Monitor style debugger for PICO-8

pico8_debugger.lua

do
	local oenv=_ENV
	if oenv==nil then
		print("do not open this code in the\npico-8 editor")
		return
	end
	local indent=0
	local type, printh, coresume, cocreate=type, printh, coresume, cocreate
	local _nvar
	local function _count(_, ...)
		if coresume(cocreate(type), ...) then
			_nvar+=1
			return _count(...)
		end
	end
	local function select_n(...)
		_nvar=0
		_count(nil, ...)
		return _nvar
	end
	local _pos, _tbl
	local function _unpack(...)
		if _pos<=0 then
			return ...
		end
		_pos-=1
		return _unpack(_tbl[_pos+1], ...)
	end
	local function unpack(tbl)
		_pos=tbl.n
		_tbl=tbl
		return _unpack()
	end
	local function pack(...)
		return {n=select_n(...), ...}
	end
	local function serialize(args)
		local str=""
		for i=1,args.n do
			local arg=args[i]
			local targ=type(arg)
			if targ=="string" then
				str=str.."\""..arg.."\""
			elseif targ=="number" then
				str=str..arg
			elseif targ=="boolean" then
				str=str..(arg and "true" or "false")
			else
				str=str..targ
			end
			if i<args.n then
				str=str..", "
			end
		end
		return str
	end
	local function rep(str, n)
		if (n==1) return str
		local nstr=""
		for i=1,n do
			nstr=nstr..str
		end
		return nstr
	end
	_ENV=setmetatable({}, {
	__index=function(_, k)
		if type(oenv[k])=="function" then
			return function(...)
				printh(rep("\t",indent).."enter "..k.."("..serialize(pack(...))..")")
				indent+=1
				local out=pack(oenv[k](...))
				indent-=1
				local outs=""
				if out.n>0 then
					outs="=("..serialize(out)..")"
				end
				printh(rep("\t",indent).."exit "..k..outs)
				return unpack(out)
			end
		else
			return oenv[k]
		end
	end,
	__newindex=function(_, k, v)
		oenv[k]=v
	end})
end