From e82440a096cf6a84a7ecbf3676b7337d9051a384 Mon Sep 17 00:00:00 2001
From: Starbeamrainbowlabs <sbrl@starbeamrainbowlabs.com>
Date: Wed, 10 Nov 2021 02:07:13 +0000
Subject: [PATCH] Add deep copy table function

---
 worldeditadditions/utils/tables/deepcopy.lua | 40 ++++++++++++++++++++
 worldeditadditions/utils/tables/init.lua     |  1 +
 2 files changed, 41 insertions(+)
 create mode 100644 worldeditadditions/utils/tables/deepcopy.lua

diff --git a/worldeditadditions/utils/tables/deepcopy.lua b/worldeditadditions/utils/tables/deepcopy.lua
new file mode 100644
index 0000000..e99b065
--- /dev/null
+++ b/worldeditadditions/utils/tables/deepcopy.lua
@@ -0,0 +1,40 @@
+
+
+-- 4. Supporting recursive structures.
+--
+-- The issue here is that the following code will call itself
+-- indefinitely and ultimately cause a stack overflow:
+-- 
+-- local my_t = {}
+-- my_t.a = my_t
+-- local t_copy = copy2(my_t)
+--
+-- This happens to both copy1 and copy2, which each try to make
+-- a copy of my_t.a, which involves making a copy of my_t.a.a,
+-- which involves making a copy of my_t.a.a.a, etc. The
+-- recursive table my_t is perfectly legal, and it's possible to
+-- make a deep_copy function that can handle this by tracking
+-- which tables it has already started to copy.
+--
+-- Thanks to @mnemnion for pointing out that we should not call
+-- setmetatable() until we're doing copying values; otherwise we
+-- may accidentally trigger a custom __index() or __newindex()!
+
+--- Deep clones a given table.
+-- @source	https://gist.github.com/tylerneylon/81333721109155b2d244
+-- @param	obj		table	The table to clone.
+-- @returns	table	A deep copy of the given table.
+local function deepcopy(obj, seen)
+    -- Handle non-tables and previously-seen tables.
+    if type(obj) ~= 'table' then return obj end
+    if seen and seen[obj] then return seen[obj] end
+  
+    -- New table; mark it as seen and copy recursively.
+    local s = seen or {}
+    local res = {}
+    s[obj] = res
+    for k, v in pairs(obj) do res[deepcopy(k, s)] = deepcopy(v, s) end
+    return setmetatable(res, getmetatable(obj))
+end
+
+return deepcopy
diff --git a/worldeditadditions/utils/tables/init.lua b/worldeditadditions/utils/tables/init.lua
index 75bf05c..f77cdbf 100644
--- a/worldeditadditions/utils/tables/init.lua
+++ b/worldeditadditions/utils/tables/init.lua
@@ -13,6 +13,7 @@ local wea = worldeditadditions
 wea.table = {
 	apply		= dofile(wea.modpath.."/utils/tables/table_apply.lua"),
 	contains	= dofile(wea.modpath.."/utils/tables/table_contains.lua"),
+	deepcopy	= dofile(wea.modpath.."/utils/tables/deepcopy.lua"),
 	filter		= dofile(wea.modpath.."/utils/tables/table_filter.lua"),
 	get_last	= dofile(wea.modpath.."/utils/tables/table_get_last.lua"),
 	makeset		= dofile(wea.modpath.."/utils/tables/makeset.lua"),