import string


def minpositive(px,px1):
   if px<0:
      if px1>=0:
         return px1
      return -1
   if px1<0:
      return px
   return min(px,px1)


def addhrefs(text):
   tags=text.split("<")
   newtags=[]
   in_link=0
   for tag in tags:
      ltag=tag.lower()
      if not tag:
         newtags.append("")
         continue
      if ltag[0]=="a":
         in_link=1
      elif ltag[0:1]=="/a":
         in_link=0
      if not in_link:
         p=tag.find(">")
         if p<0:
            p=0
         tag_pre=tag[:p]
         tag=tag[p:]
         ltag=ltag[p:]
         while tag:
            is_maillink=0
            has_address=ltag.find("www.")
            has_address=minpositive(has_address,ltag.find("http://"))
            has_address=minpositive(has_address,ltag.find("ftp://"))
            has_address=minpositive(has_address,ltag.find("@"))
            if has_address>=0:
               address_start=has_address
               while address_start>=p:
                  if tag[address_start] in (">"," ","\t","\r","\n",'"',"'"):
                     break
                  address_start-=1
               if tag[address_start] in (">"," ","\t","\r","\n",'"',"'"):
                  address_start+=1
               address_end=has_address
               while address_end<len(tag):
                  if tag[address_end] in (" ","\t","\r","\n",'"',"'"):
                     break
                  address_end+=1
               address=tag[address_start:address_end]
               if address.find("@")>=0:
                  link="<a href='mailto:"+address+"'>"+address+"</a>"
               else:
                  if address[:3].lower()=="www":
                     link="<a href='http://"+address+"'>"+address+"</a>"
                  else:
                     link="<a href='"+address+"'>"+address+"</a>"
               tag_pre+=tag[:address_start]+link
               tag=tag[address_end:]
               ltag=ltag[address_end:]
            else:
               tag_pre+=tag
               tag=ltag=""
         tag=tag_pre
      newtags.append(tag)
   return string.join(newtags,"<")