensions["y"],1 do
        local setlists = {
            {1,4},
            {1},
            {1,3,4},
        }
        for clayer=1,3,1 do -- build walls
            local pbuf = {}
            while true do
                local target = getnearestunplaced(buf, pbuf, cx,cy,cz,clayer, dimensions["x"],dimensions["z"], direction)
                if not target then break end

                render(buf, pbuf, cx,cy,cz, target[1],target[2], dimensions["x"],dimensions["z"], setlists[clayer])

                --read("")

                cx,cz,direction = moveto(target[1],target[2],cx,cz,direction)
                place("down")
                pbuf[posasstring(cx,cy,cz)] = true
            end
            move("up")
        end
        -- build ceiling/floor
        local pbuf = {}
        local cbuf = {}
        for _cz=1,dimensions["z"],1 do
            for _cx=1,dimensions["x"],1 do
                if buf[posasstring(_cx,cy,_cz)] ~= 2 then
                    cbuf[posasstring(_cx,0,_cz)] = 1
                else
                    cbuf[posasstring(_cx,0,_cz)] = 0
                end
            end
        end
        while true do
            local target = getnearestunplaced(cbuf, pbuf, cx,0,cz,0, dimensions["x"],dimensions["z"], direction)
            if not target then break end

            render(cbuf, pbuf, cx,0,cz, target[1],target[2], dimensions["x"],dimensions["z"], {1})

            cx,cz,direction = moveto(target[1],target[2],cx,cz,direction)
            place("down")
            pbuf[posasstring(cx,0,cz)] = true
        end
        -- return to standard pos but +1 to y
        cx,cz,direction = moveto(1,1,cx,cz,direction)
        move("up")
    end
    cx,cz,direction = moveto(0,1, cx,cz, direction)
    for _=1,dimensions["y"]*(4)+1,1 do -- go back to starting position
        move("down")
    end
    center(direction)
end

-- vertical stack printing
local function VP_movetoy(y, target)
    while y > target do
        move("down", true)
        y = y - 1
    end
    while y < target do
        move("up", true)
        y = y + 1
    end
    return target
end
local function VP_moveto(x,z, cx,cz,direction)
    local y = 0
    --[[
    y lanes for directions:
    1: +x
    2: -x
    3: +z
    4: -z
    ]]--
    while x ~= cx do
        if cx < x then -- x
            center(direction)
            direction = 0
            y = VP_movetoy(y, 1)
            cx = cx + 1
            move("forward", true)
        end
        if cx > x then
            center(direction)
            direction = 0
            y = VP_movetoy(y, 2)
            cx = cx - 1
            move("back", true)
        end
    end
    while z ~= cz do
        if z > cz then -- z
            if center(direction, 1) then move("right") end
            y = VP_movetoy(y, 3)
            cz = cz + 1
            move("forward", true)
            direction = 1
        end
        if z < cz then
            if center(direction, -1) then move("left") end
            y = VP_movetoy(y, 4)
            cz = cz - 1
            move("forward", true)
            direction = -1
        end
    end
    VP_movetoy(y, 0)
    return cx,cz,direction
end
local function VP_optimizestack(target)
    -- go from bottom to top and erase false entries until we encounter a true one.
    while #target > 0 do
        if target[1] then break else
            table.remove(target, 1)
        end
    end

    return target
end
local function VP_createstack(buf, dimensions)
    local fout = {
        ["height"] = dimensions["y"]*(4)+1,
        ["dimensions"] = dimensions,
    }
    local out = {}


    for x=1,dimensions["x"],1 do
        for z=1,dimensions["z"],1 do

            local tempbuf = {}
            for y=1,dimensions["y"],1 do -- for each y dimension
                local placecode = buf[posasstring(x,y,z)]
                for layer=1,3,1 do -- layers
                    table.insert(tempbuf, needstobeplaced(placecode, layer))
                end
                -- ceiling
                table.insert(tempbuf, buf[posasstring(x,y,z)] ~= 2)
            end
            VP_optimizestack(tempbuf)

            if #tempbuf > 0 then
                out[posasstring(x,z)] = tempbuf
            end
        end
    end


    fout["stacks"] = out
    return fout
end
local function VP_lengthofdict(target)
    local out = 0
    for _,v in pairs(target) do out = out + 1 end
    return out
end
local function VP_splitstack(_stack, x)
    local stack = _stack["stacks"]
    local height = _stack["height"]
    local stacks = {}
    local spliteverx = math.floor(VP_lengthofdict(stack)/x)
    local ind = 0
    local buf = {}
    for i,v in pairs(stack) do
        if ind == spliteverx then
            ind = 0
            table.insert(stacks, buf)
            buf = {}
        end
        buf[i] = v
        ind = ind + 1
    end
    table.insert(stacks, buf)

