local velx_spec = struct {
	endian = "<",
	{magic="c5"},
	{fver="B"},
	{compression="B"},
	{lver="B"},
	{os="B"},
	{arctype="c4"},
	{psize="I3"},
	{lsize="I3"},
	{ssize="I3"},
	{rsize="I4"}
}

local velx = {}

local exec = {}

function velx.identify(path)
	local h = io.open(path, "rb")
	local header = velx_spec(h:read(#velx_spec))
	h:close()
	return header.magic == "\27VelX"
end

function velx.load(path)
	local h = io.open(path, "rb")
	local header = velx_spec(h:read(#velx_spec))
	local code = h:read(header.psize)
	h:seek("cur", lsize)
	local sig = h:read(header.ssize)
end

function velx.verify(path)
	local h = io.open(path, "rb")
	local header = velx_spec(h:read(#velx_spec))
	local code = h:read(header.psize)
	h:seek("cur", lsize)
	local sig = h:read(header.ssize)
	h:close()
	return security.verify(code, sig)
end

function exec:link()
	self.file:seek("set", #velx_spec+self.header.psize)
	local linkinfo = self.file:read(self.header.lsize)
	local linker = {}
	local pos = 1
	while true do
		local size = string.unpack("<H", linkinfo:sub(pos))
		pos = pos + 2
		local name = linkinfo:sub(pos, pos+size-1)
		pos = pos + size
		size = string.unpack("<H", linkinfo:sub(pos))
		pos = pos + 2
		local library = linkinfo:sub(pos, pos+size-1)
		pos = pos + size
		if (name == "" or library == "") then
			break
		end
		linker[#linker+1] = {name, library}
	end
	local linkscript = ""
	for i=1, #linker do
		linkscript = linkscript .. "local " .. linker[i][1] .. "=require(\"" .. linker[i][2] .. "\")\n"
	end
	self.code = linkscript .. self.code
	return true
end

function exec:load()
	self.file:seek("set", #velx_spec)
	local code = self.file:read(self.header.psize)
	if (self.header.compression == 0) then
		self.code = code
	elseif (self.header.compression == 1) then
		self.code = lzss.decompress(self.code)
	else
		return nil, "invalid compression method"
	end
	return true
end

function exec:run(args, evar)
	system.load(self.code, args, system.getglobalenv({_ARCHIVE=self.arc}), system.getevars(evar))
end