platform

local size,side,blockType = ...

-- [S] = ^
-- [E] = stop
--| > > > > > > > v
--| ^ > > > > > v v
--| ^ ^ > > > v v v
--| ^ ^ ^ > v v v v
--| ^ ^ ^[S]v v v v
--| ^ ^ ^ < < v v v
--| ^ ^ < < < < v v
--| ^ < < < < < <[E]

local function usage()
    textutils.pagedPrint([[Usage:
platform <size> [down|up] <blockName>

Build a square platform.]])
end

if size=="help" then
    usage()
    return
end

if not size or not tonumber(size) or tonumber(size)<1 then
    error("<size> Should be a positive number",0)
    usage()
    return
end
size = tonumber(size)
local blockNeeds = size*size

if not side then side = "down"
elseif side~="down" and side~="up" then
    error("Wrong parameter\nside should be down or up",0)
    usage()
    return
end

local function supply(s)
    s = s or 1
    local _s
    for _s=s,16 do
        if blockType then
            local data = turtle.getItemDetail(_s)
            if data and data.name==blockType then
                return _s
            end
        elseif turtle.getItemCount(_s) then
            return _s
        end
    end
    return false
end

local function supplyCount()
    local total,s=0
    for s=1,16 do
        if blockType then
            local data = turtle.getItemDetail(s)
            if data and data.name==blockType then
                total = total + turtle.getItemCount(s)
            end
        else
            total = total + turtle.getItemCount(s)
        end
    end
    return total
end

local slot = supply()
if not slot then
    error(blockType and "You should supply "..blockType or "You should supply blocks",-1)
    usage()
    return
end

local blockCount = supplyCount()
if blockNeeds > 16*64 then
    print(string.format([[A %dx%d platform require %d blocks.
A Turtle can't supply more than %d blocks.
Continue ? Y/N]],size,size,blockNeeds,16*64))
    local confirm=false
    while not confirm do
        local e,k=os.pullEvent("key")
        if k==keys.n then sleep(.3) return end
        confirm = k==keys.y
        sleep(.3)
    end
    print("Yes")
elseif blockNeeds > blockCount then
    print(string.format([[A %dx%d platform require %d blocks.
You should put %d blocks more.
Continue ? Y/N]],size,size,blockNeeds,blockNeeds-blockCount))
    local confirm=false
    while not confirm do
        local e,k=os.pullEvent("key")
        if k==keys.n then sleep(.3) return end
        confirm = k==keys.y
        sleep(.3)
    end
    print("Yes")
end

function build()
    local place,detect
    if side=="up" then
        place = function() return turtle.placeUp() end
        detect = function() return turtle.detectUp() end
    else
        place = function() return turtle.placeDown() end
        detect = function() return turtle.detectDown() end
    end
    local sections = (size*2)-1
    local step,step_z,length
    local last_x, last_z
    for step=1,sections do
        local length=math.ceil(step/2)
        turtle.turnRight()
        for step_z=1,length do
            if turtle.getItemCount(slot)<=0 then
                slot = supply(slot)
                if not slot then
                    print("Not enough blocks...")
                    return length,step_z
                end
            end
            if turtle.getSelectedSlot() ~= slot then
                turtle.select(slot)
            end
            while not place() and not detect() do
                slot = supply(slot)
                if not slot then
                    print("Not enough placable blocks...")
                    return length,step_z
                end
                turtle.select(slot)
            end
            if not (step==sections and step_z==length) then
                turtle.forward()
                last_x, last_z = length,step_z
            end
        end
    end
    return last_x, last_z
end

local last_x, last_z = build()

-- Back to center
local i
local stepBack_x = last_x - math.ceil(size/2)
local stepBack_z = last_z - math.floor(size/2)
turtle.turnRight()
for i=1,math.abs(stepBack_x) do
    if stepBack_x < 1 then turtle.back()
    else turtle.forward() end
end
turtle.turnRight()
for i=1,math.abs(stepBack_z) do
    if stepBack_z < 1 then turtle.back()
    else turtle.forward() end
end