mine-return-magnet

-- Globals
local SQUARE_SIZE = 3
local DOWN_SQUARE = 0
local UP_SQUARE = 1
local CONTAINER_SUBSTRINGS = {"chest"}

local squareType = DOWN_SQUARE
local height = 1
local magnet = nil
local target = nil

-- http://lua-users.org/wiki/SimpleRound
local function round(num, numDecimalPlaces)
	local mult = 10^(numDecimalPlaces or 0)
	return math.floor(num * mult + 0.5) / mult
end

-- Gets a magnet located on <side> of turtle
local function getMagnet(side)
	local name = peripheral.getType(side)
	if(not name:lower():find("magnet")) then
		print("No magnet attached to " .. side)
		return nil
	end

	return peripheral.wrap(side)
end

-- Determines if the block in front of a turtle is a chest
local function isChest()
	local status, data = turtle.inspect()

	if(not status) then
		print("No chest available")
		return false
	end

	local itemName = data["name"]:match(":(.+)"):lower()
	for index, container in pairs(CONTAINER_SUBSTRINGS) do
		if(itemName:find(container)) then
			return true
		end
	end

	return false
end

-- Attempt to refuel the turtle
local function attemptRefuel(amount)
	local amount = amount or 1

	if(turtle.getFuelLevel() >= amount) then
		return
	end

	local index = 1
	local hasRefueled = false
	while(index <= 16 and not hasRefueled) do
		turtle.select(index)
		local refuelling = true
		while(refuelling) do
			if(turtle.refuel(0)) then
				if(turtle.getFuelLevel() < amount) then
					turtle.refuel(1)
				else
					refuelling = false
					hasRefueled = true
				end
			else
				refuelling = false
			end
		end
		index = index + 1
	end
end

-- Attempt to dump non-fuel items into a chest in front of the turtle
local function attemptDumpInv()
	if(not isChest()) then
		return
	end

	for index=1, 16 do
		turtle.select(index)
		if(not turtle.refuel(0)) then
			turtle.drop()
		end
	end
end

-- Wraps magnet.setTarget to also keep a local target state
local function setTargetWrapper(x, y, z)
	target = {["x"] = x, ["y"] = y, ["z"] = z}
	magnet.setTarget(x, y, z)
end

-- Orbits the magnet around the turtle right or left in 90 deg turns
local function orbitMagnet(direction)
	attemptRefuel(5)

	local x = target["x"]
	local y = target["y"]
	local z = target["z"]
	local theta = 0

	if(direction == "cw") then
		theta = -math.pi/2
	elseif(direction == "ccw") then
		theta = math.pi/2
	else
		print("Direction: " .. direction .. " not a valid magnet orbit")
		return false
	end

	-- TODO split this out into own function
	if(squareType == DOWN_SQUARE) then
		if(height >= 2) then
			y = 0	-- Drop magnet one block so it doesn't get hit
		end
	else
		if(height <= 2) then
			y = 1	-- Raise magnet one block
		end
	end

	local x_ = round(z * math.cos(theta) + z * -math.sin(theta))
	local z_ = round(x * math.sin(theta) + x * math.cos(theta))

	print(x, " ", y, " ", z, "\t->", x_, " ", y, " ", z_)
	setTargetWrapper(x_, y, z_)
end

-- Turns in a direction one or more times, also tries to keep magnet in same orientation. Assumes magnet is behind turtle
local function turn(direction, turns)
	local turns = tonumber(distance) or 1

	if(direction == "right") then
		turtle.turnRight()
		if(magnet) then
			orbitMagnet("ccw")
		end
	elseif(direction == "left") then
		turtle.turnLeft()
		if(magnet) then
			orbitMagnet("cw")
		end
	else
		print("Direction: " .. direction .. " not a valid rotation")
		return false
	end

