local load = load
local loadfile = loadfile
local debug = debug
local xpcall = xpcall
local type = type
local debugGetupvalue = debug.getupvalue
local debugUpvaluejoin = debug.upvaluejoin
local error = error
local debugGetinfo = debug.getinfo
local getmetatable = getmetatable
local setmetatable = setmetatable
local debugGetlocal = debug.getlocal
local mathAtan = math.atan
local stringFormat = string.format
local stringMatch = string.match
local tonumber = tonumber
local mathLog = math.log
local osExit = os.exit
local stringRep = string.rep
local stringGmatch = string.gmatch
local tableConcat = table.concat
local pairs = pairs
local ipairs = ipairs
local loadfile = loadfile
local EXP = math.exp(1)
local PI = math.pi
local RAD = PI / 180.0

local lua51 = {}

local FenvCache = setmetatable({}, { __mode = 'kv' })

---@param obj any
---@param expect string | "'nil'" | "'number'" | "'string'" | "'boolean'" | "'function'" | "'table'" | "'userdata'" | "'thread'"
local function checkType(obj, expect, level)
    local tp = type(obj)
    if tp ~= expect then
        error(stringFormat("%s expected, got %s", expect, tp), level and (level + 1) or 3)
    end
end

local function getFunc(f, level)
    if type(f) == 'function' then
        return f
    end
    if not level then
        level = 3
    end
    checkType(f, 'number', level)
    if f < 0 then
        error('level must be non-negative', level)
    end
    local info = debugGetinfo(f + level - 1, 'f')
    if not info then
        error('invalid level', level)
    end
    if not info.func then
        error(stringFormat('no function environment for tail call at level %d', f), level)
    end
    return info.func
end

local function findTable(name)
    local pg = {}
    local current = lua51
    for id in stringGmatch(name, '[^%.]+') do
        id = stringMatch(id, '^%s*(.-)%s*$')
        pg[#pg+1] = id
        local field = current[id]
        if field == nil then
            field = {}
            current[id] = field
        elseif type(field) ~= 'table' then
            return nil, tableConcat(pg, '.')
        end
        current = field
    end
    return current
end

local function setfenv(f, tbl)
    local tp = type(f)
    if tp ~= 'function' and tp ~= 'userdata' and tp ~= 'thead' then
        error [['setfenv' cannot change environment of given object]]
    end
    FenvCache[f] = tbl
    if debugGetupvalue(f, 1) ~= '_ENV' then
        return
    end
    local function dummy()
        return tbl
    end
    debugUpvaluejoin(f, 1, dummy, 1)
end

local function getfenv(f)
    if FenvCache[f] then
        return FenvCache[f]
    end
    local _, v = debugGetupvalue(f, 1)
    return v
end

local function copyTable(t)
    local nt = {}
    for k, v in pairs(t) do
        nt[k] = v
    end
    return nt
end

local function requireLoad(name)
    local msg = ''
    if type(package.searchers) ~= 'table' then
        error("'package.searchers' must be a table", 3)
    end
    for _, searcher in ipairs(package.searchers) do
        local f = searcher(name)
        if type(f) == 'function' then
            return f
        elseif type(f) == 'string' then
            msg = msg .. f
        end
    end
    error(("module '%s' not found:%s"):format(name, msg), 3)
end

local function requireWithEnv(name, env)
    local loaded = package.loaded
    if type(name) ~= 'string' then
        error(("bad argument #1 to 'require' (string expected, got %s)"):format(type(name)), 2)
    end
    local p = loaded[name]
    if p ~= nil then
        return p
    end
    local init = requireLoad(name)
    if type(env) == 'table' then
        if debug.getupvalue(init, 1) == '_ENV' then
            debug.setupvalue(init, 1, env)
        end
    end
    local res = init(name)
    if res ~= nil then
        loaded[name] = res
    end
    if loaded[name] == nil then
        loaded[name] = true
    end
    return loaded[name]
end

