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Module:Buffer/sandbox

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--[[=============================
This Module was written by Alexander Zhikun He, also known as, User:Codehydro on the English Wikipedia

All methods were developed independently and any resemblance to other string buffer libraries would be coincidental.
Furthermore, many methods will not work when compiled by standard Lua libraries as they depend on behaviors unique to
the MediaMiki Scribunto mod, which, for example, has a getmetatable() method that always returns nil on non-tables.
https://www.mediawiki.org/wiki/Extension:Scribunto/Lua_reference_manual

Source code comments may be thin at some points because they are intended to be supplemented by the documentation page:
https://en.wikipedia.org/wiki/Module:Buffer/doc

Licensed under Creative Commons Attribution-ShareAlike 3.0 Unported License
https://en.wikipedia.org/wiki/Wikipedia:Text_of_Creative_Commons_Attribution-ShareAlike_3.0_Unported_License

https://en.wikipedia.org/wiki/Module:Buffer
https://en.wikipedia.org/wiki/User:Codehydro
============================= -- ]]

-- Performs type validation
local function Valid(v)
	if v and v ~= true then --reject nil/boolean; faster than 2 type() comparisons
		local str = tostring(v) --functions not filtered since unlikely passed by accident (Scribunto does not have userdata/thread types)
		--tostring(string-type) returns same ref; same refs compare faster than type()
		if str ~= v and str == 'table' then
			return rawget(v, 1) and table.concat(v)
		end
		--numbers are coerced to string per table.concat op; appending in string form saves ops on repeat concat
		if str ~= '' then
			return str
		end
	end
end

local MBpairs
local noOp = function() end
do
	local iMap, vMap, oMap, pIter, pOther, pFast, Next --Map
	local function init() -- init = noOp after first run
		function Next(t)
			return next, t -- slightly faster to do this than to use select()
		end

		function pIter(t, k)
			-- don't use rawget; accepting unmapped tables does not measurably affect performance.
			k = (iMap[t] or MBpairs(t, true) and iMap[t])[not k and 1 or vMap[t][k]]
			return k, t[k]
		end

		function pOther(t, k)
			-- comparison to nil because false is a valid key
			k = (oMap[t] or MBpairs(t, true) and oMap[t])[nil==k and 1 or vMap[t][k]]
			return k, t[k]
		end

		function pFast(t, k)
			-- mapless iterator; almost as fast as native ipairs; slight performance penalty when length not cached
			k = not k and 1 or k < (vMap[t] or #t) and k + 1 or nil
			return k, t[k]
		end

		local mk = {__mode = 'k'} -- use mode 'k'; found that mode 'kv' sometimes garbage collects maps mid-loop (may not error because iterators auto re-map, but that's expensive)
		init = noOp
		iMap = setmetatable({}, mk) -- numeric keys
		vMap = setmetatable({}, mk) -- next key
		oMap = setmetatable({}, mk) -- non-numeric keys
	end

	function MBpairs(t, ...) -- pairs always iterates in order
		local iter, ex = ...
		init()
		iter = iter == nil
		if iter and not oMap[t] and ex==nil and rawget(t, 1)~=nil and next(t, #t)==nil then--while possible to miss keys, more thorough check would negate the benefit of pFast
			vMap[t] = #t return pFast, t, nil
		elseif ... or not vMap[t] or select('#', ...) ~= 1 then
			local ti, tn, to, n = {}, {}, {}, #t --reduces table lookups
			iMap[t], vMap[t], oMap[t] = ti, tn, to
			for k = 1, n do
				--stage one avoids number type checking op in stage two for most numeric keys
				ti[k], tn[k] = k, k + 1
			end
			for k in (ex or Next)(t) do
				if not tn[k] then
					table.insert(tonumber(k) ~= k and to or ti, k)
				end
			end
			if #ti ~= n then
				table.sort(ti)
				for k = 1, #ti do
					-- somewhat wasteful, but trying to avoid overwriting can be even more expensive
					tn[ti[k]] = k + 1
				end
			end
			for k = 1, #to do
				tn[to[k]] = k + 1
			end
		end
		return iter and pIter or oMap[t] and pOther or noOp, t --noOp for mapless
	end
end

