--[[
clumpfall
Copyright (C) 2018-2020 Noodlemire

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
--]]

clumpfall.override = {} --global override variable

--[[
Description:
	Overrides the on_punch event of the given node in such a way that it adds the provided function to on_punch, without deleting the old on_punch method
Parameters:
	nodename: The internal name of the node that will be overridden
	new_on_punch: The name of the function that will be called in addition to nodename's usual on_punch event
Returns: 
	Nothing
--]]
function clumpfall.override.add_punch_event(nodename, new_on_punch)
	--Store the old on_punch event for later use
	local old_on_punch = minetest.registered_nodes[nodename].on_punch
	--Create a function that calls both the old and new on_punch methods
	local master_on_punch = function(pos, node, player, pointed_thing)
		--Call the old on_punch function if there is one set
		if old_on_punch then 
			old_on_punch(pos, node, player, pointed_thing)
		end

		--Then, call the new on_punch method
		new_on_punch(pos, node, player, pointed_thing)
	end

	--Override the given node with the combination of old and new on_punch functions
	minetest.override_item(nodename, {on_punch = master_on_punch})
end

--[[
Description:
	Add a punch event to beds so that if a player punches a half bed, that bed will instantly spawn its other half in the event that said other half doesn't exist, or it will destroy itself if it is unable to spawn its other half
Parameters:
	bed_to_override: The name of the bed half to make fixable via punching
Returns: 
	Nothing
--]]
function clumpfall.override.bed_update_on_punch(bed_to_override)
	clumpfall.override.add_punch_event(bed_to_override, function(pos, node)
		--If this is indeed a bed being affected and it doens't need to clump fall instead, then
		if clumpfall.functions.check_individual_for_fall(pos) == false and minetest.get_item_group(node.name, "bed") ~= 0 then
			--Create local variables to store the bed's name without _top or _bottom at the end, the suffix of its other half, and the position of its other half
			local base_node_name
			local other_suffix
			local other_pos

			--If this half's name ends in "_bottom", then
			if node.name:sub(#node.name - #"bottom", #node.name) == "_bottom" then
				--The other half must be the top half, so update variables accordingly.
				base_node_name = node.name:sub(1, #node.name - #"_bottom")
				other_suffix = "_top"
				other_pos = vector.add(pos, minetest.facedir_to_dir(node.param2))
			else
				--Otherwise, the other half is the bottom half.
				base_node_name = node.name:sub(1, #node.name - #"_top")
				other_suffix = "_bottom"
				other_pos = vector.subtract(pos, minetest.facedir_to_dir(node.param2))
			end

			--If the name of the node at the other half's position is not actually the name of the other half or that other half is turned incorrectly, then...
			if minetest.get_node(other_pos).name ~= base_node_name..other_suffix or minetest.get_node(other_pos).param2 ~= node.param2 then
				--Check if the other half is simply missing by seeing it the node at the other half's position is walkable.
				if minetest.registered_nodes[minetest.get_node(other_pos).name].walkable == false then
					--If not, spawn the other half with the correct position and direction
					minetest.set_node(other_pos, {name = base_node_name..other_suffix, param2 = node.param2})
				else
					--Otherwise, replace this bed half with air and spawn it as an item
					minetest.set_node(pos, {name = "air"})
					minetest.spawn_item(pos, base_node_name.."_bottom")
				end
			end
		end
	end)
end

--[[
Description:
	Completely override the on_destruct method of a given bed with a fixed version of the destruct_bed function
Parameters:
	bed_name: The name of the bed half to override
Returns: 
	Nothing
--]]
function clumpfall.override.set_fix_destruct_bed(bed_name)
	--Stores a number reporesenting which half of a bed this is
	local bed_half

	--If this bed half's name ends in _bottom, 
	if bed_name:sub(#bed_name - #"bottom", #bed_name) == "_bottom" then
		--Set bed_half = 1.
		bed_half = 1
	else
		--Otherwise, this is half 2.
		bed_half = 2
	end

	--Override the on_dustruct of the node known by the given name
	minetest.override_item(bed_name, 
	{
		on_destruct = function(pos)
			--Call the fixed destruct_bed at on_destruct's postion and the value of bed_half
			clumpfall.override.fix_destruct_bed(pos, bed_half)
			--Just in case there was only one bed punched, reset reverse to false afterwards
			reverse = false
		end
	})
end

--[[
Description:
	Destroy a bed in such a way that the other half will also be destroyed, but only if that other half actually exists and this half hasn't already been destroyed
Parameters:
	pos: The position of the bed half to destroy
	n: A number representing which half of the bed is currently being destoryed
Returns: 
	Nothing
--]]
--reverse: global variable that defaults to false, and is used in determining if the other bed half should be destroyed
reverse = false
function clumpfall.override.fix_destruct_bed(pos, n)
	--Store the node at the given position
	local node = minetest.get_node(pos)
	--Will be used to store the position of the other bed half
	local other

	--Based on n and this node's param2 (direction), get the other half's postion
	if n == 2 then
		local dir = minetest.facedir_to_dir(node.param2)
		other = vector.subtract(pos, dir)
	elseif n == 1 then
		local dir = minetest.facedir_to_dir(node.param2)
		other = vector.add(pos, dir)
	end

	--Flip the value inside of reverse. If reverse was false before, it is true now and this bed will destroy the other half. If not, this half will do nothing more.
	reverse = not reverse

	--If the other half is indeed a bed, it is this bed's other half (and not the other half of a completely different bed), and reverse is true, then
	if minetest.get_item_group(minetest.get_node(other).name, "bed") ~= 0 and minetest.get_node(other).param2 == node.param2 and reverse then
		--Delete the other node without spawning an item; this will call the entirety of that bed half's on_destruct before reverse is automatically reset to false
		minetest.remove_node(other)
		--Use the helper function check_for_falling to update nodes near the other half
		minetest.check_for_falling(other)
	end
end


