#!/usr/bin/env rc

# Simplistic session management for `surf`.
#
# Only URLs are remembered, no cookie, HTTP session, or browsing
# history is stored.  The script is supposed to be called
# automatically by `surf` to update URL data, and by user commands to
# resume them.  File locking via `flock` is used to ensure atomicity
# of modifications to `.surf/sessions`.
#
# An URL is considered an "orphan" if its listed PID no longer
# refers to a live process.
#
# The first argument to `surfsession` indicates the action to be
# taken, with the following actions being supported:
#
# * `add _pid_ _url_`: store `_url_` as being browsed by the process
#   `_pid_`.
#
# * `remove _pid_ _url_`: remove any `_url_` being browsed by `_pid_`.
#
# * `purge _url_`: remove any `_url_` being browse by any process.
#
# * `restore`: start `surf` for all orphan URLs.
#
# * `resume`: use `dmenu` to select an orphan URL, which will be
#   opened in `surf`.

# Uses 9base/plan9port commands.
9base=$PLAN9
path=($9base/bin $path)

# dmenu setup shamelessly cribbed from surf.sh.
font='-*-terminus-medium-*-*-*-*-*-*-*-*-*-*-*'
normbgcolor='#181818'
normfgcolor='#e9e9e9'
selbgcolor='#dd6003'
selfgcolor='#e9e9e9'
dmenu=(dmenu -fn $font -nb $normbgcolor -nf $normfgcolor \
       -sb $selbgcolor -sf $selfgcolor -l 10 -b)

fn escape {
   # Make URL safe as target for sed.
   echo $1 | sed 's,\[|\]|\?|\+|\*|\.|\(|\)|\\|\|\||/,\\&,g'
}

fn orphans {
   awk '{ if (system("test -d /proc/"$1)) { print $2 }}' $sessionfile
}

sessionfile=$home/.surf/sessions

if (touch $sessionfile) {
   # We translate command foo to foo-locked surrounded by locking of
   # $sessionfile.
   hub ($1) {
       case add-locked
          echo $2 $3 >> $sessionfile
       case remove-locked
          {echo 'g/'^$2^' '^`{escape $3}^'/d'; echo 'w '^$sessionfile} | ed $sessionfile
       case purge-locked
          {echo 'g/'`{escape $2}^'/d'; echo 'w '^$sessionfile} | ed $sessionfile
       case restore-locked
          echo `{orphans}
          for (url in `{orphans}) { surf $url & }
          rm $sessionfile
       case resume-locked
           res=`{orphans|$dmenu}
           if (! ~ $status '') exit 1
           $0 purge-locked $res && surf $res &
       # Don't deadlock on unknown commands...
       case *-locked
          exit 1
       # Wrap a command in file locking and rerun the script.
       case *
          cmd=$1-locked
          shift
          flock -o $sessionfile -c $0^' '^$cmd^' '^$"*
   }
}
if not {
    echo 'Cannot write to '$sessionfile >[1=2]
    exit 1
}