local parent, rawkey, spec
do
	--new scope for variables not reused outside (reduces number of var names that need to checked outside of scope)
	--shared meta for Buffer parent property, raw mode, and specialized functions
	local mkv = {
		__mode = 'kv',
		__call = function(t,k,v)
			t[k] = v
			return k
		end
	}
	--shared meta less memory
	parent = setmetatable({}, mkv)
	rawkey = setmetatable({}, mkv)
	spec = setmetatable({}, mkv)
end

local MB, MBi, MBmix, buffHTML, gfuncs, noCache, Element
do
	--minimize number of locals per scope to reduce time spent sifting through irrelevant variable names
	local _stream
	do
		local stream --keep stream near top of scope

		local function init(f) --init = noOp after first run
			local function each(self, ...)
				for k = 1, select('#', ...) do
					k = Valid(select(k, ...)) -- slightly faster than table.insert(self, (Valid(select(k, ...))))
					if k then
						table.insert(self, k)
					end
				end
				return self
			end
			init = noOp
			stream = {
				__call = function(t, v)
					v = v and Valid(v)
					--last_concat cleared before entering stream mode
					return v and table.insert(t, v) or t
				end,
				__index = function(t, i)
					--no table look up minimizes resources to retrieve the only stream function
					return i == 'each' and each or MB.__index(t, i) and setmetatable(t, MB)[i]
				end,
				__tostring = function(t)
					return setmetatable(t, MB)()
				end
			}
			for k, v in next, MB do
				stream[k] = stream[k] or v
			end
			setmetatable(stream, getmetatable(MB))
		end

		function _stream(self, ...)
			init()
			self.last_concat = nil
			return setmetatable(self, stream):each(...)
		end
	end

	-- helper for :getParent()-like methods (including getBuffer which does not return a parent)
	local function isMBfunc(Buffer, s, ...)
		--eventually should figure out to make this work for :getHTML which is very similar
		return s and
			(
				select('#', ...) == 0 and
				(
					--unprefixed function names append as a string
					not rawkey[s] and
					tostring(s):match('^_.*') and
					MB.__index(Buffer, s) and
					MB.__index(Buffer, s)(Buffer) or
					MBmix(Buffer, s)
				) or assert( --getParent is a one-way trip so one-time assert not expensive
					MB.__index(Buffer, s),
					('" %s " does not match any available Module:Buffer function'):format(s)
				)(Buffer, ...)
			) or Buffer
	end

	-- helper for :_out and :_str
	local function MBselect(n, ...)
		local n, seps = n - 1, {select(2, ...)}
		if type(seps[n])=='table' then 
			if buffHTML and rawget(seps[n], buffHTML) then
				return ...
			end
			setmetatable(seps, {
				__index = setmetatable(seps[n], {
					__index = function(t)
						return rawget(t, 1)
					end
				})
			})[n] = nil
		end
		return ..., seps
	end

local _inHTML
do
	local lastBuffer, lastHTML
	local function init(...) -- init replaced and new version called on return
		local create, mwFunc = mw.html.create
		do
		local mwHTMLmeta = getmetatable(create())
		buffHTML, mwFunc, _inHTML = setmetatable(mw.clone(mwHTMLmeta), getmetatable(MB)), mwHTMLmeta.__index -- buffHTML declared near top of module; remove _inHTML from outer scope
		function init(nodes, ...)
			local name, args, tag = select(... and type(...) == 'table' and 1 or 2, nil, ...)
			tag = create(Valid(name), args)
			if nodes then
				table.insert(nodes, tag.parent and tag or rawset(tag, 'parent', parent[nodes]))
			end
			if args then
				local a, b = args.selfClosing, args.parent
				args.selfClosing, args.parent = nil
				if next(args) then
					Element._add(parent(tag.nodes, tag), args)
				end
				args.selfClosing, args.parent = a, b -- in case args is reused
			end
			return tag
		end
		for k, v in next, {[mw] = mwHTMLmeta,
			__call = function(h, v)
				return MBmix(spec[h.nodes] and h.nodes or spec(setmetatable(parent(h.nodes, h), MB), Element), v)
			end,
			__concat = false, -- false means take from MB
			__eq = false
		} do
		buffHTML[k] = v or MB[k]
	end
end

