#!/bin/bash

#
#    Copyright 2011-2016 Nest Labs Inc. All Rights Reserved.
#
#    Licensed under the Apache License, Version 2.0 (the "License");
#    you may not use this file except in compliance with the License.
#    You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS,
#    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#    See the License for the specific language governing permissions and
#    limitations under the License.
#

#
#    Description:
#      This file attempts to find and generate a package version
#      including, if necessary, the number of commits from the last
#      GIT tag and the current GIT hash corresponding to HEAD for the
#      current branch.
#
#      This is largely cobbled together from similar scripts in other
#      packages that are maintained in GIT (linux, u-boot, parted, etc.).
#
#      This can produce version information such as:
#
#        1.0.1
#        1.0.1-dirty
#        1.0.1-00032-gab50dbb
#        1.0.1-00032-gab50dbb-dirty
#

# Constants

ROOTDIR=${PREFIX}/

BINDIR=${ROOTDIR}bin
DATADIR=${ROOTDIR}share
DEVICEDIR=${ROOTDIR}dev
CONFDIR=${ROOTDIR}etc
LIBDIR=${ROOTDIR}lib
LIBEXECDIR=${ROOTDIR}libexec
VARDIR=${ROOTDIR}var
LOGDIR=${VARDIR}/log
MANDIR=${ROOTDIR}man
SBINDIR=${ROOTDIR}sbin

USRDIR=${ROOTDIR}usr
USRBINDIR=${USRDIR}/bin
USRDATADIR=${USRDIR}/share
USRLIBDIR=${USRDIR}/lib
USRLIBEXECDIR=${USRDIR}/libexec
USRSBINDIR=${USRDIR}/sbin

AWK=${USRBINDIR}/awk
BASENAME=${USRBINDIR}/basename
CAT=${BINDIR}/cat
ECHO="${BINDIR}/echo"
NULL=${DEVICEDIR}/null
PRINTF=${USRBINDIR}/printf
RM=${BINDIR}/rm
SED=${BINDIR}/sed

VERSION=""

#
# usage <status>
#
# Description:
#   This routine prints out the proper command line usage for this
#   program and then exits with the specified status.
#
# Input(s):
#   status - Exit status to exit the program with.
#
# Returns:
#   This subroutine does not return.
#
usage() {
	local name=`${BASENAME} ${0}`

	${ECHO} "Usage: ${name} [options] [ <project root> ]"

	if [ ${1} -ne 0 ]; then
		${ECHO} "Try '${name} -h' for more information."
	fi

	if [ ${1} -ne 1 ]; then
${CAT} << EOF
  -b, --build-version=VERSION  Specify VERSION as the build version to generate
                               extra build information against.
  -h, --help                   Print this help, then exit.
EOF
	fi

	exit ${1}
}

#
# gitversion <string> <directory> <version>
#
# Description:
#   This routine prints out any GIT version information appended to the
#   end of the package version, including the number of commits from
#   the last GIT tag and the current GIT hash corresponding to HEAD
#   for the current branch.
#
# Input(s):
#   string    - The current version string which may be empty.
#   directory - The current directory.
#   version   - The optional current package version.
#
# Returns:
#   N/A
#
gitversion() {
	local string="${1}"
	local dir="${2}"
	local version="${3}"
	local head
	local exact
	local dtag
	local gitversion

	# Retrieve the shortened, unique GIT hash associated with the
	# 'HEAD' GIT object

	head=`test -d .git && git rev-parse --verify --short HEAD 2> ${NULL}`

	# If we found a hash, we are actually in a GIT repository; continue.

	if [ -n "${head}" ]; then
	    	# Check to see if we have a position in GIT that is
	    	# exactly at an existing tag (e.g. 1.0.2). If we are,
	    	# just use it and add a dirty qualifier. Otherwise,
	    	# work through the logic to determine how far off the
	    	# tag the tree is.

	    	exact="`git describe --exact-match 2> ${NULL}`"

		if [ -z "${exact}" ] || [ -n "${version}" ] && [ "${version}" != "${exact}" ]; then
			dtag="`git describe 2> ${NULL}`"

			# If we are n commits away from a tag, then
			# print n and a shortened version of the
			# hash. Otherwise, just print the hash.
			#
			# If we are at an exact version, then there
			# won't be a delta or a hash, just use the
			# exact tag.

			if [ -n "${dtag}" ]; then
				if [ "${dtag}" == "${exact}" ]; then
					gitversion="${dtag}"
				else
					gitversion=`${PRINTF} "${dtag}" | ${AWK} -F '-' '{printf("%s-%05d-%s", $(NF-2),$(NF-1),$(NF))}' 2> ${NULL}`
				fi

			else
				gitversion=`${PRINTF} "g${head}"`

			fi

                else
			gitversion="${exact}"

		fi

		# Update the index if we are in a writable directory
		# so that we can successfully check for a dirty (has
		# uncommitted changes or unresolved merges) tree.

		if [ -w "${dir}" ]; then
			git update-index --refresh --unmerged > ${NULL}
		fi

		# Now check for such a dirty tree and add to the "string"
		# if we found one.

		if git diff-index --name-only HEAD | read dummy; then
		    	if [ -n "${gitversion}" ]; then
				gitversion="${gitversion}-dirty"
			else
				gitversion="dirty"
			fi
    		fi

	else
		gitversion="${version}"

	fi

	if [ -n "${string}" ] && [ -n "${gitversion}" ]; then
		string="${string}-${gitversion}"
	else
		string="${gitversion}"
	fi

	${PRINTF} "${string}"
}

#
# Main Program Body
#

while [ ${#} -gt 0 ]; do
    	if [ ${1:0:1} == "-" ]; then
		if [ "${1}" == "-h" ] || [ "${1}" == "--help" ]; then
			usage 0

		elif [ "${1}" == "-b" ] || [ "${1}" == "--build-version" ]; then
			version="${2}"
			shift 2

		else
		    	${ECHO} "Unknown argument '${1}'."
			usage 1

		fi

	else
		break

	fi
done

if [ ${#} -gt 1 ]; then
	usage 1
elif [ ${#} -eq 1 ]; then
	tree="${1}"
else
	tree="."
fi

if [ "${tree}" != "." ]; then
	cd "${tree}"
fi

VERSION="`gitversion \"${VERSION}\" . ${version}`"

${PRINTF} "${VERSION}"