Firefox Release Checker using RSS Feed

ffrel.lua

#!/usr/bin/lua

local xml2lua = require("xml2lua") -- Just fail early if these dont exist
local handler = require("xmlhandler.tree")
-- Requires either curl, lua-curl or luasec later
-- Uses either notify-send if available or prints new releases to stdout

local DEBUG = false
local VERSION = 20210229
local RSSURL = "https://hg.mozilla.org/mozilla-unified/rss-tags"
local NOTIFY_TITLE = "New Firefox Release"
local NOTIFY_TEXT = "Firefox %s was released on %s."

local function helpExit(err)
    if err then print("Error: " .. tostring(err)) end
    print(([[
Firefox release notifier script version %d
]]):format(VERSION))
    os.exit()
end

local function perhaps(...) local s, l = pcall(require, ...) if s then return l end end
local _ = function(s) if type(s) ~= "nil" then return tostring(s) end end

local notify
local fetch = DEBUG and (function() local f = io.open("rssdump", "r"); local c = f:read("*a"); f:close(); return c end) or nil
local which

local sh = perhaps("sh")
if type(sh) == "table" and type(sh.fork) == "string" and sh.fork == "folknor" and sh.version >= 4 then
    if not which then which = function(c) return sh._(("which " .. tostring(c))).__exitcode == 0 end end
    if not notify and which("notify-send") then
        notify = function(t, m) sh._(("notify-send -i firefox %q %q"):format(t, m)) end
    end
    if not fetch and which("curl") then
        fetch = function(url) return _(sh.command("curl")("-s", url)) end
    end
end

if not which then
    which = function(c)
        local h = io.popen("which " .. tostring(c))
        local r = h:read("*a"); h:close()
        return #r > 0
    end
end

if not notify then
    if which("notify-send") then
        notify = function(t, m) os.execute(("notify-send -i firefox %q %q"):format(t, m)) end
    else
        notify = function(t, m) print("[" .. tostring(t) .. "][" .. tostring(m) .. "]") end
    end
end

if not fetch then
    local sec = perhaps("ssl.https")
    if type(sec) == "table" then
        fetch = function(url)
            local res, code = sec.request(url)
            if code == 200 then return res end
        end
    else
        local curl = perhaps("lcurl")
        if type(curl) == "table" then
            fetch = function(url)
                local raw = ""
                local easy = curl.easy({
                    url = url,
                    writefunction = function(inc)
                        raw = raw .. inc
                        return true
                    end
                })
                easy:perform()
                easy:close()
                return raw
            end
        end
    end
end

if not fetch then helpExit("Can't fetch.") end

local versionMt = {
    __eq = function(self, other) return self[1] == other[1] and self[2] == other[2] and self[3] == other[3] end,
    __lt = function(self, other)
        if self[1] ~= other[1] then return self[1] < other[1] end
        if self[2] ~= other[2] then return self[2] < other[2] end
        return self[3] < other[3]
    end,
    __tostring = function(self) return ("%d.%d.%d"):format(unpack(self)) end,
}
local function parseVersion(...)
    local v = {...}
    if select("#", ...) == 1 then
        v[1], v[2], v[3] = tostring((select(1, ...))):match("^(%d+)%.?(%d*)%.?(%d*)")
    end
    v[1], v[2], v[3] = tonumber(v[1]) or 0, tonumber(v[2]) or 0, tonumber(v[3]) or 0
    if v[1] == 0 then return false end
    return setmetatable(v, versionMt)
end

local lN -- last notified
do
    local f = io.open("notified", "r")
    lN = parseVersion(f:read("*a"))
    f:close()
end

local content = fetch(RSSURL)
if type(content) ~= "string" then helpExit("Unable to fetch " .. RSSURL) end

local parser = xml2lua.parser(handler)
parser:parse(content)

for i, ev in next, handler.root.rss.channel.item do
    if ( ev.title:find("^FIREFOX%_") and ev.title:find("%_RELEASE$") ) then
        local sv = parseVersion(ev.title:match("^FIREFOX%_(%d+)%_?(%d*)%_?(%d*)%_?RELEASE$"))
        if sv and sv > lN then
            notify(NOTIFY_TITLE:format(tostring(sv)), NOTIFY_TEXT:format(tostring(sv), tostring(ev.pubDate)))
            if not DEBUG then
                lN = sv
                local f = io.open("notified", "w+")
                f:write(tostring(lN))
                f:close()
            end
        end
    end
end