local nonSelf, BHi = {tag = true,done = true,allDone = true}, buffHTML.__index
do
	local g
	g = {__index = function(t, i)
		if gfuncs and gfuncs[i] then
			g.__index, gfuncs = gfuncs
			return g.__index[i]
		end
	end}
	setmetatable(nonSelf, g)
	setmetatable(BHi, g)
end
for k in next, nonSelf do
	-- any HTML objects returned by these funcs will be granted Module:Buffer enhancements
	local func = mwFunc[k]
	BHi[k] = function(t, ...)
		local HTML = func(t, ...)
		return parent[HTML] and HTML or setmetatable(parent(HTML, t), buffHTML)
	end
end
do
	local function joinNode(HTML, sep)
		local nodes, join = HTML.nodes
		if noCache and rawkey[sep] or Valid(sep) then
			join, HTML.nodes = tostring(rawset(HTML, 'nodes', {MB.__call(nodes, sep)})), nodes
		end
		return join or tostring(HTML)
	end
	for k, v in next, {
		getParent = function(HTML, ...)
			lastHTML = HTML
			return MBi.getParent(HTML:allDone(), ...)
		end, -- return to Buffer that created the HTML tree
		getBuffer = function(HTML, ...)
			lastHTML = HTML
			return isMBfunc(lastBuffer, ...)
		end, -- return to last used
		killParent = function(HTML, ...)
			MBi.killParent(HTML:allDone(), ...)
			return HTML
		end,
		_out = function(HTML, ...)
			if ... == 0 then
				MBi._out(HTML.nodes, ...)
				return HTML
			end
			lastHTML, HTML = HTML, HTML:allDone()
			local n, ops, seps = select('#', ...)
			if n > 1 then
				local ops, seps = MBselect(n, ...)
				return parent[HTML]:_in(joinNode(HTML, rawget(seps, 0))):_out(ops, rawset(seps, buffHTML, true))
			end
			return parent[HTML]:_(joinNode(HTML, ...))
		end,
		_str = function(HTML, ...)
			-- does not set lastHTML
			if ... == 0 then
				return joinNode(HTML, select(2, ...))
			end -- passing 0 strings without calling allDone()
			local HTML, n = HTML:allDone(), select('#', ...)
			if n > 1 then
				local ops, seps = MBselect(n, ...)
				return parent[HTML]:_in(joinNode(HTML, rawget(seps, 1))):_str(ops, rawset(seps, buffHTML, true))
			end
			return joinNode(HTML, ...)
		end,
		_parent = function(HTML, ...)
			table.insert(HTML.nodes, parent[HTML:allDone()]:_str(...))
			return HTML
		end
	} do
	BHi[k] = v
end
	end
	do
		local htmlArg, skip, outFuncs = {parent = true,selfClosing = true,tagName = true}, {}
		do
			local out local function func(nodes, ...)
				return out(parent[nodes], ...)
			end
			outFuncs = setmetatable({
				tag = function(nodes, ...)
					return parent(setmetatable(init(nodes, ...), buffHTML), parent[nodes])
				end,
				done = function(b, ops)
					b = parent[b] 
					while b.parent and ops ~= 0 do
						b, ops = b.parent, ops and ops - 1 or 0
					end
					return b
				end
			}, {__index = function(nodes, i)
				if rawget(BHi, i) then
					out = BHi[i]
					return func
				end -- rawget to exclude globals
			end})
		end
