#!/bin/bash

# name:		watch_containers.sh
# author:	david@socialnerds.org
# version:	0.1
# license:	GPLv3
# description:	Checks if the running container count
#		matches a number provided as $1 and optionally
#		reports results to a healthchecks endpoint.

# usage: ./watch_containers.sh <number> <optional-healthchecks-url>

# **** function definitions ****
function usage {
  echo "usage: ./watch_containers.sh <number> <optional-healthchecks-url>"
}

function get_container_count {
  local CNT=$(docker ps --format {{.Names}} | wc -l)
  if is_int "$CNT"; then
    echo $CNT
  fi
}

function is_int {
  local INT_EXPR='^[0-9]+$'
  if [[ $1 =~ $INT_EXPR ]]; then
    return 0
  else
    return 1
  fi
}

function is_url {
  local URL_EXPR='^https?://.+$'
  if [[ $1 =~ $URL_EXPR ]]; then
    return 0
  else
    return 1
  fi
}

# **** start ****

#exit if no options
if [ -z "$1" ]; then
  usage
  exit 1
fi

#exit if $1 is no intager
if ! is_int "$1"; then
  usage
  exit 1
fi

#set expected running containers
NUM=$1

#get running container count
CNT=$(get_container_count)

#set healthchecks url if not empty
URL=""
if [ -n "$2" ]; then
 #exit if $2 is no valid url
  if ! is_url "$2"; then
    usage
    exit 1
  fi
  URL="$2"
fi

MSG="Running containers: $CNT
Expected containers: $NUM"

echo "$MSG"

#report to healthchecks
if [ -n "$URL" ]; then
  if [ $NUM -eq $CNT ]; then
    curl -m 10 --retry 5 --data-raw "$MSG" "$URL"
  else
    curl -m 10 --retry 5 --data-raw "$MSG" "$URL/fail"
  fi
fi

# **** end ****
exit 0