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local setmetatable = setmetatable
local pairs = pairs
local type = type
local table_sort = table.sort
return function (root)
local env = {root}
local is_table = {}
for key, value in pairs(root) do
if type(value) == 'table' then
is_table[key] = true
end
end
root._next = nil
root._cut = {}
local mt = { _env = env }
function mt:push()
env[#env+1] = { _next = env[#env], _cut = {} }
end
function mt:pop()
env[#env] = nil
end
function mt:cut(key)
env[#env]._cut[key] = true
end
function mt:__index(key)
local origin = env[#env]
if is_table[key] then
return setmetatable({}, {
__index = function (_, ckey)
local o = origin
while o do
local t = o[key]
if t and t[ckey] ~= nil then
return t[ckey]
end
o = not o._cut[key] and o._next
end
end,
__newindex = function (_, ckey, value)
local o = origin
if not o[key] then
o[key] = {}
end
o[key][ckey] = value
end,
__pairs = function ()
local o = origin
local tbl = {}
while o do
local t = o[key]
if t then
for k, v in pairs(t) do
if tbl[k] == nil then
tbl[k] = v
end
end
end
o = not o._cut[key] and o._next
end
return next, tbl
end,
})
else
local o = origin
while o do
if o[key] ~= nil then
return o[key]
end
o = not o._cut[key] and o._next
end
end
end
function mt:__newindex(key, value)
local o = env[#env]
if is_table[key] then
if type(o[key]) ~= 'table' then
o[key] = {}
end
if type(value) == 'table' then
for k, v in pairs(value) do
o[key][k] = v
end
else
error(('[env.%s] should be table, got [%s]'):format(key, value))
end
else
o[key] = value
end
end
function mt:__pairs()
local keys = {}
local cuted = {}
local result = {}
local o = env[#env]
while true do
for key in pairs(o._cut) do
cuted[key] = true
end
for key, value in pairs(o) do
if key == '_cut' or key == '_next' then
goto CONTINUE
end
if cuted[key] then
goto CONTINUE
end
if result[key] == nil then
keys[#keys+1] = key
if is_table[key] then
result[key] = {}
else
result[key] = value
end
end
if is_table[key] then
for k, v in pairs(value) do
if result[key][k] == nil then
result[key][k] = v
end
end
end
::CONTINUE::
end
o = o._next
if not o then
break
end
end
table_sort(keys)
local i = 0
return function ()
i = i + 1
local k = keys[i]
return k, result[k]
end
end
return setmetatable(mt, mt)
end
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