#!/bin/bash
#
# Build version retrieval script.
# Prints the current version or 'UNKNOWN' if version could not be determined.
#
# 1. see if there is a version file (provided as first argument)
# 2. then try git-semver to get a semver compliant version tag
#    - append '.dirty` metadata if local changes are found
#    - see: https://github.com/mdomke/git-semver
# 3. then try git-describe to retrieve (a non semver compatible) version tag
#    - append '-dirty' if local changes are found
#    - see: https://git-scm.com/docs/git-describe
#    Examples:
#    - build from a version tag: v0.2.0
#    - build from a develop branch which is 16 commits ahead of the latest
#      version tag: v0.2.0-16-g60e1688
#    - build with local modifications: v0.2.0-16-g60e1688-dirty
# 4. otherwise fallback: 'UNKNOWN'
#
# Inspired by:
# https://git.kernel.org/pub/scm/git/git.git/tree/GIT-VERSION-GEN?id=HEAD

VERSION_FILE=$1
DEF_VER=UNKNOWN
LF='
'
SCRIPT_DIR="$( cd "$(dirname "$0")" >/dev/null 2>&1 ; pwd -P )"
cd "$SCRIPT_DIR"

# use system version of git-semver by default
git_semver_path=""
if [[ ! -x "$(command -v git-semver)" ]]; then
    echo 'WARN: git-semver is not installed, using local Linux version' >&2
    git_semver_path="${SCRIPT_DIR}/"

    if [[ "$(uname)" == "Darwin" ]] || [[ ! -x "${git_semver_path}git-semver" ]]; then
        echo 'ERROR: git-semver is not available. Check https://github.com/mdomke/git-semver#installation' >&2
        exit 1
    fi
fi

if test -f "$VERSION_FILE"
then
	BUILD_VERSION=$(cat "$VERSION_FILE") || BUILD_VERSION="$DEF_VER"
# semver compatible version tags with https://github.com/mdomke/git-semver
# Attention: git-semver MUST be run in the git repo root directory! And it has no dirty flag support.
elif BUILD_VERSION=$(cd .. && "${git_semver_path}git-semver" 2>/dev/null) &&
	case "$BUILD_VERSION" in
	*$LF*) (exit 1) ;;
	v[0-9]* | [0-9]*)
	    # added or modified files? Mark it dirty! (New files are not considered)
		git update-index -q --refresh
		test -z "$(git diff-index --name-only HEAD --)" || {
			if [[ $BUILD_VERSION =~ "-" ]]; then
				BUILD_VERSION="$BUILD_VERSION.dirty"
			else
				BUILD_VERSION="$BUILD_VERSION+dirty"
			fi
		} ;;
	esac
then
	:
# Fallback: get version from last release tag (e.g. v0.2.0).
# Attention: development / pre-release versions are NOT semver compatible!
# see https://git-scm.com/docs/git-describe
elif BUILD_VERSION=$(git describe --match "v[0-9]*" --tags HEAD 2>/dev/null) &&
	case "$BUILD_VERSION" in
	*$LF*) (exit 1) ;;
	v[0-9]*)
	    # added or modified files? Mark it dirty! (New files are not considered)
		git update-index -q --refresh
		test -z "$(git diff-index --name-only HEAD --)" || {
			if [[ $BUILD_VERSION =~ "-" ]]; then
				BUILD_VERSION="$BUILD_VERSION.dirty"
			else
				BUILD_VERSION="$BUILD_VERSION+dirty"
			fi
		} ;;
	esac
then
    # here we could adjust the version from the Git tag. E.g. replace dash with dot
	# BUILD_VERSION=$(echo "$BUILD_VERSION" | sed -e 's/-/./g');
	:
else
	BUILD_VERSION="$DEF_VER"
fi

# strip leading 'v'
BUILD_VERSION=$(expr "$BUILD_VERSION" : v*'\(.*\)')

echo "$BUILD_VERSION"