#!/bin/bash

if ! test "$BASH_VERSION"; then echo "error: shell is not bash" >&2; exit 1; fi
shopt -s inherit_errexit 2>/dev/null ||: # ignore fail in bash < 4.4
set -eE -o pipefail
trap 'echo "$0:$LINENO:error: \"$BASH_COMMAND\" exit status: $?, PIPESTATUS: ${PIPESTATUS[*]}" >&2' ERR

[[ $EUID == 0 ]] || exec sudo -E "${BASH_SOURCE[0]}" "$@"


usage() {
  cat <<EOF
Usage: ${0##*/} [-d]
Install prometheus-node-exporter for debian based system with sysv or systemd

-d         Skip downloading and installing the latest binary
-s         Skip setup: config files, user, init scripts.
-l         Listen only on local interface.
-h|--help  Print help and exit.

For downloading, requires curl wget and jq

EOF
  exit $1
}

##### begin command line parsing ########


# defaults
dl_bin=true
do_setup=true
listen_address=0.0.0.0

while [[ $1 ]]; do
  case $1 in
    -d) dl_bin=false ;;
    -s) do_setup=false ;;
    -l) listen_address=127.0.0.1 ;;
    -h|--help) usage 0 ;;
  esac
  shift
done
readonly dl_bin do_setup

##### end command line parsing ########

if $dl_bin; then
  for p in curl wget jq; do
    if ! type -t $p &>/dev/null; then
      apt-get -y install $p
    fi
  done
fi
if $do_setup && ! type -t rsync &>/dev/null; then
  # note: we could use diff or cmp instead.
  apt-get -y install rsync
fi

sysd_reload=false
installed_file=false

i() { # install file
  local tmp tmpdir dest="$1"
  local base="${dest##*/}"
  local dir="${dest%/*}"
  if [[ $dir != "$base" ]]; then
    # dest has a directory component
    mkdir -p "$dir"
  fi
  tmpdir=$(mktemp -d)
  cat >$tmpdir/"$base"
  tmp=$(rsync -ic $tmpdir/"$base" "$dest")
  if [[ $tmp ]]; then
    printf "%s\n" "$tmp"
    installed_file=true
    if [[ $dest == /etc/systemd/system/* ]]; then
      sysd_reload=true
    fi
  fi
  rm -rf $tmpdir
}


if $dl_bin; then
  if [[ -s /usr/local/src/node-exporter-url ]]; then
    installed_url=$(cat /usr/local/src/node-exporter-url)
  fi
  url=$(curl -s https://api.github.com/repos/prometheus/node_exporter/releases/latest | jq -r '.assets[].browser_download_url | match(".*linux-amd64.tar.gz$").string')
  if [[ ! $url ]]; then
    echo $0: error failed to get url
    exit 1
  fi
  if [[ $url != "$installed_url" ]]; then
    tmpdir=$(mktemp -d)
    cd $tmpdir
    f=${url##*/}
    wget -nv $url
    tar -xf $f
    dir=${f%.tar.gz}
    install $dir/node_exporter /usr/local/bin/prometheus-node-exporter
    printf "%s\n" "$url" >/usr/local/src/node-exporter-url
    cd
    rm -rf $tmpdir
  fi
fi

if ! $do_setup; then
  exit 0
fi

# taken from postinstall script
if ! getent passwd prometheus &>/dev/null; then
  adduser --quiet --system --home /var/lib/prometheus --no-create-home \
          --group --gecos "Prometheus daemon" prometheus
fi


# textfile collector dir
mkdir -p /var/lib/prometheus/node-exporter

chown prometheus:prometheus /var/lib/prometheus


i /etc/default/prometheus-node-exporter <<EOF
# Set the command-line arguments to pass to the server.
# Due to shell scaping, to pass backslashes for regexes, you need to double
# them (\\d for \d). If running under systemd, you need to double them again
# (\\\\d to mean \d), and escape newlines too.

