#!/bin/sh

set -eu

case $# in
    0|1)
        # extra_hash describes a git repository other than the current
        # one. It gets embedded as an additional commit hash in built
        # binaries, to help us locate the exact set of tools and code
        # that were used.
        extra_hash="${1:-}"
        if [ -z "$extra_hash" ]; then
            # Nothing, empty extra hash is fine.
            extra_hash=""
        elif [ -e "$extra_hash/.git" ]; then
            extra_hash=$(cd "$extra_hash" && git describe --always --dirty --exclude '*' --abbrev=200)
        elif ! expr "$extra_hash" : "^[0-9a-f]*$"; then
            echo "Invalid extra hash '$extra_hash', must be a git commit hash or path to a git repo" >&2
            exit 1
        fi

        # Load the base version and optional corresponding git hash
        # from the VERSION file. If there is no git hash in the file,
        # we use the hash of the last change to the VERSION file.
        version_file="$(dirname $0)/../VERSION.txt"
        IFS=".$IFS" read -r major minor patch base_git_hash <"$version_file"
        if [ -z "$base_git_hash" ]; then
            base_git_hash=$(git rev-list --max-count=1 HEAD -- $version_file)
        fi

        # The full git has we're currently building at. --abbrev=200 is an
        # arbitrary large number larger than all currently-known hashes, so
        # that git displays the full commit hash.
        git_hash=$(git describe --always --dirty --exclude '*' --abbrev=200)
        # The number of extra commits between the release base to git_hash.
        change_count=$(git rev-list ${base_git_hash}..HEAD | wc -l | sed 's/ *//')
        ;;
    6)
        # Test mode: rather than run git commands and whatnot, take in
        # all the version pieces as arguments.
        git_hash=$1
        extra_hash=$2
        major=$3
        minor=$4
        patch=$5
        change_count=$6
        ;;
    *)
        echo "Usage: $0 [extra-git-hash-or-checkout]"
        exit 1
esac

# Shortened versions of git hashes, so that they fit neatly into an
# "elongated" but still human-readable version number.
short_git_hash=$(echo $git_hash | cut -c-9)
short_extra_hash=$(echo $extra_hash | cut -c-9)

# Convert major/minor/patch/change_count into an adjusted
# major/minor/patch. This block is where all our policies on
# versioning are.
if expr "$minor" : "[0-9]*[13579]$" >/dev/null; then
    # Odd minor numbers are unstable builds.
    if [ "$patch" != "0" ]; then
        # This is a fatal error, because a non-zero patch number
        # indicates that we created an unstable git tag in violation
        # of our versioning policy, and we want to blow up loudly to
        # get that fixed.
        echo "Unstable release $major.$minor.$patch has a non-zero patch number, which is not allowed" >&2
        exit 1
    fi
    patch="$change_count"
elif [ "$change_count" != "0" ]; then
    # Even minor numbers are stable builds, but stable builds are
    # supposed to have a zero change count. Therefore, we're currently
    # describing a commit that's on a release branch, but hasn't been
    # tagged as a patch release yet. We allow these commits to build
    # for testing purposes, but force their version number to 0.0.0,
    # to reflect that they're an unreleasable build. The git hashes
    # still completely describe the build commit, so we can still
    # figure out what this build is if it escapes into the wild.
    major="0"
    minor="0"
    patch="0"
fi

# Hack for 1.1: add 1000 to the patch number. We switched from using
# the proprietary repo's change_count over to using the OSS repo's
# change_count, and this was necessary to avoid a backwards jump in
# release numbers.
if [ "$major.$minor" = "1.1" ]; then
    patch="$((patch + 1000))"
fi

# At this point, the version number correctly reflects our
# policies. All that remains is to output the various vars that other
# code can use to embed version data.
if [ -z "$extra_hash" ]; then
    long_version_suffix="-t$short_git_hash"
else
    long_version_suffix="-t${short_git_hash}-g${short_extra_hash}"
fi
cat <<EOF
VERSION_SHORT="${major}.${minor}.${patch}"
VERSION_LONG="${major}.${minor}.${patch}${long_version_suffix}"
VERSION_GIT_HASH="${git_hash}"
VERSION_EXTRA_HASH="${extra_hash}"
VERSION_XCODE="$((major + 100)).${minor}.${patch}"
VERSION_WINRES="${major},${minor},${patch},0"
EOF