knapping = {
	config = {
		-- time after which the knapping process gets aborted,
		-- to prevent players from cluttering a world with thousands of entities
		timeout = core.settings:get("knapping_timeout") or 600,
		-- how many knapping processes can run simultaneously,
		-- again, to prevent players from cluttering a world with entities
		max_crafts = core.settings:get("knapping_max_crafts") or 25
	},
	path = core.get_modpath('knapping'),
	S = core.get_translator('knapping'),
	default_recipes = {
		pick = {
			{ 0, 0, 0, 0, 0, 0, 0, 0 },
			{ 0, 0, 0, 1, 1, 0, 0, 0 },
			{ 0, 1, 1, 1, 1, 1, 1, 0 },
			{ 1, 1, 1, 1, 1, 1, 1, 1 },
			{ 1, 1, 1, 0, 0, 1, 1, 1 },
			{ 1, 0, 0, 0, 0, 0, 0, 1 },
			{ 0, 0, 0, 0, 0, 0, 0, 0 },
			{ 0, 0, 0, 0, 0, 0, 0, 0 },
		},
		axe = {
			{ 0, 0, 1, 1, 0, 0, 0, 0 },
			{ 0, 1, 1, 1, 1, 0, 0, 0 },
			{ 0, 1, 1, 1, 1, 1, 0, 0 },
			{ 0, 1, 1, 1, 1, 1, 1, 0 },
			{ 0, 1, 1, 1, 1, 1, 1, 0 },
			{ 0, 1, 1, 1, 0, 1, 0, 0 },
			{ 0, 1, 1, 1, 0, 0, 0, 0 },
			{ 0, 0, 1, 1, 0, 0, 0, 0 },
		},
		shovel = {
			{ 0, 0, 0, 1, 1, 0, 0, 0 },
			{ 0, 0, 1, 1, 1, 1, 0, 0 },
			{ 0, 1, 1, 1, 1, 1, 1, 0 },
			{ 0, 1, 1, 1, 1, 1, 1, 0 },
			{ 0, 1, 1, 1, 1, 1, 1, 0 },
			{ 0, 1, 1, 1, 1, 1, 1, 0 },
			{ 0, 1, 1, 1, 1, 1, 1, 0 },
			{ 0, 0, 1, 0, 0, 1, 0, 0 },
		},
		sword = {
			{ 0, 0, 0, 0, 0, 0, 1, 1 },
			{ 0, 0, 0, 0, 0, 1, 1, 1 },
			{ 0, 0, 0, 0, 1, 1, 1, 0 },
			{ 0, 0, 0, 1, 1, 1, 0, 0 },
			{ 0, 0, 1, 1, 1, 0, 0, 0 },
			{ 0, 1, 1, 1, 0, 0, 0, 0 },
			{ 1, 1, 1, 0, 0, 0, 0, 0 },
			{ 1, 1, 0, 0, 0, 0, 0, 0 },
		},
	},
	registered_recipes = {},
	registered_callbacks = {},
	crafting_processes = {},
}

local fallback_texture = "knapping_stone.png"
local initial_properties = {
	visual = "cube",
	collisionbox = { -0.5 / 8, -0.5 / 8, -0.5 / 8, 0.5 / 8, 0.5 / 8, 0.5 / 8 },
	textures = { fallback_texture, fallback_texture, fallback_texture,
		fallback_texture, fallback_texture, fallback_texture },
	visual_size = { x = 1 / 8, y = 1 / 8, z = 1 / 8 },
	physical = false,
	static_save = false,
}

core.register_entity('knapping:stone_piece_go', {
	initial_properties = initial_properties,
	on_punch = function(self, puncher)
		if puncher:get_wielded_item():get_name() ~= self.material then return end
		self.get_removed()
		self.object:remove()
		core.sound_play("thunk", { gain = 0.3, to_player = puncher:get_player_name() }, true)
	end,
})

core.register_entity('knapping:stone_piece', {
	initial_properties = initial_properties,
})

local function get_empty_slot(t)
	local i = 1
	while t[i] do
		i = i + 1
	end
	return i
end

local function clear_craft(id, cp_table)
	-- first check if this crafting process even still exists
	if not knapping.crafting_processes[id] then return end
	if cp_table and knapping.crafting_processes[id] ~= cp_table then return end

	if cp_table and knapping.crafting_processes[id] == cp_table then
		core.chat_send_player(cp_table.player,
			knapping.S("The knapping process you started at: @1 crumbled away due to time.",
			core.pos_to_string(cp_table.pos)))
	end

	local pos = knapping.crafting_processes[id].pos
	local bits = core.get_objects_inside_radius(pos, 1)
	for _, v in pairs(bits) do
		if not v:is_player() and v:get_luaentity().id == id then
			v:remove()
		end
	end
	knapping.crafting_processes[id] = nil
end

local function finish_craft(id)
	local crafting_process = knapping.crafting_processes[id]
	local pos = crafting_process.pos
	core.add_item(pos, crafting_process.recipe.output)
	for _, func in pairs(knapping.registered_callbacks) do
		func(crafting_process.recipe, pos, crafting_process.player)
	end
	clear_craft(id)
end

local function place_knapping_plane(id)
	local crafting_process = knapping.crafting_processes[id]
	local recipe = crafting_process.recipe
	local node_pos = crafting_process.pos

	local start_pos = vector.add(node_pos, -7 / 16)

