physics: Add sanity checks and minor optimizations (#650)

- Throw error if an unsupported attribute is encountered.
- Throw errors for invalid function arguments.
- Optimize out attributes with a value of 1.

mods/other/physics/init.lua

@@ -1,6 +1,11 @@
 physics = {}
 
 local players = {}
+local default_overrides = {
+	speed   = 1,
+	jump    = 1,
+	gravity = 1
+}
 
 minetest.register_on_joinplayer(function(player)
 	players[player:get_player_name()] = {}
@@ -13,11 +18,7 @@ end)
 local function update(name)
 	assert(players[name])
 	local player = minetest.get_player_by_name(name)
-	local override = {
-		speed   = 1,
-		jump    = 1,
-		gravity = 1
-	}
+	local override = table.copy(default_overrides)
 
 	for _, layer in pairs(players[name]) do
 		for attr, val in pairs(layer) do
@@ -28,20 +29,40 @@ local function update(name)
 	player:set_physics_override(override)
 end
 
-function physics.set(pname, name, modifiers)
-	if not players[pname] then
+function physics.set(name, layer, modifiers)
+	-- Basic sanity checks
+	assert(
+		type(name) == "string" and type(layer) == "string" and type(modifiers) == "table",
+		"physics.set: Invalid function arguments!"
+	)
+
+	if not players[name] then
 		return
 	end
 
-	players[pname][name] = modifiers
-	update(pname)
+	for attr, val in pairs(modifiers) do
+		-- Throw error if an unsupported attribute is encountered
+		assert(default_overrides[attr], "physics: Unsupported attribute!")
+
+		-- Remove an attribute if its value is 1
+		if val == 1 then
+			modifiers[attr] = nil
+		end
+	end
+
+	players[name][layer] = modifiers
+	update(name)
 end
 
-function physics.remove(pname, name)
-	if not players[pname] then
+function physics.remove(name, layer)
+	-- Basic sanity checks
+	assert(type(name) == "string" and type(layer) == "string",
+		"physics.remove: Invalid function arguments!")
+
+	if not players[name] then
 		return
 	end
 
-	players[pname][name] = nil
-	update(pname)
+	players[name][layer] = nil
+	update(name)
 end