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#!/bin/bash

# Build OS monitor. It starts as a systemd service and performs the following
# steps:
#
# 1. Bootstrap the build2 toolchain.
# 2. Build and start bbot.
# 3. Build and start bslave.
# 4. Monitor for OS and toolchain changes and reboot if detected.
#

# @@ What do we do in case or error, trap? Send email? Reboot? Probably
#    reboot bad idea since someone may need to login to examine what's
#    going on.
#
# @@ What will systemd do if we fail? Perhaps configure it to restart
#    us? Or not since we may hose the logs.
#
trap "exit 1" ERR
set -o errtrace # Trap in functions.

# Note: diagnostics goes to stdout.
#
function info () { echo "$*" 1>&2; }
function error ()
{
  if [ "$#" -gt 0 ]; then
    info "$*";
  fi

  exit 1
}

info "starting buildos monitor..."

# Parse the kernel command line. This is complicated by the fact that the
# values can be quoted, for example:
#
# foo='foo fox'
# bar="bar 'box'"
#
# First we separete quoted variables and arguments with newlines (giving
# priority to assignments). Then we replace whitespaces with newline on
# lines that don't contain quites. Finally, clean up by removing blank
# lines.
#
# Note: the same code as in init.
#
readarray -t cmdline < <(cat /proc/cmdline | \
  sed -r -e "s/([^ ]+=)?('[^']*'|\"[^\"]*\")/\n\1\2\n/g" | \
  sed -r -e "/['\"]/!s/ /\n/g" |
  sed -r -e '/^\s*$/d')

# Enter all buildos variables as bash variables.
#
for v in "${cmdline[@]}"; do
  var="$(sed -r -n -e 's/^buildos\.([^=]+)=.*$/\1/p' <<<"$v")" # Extract name.

  if [ -n "$var" ]; then
    val="$(sed -r -e 's/^[^=]+=(.*)$/\1/' <<<"$v")"            # Extract value.
    val="$(sed -r -e "s/^('(.*)'|\"(.*)\")$/\2\3/" <<<"$val")" # Strip quoted.
    declare "$var=$val"
  fi
done

function email () # <subject> < <body>
{
  (echo -e "Subject: $1\n"; cat -) | sendmail -i "$admin_email"
}

email "starting buildos monitor on $(hostname)" <<<""

while true; do
  info "monitoring..."
  sleep 2
done