	if(turns > 1) then
		turn(direction, turns - 1, magnetAttached)
	end

	os.sleep(5)	-- sleep to let magnet catch up
	return true
end

-- Move in a direction 1 or more times
local function move(direction, distance)
	local distance = tonumber(distance) or 1
	attemptRefuel()

	if(direction == "up") then
		turtle.up()
		height = height + 1
	elseif(direction == "down") then
		turtle.down()
		height = height - 1
	elseif(direction == "forward") then
		turtle.forward()
	elseif(direction == "back") then
		turtle.back()
	else
		print("Direction: " .. direction .. " not a valid movement")
		return false
	end

	if(distance > 1) then
		move(direction, distance - 1)
	end
	return true
end

-- Dig out a block and move into it
local function digMove(direction)
	if(direction == "up") then
		turtle.digUp()
		move("up")
	elseif(direction == "down") then
		turtle.digDown()
		move("down")
	elseif(direction == "forward") then
		turtle.dig()
		move("forward")
	elseif(direction == "back") then
		turn("left", 2)
		turtle.dig()
		turn("left", 2)
		move("back")
	else
		print("Direction: " .. direction .. " not a valid movement")
		return false
	end
	return true
end

-- Dig out a 3x3 vertical square
local function tunnelSquare()
	-- Dig out adjacent left and right blocks
	local function tunnelAdjacentLR()
		turn("left")
		turtle.dig()
		turn("left", 2)
		turtle.dig()
		turn("left")
	end

	digMove("forward")  -- Move into next vertical square
	for i=1, SQUARE_SIZE do
		tunnelAdjacentLR()
		if(i < 3) then
			if(DOWN_SQUARE == squareType) then
				digMove("up")
			else
				digMove("down")
			end
		end
	end

	if(DOWN_SQUARE == squareType) then
		squareType = UP_SQUARE
	else
		squareType = DOWN_SQUARE
	end
end

-- Tunnel
local function tunnel(distance, tunnelFunc)
	-- Don't bother with tunnelling negative distances
	if(distance < 1) then
		return
	end

	-- Default to tunnelSquare
	local tunnelFunc = tunnelFunc or tunnelSquare

	-- Tunnel over a distance using specified tunneling function
	for i=1, distance do
		tunnelFunc()
	end
end

-- Display usage info
local function help()
	local name = "<name>"
	if(shell) then
		name = shell.getRunningProgram()
	end

	print("Usage: " .. name .. " <distance to tunnel >= 3> [shaft center spacing (-  left, + right)]\nAlso, if a chest is placed to the turtle's right it'll dump non-fuel items into that")
end

-- Main
local function main(distance, spacing, magnetSide)
	-- Handle args
	local distance = tonumber(distance) or 0
	local spacing = tonumber(spacing) or 0
	local magnetSide = magnetSide or "left"

	if(distance < 3) then
		-- Small distances cause inaccuracies
		help()
		return
	end

	-- Init the magnet and get the anchor
	attemptRefuel(5)
	magnet = getMagnet(magnetSide)
	magnet.activate()
	setTargetWrapper(-1, 1, 0)
	os.sleep(2)
	magnet.toggle()

	-- Initial tunneling distance
	tunnel(distance)

	magnet.toggle()
	magnet.deactivate()

	-- Tunnel over to return shaft
	move("back")
	if(spacing > 0) then
		turn("right")
		move("forward")
		tunnel(spacing)
		move("back")
		turn("right")
	elseif(spacing < 0) then
		turn("left")
		move("forward")
		tunnel(spacing * -1)
		move("back")
		turn("left")
	else
		turn("left", 2)
	end

	-- Move to edge of return shaft
	move("forward")

	-- Tunnel/move back to start
	if(spacing == 0) then
		move("forward", distance - 2)
	else
		tunnel(distance - 3)
		move("forward")
	end

	if(UP_SQUARE == squareType) then
		move("down", 2)
	end

	-- Spin back around, dump non-fuel into adjacent chest
	turn("left")
	attemptDumpInv()
	turn("left")
end

main(unpack({...}))