turtle circle program

print("please enter radius")
radius = tonumber(read())

-- Record Keeping Variables: These are for recoding the blocks and fuel used
local blocks = 0
local fuel = 0

local facing = 0

function checkFuel()
	if (not(tonumber(turtle.getFuelLevel()) == nil)) then
		while turtle.getFuelLevel() < 50 do
			writeOut("Turtle almost out of fuel, pausing. Please drop fuel in inventory. And press enter.")
			io.read()
			turtle.refuel()
		end
	end
end

function simulationCheck() -- checks state of the simulation
	if sim_mode then
		if compareProgress() then
			setSimFlags(false) -- If we're caught up, un-set flags
		else
			setSimFlags(true)  -- If not caught up, just re-affirm that the flags are set
		end
	end
end

function progressUpdate()  -- This ONLY updates the local table variable.  Writing is handled above. -- I want to change this to allow for any number of params
	progTable = {shape = choice, enderchest_refilling = tempProgTable.enderchest_refilling, param1 = tempProgTable.param1, param2 = tempProgTable.param2, param3 = tempProgTable.param3, param4 = tempProgTable.param4, x = positionX, y = positionY, z = positionZ, facing = facing, blocks = blocks}
	if not sim_mode then
		writeProgress()
	end
end

function placeBlock()
	blocks = blocks + 1
	simulationCheck()
	if cost_only then
		return
	end
	if turtle.detectDown() and not turtle.compareDown() then
		turtle.digDown()
	end
	checkResources()
	turtle.placeDown()
	progressUpdate()
end

function turnRightTrack()
	simulationCheck()
	facing = facing + 1
	if facing >= 4 then
		facing = 0
	end
	progressUpdate()
	if cost_only then
		return
	end
	turtle.turnRight()
end

function turnLeftTrack()
	simulationCheck()
	facing = facing - 1
	if facing < 0 then
		facing = 3
	end
	progressUpdate()
	if cost_only then
		return
	end
	turtle.turnLeft()
end

function turnAroundTrack()
	turnLeftTrack()
	turnLeftTrack()
end

function safeForward()
	simulationCheck()
	if facing == 0 then
		positionY = positionY + 1
	elseif facing == 1 then
		positionX = positionX + 1
	elseif facing == 2 then
		positionY = positionY - 1
	elseif facing == 3 then
		positionX = positionX - 1
	end
	fuel = fuel + 1
	progressUpdate()
	if cost_only then
		return
	end
	checkFuel()
	local success = false
	local tries = 0
	while not success do
		success = turtle.forward()
		if not success then
			while (not success) and tries < 6 do
				tries = tries + 1
				turtle.dig()
				success = turtle.forward()
				sleep(0.3)
			end
			if not success then
				writeOut("Blocked attempting to move forward.")
				writeOut("Please clear and press enter to continue.")
				io.read()
			end
		end
	end
end

function safeBack()
	simulationCheck()
	if facing == 0 then
		positionY = positionY - 1
	elseif facing == 1 then
		positionX = positionX - 1
	elseif facing == 2 then
		positionY = positionY + 1
	elseif facing == 3 then
		positionX = positionX + 1
	end
	fuel = fuel + 1
	progressUpdate()
	if cost_only then
		return
	end
	checkFuel()
	local success = false
	local tries = 0
	while not success do
		success = turtle.back()
		if not success then
			turnAroundTrack()
			while turtle.detect() and tries < 6 do
				tries = tries + 1
				if turtle.dig() then
					break
				end
				sleep(0.3)
			end
			turnAroundTrack()
			success = turtle.back()
			if not success then
				writeOut("Blocked attempting to move back.")
				writeOut("Please clear and press enter to continue.")
				io.read()
			end
		end
	end
end

function safeUp()
	simulationCheck()
	positionZ = positionZ + 1
	fuel = fuel + 1
	progressUpdate()
	if cost_only then
		return
	end
	checkFuel()
	local success = false
	while not success do
		success = turtle.up()
		if not success then
			while turtle.detectUp() do
				if not turtle.digUp() then
					writeOut("Blocked attempting to move up.")
					writeOut("Please clear and press enter to continue.")
					io.read()
				end
			end
		end
	end
end

function safeDown()
	simulationCheck()
	positionZ = positionZ - 1
	fuel = fuel + 1
	progressUpdate()
	if cost_only then
		return
	end
	checkFuel()
	local success = false
	while not success do
		success = turtle.down()
		if not success then
			while turtle.detectDown() do
				if not turtle.digDown() then
					writeOut("Blocked attempting to move down.")
					writeOut("Please clear and press enter to continue.")
					io.read()
				end
			end
		end
	end
end

