#!/bin/sh


# max attempts before failure
ATTEMPTS=5
if [ $# -gt 1 ]; then
  ATTEMPTS=$1
  shift
fi

TIMEOUT=1
if [ $# -gt 1 ]; then
  TIMEOUT=$1
  shift
fi

REINIT_AFTER=3600
if [ $# -gt 1 ]; then
  REINIT_AFTER=$4
  shift
fi

# process to watch
PROCESS=$1

STATE_FILE="/var/run/backoff/$PROCESS.state"

if ! [ -f "$STATE_FILE" ]; then
  mkdir -p $(dirname "$STATE_FILE")
  echo 0 > "$STATE_FILE"
fi

function get_time_delta_of_last_attempt {
  let diff=$(date +%s)-$(stat -c %Y "$STATE_FILE")
  echo $diff
}

if [ $(get_time_delta_of_last_attempt) -gt $REINIT_AFTER ]; then
  echo 0 > "$STATE_FILE"
fi

function with_backoff {
  local max_attempts=$ATTEMPTS
  local timeout=$TIMEOUT
  local attempt=$(cat "$STATE_FILE")
  local exitCode=0

  i=0
  while [ $i -lt $attempt ]; do
    let i=$i+1
    let timeout=$timeout*2
    if [ $timeout -gt $REINIT_AFTER ]; then
      timeout=$REINIT_AFTER
    fi
  done

  let attempt=$attempt+1
  echo $attempt > "$STATE_FILE"
  sleep $timeout
  if [ $attempt -le $max_attempts ] || [ $max_attempts -eq 0 ]; then
    exec "$@"
  fi

}

with_backoff "$@"