		Element = {
			_add = function(nodes, t)
				for k, v in MBpairs(t), t, skip[t] do
					(v ~= true and MBmix or noOp)(nodes, v)
				end
				local HTML = parent[nodes] for k, v in MBpairs(t, false) do
				if htmlArg[k] then
					HTML[k] = v
				elseif v and v ~= true then
					if nonSelf[k] then
						if k == 'tag' then
							if type(v) == 'table' then
								skip[v], k = 1, rawset(create(Valid(v[1])), 'parent', HTML)
								Element._add(spec(parent(k.nodes, k, table.insert(nodes, k)), Element), v)
								if k.selfClosing then
									k.nodes = nil else spec[k.nodes], parent[k.nodes] = nil
								end -- free memory/reduce clutter; parent ref will auto-unset when k.nodes is nil
								if not k.tagName then
									k.styles, k.attributes = nil
								end
							else table.insert(nodes, create(v))
							end
						elseif mwFunc[k] then
							if k == 'done' and tonumber(v) ~= v and v[1] and tonumber(v[1]) == v[1] then
								skip[v] = 1
							end
							MBmix(outFuncs[k](nodes, skip[v] and v[1]).nodes, v)
						elseif v[1] or v[2] then
							k = MBi[k](nodes, unpack(v, 1, rawset(skip, v, k == '_B' and 1 or 2)[v]))
							Element._add(getmetatable(k) and rawget(k, 'nodes') or k, v) -- if k is not a table, then v should not contain any extra keys or this may error.
						else MBi[k](nodes, v)
						end -- k probably == '_G' or '_R'
					elseif mwFunc[k] then
						if type(v) ~= 'table' or rawget(v, 'nodes') then
							mwFunc[k](HTML, v)
						else
							local css = k == 'css'
							for x, y in MBpairs(v, true) do
								(y and y ~= true and mwFunc[k] or noOp)(HTML, css and x:gsub('_', '-') or x, y)
							end -- iterate non-numbers first
							for _, y in MBpairs(v, nil) do
								(y and y ~= true and mwFunc[k] or noOp)(HTML, y)
							end -- don't bother with gsub since text must be quoted anyhow
						end
					elseif rawget(Element, k) or rawget(MBi, k) then
						if tonumber(v) == v or v[1] == nil or getmetatable(v) then
							(Element[k] or MBi[k])(nodes, v) -- v is probably string-able object, or a table to be handled by :_all
						else (Element[k] or MBi[k])(nodes, unpack(v, 1, table.maxn(v)))
						end -- v is definitely a table
					else mwFunc.css(HTML, k:gsub('_', '-', 1), tostring(v))
					end -- oddly enough, :_add clocked its fastest runtime after adding auto-gsub as a feature
					skip[v] = nil
				end
			end
			return nodes
		end
	}
	local tempMeta = {mode = 'v', copy = {styles = true,attributes = true}}
	function tempMeta.__index(t, i)
		return tempMeta.copy[i] and rawset(t, i, MBi._cc(false, 0, t.orig[i]))[i] or t.orig[i]
	end
	rawkey[setmetatable(Element, {__index = outFuncs, __concat = function(Element, v)
		return setmetatable({nodes = spec({}, Element),orig = parent[v]}, tempMeta)
	end})] = math.huge
end