--[[
Description: 
	Overrides falling_node entities so that they punch their position when spawning and landing, so that they interact properly with clump fall nodes.
Parameters: 
	None
Returns: 
	Nothing
--]]
function clumpfall.override.fix_falling_nodes()
	entitycontrol.override_entity("__builtin:falling_node", 
	{
		on_activate = function(self, staticdata)
			self.object:set_armor_groups({immortal = 1})

			local ds = minetest.deserialize(staticdata)
			if ds and ds.node then
				self:set_node(ds.node, ds.meta)
			elseif ds then
				self:set_node(ds)
			elseif staticdata ~= "" then
				self:set_node({name = staticdata})
			end

			--Punch node at position after a delay of spawning (default: 1 second), so clump fall nodes on top don't float
			minetest.after(clumpfall.clump_interval, minetest.punch_node, self.object:get_pos())
		end,

		on_step = function(self, dtime)
			-- Set gravity
			local acceleration = self.object:get_acceleration()
			if not vector.equals(acceleration, {x = 0, y = -10, z = 0}) then
				self.object:set_acceleration({x = 0, y = -10, z = 0})
			end
			-- Turn to actual node when colliding with ground, or continue to move
			local pos = self.object:get_pos()
			-- Position of bottom center point
			local bcp = {x = pos.x, y = pos.y - 0.7, z = pos.z}
			-- 'bcn' is nil for unloaded nodes
			local bcn = minetest.get_node_or_nil(bcp)
			-- Delete on contact with ignore at world edges
			if bcn and bcn.name == "ignore" then
				self.object:remove()
				return
			end
			local bcd = bcn and minetest.registered_nodes[bcn.name]
			if bcn and
					(not bcd or bcd.walkable or
					(minetest.get_item_group(self.node.name, "float") ~= 0 and
					bcd.liquidtype ~= "none")) then
				if bcd and bcd.leveled and
						bcn.name == self.node.name then
					local addlevel = self.node.level
					if not addlevel or addlevel <= 0 then
						addlevel = bcd.leveled
					end
					if minetest.add_node_level(bcp, addlevel) == 0 then
						self.object:remove()
						return
					end
				elseif bcd and bcd.buildable_to and
						(minetest.get_item_group(self.node.name, "float") == 0 or
						bcd.liquidtype == "none") then
					minetest.remove_node(bcp)
					return
				end
				local np = {x = bcp.x, y = bcp.y + 1, z = bcp.z}
				-- Check what's here
				local n2 = minetest.get_node(np)
				local nd = minetest.registered_nodes[n2.name]
				-- If it's not air or liquid, remove node and replace it with
				-- it's drops
				if n2.name ~= "air" and (not nd or nd.liquidtype == "none") then
					minetest.remove_node(np)
					if nd and nd.buildable_to == false then
						-- Add dropped items
						local drops = minetest.get_node_drops(n2, "")
						for _, dropped_item in pairs(drops) do
							minetest.add_item(np, dropped_item)
						end
					end
					-- Run script hook
					for _, callback in pairs(minetest.registered_on_dignodes) do
						callback(np, n2)
					end
				end
				-- Create node and remove entity
				local def = minetest.registered_nodes[self.node.name]
				if def then
					--After landing, punch the node it set so that it causes a floating clump fall node to realize it should fall.
					minetest.set_node(np, self.node)
					minetest.punch_node(np)
					if self.meta then
						local meta = minetest.get_meta(np)
						meta:from_table(self.meta)
					end
					if def.sounds and def.sounds.place then
						minetest.sound_play(def.sounds.place, {pos = np})
					end
				end
				self.object:remove()
				minetest.check_for_falling(np)
				return
			end
			local vel = self.object:get_velocity()
			if vector.equals(vel, {x = 0, y = 0, z = 0}) then
				local npos = self.object:get_pos()
				self.object:set_pos(vector.round(npos))
			end
		end
	})
end

--[[
Description:
	This function iterates through every registered node, including those that were registered by other mods, and turns ones that don't already fall by themselves and aren't unbreakable into clump_fall_nodes
Parameters:
	None
Returns:
	Nothing
--]]
function clumpfall.override.make_nodes_fallable()
	--Inspect each registered node, one at a time
	for nodename, nodereal in pairs(minetest.registered_nodes) do
		--create a temporary list of the current node's groups
		local temp_node_group_list = nodereal.groups

		--Ensure that the nodes being modified aren't the placeholder block types that tecnically don't exist
		if nodename ~= "air" and nodename ~= "ignore" and 
				minetest.get_item_group(nodename, "falling_node") == 0 and --Don't need to affect nodes that already fall by themselves
				minetest.get_item_group(nodename, "attached_node") == 0 and --Same thing for nodes in this group, which fall when no longer attached to another node
				minetest.get_item_group(nodename, "liquid") == 0 and --Same thing for nodes in this group, which do technically fall and spread around
				minetest.get_item_group(nodename, "unbreakable") == 0 then --Lastly, if a block is invulnerable to begin with, it shouldn't fall down like a typical node
			--Initialize a new group variable in the temp list known as "clump_fall_node" as 1
			temp_node_group_list.clump_fall_node = 1
		
			--Override the node's previous group list with the one that includes the new clump_fall_node group
			--minetest.override_item(nodename, {groups = temp_node_group_list})
		end

		if minetest.get_item_group(nodename, "bed") ~= 0 then
			clumpfall.override.bed_update_on_punch(nodename)
			clumpfall.override.set_fix_destruct_bed(nodename)
		end
	end
end