# sometime before 1.5 systemd was a default collector
ARGS="--web.listen-address=${listen_address}:9100 --collector.textfile.directory=/var/lib/prometheus/node-exporter --collector.systemd"
# to see all possible args, run with --help
EOF

if [[ -d /etc/systemd/system ]]; then # we are using systemd

  # this is just fixing a screwed up state we shouldnt get into normally.
  if [[ -e /etc/init.d/prometheus-node-exporter ]]; then
    sysd_reload=true
    rm -f /etc/init.d/prometheus-node-exporter
  fi


  # I used to have logic to handle having the distro package installed, which would then just override it's service file in some ways.  The only differences of the
  # packaged version in t11 is that it creates /var/log/prometheus and a
  # logrotate, but nothing is logged there. And it depends on
  # prometheus-node-exporter-collectors, which is useful, but
  # depends on prometheus-node-exporter. We would have no
  # reason to install prometheus-node-exporter except that
  # dependency. But since the collectors package is just a few
  # small scripts we don't even currently use, and of course are not
  # there on old versions, lets not try to use that package, and
  # just manually install the files we want from upstream.
  # https://github.com/prometheus-community/node-exporter-textfile-collector-scripts

  if [[ -e /lib/systemd/system/prometheus-node-exporter.service ]]; then
    apt -y remove --purge prometheus-node-exporter
    rm -fv /lib/systemd/system/prometheus-node-exporter.service
  fi

  i /etc/systemd/system/prometheus-node-exporter.service <<'EOF'
[Unit]
Description=Prometheus exporter for machine metrics
Documentation=https://github.com/prometheus/node_exporter

# addition to the distro package
StartLimitIntervalSec=0


[Service]
Restart=on-failure
User=prometheus
EnvironmentFile=/etc/default/prometheus-node-exporter
ExecStart=/usr/local/bin/prometheus-node-exporter $ARGS
ExecReload=/bin/kill -HUP $MAINPID
TimeoutStopSec=20s
SendSIGKILL=no

# additions to the distro package
Restart=always
RestartSec=600


[Install]
WantedBy=multi-user.target
EOF
  if $sysd_reload; then
    systemctl daemon-reload
  fi
  systemctl enable prometheus-node-exporter
  if $installed_file; then
    systemctl restart prometheus-node-exporter
  fi
else # not using systemd
  i /etc/init.d/prometheus-node-exporter <<'EOF'
#!/bin/sh
# kFreeBSD do not accept scripts as interpreters, using #!/bin/sh and sourcing.
if [ true != "$INIT_D_SCRIPT_SOURCED" ] ; then
    set "$0" "$@"; INIT_D_SCRIPT_SOURCED=true . /lib/init/init-d-script
fi
### BEGIN INIT INFO
# Provides:          prometheus-node-exporter
# Required-Start:    $remote_fs
# Required-Stop:     $remote_fs
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: Prometheus exporter for machine metrics
# Description:       Prometheus exporter for machine metrics, written in Go
#                    with pluggable metric collectors.
### END INIT INFO

# Author: Martina Ferrari <tina@debian.org>
# Author: Guillem Jover <gjover@sipwise.com>

DESC="Prometheus exporter for machine metrics"
NAME=prometheus-node-exporter
USER=prometheus
GROUP=$USER
DAEMON=/usr/bin/$NAME
PIDFILE=/run/prometheus/$NAME.pid
LOGFILE=/var/log/prometheus/$NAME.log

START_ARGS="--no-close --background --make-pidfile"
STOP_ARGS="--remove-pidfile"

do_start_prepare()
{
  mkdir -p $(dirname $PIDFILE)
}

do_start_cmd_override()
{
  start-stop-daemon --start --quiet --oknodo \
    --exec $DAEMON --pidfile $PIDFILE --user $USER --group $GROUP \
    --chuid $USER:$GROUP $START_ARGS -- $ARGS >>$LOGFILE 2>&1
}

do_stop_cmd_override()
{
  start-stop-daemon --stop --quiet --oknodo --retry=TERM/30/KILL/5 \
    --exec $DAEMON --pidfile $PIDFILE --user $USER $STOP_ARGS
}

alias do_reload=do_reload_sigusr1
EOF
  chmod +x /etc/init.d/prometheus-node-exporter

  mkdir -p /var/log/prometheus
  chown prometheus:prometheus /var/log/prometheus
  update-rc.d prometheus-node-exporter defaults

  running=false
  if type -t pgrep &>/dev/null && pgrep -f prometheus-node-exporter &>/dev/null; then
    running=true
  fi
  if $installed_file || ! $running; then
    /etc/init.d/prometheus-node-exporter restart
  fi

  i /etc/logrotate.d/prometheus-node-exporter <<'EOF'
/var/log/prometheus/prometheus-node-exporter.log {
    weekly
    rotate 10
    copytruncate
    compress
    delaycompress
    notifempty
    missingok
}
EOF

fi