const ID = Union{Int,Nothing}
function getDisk()
	local blocks::Vector{Int8} = [ x - Int('0') for x in collect(read("input/9")) ][1:end-1]
	local disk::Vector{ID} = Vector()
	for b in 1:length(blocks)
		local id = (b - 1) ÷ 2
		local size = blocks[b]
		local isFile = b & 1 == 1
		for i in 1:size
			push!(disk, isFile ? id : nothing)
		end
	end
	return disk
end

const disk = getDisk()

function compress!(arr::AbstractVector, selectRange = (arr, i) -> i:i)
	for i in reverse(1:length(arr))
		if !isnothing(arr[i])
			local fillerRange = selectRange(arr, i)
			local head = 1
			while head < i
				if isnothing(arr[head])
					local emptyRange = selectRange(arr, head)
					local l = length(fillerRange)
					if length(emptyRange) >= l
						local s = emptyRange[1]
						arr[s:s+l-1] = arr[fillerRange]
						arr[fillerRange] .= nothing
						break
					else
						head += l
						continue
					end
				else
					head += 1
				end
			end
		end
	end
	return arr
end

function selectRangeChunk(arr, i)
	local c, lower, upper = arr[i], i, i
	while lower > 1 && arr[lower-1] == c
		lower -= 1
	end
	while upper < length(arr) && arr[upper+1] == c
		upper += 1
	end
	return lower:upper
end

checksum(arr) = mapreduce(x -> isnothing(x[2]) ? 0 : (x[1]-1) * x[2], +, enumerate(arr))

println("Part one ", checksum(compress!(copy(disk))))
println("Part two ", checksum(compress!(copy(disk), selectRangeChunk)))