#!/bin/bash

readonly user_agent=(--user-agent 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/33.0.1750.152 Safari/537.36')

usage() {
  local program exit_status

  program="$(basename "$0")"
  exit_status="$1"

  echo "usage: ${program} <path_to_app>"
  exit "${exit_status}"
}

absolute_path() {
  echo "$(cd "$(dirname "$1")" && pwd)/$(basename "$1")"
}

appcast_found_error() {
  local error_reason="$1"

  echo "An appcast was found pointing to ${appcast_url}, but it ${error_reason}. You should:

  1. Check your internet connection.
  2. Try again later.
  3. Contact the developer."

  exit 1
}

# exit if no argument (or more than one) was given
if [[ -z "$1" ]] || [[ -n "$2" ]]; then
  usage 1
fi

# get plist
path_to_app="$(absolute_path "$1")"
path_to_plist="${path_to_app}/Contents/Info.plist"

if [[ ! -f "${path_to_plist}" ]]; then
  echo 'You need to use this on a .app bundle. Please verify your target.'
  usage 1
fi

# get appcast
appcast_url="$(defaults read "${path_to_plist}" 'SUFeedURL' 2>/dev/null)"

if [[ -z "${appcast_url}" ]]; then
  echo 'It appears this app does not have a Sparkle appcast'
  exit 0
fi

# validate appcast
appcast_http_response="$(curl --silent --head "${user_agent[@]}" --write-out '%{http_code}' "${appcast_url}" -o /dev/null)"
[[ "${appcast_http_response}" != '200' ]] && appcast_found_error "returned a non-200 (OK) HTTP response code (${appcast_http_response})"

appcast_checkpoint=$(brew cask _appcast_checkpoint --calculate "${appcast_url}")
[[ "${appcast_checkpoint}" == 'e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855' ]] && appcast_found_error 'seems to be empty'

# output appcast
echo "A Sparkle appcast was found. You should add it to your cask as

  appcast '${appcast_url}',
          checkpoint: '${appcast_checkpoint}'

You should likely also add 'auto_updates true'"

exit 0