lua51.arg = arg
lua51.assert = assert
lua51.collectgarbage = collectgarbage
function lua51.dofile(name)
    local f, err
    if name then
        f, err = loadfile(name)
    else
        f, err = loadfile()
    end
    if not f then
        error(err, 2)
    end
    return f()
end
lua51.error = error
lua51._G = lua51
function lua51.getfenv(f)
    f = getFunc(f)
    return getfenv(f)
end
lua51.getmetatable = getmetatable
lua51.ipairs = ipairs
function lua51.load(func, name)
    checkType(func, 'function')
    return load(func, name, 'bt', lua51)
end
function lua51.loadfile(name)
    return loadfile(name, 'bt', lua51)
end
function lua51.loadstring(str, name)
    checkType(str, 'string')
    return load(str, name, 'bt', lua51)
end
function lua51.module(name, ...)
    checkType(name, 'string')
    local loaded = lua51.package.loaded
    local mod = loaded[name]
    if type(mod) ~= 'table' then
        local err
        mod, err = findTable(name)
        if not mod then
            error('name conflict for module ' .. err)
        end
        loaded[name] = mod
    end
    if mod._NAME == nil then
        mod._M = mod
        mod._NAME = name
        mod._PACKAGE = stringMatch(name, '(.-)[^%.]+$')
    end
    local f = getFunc(1)
    setfenv(f, mod)
    for _, func in ipairs {...} do
        func(mod)
    end
end
lua51.next = next
lua51.pairs = pairs
lua51.pcall = pcall
lua51.print = print
lua51.rawequal = rawequal
lua51.rawget = rawget
lua51.rawlen = rawlen
lua51.rawset = rawset
lua51.select = select
function lua51.setfenv(f, tbl)
    f = getFunc(f)
    setfenv(f, tbl)
end
lua51.setmetatable = setmetatable
lua51.tonumber = tonumber
lua51.tostring = tostring
lua51.type = type
lua51._VERSION = 'Lua 5.1'
function lua51.xpcall(f, msgh)
    checkType(f, 'function')
    checkType(f, 'function')
    return xpcall(f, msgh)
end
function lua51.require(name)
    return requireWithEnv(name, lua51)
end
lua51.unpack = table.unpack

lua51.coroutine = {}
lua51.coroutine.create = coroutine.create
lua51.coroutine.isyieldable = coroutine.isyieldable
lua51.coroutine.resume = coroutine.resume
lua51.coroutine.running = coroutine.running
lua51.coroutine.status = coroutine.status
lua51.coroutine.wrap = coroutine.wrap
lua51.coroutine.yield = coroutine.yield

lua51.debug = {}
lua51.debug.debug = debug.debug
lua51.debug.getfenv = getfenv
lua51.debug.gethook = debug.gethook
lua51.debug.getinfo = debug.getinfo
function lua51.debug.getlocal(...)
    local n = select('#', ...)
    if n == 2 then
        local level, loc = ...
        checkType(level, 'number')
        return debugGetlocal(level, loc)
    else
        local th, level, loc = ...
        return debugGetlocal(th, level, loc)
    end
end
lua51.debug.getmetatable = debug.getmetatable
lua51.debug.getregistry = debug.getregistry
lua51.debug.getupvalue = debug.getupvalue
lua51.debug.getuservalue = debug.getuservalue
lua51.debug.setfenv = setfenv
lua51.debug.sethook = debug.sethook
lua51.debug.setlocal = debug.setlocal
lua51.debug.setmetatable = debug.setmetatable
lua51.debug.setupvalue = debug.setupvalue
lua51.debug.setuservalue = debug.setuservalue
lua51.debug.traceback = debug.traceback

lua51.io = {}
lua51.io.stdin = io.stdin
lua51.io.stdout = io.stdout
lua51.io.stderr = io.stderr
lua51.io.close = io.close
lua51.io.flush = io.flush
lua51.io.input = io.input
lua51.io.lines = io.lines
lua51.io.open = io.open
lua51.io.output = io.output
lua51.io.popen = io.popen
lua51.io.read = io.read
lua51.io.tmpfile = io.tmpfile
lua51.io.type = io.type
lua51.io.write = io.write

