#!/bin/bash

check_and_set_parameters() {
  if [ "$#" -lt 1 ]; then
    echo "Missing parameter for download directory"
    exit 1
  elif [ "$#" -lt 2 ]; then
    DOWNLOAD_AMOUNT=65535
  fi
  DOWNLOAD_DIRECTORY=$1
  [ -z $DOWNLOAD_AMOUNT ] && DOWNLOAD_AMOUNT=$2
}

check_installation_of_wget() {
  which wget > /dev/null 2>&1
  if [ $? -ne 0 ]; then
    echo "wget is not installed"
    exit 1
  fi
}

download_from_link_to_dir() {
  local link=$1
  local directory=$2
  echo "--------------------------------------------------"
  echo $link
  local file="$directory/${link##*/}"
  if [ -f $file ]; then
    echo "File already exists, skip downloading."
  else
    echo "Start to download Gradle distribution..."
    wget -q --show-progress -P $directory $link
    printf "\n"
  fi
}

parse_gradle_distributions_links_and_download() {
  local url="https://services.gradle.org/distributions/"
  local links=(`wget -q -O- $url | grep -o "\".*distributions.*all\.zip\"" | grep -v "rc\|milestone" | sed "s/\"//g" | sed "s/.*distributions/https:\/\/services.gradle.org\/distributions/g"`)
  local downloaded=0
  for i in "${!links[@]}"; do
    [ $i -eq $DOWNLOAD_AMOUNT ] && break
    download_from_link_to_dir ${links[i]} $DOWNLOAD_DIRECTORY
    downloaded=$((downloaded+1))
  done
  echo "$downloaded Gradle distributions have been downloaded."
  echo "--------------------------------------------------"
}

check_and_set_parameters "$@"
check_installation_of_wget
parse_gradle_distributions_links_and_download