--- Flood-fill command for complex lakes etc.
-- @module worldeditadditions.floodfill

-------------------------------------------------------------------------------
--- A Queue implementation, taken & adapted from https://www.lua.org/pil/11.4.html
-- @submodule worldeditadditions.utils.queue

local Queue = {}
function Queue.new()
	return { first = 0, last = -1 }
end

function Queue.enqueue(queue, value)
	local new_last = queue.last + 1
	queue.last = new_last
	queue[new_last] = value
end

function Queue.contains(queue, value)
	for i=queue.first,queue.last do
		if queue[i] == value then
			return true
		end
	end
	return false
end

function Queue.is_empty(queue)
	return queue.first > queue.last
end

function Queue.dequeue(queue)
	local first = queue.first
	if Queue.is_empty(queue) then
		error("Error: The queue is empty!")
	end
	
	local value = queue[first]
	queue[first] = nil -- Help the garbage collector out
	queue.first = first + 1
	return value
end

-------------------------------------------------------------------------------

-- These really should be in a utilities file, but Lua is being stupid and preventing access to it (and minetest is also being stupid, as we can't modularise our code the way you ought to be able to - or at least the documentation on dofile() is so poor I've no idea at this point)
local function vector2string(v)
	return "(" .. v.x ..", " .. v.y ..", " .. v.z ..")"
end

local clock = os.clock
function sleep(n)  -- seconds
  local t0 = clock()
  while clock() - t0 <= n do end
end


function worldedit.floodfill(start_pos, radius, replace_node)
	-- Calculate the area we want to modify
	local pos1 = vector.add(start_pos, { x = radius, y = 0, z = radius })
	local pos2 = vector.subtract(start_pos, { x = radius, y = radius, z = radius })
	pos1, pos2 = worldedit.sort_pos(pos1, pos2) -- Just in case
	
	minetest.log("action", "radius: " .. radius)
	minetest.log("action", "pos1: " .. vector2string(pos1))
	minetest.log("action", "pos2: " .. vector2string(pos2))
	
	-- Fetch the nodes in the specified area
	local manip, area = worldedit.manip_helpers.init(pos1, pos2)
	local data = manip:get_data()
	
	-- Setup for the floodfill operation itself
	local start_pos_index = area:index(start_pos.x, start_pos.y, start_pos.z);
	
	local search_id = data[start_pos_index]
	local replace_id = minetest.get_content_id(replace_node)
	
	minetest.log("action", "ids: " .. search_id .. " -> " .. replace_id)
	
	local count = 0
	local remaining_nodes = Queue.new()
	Queue.enqueue(remaining_nodes, start_pos_index)
	
	-- Do the floodfill
	while Queue.is_empty(remaining_nodes) == false do
		local cur = Queue.dequeue(remaining_nodes)
		
		-- TODO: Check distance from start_pos
		
		-- Replace this node
		data[cur] = replace_id
		count = count + 1
		
		-- Check all the nearby nodes
		-- We don't need to go upwards here, since we're filling in lake-style
		local xplus = cur + 1 -- +X
		if data[xplus] == search_id and not Queue.contains(remaining_nodes, xplus) then
			-- minetest.log("action", "[floodfill] [+X] index " .. xplus .. " is a " .. data[xplus] .. ", searching for a " .. search_id)
			Queue.enqueue(remaining_nodes, xplus)
		end
		local xminus = cur - 1 -- -X
		if data[xminus] == search_id and not Queue.contains(remaining_nodes, xminus) then
			-- minetest.log("action", "[floodfill] [-X] index " .. xminus .. " is a " .. data[xminus] .. ", searching for a " .. search_id)
			Queue.enqueue(remaining_nodes, xminus)
		end
		local zplus = cur + area.zstride -- +Z
		if data[zplus] == search_id and not Queue.contains(remaining_nodes, zplus) then
			-- minetest.log("action", "[floodfill] [+Z] index " .. zplus .. " is a " .. data[zplus] .. ", searching for a " .. search_id)
			Queue.enqueue(remaining_nodes, zplus)
		end
		local zminus = cur - area.zstride -- -Z
		if data[zminus] == search_id and not Queue.contains(remaining_nodes, zminus) then
			-- minetest.log("action", "[floodfill] [-Z] index " .. zminus .. " is a " .. data[zminus] .. ", searching for a " .. search_id)
			Queue.enqueue(remaining_nodes, zminus)
		end
		local yminus = cur - area.ystride -- -Y
		if data[yminus] == search_id and not Queue.contains(remaining_nodes, yminus)  then
			-- minetest.log("action", "[floodfill] [-Y] index " .. yminus .. " is a " .. data[yminus] .. ", searching for a " .. search_id)
			Queue.enqueue(remaining_nodes, yminus)
		end
		
		count = count + 1
	end
	
	-- Save the modified nodes back to disk & return
	worldedit.manip_helpers.finish(manip, data)
	
	return count
end


return floodfill