function moveY(targetY)
	if targetY == positionY then
		return
	end
	if (facing ~= 0 and facing ~= 2) then -- Check axis
		turnRightTrack()
	end
	while targetY > positionY do
		if facing == 0 then
			safeForward()
		else
			safeBack()
		end
	end
	while targetY < positionY do
		if facing == 2 then
			safeForward()
		else
			safeBack()
		end
	end
end

function moveX(targetX)
	if targetX == positionX then
		return
	end
	if (facing ~= 1 and facing ~= 3) then -- Check axis
		turnRightTrack()
	end
	while targetX > positionX do
		if facing == 1 then
			safeForward()
		else
			safeBack()
		end
	end
	while targetX < positionX do
		if facing == 3 then
			safeForward()
		else
			safeBack()
		end
	end
end

function moveZ(targetZ)
	if targetZ == positionZ then
		return
	end
	while targetZ < positionZ do
		safeDown()
	end
	while targetZ > positionZ do
		safeUp()
	end
end

function navigateTo(targetX, targetY, targetZ, move_z_first)
	targetZ = targetZ or positionZ -- If targetZ isn't used in the function call, it defaults to its current z position, this should make it compatible with all previous implementations of navigateTo()
	move_z_first = move_z_first or false -- Defaults to moving z last, if true is passed as 4th argument, it moves vertically first

	if move_z_first then
		moveZ(targetZ)
	end

	if facing == 0 or facing == 2 then -- Y axis
		moveY(targetY)
		moveX(targetX)
	else
		moveX(targetX)
		moveY(targetY)
	end

	if not move_z_first then
		moveZ(targetZ)
	end
end

function blockInSphereIsFull(offset, x, y, z, radiusSq)
	x = x - offset
	y = y - offset
	z = z - offset
	x = x ^ 2
	y = y ^ 2
	z = z ^ 2
	return x + y + z <= radiusSq
end


function isSphereBorder(offset, x, y, z, radiusSq)
	spot = blockInSphereIsFull(offset, x, y, z, radiusSq)
	if spot then
		spot = not blockInSphereIsFull(offset, x, y - 1, z, radiusSq) or
			not blockInSphereIsFull(offset, x, y + 1, z, radiusSq) or
			not blockInSphereIsFull(offset, x - 1, y, z, radiusSq) or
			not blockInSphereIsFull(offset, x + 1, y, z, radiusSq) or
			not blockInSphereIsFull(offset, x, y, z - 1, radiusSq) or
			not blockInSphereIsFull(offset, x, y, z + 1, radiusSq)
	end
	return spot
end

function circle(diameter)
	odd = not (math.fmod(diameter, 2) == 0)
	radius = diameter / 2
	if odd then
		width = (2 * math.ceil(radius)) + 1
		offset = math.floor(width/2)
	else
		width = (2 * math.ceil(radius)) + 2
		offset = math.floor(width/2) - 0.5
	end
	--diameter --radius * 2 + 1
	sqrt3 = 3 ^ 0.5
	boundaryRadius = radius + 1.0
	boundary2 = boundaryRadius ^ 2
	radius2 = radius ^ 2
	z = math.floor(radius)
	cz2 = (radius - z) ^ 2
	limitOffsetY = (boundary2 - cz2) ^ 0.5
	maxOffsetY = math.ceil(limitOffsetY)
	-- We do first the +x side, then the -x side to make movement efficient
	for side = 0,1 do
			-- On the right we go from small y to large y, on the left reversed
			-- This makes us travel clockwise (from below) around each layer
			if (side == 0) then
				yStart = math.floor(radius) - maxOffsetY
				yEnd = math.floor(radius) + maxOffsetY
				yStep = 1
			else
				yStart = math.floor(radius) + maxOffsetY
				yEnd = math.floor(radius) - maxOffsetY
				yStep = -1
			end
			for y = yStart,yEnd,yStep do
				cy2 = (radius - y) ^ 2
				remainder2 = (boundary2 - cz2 - cy2)
				if remainder2 >= 0 then
					-- This is the maximum difference in x from the centre we can be without definitely being outside the radius
					maxOffsetX = math.ceil((boundary2 - cz2 - cy2) ^ 0.5)
					-- Only do either the +x or -x side
					if (side == 0) then
						-- +x side
						xStart = math.floor(radius)
						xEnd = math.floor(radius) + maxOffsetX
					else
						-- -x side
						xStart = math.floor(radius) - maxOffsetX
						xEnd = math.floor(radius) - 1
					end
					-- Reverse direction we traverse xs when in -y side
					if y > math.floor(radius) then
						temp = xStart
						xStart = xEnd
						xEnd = temp
						xStep = -1
					else
						xStep = 1
					end

					for x = xStart,xEnd,xStep do
						-- Only blocks within the radius but still within 1 3d-diagonal block of the edge are eligible
						if isSphereBorder(offset, x, y, z, radius2) then
							navigateTo(x, y)
							placeBlock()
						end
					end
				end
			end
		end
end

checkFuel()
circle(radius * 2)