--[[
LuCI - Filesystem tools

Description:
A module offering often needed filesystem manipulation functions

FileId:
$Id$

License:
Copyright 2008 Steven Barth <steven@midlink.org>

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

	http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

]]--

local io    = require "io"
local os    = require "os"
local ltn12 = require "luci.ltn12"
local fs	= require "nixio.fs"
local nutil = require "nixio.util"
-- The section types used to be written with a hyphen, convert the stored package once.
do
	local sys = require "luci.sys"
	if sys.call("grep -q '^config proxy-groups\\|^config proxy-providers' /etc/config/openclash /tmp/.uci/openclash 2>/dev/null") == 0 then
		sys.call("sed -i 's/^config proxy-groups/config proxy_groups/;s/^config proxy-providers/config proxy_providers/' /etc/config/openclash /tmp/.uci/openclash 2>/dev/null")
	end
end

local uci = require "luci.model.uci".cursor()
local dynamic_uci = require "luci.model.uci".cursor()
local SYS  = require "luci.sys"
local HTTP = require "luci.http"
local json = require "luci.jsonc"
local UTIL = require "luci.util"
local i18n = require "luci.i18n"

local type  = type
local string  = string
local tostring = tostring
local table = table
local math = math
local pcall = pcall
local b64chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'

--- LuCI filesystem library.
module "luci.openclash"

--- Browser-like User-Agent for plugin HTTP requests, some endpoints reject curl's default.
user_agent = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/156.0.0.0 Safari/537.36"

--- sec-ch-ua client hint of user_agent, the Chrome version has to be bumped together.
user_agent_ch_ua = '"Google Chrome";v="156", "Chromium";v="156", "Not.A/Brand";v="24"'

--- Test for file access permission on given path.
-- @class		function
-- @name		access
-- @param str	String value containing the path
-- @return		Number containing the return code, 0 on sucess or nil on error
-- @return		String containing the error description (if any)
-- @return		Number containing the os specific errno (if any)
access = fs.access

--- Evaluate given shell glob pattern and return a table containing all matching
-- file and directory entries.
-- @class			function
-- @name			glob
-- @param filename	String containing the path of the file to read
-- @return			Table containing file and directory entries or nil if no matches
-- @return			String containing the error description (if no matches)
-- @return			Number containing the os specific errno (if no matches)
function glob(...)
	local iter, code, msg = fs.glob(...)
	if iter then
		return nutil.consume(iter)
	else
		return nil, code, msg
	end
end

--- Checks wheather the given path exists and points to a regular file.
-- @param filename	String containing the path of the file to test
-- @return			Boolean indicating wheather given path points to regular file
function isfile(filename)
	return fs.stat(filename, "type") == "reg"
end

--- Checks wheather the given path exists and points to a directory.
-- @param dirname	String containing the path of the directory to test
-- @return			Boolean indicating wheather given path points to directory
function isdirectory(dirname)
	return fs.stat(dirname, "type") == "dir"
end

--- Read the whole content of the given file into memory.
-- @param filename	String containing the path of the file to read
-- @return			String containing the file contents or nil on error
-- @return			String containing the error message on error
-- Wrapped readfile: if file is age-encrypted, try to decrypt with matching UCI secret first
function readfile(filename)
	local content, err = fs.readfile(filename)
	if not content then return nil, err end
	if content:sub(1, 1024):find("BEGIN AGE ENCRYPTED FILE", 1, true) then
		local keys = get_age_keys(filename)
		if keys and keys.secret and keys.secret ~= "" then
			return age_decrypt(keys.secret, content) or content
		else
			return content
		end
	end
	return content
end

--- Write the contents of given string to given file.
-- @param filename	String containing the path of the file to read
-- @param data		String containing the data to write
-- @return			Boolean containing true on success or nil on error
-- @return			String containing the error message on error
-- Wrapped writefile: if public key exists for filename, encrypt before writing
function writefile(filename, data)
	local keys = get_age_keys(filename)
	if keys and keys.public and keys.public ~= "" then
		return fs.writefile(filename, age_encrypt(keys.public, data) or data)
	end
	return fs.writefile(filename, data)
end

--- Copies a file.
-- @param source	Source file
-- @param dest		Destination
-- @return			Boolean containing true on success or nil on error
copy = fs.datacopy

--- Renames a file.
-- @param source	Source file
-- @param dest		Destination
-- @return			Boolean containing true on success or nil on error
rename = fs.move

