semver

#!/usr/bin/env bash
# SPDX-License-Identifier: MIT
#
# Regex copied from semver-tool by François Saint-Jacques
# https://github.com/fsaintjacques/semver-tool
#
# Generate version numbers based on git tags

VERSION="1.0.0"

####### Below is copied from original
NAT='0|[1-9][0-9]*'
ALPHANUM='[0-9]*[A-Za-z-][0-9A-Za-z-]*'
IDENT="${NAT}|${ALPHANUM}"
FIELD='[0-9A-Za-z-]+'

SEMVER_REGEX="\
^[vV]?\
(${NAT})\\.(${NAT})\\.(${NAT})\
(\\-(${IDENT})(\\.(${IDENT}))*)?\
(\\+${FIELD}(\\.${FIELD})*)?$"
####### Above is copied from original

SHA='[0-9a-f]{4,40}'

GIT_DESCRIBE_REGEX="\
^[vV]?\
(${NAT})\\.(${NAT})\\.(${NAT})\
(\\-((${IDENT})(\\.(${IDENT}))*))?\
(\\+(${FIELD}(\\.${FIELD})*))?\
\\-(${NAT})\\-g(${SHA})(\\-(dirty|broken))?$"

semver() {
  # Keep a copy of entry arguments
  NUM_ARGS="$#"
  ARGS=("$@")

  # Stop on error
  set -euo pipefail

  parse
}

git_version() {
  declare -n _ver="$1"

  local git_describe=0
  git_describe="$(git describe --long --broken)"

  if [[ "${git_describe}" =~ ${GIT_DESCRIBE_REGEX} ]]; then
    local major=${BASH_REMATCH[1]}
    local minor=${BASH_REMATCH[2]}
    local patch=${BASH_REMATCH[3]}
    local prere=${BASH_REMATCH[4]}
    local meta=${BASH_REMATCH[10]}
    local num=${BASH_REMATCH[12]}
    local sha=${BASH_REMATCH[13]}
    local dirt=${BASH_REMATCH[15]}

    _ver="${major}.${minor}.${patch}${prere}+"

    if [[ -z "${meta}" ]]; then
      _ver=${_ver}${num}.${sha}
    else
      _ver=${_ver}${meta}.${num}.${sha}
    fi

    if [[ -n "${dirt}" ]]; then
      _ver=${_ver}.${dirt}
    fi

    # Let's just make a final validation it matches the official regex
    if [[ "${_ver}" =~ ${SEMVER_REGEX} ]]; then
      return 0
    else
      _ver=""
      return 1
    fi
  else
    _ver=""
    return 1
  fi
}

parse() {
  if [[ ${NUM_ARGS} -eq 0 ]]; then
    local ver
    git_version ver
    echo "${ver}"
  else
    for i in "${ARGS[@]}"; do
      case ${i} in
      -h | --help)
        print_help
        ;;
      -v | --version)
        echo "${VERSION}"
        ;;
      --file | --file=?*)
        local file="version.properties"
        if [[ "${i}" != '--file' ]]; then
          file=${i##*=}
        fi
        local ver
        git_version ver
        echo "VERSION=${ver}" >"${file}"
        ;;
      *)
        print_help
        echo "Unexpected arguments (${NUM_ARGS}): ${ARGS[*]}"
        exit 1
        ;;
      esac
    done
  fi
}

print_help() {
  local script
  script="semver"

  echo "Generates a version number based on git tag information"
  echo "This assumes you use Semantic Versioning 2.0.0 to tag your tree"
  echo ""
  echo "Usage: ${script} [--file[=<file>]]"
  echo "       ${script} [-h|--help|]"
  echo "       ${script} [-v|--version]"
  echo ""
  echo "Options:"
  echo "  --file[=<file>] Output to a file instead of the console. If no value is given,"
  echo "                  a file named 'version.properties' will be created in the CWD"
  echo "                  with a single key=value pair. Key is 'VERSION'"
  echo "  -h,--help       Print this usage message"
  echo "  -v,--version    Print the version of this tool"
  echo ""
}

###########################
###### Startup logic ######
###########################

if [[ ${BASH_SOURCE[0]} != "${0}" ]]; then
  export -f semver
else
  semver "${@}"
  exit $?
fi