#!/usr/bin/env bash
set -euo pipefail

tag=${1:-}

die() {
  printf 'invalid release tag: %s\n' "$tag" >&2
  exit 1
}

[[ $tag == v* ]] || die
version=${tag#v}

# Bash arrays discard trailing empty fields, so parsing first would accept
# values such as v1.2.3. and v1.2.3-alpha. Validate the complete string with
# the SemVer 2.0.0 grammar before doing anything else with the tag.
semver_pattern='^(0|[1-9][0-9]*)\.(0|[1-9][0-9]*)\.(0|[1-9][0-9]*)(-((0|[1-9][0-9]*|[0-9]*[A-Za-z-][0-9A-Za-z-]*)(\.(0|[1-9][0-9]*|[0-9]*[A-Za-z-][0-9A-Za-z-]*))*))?(\+([0-9A-Za-z-]+(\.[0-9A-Za-z-]+)*))?$'
LC_ALL=C
export LC_ALL
[[ $version =~ $semver_pattern ]] || die

printf 'release_tag=PASS tag=%s\n' "$tag"