--- Get the last modification time of given file path in Unix epoch format.
-- @param path	String containing the path of the file or directory to read
-- @return		Number containing the epoch time or nil on error
-- @return		String containing the error description (if any)
-- @return		Number containing the os specific errno (if any)
function mtime(path)
	return fs.stat(path, "mtime")
end

--- Set the last modification time  of given file path in Unix epoch format.
-- @param path	String containing the path of the file or directory to read
-- @param mtime	Last modification timestamp
-- @param atime Last accessed timestamp
-- @return		0 in case of success nil on error
-- @return		String containing the error description (if any)
-- @return		Number containing the os specific errno (if any)
function utime(path, mtime, atime)
	return fs.utimes(path, atime, mtime)
end

--- Return the last element - usually the filename - from the given path with
-- the directory component stripped.
-- @class		function
-- @name		basename
-- @param path	String containing the path to strip
-- @return		String containing the base name of given path
-- @see			dirname
basename = fs.basename

--- Return the directory component of the given path with the last element
-- stripped of.
-- @class		function
-- @name		dirname
-- @param path	String containing the path to strip
-- @return		String containing the directory component of given path
-- @see			basename
dirname = fs.dirname

--- Return a table containing all entries of the specified directory.
-- @class		function
-- @name		dir
-- @param path	String containing the path of the directory to scan
-- @return		Table containing file and directory entries or nil on error
-- @return		String containing the error description on error
-- @return		Number containing the os specific errno on error
function dir(...)
	local iter, code, msg = fs.dir(...)
	if iter then
		local t = nutil.consume(iter)
		t[#t+1] = "."
		t[#t+1] = ".."
		return t
	else
		return nil, code, msg
	end
end

--- Create a new directory, recursively on demand.
-- @param path		String with the name or path of the directory to create
-- @param recursive	Create multiple directory levels (optional, default is true)
-- @return			Number with the return code, 0 on sucess or nil on error
-- @return			String containing the error description on error
-- @return			Number containing the os specific errno on error
function mkdir(path, recursive)
	return recursive and fs.mkdirr(path) or fs.mkdir(path)
end

--- Remove the given empty directory.
-- @class		function
-- @name		rmdir
-- @param path	String containing the path of the directory to remove
-- @return		Number with the return code, 0 on sucess or nil on error
-- @return		String containing the error description on error
-- @return		Number containing the os specific errno on error
rmdir = fs.rmdir

local stat_tr = {
	reg = "regular",
	dir = "directory",
	lnk = "link",
	chr = "character device",
	blk = "block device",
	fifo = "fifo",
	sock = "socket"
}
--- Get information about given file or directory.
-- @class		function
-- @name		stat
-- @param path	String containing the path of the directory to query
-- @return		Table containing file or directory properties or nil on error
-- @return		String containing the error description on error
-- @return		Number containing the os specific errno on error
function stat(path, key)
	local data, code, msg = fs.stat(path)
	if data then
		data.mode = data.modestr
		data.type = stat_tr[data.type] or "?"
	end
	return key and data and data[key] or data, code, msg
end

--- Set permissions on given file or directory.
-- @class		function
-- @name		chmod
-- @param path	String containing the path of the directory
-- @param perm	String containing the permissions to set ([ugoa][+-][rwx])
-- @return		Number with the return code, 0 on sucess or nil on error
-- @return		String containing the error description on error
-- @return		Number containing the os specific errno on error
chmod = fs.chmod

--- Create a hard- or symlink from given file (or directory) to specified target
-- file (or directory) path.
-- @class			function
-- @name			link
-- @param path1		String containing the source path to link
-- @param path2		String containing the destination path for the link
-- @param symlink	Boolean indicating wheather to create a symlink (optional)
-- @return			Number with the return code, 0 on sucess or nil on error
-- @return			String containing the error description on error
-- @return			Number containing the os specific errno on error
function link(src, dest, sym)
	return sym and fs.symlink(src, dest) or fs.link(src, dest)
end

--- Remove the given file.
-- @class		function
-- @name		unlink
-- @param path	String containing the path of the file to remove
-- @return		Number with the return code, 0 on sucess or nil on error
-- @return		String containing the error description on error
-- @return		Number containing the os specific errno on error
unlink = fs.unlink

