--register stoppers for movestones/pistons

mesecon.mvps_stoppers = {}
mesecon.on_mvps_move = {}
mesecon.mvps_unmov = {}

--- Objects (entities) that cannot be moved
function mesecon.register_mvps_unmov(objectname)
	mesecon.mvps_unmov[objectname] = true;
end

function mesecon.is_mvps_unmov(objectname)
	return mesecon.mvps_unmov[objectname]
end

-- Nodes that cannot be pushed / pulled by movestones, pistons
function mesecon.is_mvps_stopper(node, pushdir, stack, stackid)
	-- unknown nodes are always stoppers
	if not minetest.registered_nodes[node.name] then
		return true
	end

	local get_stopper = mesecon.mvps_stoppers[node.name]
	if type (get_stopper) == "function" then
		get_stopper = get_stopper(node, pushdir, stack, stackid)
	end

	return get_stopper
end

function mesecon.register_mvps_stopper(nodename, get_stopper)
	if get_stopper == nil then
			get_stopper = true
	end
	mesecon.mvps_stoppers[nodename] = get_stopper
end

-- Functions to be called on mvps movement
function mesecon.register_on_mvps_move(callback)
	mesecon.on_mvps_move[#mesecon.on_mvps_move+1] = callback
end

local function on_mvps_move(moved_nodes)
	for _, callback in ipairs(mesecon.on_mvps_move) do
		callback(moved_nodes)
	end
end

function mesecon.mvps_process_stack()
	-- This function is kept for compatibility.
	-- It used to call on_placenode on moved nodes, but that is now done automatically.
end

-- tests if the node can be pushed into, e.g. air, water, grass
local function node_replaceable(name)
	if minetest.registered_nodes[name] then
		return minetest.registered_nodes[name].buildable_to or false
	end

	return false
end

function mesecon.mvps_get_stack(pos, dir, maximum, all_pull_sticky)
	-- determine the number of nodes to be pushed
	local nodes = {}
	local pos_set = {}
	local frontiers = mesecon.fifo_queue.new()
	frontiers:add(vector.new(pos))

	for np in frontiers:iter() do
		local np_hash = minetest.hash_node_position(np)
		local nn = not pos_set[np_hash] and minetest.get_node(np)
		if nn and not node_replaceable(nn.name) then
			pos_set[np_hash] = true
			table.insert(nodes, {node = nn, pos = np})
			if #nodes > maximum then return nil end

			-- add connected nodes to frontiers
			if minetest.registered_nodes[nn.name]
			and minetest.registered_nodes[nn.name].mvps_sticky then
				local connected = minetest.registered_nodes[nn.name].mvps_sticky(np, nn)
				for _, cp in ipairs(connected) do
					frontiers:add(cp)
				end
			end

			frontiers:add(vector.add(np, dir))

			-- If adjacent node is sticky block and connects add that
			-- position
			for _, r in ipairs(mesecon.rules.alldirs) do
				local adjpos = vector.add(np, r)
				local adjnode = minetest.get_node(adjpos)
				if minetest.registered_nodes[adjnode.name]
				and minetest.registered_nodes[adjnode.name].mvps_sticky then
					local sticksto = minetest.registered_nodes[adjnode.name]
						.mvps_sticky(adjpos, adjnode)

					-- connects to this position?
					for _, link in ipairs(sticksto) do
						if vector.equals(link, np) then
							frontiers:add(adjpos)
						end
					end
				end
			end

			if all_pull_sticky then
				frontiers:add(vector.subtract(np, dir))
			end
		end
	end

	return nodes
end

function mesecon.mvps_set_owner(pos, placer)
	local meta = minetest.get_meta(pos)
	local owner = placer and placer.get_player_name and placer:get_player_name()
	if owner and owner ~= "" then
		meta:set_string("owner", owner)
	else
		meta:set_string("owner", "$unknown") -- to distinguish from older pistons
	end
end

function mesecon.mvps_claim(pos, player_name)
	if not player_name or player_name == "" then return end
	local meta = minetest.get_meta(pos)
	if meta:get_string("infotext") == "" then return end
	if meta:get_string("owner") == player_name then return end -- already owned
	if minetest.is_protected(pos, player_name) then
		minetest.chat_send_player(player_name, "Can't reclaim: protected")
		return
	end
	meta:set_string("owner", player_name)
	meta:set_string("infotext", "")
	return true
end

local function add_pos(positions, pos)
	local hash = minetest.hash_node_position(pos)
	positions[hash] = pos
end

local function are_protected(positions, player_name)
	local mode = mesecon.setting("mvps_protection_mode", "compat")
	if mode == "ignore" then
		return false
	end
	local name = player_name
	if player_name == "" or not player_name then -- legacy MVPS
		if mode == "normal" then
			name = "$unknown" -- sentinel, for checking for *any* protection
		elseif mode == "compat" then
			return false
		elseif mode == "restrict" then
			return true
		else
			error("Invalid protection mode")
		end
	end
	local is_protected = minetest.is_protected
	for _, pos in pairs(positions) do
		if is_protected(pos, name) then
			return true
		end
	end
	return false
end

