#!/bin/bash

log="@GENTOO_PORTAGE_EPREFIX@/var/tmp/portage/*/*/temp/build.log"
cmd="tailf"
c=0

die() { echo -e "$*" >&2; exit 1; }

if [[ $(echo $log) = "$log" ]]; then
  echo "No running build found"
  exit 0
elif [[ ! $1 ]]; then
  echo "Running builds - use '${0##*/} NUMBER' to select"
  for i in $log; do
    [[ $i =~ ^${log%%\**}([^/]*)/([^/]*)${log##*\*}$ ]] || continue
    echo -e "$((++c))\t${BASH_REMATCH[2]}\t(${BASH_REMATCH[1]})"
  done
else
  [[ -z ${1//[0-9]} && $1 -gt 0 ]] || die "Argument should be a number greater 0"
  for i in $log; do
    [[ $i =~ ^${log%%\**}([^/]*)/([^/]*)${log##*\*}$ ]] || continue
    [[ $((++c)) -eq $((10#$1)) ]] || continue
    [[ -f ${i} ]] || die "Build number $1 was gone in the meanwhile"
    echo -ne "\033]0;Viewing: ${BASH_REMATCH[2]}\t(${BASH_REMATCH[1]})\007"
    exec $cmd $i
  done
  die "Build number $1 not found (there are only $((c--)) build(s) running)" 
fi