From 9904be916012ffdbb031dd5dcbab706d50bbcdfc Mon Sep 17 00:00:00 2001
From: cheapie <no-email-for-you@example.com>
Date: Sun, 21 Mar 2021 00:56:38 -0500
Subject: [PATCH] Add library support to Luacontrollers This allows mods to
 provide their own libraries that can be accessed from within a Luacontroller,
 for example to make working with advanced digilines peripherals somewhat
 easier. Libraries can be added to the mesecon.luacontroller_libraries table,
 and then the code running in the Luacontroller can use require() to request
 one. require() will return nil if the library is not present.

---
 mesecons/util.lua               | 19 +++++++++++++++++++
 mesecons_luacontroller/init.lua | 12 ++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/mesecons/util.lua b/mesecons/util.lua
index 3cdeb64..d5d42ef 100644
--- a/mesecons/util.lua
+++ b/mesecons/util.lua
@@ -193,6 +193,25 @@ function mesecon.tablecopy(obj) -- deep copy
 	return obj
 end
 
+-- Performs a deep copy of a table, changing the environment of any functions.
+-- Adapted from the builtin table.copy() function.
+function mesecon.tablecopy_change_env(t, env, seen)
+	local n = {}
+	seen = seen or {}
+	seen[t] = n
+	for k, v in pairs(t) do
+		if type(v) == "function" then
+			local newfunc = v
+			setfenv(newfunc, env)
+			n[(type(k) == "table" and (seen[k] or mesecon.tablecopy_change_env(k, env, seen))) or k] = newfunc
+		else
+		n[(type(k) == "table" and (seen[k] or mesecon.tablecopy_change_env(k, env, seen))) or k] =
+			(type(v) == "table" and (seen[v] or mesecon.tablecopy_change_env(v, env, seen))) or v
+		end
+	end
+	return n
+end
+
 -- Returns whether two values are equal.
 -- In tables, keys are compared for identity but values are compared recursively.
 -- There is no protection from infinite recursion.
diff --git a/mesecons_luacontroller/init.lua b/mesecons_luacontroller/init.lua
index 1c411dd..44880c9 100644
--- a/mesecons_luacontroller/init.lua
+++ b/mesecons_luacontroller/init.lua
@@ -459,6 +459,16 @@ local function get_digiline_send(pos, itbl, send_warning)
 	end
 end
 
+mesecon.luacontroller_libraries = {}
+
+local function get_require(env)
+	return function(name)
+		if mesecon.luacontroller_libraries[name] then
+			return mesecon.tablecopy_change_env(mesecon.luacontroller_libraries[name],env)
+		end
+	end
+end
+
 local safe_globals = {
 	-- Don't add pcall/xpcall unless willing to deal with the consequences (unless very careful, incredibly likely to allow killing server indirectly)
 	"assert", "error", "ipairs", "next", "pairs", "select",
@@ -546,6 +556,8 @@ local function create_environment(pos, mem, event, itbl, send_warning)
 	for _, name in pairs(safe_globals) do
 		env[name] = _G[name]
 	end
+	
+	env.require = get_require(env)
 
 	return env
 end