#!/opt/Lua51/bin/lua

-- Created by jiaqiang.ye@lnxall.com
-- Simple System release unpacker
-- 2025/12/10

local cjson      = require "cjson"
local invoker    = require "invoker"
local gfmt       = string.format

local g_TOPDIR   = nil
local g_INSTXZ   = nil

local function badstr(s)
	if type(s) ~= "string" then return true end
	if string.len(s) == 0 then return true end
	return false
end

local function unpack_init(arg0, arg1)
	local topdir = os.getenv("FTOPDIR")
	if badstr(topdir) then
		topdir = invoker.readlink(arg0)
		if not badstr(topdir) then topdir = string.match(topdir, "^(.+)/[^/]+$") end
		if not badstr(topdir) then topdir = invoker.realpath(topdir .. "/..") end
	end
	if badstr(topdir) then
		io.stderr:write("Error, failed to determine FTOPDIR.\n")
		io.stderr:flush()
		return false
	end
	g_TOPDIR = topdir

	local instxz = invoker.realpath(arg1)
	if invoker.statfile(instxz) ~= "regular" then
		io.stderr:write("Error, invalid install.tar.xz specified.\n")
		io.stderr:flush()
		return false
	end
	g_INSTXZ = instxz
	return true
end

local function unpack_install()
	-- go to TOPDIR directory and invoke ./build.bash clean
	if not invoker.chdir(g_TOPDIR) then
		io.stderr:write(gfmt("Error, failed to goto directory: %s\n", g_TOPDIR))
		io.stderr:flush()
		return false
	end

	if invoker.statfile("./build.bash") ~= "regular" then
		io.stderr:write(gfmt("Error, top-level build script not found.\n"))
		io.stderr:flush()
		return false
	end

	io.stdout:write(gfmt("Invoking ./build.bash clean at directory: %s ...\n", g_TOPDIR))
	io.stdout:flush()
	invoker.invoke(invoker.NOSTDIO, "bash", "./build.bash", "clean")

	-- go to install directory
	local tdir = g_TOPDIR .. "/target"
	if not invoker.chdir(tdir) then
		io.stderr:write(gfmt("Error, cannot goto directory: %s\n", tdir))
		io.stderr:flush()
		return false
	end

	-- create directory `install
	invoker.mkdir("./install")
	if not invoker.chdir("./install") then
		io.stderr:write(gfmt("Error, cannot goto directory: %s/install\n", tdir))
		io.stderr:flush()
		return false
	end

	-- remove existing files
	io.stdout:write("Removing existing directories: ipkg-dirs/ipkg-info/opt ...\n")
	io.stdout:flush()
	invoker.invoke(0, "rm", "-rf", "ipkg-dirs", "iipkg-info", "opt")

	io.stdout:write(gfmt("Extract prebuilt system files from: %s ...\n", g_INSTXZ))
	io.stdout:flush()
	if invoker.invoke(0, "tar", "-Jxf", g_INSTXZ) ~= 0 then
		io.stderr:write(gfmt("Error, failed to extract prebuilt image from: %s\n", g_INSTXZ))
		io.stderr:flush()
		invoker.invoke(0, "bash", "-c", "rm -rf *")
		return false
	end
	return true
end

if not unpack_init(arg[0], arg[1]) then os.exit(1) end
if not unpack_install() then os.exit(2) end
os.exit(0)