--- Retrieve target of given symlink.
-- @class		function
-- @name		readlink
-- @param path	String containing the path of the symlink to read
-- @return		String containing the link target or nil on error
-- @return		String containing the error description on error
-- @return		Number containing the os specific errno on error
readlink = fs.readlink

function filename(str)
	if not str then
		return nil
	end
	local idx = str:match(".+()%.%w+$")
	if idx then
		return str:sub(1, idx-1)
	else
		return str
	end
end

function filesize(e)
	local t=0
	local a={' KB',' MB',' GB',' TB',' PB'}
	if e < 0 then
		e = -e
	end
	repeat
		e=e/1024
		t=t+1
	until(e<=1024)
	return string.format("%.1f",e)..a[t] or "0.0 KB"
end

function lanip(loopback)
	if loopback then
		return "127.0.0.1"
	end
	local lan_int_name = uci:get("openclash", "@overwrite[0]", "lan_interface_name") or uci:get("openclash", "config", "lan_interface_name") or "0"
	local lan_ip
	if lan_int_name == "0" then
		lan_ip = SYS.exec("uci -q get network.lan.ipaddr 2>/dev/null |awk -F '/' '{print $1}' 2>/dev/null |tr -d '\n'")
	else
		lan_ip = SYS.exec(string.format("ip address show %s 2>/dev/null | grep -w 'inet' 2>/dev/null | grep -Eo 'inet [0-9\.]+' | awk '{print $2}' | head -1 | tr -d '\n'", lan_int_name))
	end
	if not lan_ip or lan_ip == "" then
		lan_ip = SYS.exec("ip address show $(uci -q -p /tmp/state get network.lan.device || uci -q -p /tmp/state get network.lan.device) | grep -w 'inet'  2>/dev/null | grep -Eo 'inet [0-9\.]+' | awk '{print $2}' | head -1 | tr -d '\n'")
	end
	if not lan_ip or lan_ip == "" then
		lan_ip = SYS.exec("ip addr show 2>/dev/null | grep -w 'inet' | grep 'global' | grep 'brd' | grep -Eo 'inet [0-9\.]+' | awk '{print $2}' | head -n 1 | tr -d '\n'")
	end
	return lan_ip
end

function find_case_insensitive_path(path)
	local dir = dirname(path)
	local base = basename(path)
	local files = dir and fs.dir(dir)
	if not files then
		return nil
	end

	for f in files do
		if f:lower() == base:lower() then
			return dir .. "/" .. f
		end
	end
	return nil
end

function get_resourse_mtime(path)
	local real_path = path
	if not fs.access(path) then
		local found = find_case_insensitive_path(path)
		if found then
			real_path = found
		elseif uci_get_config("config", "small_flash_memory") == "1" then
			local fallback_path = path:gsub("^/etc/openclash/", "/tmp/etc/openclash/")
			local fallback_found = find_case_insensitive_path(fallback_path)
			if fallback_found then
				real_path = fallback_found
			else
				return "File Not Exist"
			end
		else
			return "File Not Exist"
		end
	end
	local file = fs.readlink(real_path) or real_path
	local resourse_etag_version = SYS.exec(string.format("source /usr/share/openclash/openclash_etag.sh && GET_ETAG_TIMESTAMP_BY_PATH '%s'", file))
	if resourse_etag_version and resourse_etag_version ~= "" then
		return resourse_etag_version
	end
	local resourse_version = os.date("%Y-%m-%d %H:%M:%S", mtime(file))
	if resourse_version and resourse_version ~= "" then
		return resourse_version
	end
	return "Unknown"
end

function uci_get_config(section, key)
	local val
	if section == "config" then
		val = uci:get("openclash", "@overwrite[0]", key)
	end
	if val == nil then
		val = uci:get("openclash", section, key)
	end
	return val
end

function get_file_path_from_request()
	local file_path = HTTP.formvalue("file")

	if not file_path or file_path == "" then
		local referer = HTTP.getenv("HTTP_REFERER")
		if referer then
			local file_value = referer:match("[?&]file=([^&]*)")
			if file_value and file_value ~= "" then
				file_path = HTTP.urldecode(file_value)
			end
		end
	end