function MBi:getHTML(...)
	lastBuffer = self
	if ... then
		if select('#', ...) == 1 then
			return not rawkey[s] and tostring(...):match'^_' and BHi[...] and BHi[...](lastHTML) or lastHTML(...)
		else
			return assert(BHi[...], ('" %s " does not match any mw.html or Buffer-mw.html function'):format(tostring(...)))(lastHTML, select(2, ...))
		end
	end
	return lastHTML
end

function MBi:_html(...)
	return MBi._(self, lastHTML, select(spec[self] == Element and select('#', ...) == 0 and 1 or 2, true, ...))
end

return init(...)
		end
		function _inHTML(self, ...)
			local HTML = init(nil, ...)
			if HTML.selfClosing and spec[self] == Element then
				self.last_concat = table.insert(self, HTML)
				return self
			end
			lastBuffer, lastHTML = self, setmetatable(parent(HTML, self), buffHTML) -- set after 'args' table processed by :_add
			return HTML
		end
	end
	local _var, unbuild do
	local prev, rebuild
	local function init(...) -- init replaced before return
		local function pick(b, v)
			return b and table.insert(b, v) or v
		end
		local function c(a, num)
			return rawset(a.a or a, 0, a[0] and a[0] + a.c or num and a[1] or a[1]:byte())[0]
		end
		local same, build, alt = {__tostring = function(a, b)
			return a.a[0] and pick(b, a.a.string and string.char(a.a[0]) or a.a.table and a.a[1][a.a[0]] or a.a[0])
		end}, {
		__index = {c = 1},
		__tostring = function(t)
			return t:_build()
		end,
		table = function(a, b)
			local i = next(a[1], a[0]) or a[0] == #a[1] and next(a[1])
			return pick(b, rawset(a.a or a, 0, i)[1][i])
		end, -- change rate (a.c) ignored since users control the table's contents
		number = function(a, b)
			return pick(b, c(a, true))
		end,
		string = function(a, b)
			return pick(b, string.char(c(a)))
		end
	}, {__index = function(a, i)
		return a.a[i]
	end, __tostring = function(a, b)
	return (rawget(a, 0) and a[0] == tostring(a[0]) and rawset(a, 0, a[0]:byte()) or a).a._build(a, b) end}
	local function shift(t, c)
		t[0] = t[0] and t[0] + c or t:_build() and t[0] - t.c + c
		if t.table then
			t[0] = (t[0] - 1) % #t[1] + 1
		end
	end
	function rebuild(...)
		local v, c = ...
		if v or select('#', ...) == 0 then
			if v and not c then
				return prev
			end
			local meta, c = select(v and 1 or 3, alt, c, same, 0)
			return setmetatable({a = prev, _build = meta.__tostring, c = c}, meta)
		elseif v == nil then
			-- no-op
		elseif c then
			shift(prev, c) -- v == false
		else prev:_build()
		end
	end
	init, noCache = function(v, c)
		prev = setmetatable({v, c = c, _build = build[type(v)] or v, [type(v)] = true, alt = {}}, build)
		return prev
	end, true
	return init(...)
end

function unbuild(sep)
	for k, v in MBpairs(sep, nil) do
		k = getmetatable(v) if k and (k == build or k == alt) then
		shift(v.a or v, -v.c)
	end
end
		end
		function _var(self, ...)
			local obj if ... and ... ~= true then
			obj = init(...)
		elseif prev then
			if ... ~= false then
				obj = rebuild(...)
			else rebuild(...)
			end
		end
		return obj and MBi._(self, obj, nil, true) or self
	end
end

local lib; MBi = setmetatable({stream = _stream,
_inHTML = _inHTML,
_var = _var,
_ = function(self, v, ...)
	local at, raw = select(select('#', ...) == 1 and ... == true and 1 or 2, nil, ...)
	if raw then
		rawkey[self] = math.huge else v = Valid(v)
	end
	if v or raw then
		if at or rawkey[self] then
			raw = #self
		end -- if length increases by more than one after table.insert, then set rawkey[self] = math.huge; rawkey[self] may be equal to a previous 'at'
		at, self.last_concat = at and (tonumber(at) ~= at and raw + at or at)
		table.insert(self, select(at and 1 or 2, at, v))
		if at and at < 0 or raw and #self - raw > 1 then
			rawkey[self] = math.huge elseif at and #self == raw then rawkey[self] = rawkey[self] and math.max(rawkey[self], at) or at
		end
	end -- above line looks bizarre because one table.insert op may make length jump from 0 to 8: local wtf = {[2] = 2,[4] = 4,[8] = 8}mw.log(#wtf,table.insert(wtf,1),#wtf)
	return self
end,
_nil = function(self, at, ...)
	if ... ~= true and ... ~= false then
		-- faster than type(...) ~= 'boolean'
		if not at or at == '0' then
			self[#self] = ... if ... then
			rawkey[self] = math.huge
		end
	else
		local n, v = tonumber(at), ...
		if n ~= at then

			if n then
				n = #self + at
			elseif at ~= true and select('#', ...) == 0 then
				v, n = at, #self
			end
		end
		if n then

