--[[
Copyright (c) 2014, Robert 'Bobby' Zenz
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--- Various functions and constants for working with the facedir value.
facedirutil = {
	--- Attached to the node in the negative x direction.
	NEGATIVE_X = 3,
	
	--- Attached to the node in the negative z direction.
	NEGATIVE_Z = 2,
	
	--- The vector for the negative x direction.
	NEGATIVE_X_VECTOR = {
		x = -1,
		y = 0,
		z = 0
	},
	
	--- The vector for the negative z direction.
	NEGATIVE_Z_VECTOR = {
		x = 0,
		y = 0,
		z = -1
	},
	
	--- Attached to the node in the positive x direction.
	POSITIVE_X = 1,
	
	--- Attached to the node in the positive z direction.
	POSITIVE_Z = 0,
	
	--- The vector for the positive x direction.
	POSITIVE_X_VECTOR = {
		x = 1,
		y = 0,
		z = 0
	},
	
	--- The vector for the positive z direction.
	POSITIVE_Z_VECTOR = {
		x = 0,
		y = 0,
		z = 1
	}
}


--- Gets the vector for the given ID.
--
-- @param id The ID for which to get the vector.
-- @return The vector for the given ID.
function facedirutil.get_vector(id)
	if id == facedirutil.NEGATIVE_X then
		return facedirutil.NEGATIVE_X_VECTOR
	elseif id == facedirutil.NEGATIVE_Z then
		return facedirutil.NEGATIVE_Z_VECTOR
	elseif id == facedirutil.POSITIVE_X then
		return facedirutil.POSITIVE_X_VECTOR
	elseif id == facedirutil.POSITIVE_Z then
		return facedirutil.POSITIVE_Z_VECTOR
	end
	
	return facedirutil.NEGATIVE_X_VECTOR
end

--- Turns the placed node upside down if the placer was looking at
-- the underside of another node or did look steep upwards. This function is
-- supposed to be attached to the after_node_place callback of a node
-- definition.
--
-- @param pos The position of the placed node.
-- @param placer The placed, a Player object.
-- @param itemstack The user ItemStack.
-- @param pointed_thing The nodes that the placed pointed at.
function facedirutil.make_upsidedown(pos, placer, itemstack, pointed_thing)
	-- Check if the placer did look at the underside of a node
	-- or looked quite steep up.
	if (pos.y == pointed_thing.under.y - 1
		and pos.x == pointed_thing.under.x
		and pos.z == pointed_thing.under.z)
		or placer:get_look_pitch() > 0.45 then
		
		local placed_node = minetest.get_node(pos)
		placed_node.param2 = facedirutil.upsidedown(placed_node.param2)
		
		minetest.set_node(pos, placed_node)
	end
end

--- Gets the corresponding wallmounted value for the given facedir value.
--
-- @param facedir_id The facedir value/ID.
-- @return The wallmounted value/ID.
function facedirutil.to_wallmounted(facedir_id)
	if facedir_id == facedirutil.NEGATIVE_X then
		return wallmountedutil.NEGATIVE_X
	elseif facedir_id == facedirutil.NEGATIVE_Z then
		return wallmountedutil.NEGATIVE_Z
	elseif facedir_id == facedirutil.POSITIVE_X then
		return wallmountedutil.POSITIVE_X
	elseif facedir_id == facedirutil.POSITIVE_Z then
		return wallmountedutil.POSITIVE_Z
	end
	
	return wallmountedutil.NEGATIVE_Y
end

--- Gets the facedir for the given rotation as upside down.
--
-- @param facedir The facedir value.
-- @return The facedir value upside down.
function facedirutil.upsidedown(facedir)
	local upsidedown_facedir = facedir
	
	-- We need to rotate the node by 180 degrees for these values,
	-- this is because of how the rotation works.
	if upsidedown_facedir == facedirutil.POSITIVE_X
		or upsidedown_facedir == facedirutil.NEGATIVE_X then
		
		upsidedown_facedir = rotationutil.increment(upsidedown_facedir)
		upsidedown_facedir = rotationutil.increment(upsidedown_facedir)
	end
	
	return upsidedown_facedir + rotationutil.NEG_Y
end