	if file_path == "/" or file_path == "" then
		file_path = nil
	end

	return file_path
end

function restore_backup(archive)
	local quoted = UTIL.shellquote(archive)
	local listfile = "/tmp/oc_restore.list"
	-- list the archive before touching /etc/openclash: a broken upload used to report
	-- success because every tar/mv error was discarded, and members with absolute or
	-- parent-relative paths must not be extracted
	local tarok = SYS.call("tar tzf " .. quoted .. " >" .. listfile .. " 2>/dev/null") == 0
	local has_members = SYS.call("grep -q . " .. listfile) == 0
	local has_config = SYS.call("grep -Fxq './openclash' " .. listfile) == 0
	local unsafe = SYS.call("grep -qE '(^|/)\\.\\./|^/' " .. listfile) == 0
	local restored = false
	if tarok and has_members and has_config and not unsafe then
		if SYS.call("tar -C '/etc/openclash/' -xzf " .. quoted .. " >/dev/null 2>&1") == 0 then
			restored = SYS.call("mv -f /etc/openclash/openclash /etc/config/openclash >/dev/null 2>&1") == 0
		end
	end
	SYS.call("rm -f " .. listfile)
	return restored
end

function get_age_keys(file)
	local name = filename(basename(file))
	local pub, sec
	uci:foreach("openclash", "config_age_secret", function(s)
		if s and s.name then
			if s.name == name and (not s.hidden or (s.hidden ~= "true")) then
				if not pub and s.public then pub = s.public end
				if not sec and s.secret then sec = s.secret end
			end
			return false
		end
	end)
	return { public = pub, secret = sec }
end

function age_encrypt(public, content)
	if not public or public == "" or not content then return nil end

	local tmp_in = os.tmpname()
	local tmp_out = os.tmpname()
	local f = io.open(tmp_in, "w")
	if not f then return nil end
	f:write(content)
	f:close()

	local cmd = string.format(
		"/etc/openclash/core/clash_meta age encrypt %s %s %s 2>/dev/null",
		public, tmp_in, tmp_out
	)
	os.execute(cmd)

	local out = nil
	local f_out = io.open(tmp_out, "r")
	if f_out then
		out = f_out:read("*a") or ""
		f_out:close()
	end

	os.remove(tmp_in)
	os.remove(tmp_out)

	return out
end

function age_decrypt(secret, content)
	if not secret or secret == "" or not content then return nil end

	local tmp_in = os.tmpname()
	local tmp_out = os.tmpname()
	local f = io.open(tmp_in, "w")
	if not f then return nil end
	f:write(content)
	f:close()

	local cmd = string.format(
		"/etc/openclash/core/clash_meta age decrypt %s %s %s 2>/dev/null",
		secret, tmp_in, tmp_out
	)
	os.execute(cmd)

	local out = nil
	local f_out = io.open(tmp_out, "r")
	if f_out then
		out = f_out:read("*a") or ""
		f_out:close()
	end

	os.remove(tmp_in)
	os.remove(tmp_out)

	return out
end

function decode64(data)
	if not data then return nil end
	data = data:gsub('[%s]', '')
	if #data % 4 ~= 0 then return nil end

	local out = {}
	for i = 1, #data, 4 do
		local c1, c2, c3, c4 = data:byte(i, i+3)
		local i1 = b64chars:find(string.char(c1), 1, true) - 1
		local i2 = b64chars:find(string.char(c2), 1, true) - 1
		local i3 = (c3 == 61) and -1 or (b64chars:find(string.char(c3), 1, true) - 1)
		local i4 = (c4 == 61) and -1 or (b64chars:find(string.char(c4), 1, true) - 1)

		if not i1 or not i2 or (c3 ~= 61 and not i3) or (c4 ~= 61 and not i4) then
			return nil
		end

		local x = i1 * 0x40000 + i2 * 0x1000
		if i3 >= 0 then x = x + i3 * 0x40 end
		if i4 >= 0 then x = x + i4 end

		table.insert(out, string.char(math.floor(x / 0x10000) % 0x100))
		if i3 >= 0 then
			table.insert(out, string.char(math.floor(x / 0x100) % 0x100))
		end
		if i4 >= 0 then
			table.insert(out, string.char(x % 0x100))
		end
	end

	return table.concat(out)
end

function config_refs(old_file_name, new_file_name)
	if not old_file_name or old_file_name == "" then return end
	local old_name_no_ext = filename(basename(old_file_name))
	local old_file_full = basename(old_file_name)
	local is_rename = new_file_name and new_file_name ~= ""
	local new_name_no_ext, new_file_full

	if is_rename then
		new_name_no_ext = filename(basename(new_file_name))
		new_file_full = basename(new_file_name)
	end

	uci:foreach("openclash", "config_subscribe",
		function(s)
			if s.name == old_name_no_ext then
				if is_rename and new_name_no_ext ~= new_file_name then
					uci:set("openclash", s[".name"], "name", new_name_no_ext)
				else
					uci:delete("openclash", s[".name"])
				end
				return false
			end
		end
	)

