local n, v = "serpent", "0.302" -- (C) 2012-18 Paul Kulchenko; MIT License
local c, d = "Paul Kulchenko", "Lua serializer and pretty printer"
local snum = {
	[tostring(1 / 0)] = "1/0 --[[math.huge]]",
	[tostring(-1 / 0)] = "-1/0 --[[-math.huge]]",
	[tostring(0 / 0)] = "0/0",
}
local badtype = { thread = true, userdata = true, cdata = true }
local getmetatable = debug and debug.getmetatable or getmetatable
local pairs = function(t)
	return next, t
end -- avoid using __pairs in Lua 5.2+
local keyword, globals, G = {}, {}, (_G or _ENV)
for _, k in ipairs({
	"and",
	"break",
	"do",
	"else",
	"elseif",
	"end",
	"false",
	"for",
	"function",
	"goto",
	"if",
	"in",
	"local",
	"nil",
	"not",
	"or",
	"repeat",
	"return",
	"then",
	"true",
	"until",
	"while",
}) do
	keyword[k] = true
end
for k, v in pairs(G) do
	globals[v] = k
end -- build func to name mapping
for _, g in ipairs({ "coroutine", "debug", "io", "math", "string", "table", "os" }) do
	for k, v in pairs(type(G[g]) == "table" and G[g] or {}) do
		globals[v] = g .. "." .. k
	end
end