lua51.math = {}
lua51.math.abs = math.abs
lua51.math.acos = math.acos
lua51.math.asin = math.asin
function lua51.math.atan(y)
    return mathAtan(y)
end
function lua51.math.atan2(y, x)
    checkType(x, 'number')
    return mathAtan(y, x)
end
lua51.math.ceil = math.ceil
lua51.math.cos = math.cos
function lua51.math.cosh(x)
    return (EXP ^ x + EXP ^ -x) / 2.0
end
function lua51.math.deg(x)
    return x / RAD
end
function lua51.math.exp()
    return EXP
end
lua51.math.floor = math.floor
lua51.math.fmod = math.fmod
function lua51.math.frexp(x)
    if x == 0 then
        return 0.0, 0
    end
    if x ~= x then
        return x, 0
    end
    local dump = stringFormat('%q', x + 0.0)
    local mstr, estr = stringMatch(dump, '^(.-)[pP](.+)$')
    if not mstr then
        return x, 0
    end
    local m = tonumber(mstr)
    local e = tonumber(estr)
    if m == 0 then
        return m, e
    end
    m = m / 2.0
    e = e + 1
    return m, e
end
lua51.math.huge = math.huge
function lua51.math.ldexp(m, e)
    return m * (2 ^ e)
end
function lua51.math.log(x)
    return mathLog(x)
end
function lua51.math.log10(x)
    return mathLog(x, 10)
end
lua51.math.max = math.max
lua51.math.min = math.min
lua51.math.modf = math.modf
lua51.math.pi = math.pi
function lua51.math.pow(x, y)
    return x ^ y
end
function lua51.math.rad(x)
    return x * RAD
end
lua51.math.random = math.random
lua51.math.randomseed = math.randomseed
lua51.math.sin = math.sin
function lua51.math.sinh(x)
    return (EXP ^ x - EXP ^ -x) / 2.0
end
lua51.math.sqrt = math.sqrt
lua51.math.tan = math.tan
function lua51.math.tanh(x)
    local a = EXP ^ x
    local b = EXP ^ -x
    return (a - b) / (a + b)
end

lua51.os = {}
lua51.os.close = os.clock
lua51.os.date = os.date
lua51.os.difftime = os.difftime
lua51.os.execute = os.execute
function lua51.os.exit(code)
    code = tonumber(code) or 0
    osExit(code)
end
lua51.os.getenv = os.getenv
lua51.os.remove = os.remove
lua51.os.rename = os.rename
lua51.os.setlocale = os.setlocale
lua51.os.time = os.time
lua51.os.tmpname = os.tmpname

lua51.package = {}
lua51.package.config = package.config
lua51.package.cpath = package.cpath
lua51.package.loaded = copyTable(package.loaded)
lua51.package.loaders = copyTable(package.searchers)
lua51.package.loadlib = package.loadlib
lua51.package.path = package.path
lua51.package.preload = copyTable(package.preload)
function lua51.package.seeall(mod)
    local mt = getmetatable(mod)
    if not mt then
        mt = {}
        setmetatable(mod, mt)
    end
    mt.__index = lua51
end

-- WTF ('').format
lua51.string = {}
lua51.string.byte = string.byte
lua51.string.char = string.char
lua51.string.dump = string.dump
lua51.string.find = string.find
lua51.string.format = string.format
lua51.string.gmatch = string.gmatch
lua51.string.gsub = string.gsub
lua51.string.len = string.len
lua51.string.lower = string.lower
lua51.string.match = string.match
function lua51.string.rep(s, n)
    return stringRep(s, n)
end
lua51.string.reverse = string.reverse
lua51.string.sub = string.sub
lua51.string.upper = string.upper

lua51.table = {}
lua51.table.concat = table.concat
lua51.table.insert = table.insert
function lua51.table.maxn(t)
    checkType(t, 'table')
    local max = 0
    for k in pairs(t) do
        if type(k) == 'number' then
            if k > max then
                max = k
            end
        end
    end
    return max
end
lua51.table.remove = table.remove
lua51.table.sort = table.sort

return lua51