local tArgs = { ... }
if #tArgs < 1 or #tArgs > 3 then
	print("Usage: excavate <length> [<depth> [<width>]]")
	print("Put empty bucket in first slot, lava bucket in second.")
	return
end

local length = tonumber(tArgs[1])
local width = length
local depth = 256

if #tArgs > 1 then
	depth = tonumber(tArgs[2])
end
if #tArgs > 2 then
	width = tonumber(tArgs[3])
end

if length < 1 or width < 1 or depth < 1 then
	print("Excavate parameters must be positive")
	return
end

-- Mine in a quarry pattern until we hit something we can't dig
local collected = 0
local xPos,yPos,zPos = 0,0,0
local xDir,zDir = 0,1

local state = { DONE=0, FULL=1, EXCAVATING=2, ERROR=3 }


local function collect()
	collected = collected + 1
	if math.fmod(collected, 100) == 0 then
		print("Mined " .. collected .. " blocks.")
	end
	
	for n = 3, 16 do
		if turtle.getItemCount(n) == 0 then
			return true
		end
	end
	
	print("No empty slots left.")
	return false
end

local function tryForwards()
	if not turtle.detect() then
		turtle.select(1)
		if turtle.place() then
			if turtle.compareTo(2) then
				turtle.refuel()
			else
				turtle.place()
			end
		end
	else
		while turtle.dig() do
			if not collect() then
				return state.FULL
			end
			-- wait for sand/gravel
			sleep(yPos == 0 and 1 or 0.25)
		end
	end
	local tries = 0
	while not turtle.forward() and tries < 10 do
		sleep(5)
		tries = tries + 1
	end
	if tries >= 10 then
		return state.ERROR
	end
	xPos = xPos + xDir
	zPos = zPos + zDir
	return state.EXCAVATING
end

local function tryDown()
	if not turtle.detectDown() then
		turtle.select(1)
		if turtle.placeDown() then
			if turtle.compareTo(2) then
				turtle.refuel()
			else
				turtle.placeDown()
			end
		end
	else
		while turtle.digDown() do
			if not collect() then
				return state.FULL
			end
			-- wait for sand/gravel
			-- sleep(0.5)
		end
	end
	local tries = 0
	while not turtle.down() and tries < 10 do
		sleep(5)
		tries = tries + 1
	end
	if tries >= 10 then
		return state.ERROR
	end
	
	yPos = yPos + 1
	if math.fmod(yPos, 10) == 0 then
		print("Descended " .. yPos .. " metres.")
	end
	return state.EXCAVATING
end

local function tryUp()
	if not turtle.detectUp() then
		turtle.select(1)
		if turtle.placeUp() then
			if turtle.compareTo(2) then
				turtle.refuel()
			else
				turtle.placeUp()
			end
		end
	else
		while turtle.digUp() do
			if not collect() then
				return state.FULL
			end
			-- wait for sand/gravel
			sleep(1)
		end
	end
	local tries = 0
	while not turtle.up() and tries < 10 do
		sleep(5)
		tries = tries + 1
	end
	if tries >= 10 then
		return state.ERROR
	end
	
	yPos = yPos - 1
	return state.EXCAVATING
end

local function turnLeft()
	turtle.turnLeft()
	xDir, zDir = -zDir, xDir
end

local function turnRight()
	turtle.turnRight()
	xDir, zDir = zDir, -xDir
end

local function moveTo(_x, _y, _z, _xD, _zD)
	-- if going towards 0,0,0 fix in y, x, z order
	-- else fix in z, x, y order
	while _y < yPos do
		tryUp()
	end
	while _x < xPos do
		while xDir ~= -1 do
			turnRight()
		end
		tryForwards()
	end
	while _z < zPos do
		while zDir ~= -1 do
			turnRight()
		end
		tryForwards()
	end
	while _z > zPos do
		while zDir ~= 1 do
			turnRight()
		end
		tryForwards()
	end
	while _x > xPos do
		while xDir ~= 1 do
			turnRight()
		end
		tryForwards()
	end
	while _y > yPos do
		tryDown()
	end
	
	while xDir ~= _xD or zDir ~= _zD do
		turnRight()
	end
end

local function dropAll()
	print("Turtle full, dropping things")
	
	local xB, yB, zB, xDB, zDB = xPos, yPos, zPos, xDir, zDir
	moveTo(0, 0, 0, 0, 1)
	
	print("Dropping everything")
	for i=3,16 do
		turtle.select(i)
		turtle.dropUp()
	end
	
	moveTo(xB, yB, zB, xDB, zDB)
end

-- get going...
print("Excavating a " .. length .. "x" .. width .. " hole, " .. depth .. " deep.")
length = length - 1
width = width - 1
depth = depth - 1

local xInc = true

while not done do
--	print("x" .. xPos .. " y" .. yPos .. " z" .. zPos .. " xd" .. xDir .. " zd" .. zDir)
	local down = false
	if zPos == length then
		if xInc and xPos == width and xDir == 0 then
			down = true
		elseif not xInc and xPos == 0 and xDir == 0 then
			down = true
		elseif xInc and (zDir == 1 or xDir == 1) then
			turnRight()
		elseif not xInc and (zDir == 1 or xDir == -1) then
			turnLeft()
		end
	elseif zPos == 0 then
		if xInc and xPos == width and xDir == 0 then
			down = true
		elseif not xInc and xPos == 0 and xDir == 0 then
			down = true
		elseif xInc and (zDir == -1 or xDir == 1) then
			turnLeft()
		elseif not xInc and (zDir == -1 or xDir == -1) then
			turnRight()
		end		
	end
	
	local r
	if down then
		if yPos == depth then
			print("Excavation done.")
			break
		end
		turnLeft()
		turnLeft()
		r = tryDown()
		xInc = not xInc
	else
		r = tryForwards()
	end
	
	if r == state.ERROR then
		print("Something in the way")
		break
	elseif r == state.FULL then
		dropAll()
	end
end

-- done
moveTo(0, 0, 0, 0, 1)
dropAll()
print("Mined " .. collected .. " blocks total.")