local function s(t, opts)
	local name, indent, fatal, maxnum = opts.name, opts.indent, opts.fatal, opts.maxnum
	local sparse, custom, huge = opts.sparse, opts.custom, not opts.nohuge
	local space, maxl = (opts.compact and "" or " "), (opts.maxlevel or math.huge)
	local maxlen, metatostring = tonumber(opts.maxlength), opts.metatostring
	local iname, comm = "_" .. (name or ""), opts.comment and (tonumber(opts.comment) or math.huge)
	local numformat = opts.numformat or "%.17g"
	local seen, sref, syms, symn = {}, { "local " .. iname .. "={}" }, {}, 0
	local function gensym(val)
		return "_"
			.. (
				tostring(tostring(val)):gsub("[^%w]", ""):gsub(
					"(%d%w+)",
					-- tostring(val) is needed because __tostring may return a non-string value
					function(s)
						if not syms[s] then
							symn = symn + 1
							syms[s] = symn
						end
						return tostring(syms[s])
					end
				)
			)
	end
	local function safestr(s)
		return type(s) == "number" and tostring(huge and snum[tostring(s)] or numformat:format(s))
			or type(s) ~= "string" and tostring(s) -- escape NEWLINE/010 and EOF/026
			or ("%q"):format(s):gsub("\010", "n"):gsub("\026", "\\026")
	end
	local function comment(s, l)
		return comm and (l or 0) < comm and " --[[" .. select(2, pcall(tostring, s)) .. "]]" or ""
	end
	local function globerr(s, l)
		return globals[s] and globals[s] .. comment(s, l)
			or not fatal and safestr(select(2, pcall(tostring, s)))
			or error("Can't serialize " .. tostring(s))
	end
	local function safename(path, name) -- generates foo.bar, foo[3], or foo['b a r']
		local n = name == nil and "" or name
		local plain = type(n) == "string" and n:match("^[%l%u_][%w_]*$") and not keyword[n]
		local safe = plain and n or "[" .. safestr(n) .. "]"
		return (path or "") .. (plain and path and "." or "") .. safe, safe
	end
	local alphanumsort = type(opts.sortkeys) == "function" and opts.sortkeys
		or function(k, o, n) -- k=keys, o=originaltable, n=padding
			local maxn, to = tonumber(n) or 12, { number = "a", string = "b" }
			local function padnum(d)
				return ("%0" .. tostring(maxn) .. "d"):format(tonumber(d))
			end
			table.sort(k, function(a, b)
				-- sort numeric keys first: k[key] is not nil for numerical keys
				return (k[a] ~= nil and 0 or to[type(a)] or "z") .. (tostring(a):gsub("%d+", padnum))
					< (k[b] ~= nil and 0 or to[type(b)] or "z") .. (tostring(b):gsub("%d+", padnum))
			end)
		end
	local function val2str(t, name, indent, insref, path, plainindex, level)
		local ttype, level, mt = type(t), (level or 0), getmetatable(t)
		local spath, sname = safename(path, name)
		local tag = plainindex and ((type(name) == "number") and "" or name .. space .. "=" .. space)
			or (name ~= nil and sname .. space .. "=" .. space or "")
		if seen[t] then -- already seen this element
			sref[#sref + 1] = spath .. space .. "=" .. space .. seen[t]
			return tag .. "nil" .. comment("ref", level)
		end
		-- protect from those cases where __tostring may fail
		if type(mt) == "table" and metatostring ~= false then
			local to, tr = pcall(function()
				return mt.__tostring(t)
			end)
			local so, sr = pcall(function()
				return mt.__serialize(t)
			end)
			if to or so then -- knows how to serialize itself
				seen[t] = insref or spath
				t = so and sr or tr
				ttype = type(t)
			end -- new value falls through to be serialized
		end
		if ttype == "table" then
			if level >= maxl then
				return tag .. "{}" .. comment("maxlvl", level)
			end
			seen[t] = insref or spath
			if next(t) == nil then
				return tag .. "{}" .. comment(t, level)
			end -- table empty
			if maxlen and maxlen < 0 then
				return tag .. "{}" .. comment("maxlen", level)
			end
			local maxn, o, out = math.min(#t, maxnum or #t), {}, {}
			for key = 1, maxn do
				o[key] = key
			end
			if not maxnum or #o < maxnum then
				local n = #o -- n = n + 1; o[n] is much faster than o[#o+1] on large tables
				for key in pairs(t) do
					if o[key] ~= key then
						n = n + 1
						o[n] = key
					end
				end
			end
			if maxnum and #o > maxnum then
				o[maxnum + 1] = nil
			end
			if opts.sortkeys and #o > maxn then
				alphanumsort(o, t, opts.sortkeys)
			end
			local sparse = sparse and #o > maxn -- disable sparsness if only numeric keys (shorter output)
			for n, key in ipairs(o) do
				local value, ktype, plainindex = t[key], type(key), n <= maxn and not sparse
				if
					opts.valignore and opts.valignore[value] -- skip ignored values; do nothing
					or opts.keyallow and not opts.keyallow[key]
					or opts.keyignore and opts.keyignore[key]
					or opts.valtypeignore and opts.valtypeignore[type(value)] -- skipping ignored value types
					or sparse and value == nil
				then -- skipping nils; do nothing
				elseif ktype == "table" or ktype == "function" or badtype[ktype] then
					if not seen[key] and not globals[key] then
						sref[#sref + 1] = "placeholder"
						local sname = safename(iname, gensym(key)) -- iname is table for local variables
						sref[#sref] = val2str(key, sname, indent, sname, iname, true)
					end
					sref[#sref + 1] = "placeholder"
					local path = seen[t] .. "[" .. tostring(seen[key] or globals[key] or gensym(key)) .. "]"
					sref[#sref] = path
						.. space
						.. "="
						.. space
						.. tostring(seen[value] or val2str(value, nil, indent, path))
				else
					out[#out + 1] = val2str(value, key, indent, nil, seen[t], plainindex, level + 1)
					if maxlen then
						maxlen = maxlen - #out[#out]
						if maxlen < 0 then
							break
						end
					end
				end
			end
			local prefix = string.rep(indent or "", level)
			local head = indent and "{\n" .. prefix .. indent or "{"
			local body = table.concat(out, "," .. (indent and "\n" .. prefix .. indent or space))
			local tail = indent and "\n" .. prefix .. "}" or "}"
			return (custom and custom(tag, head, body, tail, level) or tag .. head .. body .. tail) .. comment(t, level)
		elseif badtype[ttype] then
			seen[t] = insref or spath
			return tag .. globerr(t, level)
		elseif ttype == "function" then
			seen[t] = insref or spath
			if opts.nocode then
				return tag .. "function() --[[..skipped..]] end" .. comment(t, level)
			end
			local ok, res = pcall(string.dump, t)
			local func = ok and "((loadstring or load)(" .. safestr(res) .. ",'@serialized'))" .. comment(t, level)
			return tag .. (func or globerr(t, level))
		else
			return tag .. safestr(t)
		end -- handle all other types
	end
	local sepr = indent and "\n" or ";" .. space
	local body = val2str(t, name, indent) -- this call also populates sref
	local tail = #sref > 1 and table.concat(sref, sepr) .. sepr or ""
	local warn = opts.comment and #sref > 1 and space .. "--[[incomplete output with shared/self-references skipped]]"
		or ""
	return not name and body .. warn or "do local " .. body .. sepr .. tail .. "return " .. name .. sepr .. "end"
end

local function deserialize(data, opts)
	local env = (opts and opts.safe == false) and G
		or setmetatable({}, {
			__index = function(t, k)
				return t
			end,
			__call = function(t, ...)
				error("cannot call functions")
			end,
		})
	local f, res = (loadstring or load)("return " .. data, nil, nil, env)
	if not f then
		f, res = (loadstring or load)(data, nil, nil, env)
	end
	if not f then
		return f, res
	end
	if setfenv then
		setfenv(f, env)
	end
	return pcall(f)
end

local function merge(a, b)
	if b then
		for k, v in pairs(b) do
			a[k] = v
		end
	end
	return a
end
return {
	_NAME = n,
	_COPYRIGHT = c,
	_DESCRIPTION = d,
	_VERSION = v,
	serialize = s,
	load = deserialize,
	dump = function(a, opts)
		return s(a, merge({ name = "_", compact = true, sparse = true }, opts))
	end,
	line = function(a, opts)
		return s(a, merge({ sortkeys = true, comment = true }, opts))
	end,
	block = function(a, opts)
		return s(a, merge({ indent = "  ", sortkeys = true, comment = true }, opts))
	end,
}