			if v == nil and n > 0 then
				table.remove(self, n)
			else self[math.floor(n)], rawkey[self] = v, math.huge
			end -- floor position for consistency with Table library
		end
	end
	self.last_concat = nil
end
return self
		end,
		_all = function(self, t, valKey)
			for k, v in MBpairs(t) do
				MBmix(self, v, valKey)
			end
			for k, v in valKey and MBpairs(t, false) or noOp, t do
				if tonumber(v) then
					MBi._(self, k, v) -- self not always a buffer
				elseif rawget(MBi, k) and v and v ~= true then
					if v[1] == nil or getmetatable(v) then
						MBi[k](self, v)
					else MBi[k](self, unpack(v, 1, table.maxn(v)))
					end
				end
			end
			return self
		end,
		_str = function(t, ...)
			local n = select('#', ...)
			if n > 1 then
				local k, ops, seps, r = 2, MBselect(n, ...)
				r = MB(t(seps[1]))
				while parent[t] and ops > 1 and r:_(parent[t](seps[k]), 1) do
					t, k, ops = parent[t], k + 1, ops - 1
				end
				return table.concat(r, seps[k] or nil)
			end
			return MB.__call(t, ...)
		end,
		_in = function (self, ...)
			return parent(MB(...), self)
		end,
		_out = function(t, ...)
			if ... == 0 then
				return parent(t, parent[t], MBi._cc(t, t, MB.__call(t, (select(2, ...))), getmetatable(t)))
			end -- love how :_cc needed nothing new to implement this *self pat on back*
			local n = select('#', ...)
			if n > 1 then
				local k, ops, seps = 1, MBselect(n, ...)
				while parent[t] and ops > 0 do
					t, k, ops = parent[t]:_(t(seps[k])), k + 1, ops - 1
				end
			elseif parent[t] then
				return parent[t]:_(t(...))
			end
			return t
		end,
		_cc = function(self, clear, copy, meta)
			if clear then
				if rawequal(clear, copy) then
					return self, spec[MBi._cc] and setmetatable(spec[MBi._cc], MB) -- rawequal to avoid re-string via __eq in case both are different Buffer objects
				elseif copy == true then
					copy = self
				end
				if clear ~= 0 then
					assert(type(clear) == 'table', debug.traceback('Buffer:_cc can only "clear" tables. Did you forget to call with a colon?', 2)) -- errors can be hard to trace without this
					for k in self and next or noOp, clear do
						rawset(clear, k, nil)
					end
				else
					return MBi._cc(false, {unpack(copy)}, copy)
				end -- copy length w/o empty strings; recursion to avoid self = false causing garbage collection (non-weak child may exist)
				if self == false or copy and type(copy) == 'table' then
					-- self == false means copy is a table (saves a type op for recursive calls)
					meta = meta or getmetatable(copy)
					if self and #copy > 1 then
						-- preserves length with empty strings; developed from studying http://www.lua.org/source/5.1/ltable.c.html		
						local n, null, i, e = #copy, {}, math.ldexp(2, select(2, math.frexp(#copy)) - 2)
						e, spec[MBi._cc], parent[null] = i - 1, null, clear
						for k = 1, e do
							table.insert(clear, false)
						end
						while i <= n do
							table.insert(clear, i, '') i, null[i] = i + math.ldexp(2, select(2, math.frexp(n - i)) - 2), ''
						end
						for k = 1, e do
							rawset(clear, k, nil)
						end
					end
					for k, v in next, copy do
						rawset(clear, k, type(v) == 'table' and MBi._cc(false, 0, v) or v)
					end
				elseif copy then
					rawset(clear, 1, (Valid(copy)))
				end
				rawkey[setmetatable(clear, meta)], parent[clear] = rawkey[copy], parent[copy]
			end
			return self and rawset(self, 'last_concat', nil) or clear
		end,
		_parent = function(self, ...)
			return parent[self] and MBi._(self, parent[self]:_str(...)) or self
		end,
		getParent = function(self, ...)
			return isMBfunc(parent[self] or parent[parent(self, setmetatable({}, MB))], ...)
		end,
		killParent = function(self, ...)
			return parent[self] and isMBfunc(parent[self], ...) and parent(self) or self
		end,
		_build = function(self, t)
			table.insert(t, self())
		end, -- for compatibility with mw.html:node()
		last_concat = false -- prevent library check
	}, {__index = function(t, i)
		-- import string, mw.text, and mw.ustring libraries on an as-needed basis
		local func = string[i] or mw.text[i] or mw.ustring[i] or type(i) == 'string' and mw.ustring[i:match'^u(.+)'] if func then
		lib	= lib or function (s, f, ...)
			if parent[s] and next(s) == nil then
				return s:_((f(tostring(parent[Element and (spec[s] == Element and s:allDone() or spec[parent[s]] == Element and parent[s]) or s]), ...)))
			end
			return f(tostring(s), ...) -- not using ternary/logical operators here to allow multiple return values
		end
		return rawset(t, i, i:match'^u?gsub' and function(self, p, r, ...)return lib(self, func, p, r or '', ...)end -- Why are ugsub/gsub special? because empty strings are against my religion!
		or function(self, ...)return lib(self, func, ...)end)[i]
	end
end})
end

