#!/usr/bin/env nix-shell
#! nix-shell -i bash -p bash coreutils curl jq nix
# vim: ft=sh sw=2 et
#
# This scripts scans the github terraform-providers repo for new releases,
# generates the corresponding nix code and finally generates an index of
# all the providers given in ./providers.txt.
set -euo pipefail

# the maximum number of attempts before giving up inside of GET and prefetch_github
readonly maxAttempts=30

GET() {
  local url=$1
  local retry=1
  echo "fetching $url" >&2
  while ! curl -#fL -u "$GITHUB_AUTH" "$url"; do
    echo "The curl command has failed. Attempt $retry/${maxAttempts}" >&2
    if [[ "${retry}" -eq "${maxAttempts}" ]]; then
      exit 1
    fi
    retry=$(( retry + 1 ))
    sleep 5
  done
}

get_org_repos() {
  local org=$1
  local page=1
  GET "https://api.github.com/orgs/$org/repos?per_page=100" | jq -r '.[].name'
}

get_repo_tags() {
  local owner=$1
  local repo=$2
  GET "https://api.github.com/repos/$owner/$repo/git/refs/tags?per_page=100" | \
    jq -r '.[].ref' | \
    grep -v 'v\.' | \
    cut -d '/' -f 3- | \
    sort --version-sort
}

prefetch_github() {
  local owner=$1
  local repo=$2
  local rev=$3
  local retry=1
  while ! nix-prefetch-url --unpack "https://github.com/$owner/$repo/archive/$rev.tar.gz"; do
    echo "The nix-prefetch-url command has failed. Attempt $retry/${maxAttempts}" >&2
    if [[ "${retry}" -eq "${maxAttempts}" ]]; then
      exit 1
    fi
    retry=$(( retry + 1 ))
    sleep 5
  done
}

echo_entry() {
  local owner=$1
  local repo=$2
  local version=${3:1}
  local sha256=$4
  cat <<EOF
{
  owner   = "$owner";
  repo    = "$repo";
  version = "$version";
  sha256  = "$sha256";
};
EOF
}

indent() { sed 's/^/    /'; }

add_repo() {
  org="${1}"
  repo="${2}"

  echo "*** $repo ***"
  name=$(echo "$repo" | cut -d - -f 3-)
  last_tag=$(get_repo_tags "$org" "$repo" | tail -1)
  last_tag_sha256=$(prefetch_github "$org" "$repo" "$last_tag")

  {
    echo "  $name ="
    echo_entry "$org" "$repo" "$last_tag" "$last_tag_sha256" | indent
  } >> data.nix
}

## Main ##

cd "$(dirname "$0")"

if [[ -z "${GITHUB_AUTH:-}" ]]; then
  cat <<'HELP'
Missing the GITHUB_AUTH env. This is required to work around the 60 request
per hour rate-limit.

Go to https://github.com/settings/tokens and create a new token with the
"public_repo" scope.

Then `export GITHUB_AUTH=<your user>:<your token>` and run this script again.
HELP
  exit 1
fi

cat <<HEADER > data.nix
# Generated with ./update-all
{
HEADER

while read line; do
  IFS=' ' read -r -a fields <<< "$line"
  if [[ "${#fields[@]}" -eq 0 ]]; then
    continue
  fi

  if [[ "${fields[0]}" = *"/"* ]]; then
    org="$(echo "${fields[0]}" | cut -d/ -f1)"
    repo="$(echo "${fields[0]}" | cut -d/ -f2)"
    add_repo "${org}" "${repo}"
  else
    org="${fields[0]}"
    repos=$(get_org_repos "$org")
    if [[ "${#fields[@]}" -ge 2 ]] && [[ -n "${fields[1]}" ]]; then
      repos="$( echo "${repos[@]}" | grep "${fields[1]}" )"
    fi
    if [[ "${#fields[@]}" -eq 3 ]] && [[ -n "${fields[2]}" ]]; then
      repos="$( echo "${repos[@]}" | grep -v "${fields[2]}" )"
    fi
    repos="$( echo "${repos[@]}" | sort )"

    for repo in $repos; do
      add_repo "$org" "$repo"
    done
  fi
done < <(grep -v '^#\|^$' providers.txt)

cat <<FOOTER >> data.nix
}
FOOTER

echo Done.