    local out = {
        height=height,
        stacks={}
    }
    for _,v in pairs(stacks) do
        table.insert(out["stacks"],v)
    end
    return out
end
--[[local function VP_inspectsplitted(stacks, dimensions) -- I will probably never finish this.
    local currentselected = 1

    while true do
        reset() -- render
        local _,y = term.getSize()
        term.setCursorPos(1,y)
        term.setcol(colors.yellow, colors.black)
        term.write("Currentlayer: ")
        term.write(tostring(currentselected))

        local event = table.pack(os.pullEvent())
        if event[1] == "key" then
            
        end
    end
end]]
local function VP_printstack(buf, dimensions, cx,cy,cz,direction)
    reset()
    move("up")
    for _=1,buf["height"]-cy,1 do
        move("up")
    end
    local ox,oz = cx,cz
    cx,cz,direction = VP_moveto(cx+1,cz, cx,cz,direction)

    for x=1,dimensions["x"],1 do
        for z=1,dimensions["z"],1 do

            local tempbuf = buf["stacks"][posasstring(x,z)]
            if tempbuf then
                cx,cz,direction = VP_moveto(x,z, cx,cz,direction)
                for _=1,#tempbuf,1 do
                    move("down", true)
                end
                for _,v in pairs(tempbuf) do
                    if v then
                        place("down")
                    end
                    move("up", true)
                end
                move("up", true)
            end
        end
    end
    VP_moveto(ox,oz, cx,cz,direction)
    for _=1,buf["height"]+1,1 do
        move("down")
    end
    center(direction, 0)
    return cx,cz,direction
end
local function VP_calccost(stacks, height,sx,sz) -- calculate needed blocks
    local cost = 0
    for cx=1,sx,1 do
        for cz=1,sz,1 do

            local tempbuf = stacks[posasstring(cx,cz)]
            if tempbuf then
                for ind=1,height,1 do
                    if tempbuf[ind] then cost = cost + 1 end
                end
            end

        end
    end
    return cost
end
local function VP_selectpos(design,dimensions,msg, cx,cz)
    cx,cz = cx or 0, cz or 0
    local camx,camz = cx,cz
    while true do
        render(design,{}, camx,1,camz, camx,camz, dimensions["x"],dimensions["z"], {1,4})
        term.setCursorPos(1,1)
        term.write(msg)
        local _,y = term.getSize()
        term.setCursorPos(1,y)
        term.write("x: ")
        term.write(tostring(camx))
        term.write(" z: ")
        term.write(tostring(camz))

        local _,key = os.pullEvent("key")
        key = keys.getName(key)
        if key == "w" then
            camz = camz - 1
        end
        if key == "s" then
            camz = camz + 1
        end
        if key == "a" then
            camx = camx - 1
        end
        if key == "d" then
            camx = camx + 1
        end
        if key == "enter" then
            break
        end
    end
    return camx,camz
end

local function expwarn()
    reset()
    term.write("This mode is experimental! Be cautious!")
    incline()
    term.write("Enter to continue.")
    read("")
end
local function randomstr(length)
    local possible = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890"
    local out = ""
    for _=1,length,1 do
        local ind = math.random(#possible)
        out = out .. string.sub(possible, ind, ind)
    end
    return out
end

while true do
    integritycheck()
    local action = selopt({
        "New Design",
        "Print Design",
        "VPrint Design",
        "Join VPrint",
        "Update",
    }, "Select Action")

    if action == 1 then
        newdesign()
    end
    if action == 2 then
        reset()
        for _,v in pairs(fs.list("designs")) do
            term.write(v)
            incline()
        end
        write("Enter name: ")
        local name = read()
        if not fs.exists("designs/"..name) or name == "" then
            printError("Design not found!")
        else
            local buf,dimensions = load(name)
            write("Calculating fuel cost...")
            local cost = dimensions["x"]*dimensions["z"]*(dimensions["y"]*4-1)
            print(tostring(turtle.getFuelLevel()).."/"..tostring(cost))
            if turtle.getFuelLevel() < cost then
                write("WARNING: Not enough fuel! Continue anyway? y/n: ")
                while true do
                    local ans = read("")
                    if ans == "y" then
                        printdes(buf, dimensions)
                        break
                    elseif ans == "n" then break end
                end
            else
                printdes(buf, dimensions)
            end
        end
    end
    if action == 3 then
        expwarn()

        peripheral.find("modem", rednet.open)
        reset()
        for _,v in pairs(fs.list("designs")) do
            term.write(v)
            incline()
        end
        write("Enter name: ")
        local name = read()
        if not fs.exists("designs/"..name) or name == "" then
            printError("Design not found!")
        else
            local buf,dimensions = load(name)
            local stacks = VP_createstack(buf, dimensions)
            local height = stacks["height"]
            print("Stacks created.")
            local code = randomstr(5)
            print("Pair code: '"..code.."'")