	uci:foreach("openclash", "subscribe_info",
		function(s)
			if s.name == old_name_no_ext then
				if is_rename and new_name_no_ext ~= new_file_name then
					uci:set("openclash", s[".name"], "name", new_name_no_ext)
				else
					uci:delete("openclash", s[".name"])
				end
				return false
			end
		end
	)

	dynamic_uci:foreach("openclash", "proxy_groups",
		function(s)
			if s.config == old_file_full then
				if is_rename and new_name_no_ext ~= new_file_name then
					dynamic_uci:set("openclash", s[".name"], "config", new_file_full)
				else
					dynamic_uci:delete("openclash", s[".name"])
				end
			end
		end
	)

	dynamic_uci:foreach("openclash", "proxy_providers",
		function(s)
			if s.config == old_file_full then
				if is_rename and new_name_no_ext ~= new_file_name then
					dynamic_uci:set("openclash", s[".name"], "config", new_file_full)
				else
					dynamic_uci:delete("openclash", s[".name"])
				end
			end
		end
	)

	dynamic_uci:foreach("openclash", "proxies",
		function(s)
			if s.config == old_file_full then
				if is_rename and new_name_no_ext ~= new_file_name then
					dynamic_uci:set("openclash", s[".name"], "config", new_file_full)
				else
					dynamic_uci:delete("openclash", s[".name"])
				end
			end
		end
	)

	uci:foreach("openclash", "config_age_secret",
		function(s)
			if s.name == old_name_no_ext then
				if is_rename and new_name_no_ext ~= new_file_name then
					uci:set("openclash", s[".name"], "name", new_name_no_ext)
				else
					uci:delete("openclash", s[".name"])
				end
				return false
			end
		end
	)

	uci:commit("openclash")
	dynamic_uci:commit("openclash")
end

--- Returns the appropriate ps command string for the system's ps implementation.
-- Detects procps-ng (ps -efw) vs busybox (ps -w).
-- @return String containing the ps command prefix
function ps_cmd()
	local ps_version = SYS.exec("ps --version 2>&1 |grep -c procps-ng |tr -d '\n'")
	if ps_version == "1" then
		return "ps -efw"
	else
		return "ps -w"
	end
end

--- Returns the package manager type (opkg or apk).
-- @return String "opkg" or "apk"
function pkg_type()
	if fs.access("/usr/bin/apk") then
		return "apk"
	else
		return "opkg"
	end
end

--- Reads the CDN proxy address list from /usr/share/openclash/res/cdn.list,
-- followed by the user-defined addresses stored in uci
-- (openclash.config.github_addr_custom, list or space-separated string).
-- Lines starting with "#" are treated as comments and skipped.
-- @return Table of CDN address strings (deduplicated, file order first)
function cdn_list()
	local list = {}
	local seen = {}
	local raw = fs.readfile("/usr/share/openclash/res/cdn.list")
	if raw then
		for line in raw:gmatch("[^\r\n]+") do
			line = line:gsub("^%s+", ""):gsub("%s+$", "")
			if line ~= "" and line:sub(1, 1) ~= "#" and not seen[line] then
				seen[line] = true
				list[#list + 1] = line
			end
		end
	end
	local custom = uci:get("openclash", "config", "github_addr_custom")
	if type(custom) == "table" then
		custom = table.concat(custom, " ")
	end
	for addr in (custom or ""):gmatch("%S+") do
		if not seen[addr] then
			seen[addr] = true
			list[#list + 1] = addr
		end
	end
	return list
end

--- Read a field of an installed package directly from the package database
-- (/usr/lib/opkg/status or /lib/apk/db/installed), avoiding the opkg/apk
-- binaries and their lock files (/var/lock/opkg.lock, /lib/apk/db/lock).
-- Safe to call repeatedly/concurrently and never blocks on a lock.
-- @param pkg   Package name, e.g. "luci-app-openclash" or "libc"
-- @param field Field name; opkg: "Version"/"Architecture", apk: "V"/"A"
-- @return String field value, or "" when not found
function read_pkg_field(pkg, field)
	local text
	if pkg_type() == "opkg" then
		text = fs.readfile("/usr/lib/opkg/status")
	else
		text = fs.readfile("/lib/apk/db/installed")
	end
	if not text then return "" end
	text = text:gsub("\r\n", "\n")

	local prefix = (pkg_type() == "opkg") and ("Package: " .. pkg .. "\n") or ("P:" .. pkg .. "\n")
	local start = text:find(prefix, 1, true)
	if not start then return "" end
	local block_end = text:find("\n\n", start + #prefix, true) or #text
	local block = text:sub(start + #prefix, block_end - 1)
	local colon = (pkg_type() == "opkg") and ": " or ":"
	local val = block:match("\n" .. field .. colon .. "([^\r\n]+)")
	if not val then
		val = block:match("^" .. field .. colon .. "([^\r\n]+)")
	end
	return val or ""
end