	-- instead of matching the in-world pattern to the recipe, we just count up
	-- how many diggable pieces there are and finnish once they are gone
	local to_remove = 0

	for x = 1, 8 do
		for z = 1, 8 do
			local pos = { x = start_pos.x + (1 / 8) * (x - 1), y = start_pos.y, z = start_pos.z + (1 / 8) * (z - 1) }

			local texture = recipe.texture and recipe.texture .. "^[sheet:8x8:" .. x - 1 .. "," .. 8 - z or
				"knapping_stone.png"

			if recipe.recipe[x][z] == 1 then
				local objref = core.add_entity(pos, 'knapping:stone_piece')
				objref:set_properties({ textures = { texture, texture, texture, texture, texture, texture } })

				local luaent = objref:get_luaentity()
				-- used during cleanup so recipes in adjacent nodes don't get messed up
				luaent.id = id
			else
				to_remove = to_remove + 1
				local objref = core.add_entity(pos, 'knapping:stone_piece_go')
				texture = texture .. "^[multiply:#b0b0b0" -- darken texture to distinguish the pattern
				objref:set_properties({ textures = { texture, texture, texture, texture, texture, texture } })

				local luaent = objref:get_luaentity()
				luaent.id = id
				luaent.material = recipe.input
				luaent.get_removed = function()
					to_remove = to_remove - 1
					if to_remove == 0 then
						finish_craft(id)
					end
				end
			end
		end
	end
	-- so the map doesn't get cluttered, this isn't supposed to be a permanent decoration after all
	core.after(knapping.config.timeout, clear_craft, id, crafting_process)
end

local function get_knapping_formspec(itemname, pos)
	local spos = core.pos_to_string(pos)
	local recipes = knapping.registered_recipes[itemname]
	local formspec = {}
	formspec[#formspec + 1] = "size["
	formspec[#formspec + 1] = #recipes
	formspec[#formspec + 1] = ",1]"

	local x = 0
	for _, v in pairs(recipes) do
		formspec[#formspec + 1] = "item_image_button["
		formspec[#formspec + 1] = x
		formspec[#formspec + 1] = ",0.125;1,1;"
		formspec[#formspec + 1] = v.output
		formspec[#formspec + 1] = ";"
		-- is there a a way to avoid passing the position through the formspec?
		formspec[#formspec + 1] = itemname .. "|" .. v.output .. "|" .. spos
		formspec[#formspec + 1] = ";]"
		x = x + 1
	end

	return table.concat(formspec)
end

local function handle_input(player, formname, fields)
	if formname ~= "knapping:choose_recipe" then return end
	if fields.quit then return end

	local player_name = player:get_player_name()

	for k, v in pairs(fields) do
		if v then
			local a = k:find("|")
			local b = k:find("|", a + 1)
			local itemname, output, pos = k:sub(1, a - 1), k:sub(a + 1, b - 1), core.string_to_pos(k:sub(b + 1, -1))
			local recipe
			for _, v in pairs(knapping.registered_recipes[itemname]) do
				if v.output == output then recipe = v end
			end

			core.close_formspec(player_name, formname)

			local id = get_empty_slot(knapping.crafting_processes)

			if id > knapping.config.max_crafts then
				core.chat_send_player(player_name, knapping.S("There are too many knapping processes going on at once."))
				core.chat_send_player(player_name, knapping.S("Try again in a few minutes."))
				return true
			end

			knapping.crafting_processes[id] = {
				pos = pos,
				recipe = recipe,
				player = player_name,
			}

			place_knapping_plane(id)

			-- remove input item if not creative
			if not core.settings:get_bool("creative_mode") and
				not core.check_player_privs(player_name, { creative = true }) then
				local itemstack = player:get_wielded_item()
				itemstack:take_item()
				player:set_wielded_item(itemstack)
			end
		end
	end
	return true
end
core.register_on_player_receive_fields(handle_input)

local function can_knapp(placer, pointed_thing)
	if pointed_thing.under.y ~= pointed_thing.above.y - 1 then return false end
	if core.get_node(pointed_thing.above).name ~= "air" then return false end
	if core.registered_nodes[core.get_node(pointed_thing.under).name].walkable ~= true then return false end
	if not placer:get_player_control().sneak then return false end
	return true
end

local function add_knapping(itemname)
	assert(core.registered_items[itemname],
		"Trying to register a knapping recipe using the nonexistent item: '" .. itemname .. "'")
	local og_on_place = core.registered_items[itemname].on_place
	core.override_item(itemname, {
		description = core.registered_items[itemname].description ..
			core.colorize("#ababab", "\n" .. knapping.S("Use on the top of a surface while sneaking to start knapping.")),
		on_place = function(itemstack, placer, pointed_thing)
			if can_knapp(placer, pointed_thing) then
				core.show_formspec(placer:get_player_name(), "knapping:choose_recipe",
					get_knapping_formspec(itemname, pointed_thing.above))
			else
				return og_on_place and og_on_place(itemstack, placer, pointed_thing)
			end
		end,
	})
end

function knapping.register_on_craft(func)
	assert(type(func) == "function", "'register_on_craft' expects a function, got: '" .. type(func) .. "'")
	table.insert(knapping.registered_callbacks, func)
end

function knapping.register_recipe(recipe)
	if not knapping.registered_recipes[recipe.input] then
		knapping.registered_recipes[recipe.input] = {}
		add_knapping(recipe.input)
	end
	table.insert(knapping.registered_recipes[recipe.input], recipe)
end