#!/usr/bin/env bash
set -eu
[ "${BASH_VERSINFO[0]}" -ge 3 ] && set -o pipefail
IFS=$'\n\t'

# This method is not stable, according to https://github.com/golang/go/issues/21667#issuecomment-325457742
BASE_URL='https://storage.googleapis.com/golang?marker='
NEXT_MARKER=''
TRUNCATED='true'

# Shamelessly stolen from: https://stackoverflow.com/questions/893585/how-to-parse-xml-in-bash {
function read_dom() {
    local IFS=\>
    read -d \< ENTITY CONTENT
    local RET=$?
    TAG_NAME=${ENTITY%% *}
    ATTRIBUTES=${ENTITY#* }
    return $RET
}

function parse_dom() {
  if [[ $TAG_NAME = "IsTruncated" ]] ; then
    #echo "Is this page truncated: $CONTENT"
    TRUNCATED=$CONTENT
  elif [[ $TAG_NAME = "NextMarker" ]] ; then
    #echo "What is the next marker: $CONTENT"
    NEXT_MARKER=$CONTENT
  elif [[ $TAG_NAME = "Key" ]] ; then
    VERSIONS+=("${CONTENT}")
  fi
}

function get_versions() {
  XML=$(curl --silent ${BASE_URL}${NEXT_MARKER})

  while read_dom; do
      parse_dom
  done <<< $XML
}
# }

function loop_versions() {
  if [[ $TRUNCATED = 'true' ]] ; then
    get_versions
    loop_versions
  fi
}

mysed () {
    if [ "$(uname | tr '[:upper:]' '[:lower:]' | sed -E 's/(darwin|freebsd)/HERE/')" = "HERE" ] ; then
      sed -Ee $1
    else
      sed -re $1
    fi
}

loop_versions

echo ${VERSIONS[@]} \
    | tr ' ' '\n' \
    | grep '.tar.gz' \
    | grep '\(linux\|darwin\|freebsd\)' \
    | grep '\-\(amd64\|386\|armv6l\|armv7l\)\.' \
    | mysed 's/^go([^.]*).([^.]*).([^.]*).*/\1.\2.\3/' \
    | mysed 's/.(linux|darwin|freebsd|src).*$//' \
    | uniq \
    | sort -t. -k 1,1 -k 2,2n -k 3,3n -k 4,4n -k 5,5n \
    | tr '\n' ' '