function mesecon.mvps_push(pos, dir, maximum, player_name)
	return mesecon.mvps_push_or_pull(pos, dir, dir, maximum, false, player_name)
end

function mesecon.mvps_pull_all(pos, dir, maximum, player_name)
	return mesecon.mvps_push_or_pull(pos, vector.multiply(dir, -1), dir, maximum, true, player_name)
end

function mesecon.mvps_pull_single(pos, dir, maximum, player_name)
	return mesecon.mvps_push_or_pull(pos, vector.multiply(dir, -1), dir, maximum, false, player_name)
end

-- pos: pos of mvps
-- stackdir: direction of building the stack
-- movedir: direction of actual movement
-- maximum: maximum nodes to be pushed
-- all_pull_sticky: All nodes are sticky in the direction that they are pulled from
-- player_name: Player responsible for the action.
--  - empty string means legacy MVPS, actual check depends on configuration
--  - "$unknown" is a sentinel for forcing the check
function mesecon.mvps_push_or_pull(pos, stackdir, movedir, maximum, all_pull_sticky, player_name)
	local nodes = mesecon.mvps_get_stack(pos, movedir, maximum, all_pull_sticky)

	if not nodes then return end

	local protection_check_set = {}
	if vector.equals(stackdir, movedir) then -- pushing
		add_pos(protection_check_set, pos)
	end
	-- determine if one of the nodes blocks the push / pull
	for id, n in ipairs(nodes) do
		if mesecon.is_mvps_stopper(n.node, movedir, nodes, id) then
			return
		end
		add_pos(protection_check_set, n.pos)
		add_pos(protection_check_set, vector.add(n.pos, movedir))
	end
	if are_protected(protection_check_set, player_name) then
		return false, "protected"
	end

	-- remove all nodes
	for _, n in ipairs(nodes) do
		n.meta = minetest.get_meta(n.pos):to_table()
		local node_timer = minetest.get_node_timer(n.pos)
		if node_timer:is_started() then
			n.node_timer = {node_timer:get_timeout(), node_timer:get_elapsed()}
		end
		minetest.remove_node(n.pos)
	end

	-- update mesecons for removed nodes ( has to be done after all nodes have been removed )
	for _, n in ipairs(nodes) do
		mesecon.on_dignode(n.pos, n.node)
	end

	-- add nodes
	for _, n in ipairs(nodes) do
		local np = vector.add(n.pos, movedir)

		minetest.set_node(np, n.node)
		minetest.get_meta(np):from_table(n.meta)
		if n.node_timer then
			minetest.get_node_timer(np):set(unpack(n.node_timer))
		end
	end

	local moved_nodes = {}
	local oldstack = mesecon.tablecopy(nodes)
	for i in ipairs(nodes) do
		moved_nodes[i] = {}
		moved_nodes[i].oldpos = nodes[i].pos
		nodes[i].pos = vector.add(nodes[i].pos, movedir)
		moved_nodes[i].pos = nodes[i].pos
		moved_nodes[i].node = nodes[i].node
		moved_nodes[i].meta = nodes[i].meta
		moved_nodes[i].node_timer = nodes[i].node_timer
	end

	on_mvps_move(moved_nodes)

	return true, nodes, oldstack
end

-- Returns whether the given area intersects any nodes in the given set of position hashes,
-- or any walkable nodes in the map if no set is given.
local function area_intersects_nodes(min_pos, max_pos, positions)
	min_pos = vector.round(min_pos)
	max_pos = vector.round(max_pos)
	local pos = vector.new(min_pos)
	while pos.x <= max_pos.x do
		while pos.y <= max_pos.y do
			while pos.z <= max_pos.z do
				if positions then
					if positions[minetest.hash_node_position(pos)] then
						return true
					end
				else
					local def = minetest.registered_nodes[minetest.get_node(pos).name]
					if not def or def.walkable then
						return true
					end
				end
				pos.z = pos.z + 1
			end
			pos.z = min_pos.z
			pos.y = pos.y + 1
		end
		pos.y = min_pos.y
		pos.x = pos.x + 1
	end
	return false
end