function MBmix(t, v, ...)
	return v and ((type(v) ~= 'table' or getmetatable(v)) and MBi._(t, v) or (select('#', ...) == 0 and spec[t] and spec[t]._add or MBi._all)(t, v, ...)) or t
end -- :_all always passes two args

local _G, new_G = _G -- localize _G for console testing (console _G ~= module _G)
return setmetatable({__index = function(t, i)
	return spec[t] and spec[t][i] or MBi[i]
end,
__call = function(t, ...)
	local rawsep, sep, i, j, raw = noCache and rawkey[...] and ..., ...
	if i or j or rawsep or Valid(sep) then
		raw, sep, i, j = rawkey[spec[t]] or rawkey[t], rawsep or Valid(sep), i and (i ~= tonumber(i) and i + #t or i), j and (j ~= tonumber(j) and j + #t or j)
		if rawsep or raw and (raw >= (j or #t) or i < 1) then
			raw, i, j = {}, i and math.floor(i), j and math.floor(j) -- floor for consistency with table.concat(t, sep, i, j), which ignores decimals
			raw.lc, t.last_concat = t.last_concat -- temporarily unset last_concat to prevent disqualification from mapless iteration
			for k, v in MBpairs(t) do
				if raw[1] or not i or k >= i then
					if j and k > j then break
					end
					if raw.s then
						raw.s = table.insert(raw, tostring(sep))
					end -- if sep contains v and v is a Buffer-variable, sep must be strung before v
					k = Valid(v) if k then
					raw.s = rawsep or sep and raw[1] and table.insert(raw, sep)
					table.insert(raw, k)
				end
			end
		end
		if rawsep and not raw.s then
			raw[#raw] = unbuild(sep)
		end -- unbuild rawsep if final index in t was invalid
		t.last_concat = raw.lc
		return table.concat(raw)
	end
	return table.concat(t, sep, i and math.max(i, 1), j and math.min(j, #t))
end
return MB.__tostring(t)
	end,
	__tostring = function(t)
		if t.last_concat then
			return t.last_concat
		end
		local r = rawkey[spec[t]] or rawkey[t]
		r = table.concat(r and r >= #t and MBi._all({}, t) or t)
		return (noCache or rawset(t, 'last_concat', r)) and r
	end,
	__concat = function(a, b)
		if buffHTML then
			for k = 1, 2 do
				local v = select(k, a, b) -- faster than for k, v in pairs{a, b} do
				if v and spec[v] and spec[v] == Element then
					if parent[v].selfClosing then
						if rawequal(a, b) then
							return (not noCache or parent[v].tagName) and v:_str(0):rep(2) or v:_str(0)..v:_str(0)
						end -- rawequal avoids premature tostring of Buffer:_var objects;
						b, a = select(k, b, parent[v], a)
					else local temp = Element .. v --helper method; returns a mirror of parent[v]
						MBmix(MBmix(parent(temp.nodes, temp), a), k == 1 and spec[b] == Element and parent[b] or b)
						return buffHTML.__tostring(setmetatable(temp, {__index = parent[v], __mode = 'v'})) -- switch from tempMeta to avoid MBi._cc op of styles/attributes
					end
				end
			end
		end
		return table.concat(MBmix(MBmix({}, a), b))
	end,
	__pairs = MBpairs,
	__ipairs = MBpairs,
	__eq = function(a, b)
		return tostring(a) == tostring(b)
	end -- avoid a == b in this module; use rawequal(a,b) when they may be different Buffers (premature tostring waste ops and is bad for Buffer:_var)
