#!/bin/bash

# decription: This script uses mcapi.us to determine
#             the status of a Minecraft server and reports
#             its findings back to a Healthchecks instance
#             at $HEALTHCHECKS_URL.
#
# author:     david@socialnerds.org
# version:    0.1
# license:    MIT
#
# usage:      ./mcapi.sh <hostname/ip> <healthchecks id>

MCAPI_URL="https://mcapi.us/server"
CURL_OPTIONS="-fsS -m 10 --retry 5"
CURL_CMD="curl $CURL_OPTIONS"
HEALTHCHECKS_URL="https://checks.socialnerds.org/ping"
DEPENDENCIES="curl jq"

# check for missing dependencies (and exit on failure)
for DEPENDENCY in $DEPENDENCIES; do
    if [ ! $(command -v $DEPENDENCY) ]; then
        echo "missing dependency [$DEPENDENCY]"
        exit 2
    fi
done

# signal script start to healthchecks
if [ $2 ]; then
  HEALTHCHECKS_ID="$2"
  $CURL_CMD -o /dev/null $HEALTHCHECKS_URL/$HEALTHCHECKS_ID/start
fi

# get server status
if [ $1 ]; then
  IP="$1"
  URL="$MCAPI_URL/status?ip=$IP"
  STATUS=$($CURL_CMD $URL | jq --raw-output '.status')
  if [ $STATUS == "success" ]; then
    NOW=$($CURL_CMD $URL | jq --raw-output '.players.now')
    MAX=$($CURL_CMD $URL | jq --raw-output '.players.max')
    # signal script success to healthchecks
    if [ $HEALTHCHECKS_ID ]; then
      $CURL_CMD -o /dev/null --data-raw "Online players: $NOW/$MAX" $HEALTHCHECKS_URL/$HEALTHCHECKS_ID
    fi
  else
    # signal script failure to healthchecks
    if [ $HEALTHCHECKS_ID ]; then
      $CURL_CMD -o /dev/null $HEALTHCHECKS_URL/$HEALTHCHECKS_ID/fail
    fi
  fi
else
  echo "first option must be the hostname/ip of a minecraft server"
  exit 1
fi

exit 0