--- Path of the shared version cache (also used by openclash_version.lua)
local VERSION_CACHE_FILE = "/tmp/openclash_version_history.json"

--- Read the shared version cache, or nil when missing/invalid
function read_version_cache()
	local raw = fs.readfile(VERSION_CACHE_FILE)
	if not raw or raw == "" then return nil end
	local ok, parsed = pcall(json.parse, raw)
	if ok and parsed and type(parsed) == "table" then
		return parsed
	end
	return nil
end

--- Update the shared version cache, keeping the other fields intact
function update_version_cache(updater)
	local parsed = read_version_cache() or {}
	updater(parsed)
	local tmp = VERSION_CACHE_FILE .. ".tmp"
	fs.writefile(tmp, json.stringify(parsed))
	os.rename(tmp, VERSION_CACHE_FILE)
end

--- Read a keyed value from the shared version cache, computing it on miss
-- @param field Top-level field name of the shared cache
-- @param key Invalidation key; an empty string disables caching
-- @param compute Function returning the value to cache, nil to skip caching
-- @return Cached or freshly computed value, nil when unavailable
function cached_value(field, key, compute)
	if key ~= "" then
		local cache = read_version_cache()
		local cached = cache and cache[field]
		if cached and cached.key == key and cached.version then
			return cached.version
		end
	end

	local v = compute()
	if v == nil or v == "" then return nil end

	if key ~= "" then
		update_version_cache(function(cache)
			cache[field] = { key = key, version = v }
		end)
	end

	return v
end

function oc_version()
	local db = (pkg_type() == "opkg") and "/usr/lib/opkg/status" or "/lib/apk/db/installed"
	local st = fs.stat(db)
	local key = st and (tostring(st.mtime) .. "-" .. tostring(st.size)) or ""

	local v = cached_value("plugin_cv_cache", key, function()
		local pkgv = read_pkg_field("luci-app-openclash", pkg_type() == "opkg" and "Version" or "V")
		if pkgv == "" then return "0" end
		return pkgv
	end)

	return v or "0"
end

--- Build/Prepare replaces the token with PKG_VERSION (files deployed without make keep it).
OC_VERSION = "@OPENCLASH_VERSION@"

--- Loads common.js + oc-common.css for pages whose templates carry no head include of their own.
function render_page_head()
	local lang = i18n.context and i18n.context.lang or ""
	HTTP.write(string.format([[
<script src="/cgi-bin/luci/admin/services/openclash/translate_js?f=common&v=%s&l=%s"></script>
<link rel="stylesheet" href="/luci-static/resources/openclash/css/oc-common.css?v=%s">
]], OC_VERSION, lang, OC_VERSION))
end

function IsYamlExt(e)
	e = e or ""
	local lower = string.lower(e)
	return lower:sub(-5) == ".yaml" or lower:sub(-4) == ".yml"
end

-- Rename the up/down buttons and drop stray <br> nodes before descriptions on newer LuCI.
-- The i18n module is pinned at the top of this file: this function also runs inside
-- the CBI template context, where looking up globals like require is not possible.
function optimize_cbi_ui()
	HTTP.write([[
		<script type="text/javascript">
			document.querySelectorAll("input.btn.cbi-button.cbi-button-up").forEach(function(btn) {
				btn.value = "]] .. i18n.translate("Move up") .. [[";
			});
			document.querySelectorAll("input.btn.cbi-button.cbi-button-down").forEach(function(btn) {
				btn.value = "]] .. i18n.translate("Move down") .. [[";
			});
			document.querySelectorAll("div.cbi-value-description").forEach(function(descDiv) {
				var prev = descDiv.previousSibling;
				while (prev && prev.nodeType === Node.TEXT_NODE && prev.textContent.trim() === "") {
					prev = prev.previousSibling;
				}
				if (prev && prev.nodeType === Node.ELEMENT_NODE && prev.tagName === "BR") {
					prev.remove();
				}
			});
		</script>
	]])
end