            write("Enter amount of partaking turtles: ")
            local expam = tonumber(read())

            write("Press enter to send pair request.")
            read("")
            rednet.broadcast({
                code=code,
            }, "HB_vprint_pair")
            print("Sent. awaiting pair accepts.")
            local accepted = {}
            while #accepted < expam do
                local id,msg = rednet.receive("HB_vprint_pairespond")
                if msg["code"] == code then
                    table.insert(accepted, id)
                    reset()
                    term.write(tostring(#accepted).."/"..tostring(expam))
                end
            end

            reset()
            print("Paired. Splitting stacks and sending out...")
            stacks = VP_splitstack(stacks, #accepted+1) -- plus 1 because we also build as the master turtle.
            if #stacks["stacks"] ~= #accepted+1 then
                printError("Internal error with VP_splitstack. It returned "..#stacks["stacks"].." stacks.")
                return
            end
            for i,v in pairs(accepted) do
                reset()
                print("ID "..tostring(v).." needs "..VP_calccost(stacks["stacks"][i], stacks["height"],dimensions["x"],dimensions["z"]).." blocks.")
                print("Please ensure that turtle has that many blocks and press enter to continue.")
                read("")
                rednet.send(v, {
                    stack=stacks["stacks"][i],
                    dimensions=dimensions,
                    height=height
                }, "HB_vprint_pairacknowledge")
            end

            print("This turtle needs "..tostring(VP_calccost(stacks["stacks"][expam+1], stacks["height"],dimensions["x"],dimensions["z"])).." blocks.")
            print("Please ensure that turtle has that many blocks and press enter to continue.")
            read("")

            local x,y = 0,0
            for _,v in pairs(accepted) do
                x,y = VP_selectpos(buf,dimensions,"Select position of turtle "..tostring(v), x,y)
                rednet.send(v, {
                    cx=x,
                    cz=y,
                }, "HB_vprint_pairpossend")
            end
            reset()
            write("Ready to begin, press enter to continue")
            read("")
            print("Sending begin signal.")
            for _,v in pairs(accepted) do
                rednet.send(v, {}, "HB_vprint_begin")
            end

            local ownstack = {
                stacks=stacks["stacks"][expam+1],
                dimensions=dimensions,
                height=height
            }
            VP_printstack(ownstack,dimensions, 0,0,1,0)
        end
    end
    if action == 4 then
        expwarn()

        peripheral.find("modem", rednet.open)
        reset()
        term.write("Enter the code: ")
        local code = read()
        local masterid = 0
        local buf = {}
        local dimensions = {}
        local height = 0
        local cx,cz = 0,0

        while true do -- await pairing request and respond
            local id,request = rednet.receive("HB_vprint_pair")
            if request["code"] == code then
                masterid = id
                print("Detected master: "..tostring(masterid))
                print("Responding...")
                rednet.send(masterid, {
                    code=code,
                }, "HB_vprint_pairespond")
                print("Waiting for response... ID: "..tostring(os.getComputerID()))
                local id,msg = -1,{}
                repeat
                    id,msg = rednet.receive("HB_vprint_pairacknowledge")
                until id == masterid
                buf = msg["stack"]
                dimensions = msg["dimensions"]
                height = msg["height"]
                break
            end
        end
        print("Received stacks and dimensions. ID: "..tostring(os.getComputerID()))
        local id,msg = -1,"" -- wait until we get our current position
        repeat
            id,msg = rednet.receive("HB_vprint_pairpossend")
        until id == masterid
        cx,cz = msg["cx"],msg["cz"]

        repeat -- wait until we can begin
            id = rednet.receive("HB_vprint_begin")
        until id == masterid

        local ownstack = {
            stacks=buf,
            dimensions=dimensions,
            height=height
        }
        VP_printstack(ownstack,dimensions, cx,0,cz,0)
    end
    if action == 5 then
        shell.run("rm", "main.lua")
        shell.run("wget", url)
        return
    end
end