}, {__tostring = function()return''end,
__call = function(self, ...)
	MB = MB or self
	if new_G then
		if ... and _G and ... == _G then new_G = ...
		end
	elseif ... and (... == _G or type(...) == 'table' and (...)._G == ...) then
		local Nil, mG = {}, (...):getmetatable() or (...):setmetatable{}:getmetatable()
		new_G, _G, gfuncs = ..., ..., { -- gfuncs stored for Buffer:_inHTML; new_G is a is a Module:Buffer local declared just before the final return statement.
		_G = function(self, i, ...)
			local X, save = rawget(new_G, i), select('#', ...) == 0 and self or ...
			if i and i ~= true and not (X and save and rawequal(X, save)) and rawset(new_G, i, save) and (X ~= nil or save == nil and new_G[i] ~= nil) then
				-- rawequal in case X is another buffer
				local mG = getmetatable(new_G) or {__call = mG.__call}
				if mG.__index then
					pcall(rawset, mG.__index, i, X)
				else mG.__index = setmetatable(new_G, mG) and {[i] = X}
				end
			end
			return self, ... -- avoiding __eq with rawequal(self,save) is overkill since buffers can self-save without being passed as save
		end,
		_R = function(self, i, v, m)
			if i ~= 'new_G' then
				if i and i ~= true then rawset(new_G, i , v)
				end
			elseif not v or v == true or v._G ~= _G then
				new_G = setmetatable(v ~= true and v or {}, {__call = mG.__call, __index = v ~= true and m ~= true and (m or new_G) or nil})
			else new_G, (not m and (m ~= nil or v == new_G) and Nil or getmetatable(v)).__index = v, m ~= true and (m or new_G) or nil
			end -- setting Nil.__index is noOp
			return self
		end,
		_2 = function(self, ...)
			if new_G[...] ~= nil then
				return new_G[...]
			end -- higher priority so Buffer:_G('new_G', ...) can prevent an overwrite
			if ... == 'new_G' then
				return rawset((select('#', ...) ~= 1 and MBi._R(new_G, ...) or new_G), '_G', _G)
			end
			return select(select('#', ...) == 1 and 1 or 2, self:_G(...)) --return only one value; 'return select(2, self:_G(...)) or self' doesn't work for returning nil
		end,
		_B = function(self, v)
			return v or v == nil and Nil
		end
	} for k, v in next, gfuncs do
	MBi[k] = v
end 
setmetatable(Nil,{__concat = MB.__concat,__newindex = noOp,__call = noOp,__tostring = noOp,__metatable = MB,__index = setmetatable({_B = MBi._B,_ = function()return Nil
end,last_concat = ''},
{__index = function(t,i)return (MBi[i] or i and not tonumber(i)) and t._ or nil
end})})
function mG.__call(G, k, ...)
	return (k._G or G.type(k) == 'table') and (G.select('#', ...) ~= 1 and G.rawset(k, ...) or G:rawset(..., k) and k) or G:rawset(k, (...)) and ...
end
		end
		local new = setmetatable({}, self)
		if ... and (...) == new_G then
			return select(2, ...) and MBmix(new:_G((select(2, ...))), select(3, ...)) or new
		end
		return ... and MBi._(new, ...) or new
	end,
	__index = function(t, i)
		MB = MB or t
		return MBi[i] and function(...)
			return MBi[i](setmetatable({}, t), select(... == t and 2 or 1,...))
		end
	end
})
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