-- Returns whether the given area intersects the node face with the given normal axis and center point.
local function area_intersects_face(min_pos, max_pos, normal_axis, center)
	for k, v in pairs(center) do
		if k == normal_axis then
			if min_pos[k] >= v or max_pos[k] <= v then
				return false
			end
		else
			if min_pos[k] >= v + 0.5 or max_pos[k] <= v - 0.5 then
				return false
			end
		end
	end
	return true
end

function mesecon.mvps_move_objects(pos, dir, nodestack, movefactor)
	local dir_k
	local dir_l
	for k, v in pairs(dir) do
		if v ~= 0 then
			dir_k = k
			dir_l = v
			break
		end
	end
	movefactor = movefactor or 1
	dir = vector.multiply(dir, movefactor)
	-- The collision box min and max positions will be extended by these values.
	-- These small scalars are so that objects next to the moved stack are also moved.
	local extension_min = vector.new(-0.01, -0.01, -0.01)
	local extension_max = vector.new(0.01, 0.01, 0.01)
	-- The collision box is extended in one direction to account for node displacement,
	-- except in the special case where no nodes are moved.
	local extension = nodestack[1] ~= nil and -dir[dir_k] or 0
	if extension < 0 then
		extension_min[dir_k] = extension
		extension_max[dir_k] = 0
	else
		extension_min[dir_k] = 0
		extension_max[dir_k] = extension
	end

	local max_distance = 0
	local moved_positions, face_center
	if movefactor == 1 or nodestack[1] ~= nil then
		-- Usually, objects are moved if they intersect with moved node positions.
		moved_positions = {}
		if nodestack[1] == nil then
			-- Push objects intersecting the mvps position.
			moved_positions[minetest.hash_node_position(pos)] = true
		end
		for _, n in ipairs(nodestack) do
			moved_positions[minetest.hash_node_position(n.pos)] = true
			max_distance = math.max(max_distance, vector.distance(pos, n.pos))
		end
	else
		-- When zero nodes are retracted, objects are moved if they intersect with the retracting face.
		face_center = vector.new(pos)
		face_center[dir_k] = face_center[dir_k] - 0.5 * dir_l
	end

	for id, obj in pairs(minetest.get_objects_inside_radius(pos, max_distance + 2)) do
		local obj_pos = obj:get_pos()
		local cbox = obj:get_properties().collisionbox
		local min_pos = vector.add(obj_pos, vector.offset(extension_min, cbox[1], cbox[2], cbox[3]))
		local max_pos = vector.add(obj_pos, vector.offset(extension_max, cbox[4], cbox[5], cbox[6]))
		local ok
		if moved_positions then
			ok = area_intersects_nodes(min_pos, max_pos, moved_positions)
		else
			ok = area_intersects_face(min_pos, max_pos, dir_k, face_center)
		end
		if ok then
			local ent = obj:get_luaentity()
			if obj:is_player() or (ent and not mesecon.is_mvps_unmov(ent.name)) then
				-- Move only if destination is not solid or object is inside stack:
				-- (A small bias is added to prevent rounding issues.)
				local min_pos = vector.offset(obj_pos, cbox[1] + 0.01, cbox[2] + 0.01, cbox[3] + 0.01)
				local max_pos = vector.offset(obj_pos, cbox[4] - 0.01, cbox[5] - 0.01, cbox[6] - 0.01)
				if not area_intersects_nodes(vector.add(min_pos, dir), vector.add(max_pos, dir)) or
						(nodestack[1] ~= nil and area_intersects_nodes(min_pos, max_pos, moved_positions)) then
					obj:move_to(vector.add(obj_pos, dir))
				end
			end
		end
	end
end

-- Never push into unloaded blocks. Don’t try to pull from them, either.
-- TODO: load blocks instead, as with wires.
mesecon.register_mvps_stopper("ignore")

-- All of the locked and internal nodes in Minetest Game
for _, name in ipairs({
	"default:chest_locked",
	"default:chest_locked_open",
	"doors:door_steel_b_1", -- old style doors
	"doors:door_steel_b_2", --
	"doors:door_steel_t_1", --
	"doors:door_steel_t_2", --
	"doors:door_steel_a",   -- new style doors
	"doors:door_steel_b",   --
	"doors:door_steel_c",   --
	"doors:door_steel_d",   --
	"doors:hidden",
	"doors:trapdoor_steel",
	"doors:trapdoor_steel_open",
	"xpanes:door_steel_bar_a",
	"xpanes:door_steel_bar_b",
	"xpanes:door_steel_bar_c",
	"xpanes:door_steel_bar_d",
	"xpanes:trapdoor_steel_bar",
	"xpanes:trapdoor_steel_bar_open",
}) do
	mesecon.register_mvps_stopper(name)
end

mesecon.register_on_mvps_move(mesecon.move_hot_nodes)
mesecon.register_on_mvps_move(function(moved_nodes)
	for i = 1, #moved_nodes do
		local moved_node = moved_nodes[i]
		mesecon.on_placenode(moved_node.pos, moved_node.node)
		minetest.after(0, function()
			minetest.check_for_falling(moved_node.oldpos)
			minetest.check_for_falling(moved_node.pos)
		end)
		local node_def = minetest.registered_nodes[moved_node.node.name]
		if node_def and node_def.mesecon and node_def.mesecon.on_mvps_move then
			node_def.mesecon.on_mvps_move(moved_node.pos, moved_node.node,
					moved_node.oldpos, moved_node.meta)
		end
	end
end)