finding a url in a string lua pattern

Question

Using Lua Pattern Matching I would like to be able to parse a string and find the following URLs

http://www.test.com/
www.test.com/
test.com/
test-test.test.com/

The slashes can be optional but if included it has to be able to find nested folders such as:

test.com/test/

That way I can use a single pattern match to find the url. The problem is that all the examples I use either dont work or cause World of Warcraft to never leave the loading screen to some error I cant resolve on my own.

I no longer have the pattern I used in my code so I could use one that will work and not hook improper URLs. I will come up with some if needed later.

Answer 1

-- all characters allowed to be inside URL according to RFC 3986 but without
-- comma, semicolon, apostrophe, equal, brackets and parentheses
-- (as they are used frequently as URL separators)
local text_with_URLs = [[
   <a href="http://www.lua.org:80/manual/5.2/contents.html">L.ua 5.2</a>
   [url=127.0.0.1:8080]forum link[/url]
   intranet links: http://test, http://retracker.local/announce
   [markdown link](https://74.125.143.101/search?q=Who+are+the+Lua+People%3F)
   long subdomain chain: very.long.name.of.my.site.co.uk
   auth link: ftp://user:[email protected]/path - not recognized yet :(
]]

local domains = [[.ac.ad.ae.aero.af.ag.ai.al.am.an.ao.aq.ar.arpa.as.asia.at.au
   .aw.ax.az.ba.bb.bd.be.bf.bg.bh.bi.biz.bj.bm.bn.bo.br.bs.bt.bv.bw.by.bz.ca
   .cat.cc.cd.cf.cg.ch.ci.ck.cl.cm.cn.co.com.coop.cr.cs.cu.cv.cx.cy.cz.dd.de
   .dj.dk.dm.do.dz.ec.edu.ee.eg.eh.er.es.et.eu.fi.firm.fj.fk.fm.fo.fr.fx.ga
   .gb.gd.ge.gf.gh.gi.gl.gm.gn.gov.gp.gq.gr.gs.gt.gu.gw.gy.hk.hm.hn.hr.ht.hu
   .id.ie.il.im.in.info.int.io.iq.ir.is.it.je.jm.jo.jobs.jp.ke.kg.kh.ki.km.kn
   .kp.kr.kw.ky.kz.la.lb.lc.li.lk.lr.ls.lt.lu.lv.ly.ma.mc.md.me.mg.mh.mil.mk
   .ml.mm.mn.mo.mobi.mp.mq.mr.ms.mt.mu.museum.mv.mw.mx.my.mz.na.name.nato.nc
   .ne.net.nf.ng.ni.nl.no.nom.np.nr.nt.nu.nz.om.org.pa.pe.pf.pg.ph.pk.pl.pm
   .pn.post.pr.pro.ps.pt.pw.py.qa.re.ro.ru.rw.sa.sb.sc.sd.se.sg.sh.si.sj.sk
   .sl.sm.sn.so.sr.ss.st.store.su.sv.sy.sz.tc.td.tel.tf.tg.th.tj.tk.tl.tm.tn
   .to.tp.tr.travel.tt.tv.tw.tz.ua.ug.uk.um.us.uy.va.vc.ve.vg.vi.vn.vu.web.wf
   .ws.xxx.ye.yt.yu.za.zm.zr.zw]]
local tlds = {}
for tld in domains:gmatch'%w+' do
   tlds[tld] = true
end
local function max4(a,b,c,d) return math.max(a+0, b+0, c+0, d+0) end
local protocols = {[''] = 0, ['http://'] = 0, ['https://'] = 0, ['ftp://'] = 0}
local finished = {}

for pos_start, url, prot, subd, tld, colon, port, slash, path in
   text_with_URLs:gmatch'()(([%w_.~!*:@&+$/?%%#-]-)(%w[-.%w]*%.)(%w+)(:?)(%d*)(/?)([%w_.~!*:@&+$/?%%#=-]*))'
do
   if protocols[prot:lower()] == (1 - #slash) * #path and not subd:find'%W%W'
      and (colon == '' or port ~= '' and port + 0 < 65536)
      and (tlds[tld:lower()] or tld:find'^%d+$' and subd:find'^%d+%.%d+%.%d+%.$'
      and max4(tld, subd:match'^(%d+)%.(%d+)%.(%d+)%.$') < 256)
   then
      finished[pos_start] = true
      print(pos_start, url)
   end
end

for pos_start, url, prot, dom, colon, port, slash, path in
   text_with_URLs:gmatch'()((%f[%w]%a+://)(%w[-.%w]*)(:?)(%d*)(/?)([%w_.~!*:@&+$/?%%#=-]*))'
do
   if not finished[pos_start] and not (dom..'.'):find'%W%W'
      and protocols[prot:lower()] == (1 - #slash) * #path
      and (colon == '' or port ~= '' and port + 0 < 65536)
   then
      print(pos_start, url)
   end
end

Output:

13    http://www.lua.org:80/manual/5.2/contents.html
61    L.ua
82    127.0.0.1:8080
197   https://74.125.143.101/search?q=Who+are+the+Lua+People%3F
281   very.long.name.of.my.site.co.uk
133   http://test
146   http://retracker.local/announce

Second line was printed because it looks like some ukrainian site :-)