local tArgs = { ... }
if #tArgs ~= 2 then
	print( "Usage: excavate <diameter> <depth>" )
	return
end

-- Mine in a quarry pattern until we hit something we can't dig
local size = tonumber( tArgs[1] )
if size < 1 then
	print( "Excavate diameter must be positive" )
	return
end

local depth = 0
local collected = 0

local xPos,zPos = 0,0
local xDir,zDir = 0,1

function check_inv()
    for n=1,9 do
        if turtle.getItemCount(n) == 0 then
            return true
        end
    end
end

local function collect()
	collected = collected + 1
	if math.fmod(collected, 25) == 0 then
		print( "Mined "..collected.." blocks." )
	end

	for n=1,9 do if turtle.getItemCount(n) == 0 then return true end end

	print( "No empty slots left." )
	return false
end

local function tryForwards()
	while not turtle.forward() do
		if turtle.dig() then
			if not collect() then
				return false
			end
	    else
			-- give sand a chance to fall
 			sleep(0.8)
	    	if turtle.dig() then
	    		if not collect() then
					return false
				end
	    	else
		    	return false
		    end
	    end
	end
	xPos = xPos + xDir
	zPos = zPos + zDir
	return true
end

local function tryDown()
	if not turtle.down() then
		if turtle.digDown() then
			if not collect() then
				return false
			end
	    end
		if not turtle.down() then
			return false
		end
	end
	depth = depth + 1
	if math.fmod( depth, 10 ) == 0 then
		print( "Descended "..depth.." metres." )
	end
	return true
end

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

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

print( "Excavating..." )

local reseal = false
if turtle.digDown() then
	reseal = true
end

local alternate = 0
local done = false

local bottom = tonumber(tArgs[2])
local depth_tracker = 0
while not done and depth < bottom do
    if done then break end
	for n=1,size do
		for m=1,size-1 do
			if not tryForwards() then
				done = true
				break
			end
		end
		if done then
			break
		end
		if n<size then
			if math.fmod(n + alternate,2) == 0 then
				turnLeft()
				if not tryForwards() then
					done = true
					break
				end
				turnLeft()
			else
				turnRight()
				if not tryForwards() then
					done = true
					break
				end
				turnRight()
			end
		end
	end
	if done then
		break
	end

	if size > 1 then
		if math.fmod(size,2) == 0 then
			turnRight()
		else
			if alternate == 0 then
				turnLeft()
			else
				turnRight()
			end
			alternate = 1 - alternate
		end
	end

	if not tryDown() then
		done = true
		break
    else depth_tracker = depth_tracker + 1
	end

end

print( "Returning to surface..." )

-- Return to where we started

while depth > 0 do
	if turtle.up() then
		depth = depth - 1
	elseif turtle.digUp() then
		collect()
	else
		sleep( 0.5 )
	end
end

if xPos > 0 then
	while xDir ~= -1 do
		turnLeft()
	end
	while xPos > 0 do
		if turtle.forward() then
			xPos = xPos - 1
		elseif turtle.dig() then
			collect()
		else
			sleep( 0.5 )
		end
	end
end

if zPos > 0 then
	while zDir ~= -1 do
		turnLeft()
	end
	while zPos > 0 do
		if turtle.forward() then
			zPos = zPos - 1
		elseif turtle.dig() then
			collected = collected + 1
		else
			sleep( 0.5 )
		end
	end
end
while zDir ~= 1 do
	turnLeft()
end

-- Seal the hole
if reseal then
	turtle.placeDown()
end

print( "Mined "..collected.." blocks total." )