#!/bin/sh
#
# (C) 2014 Alexander Huemer <alexander.huemer@xx.vu>,
#          Stefan Huber <shuber@sthu.org>
# (C) 2019 Andreas Rottmann <mail@r0tty.org>
#
# Licensed under the MIT license <https://spdx.org/licenses/MIT.html>.

set -e

usage() {
    echo "USAGE:"
    echo "  cobalt-git-deploy STAGE-DIR DEPLOY-DIR"
    echo "  cobalt-git-deploy --help"
}

invalid_args() {
    usage >&2
    exit 1
}

help() {
    usage
    echo
    cat <<'EOF'
Deploy a cobalt site atomically from a bare git repository. This
script is intended to be run from a git `post-update` hook. It takes
two arguments:

- STAGE-DIR: The working area directory, which will be created if
  it does not exist. This directory is intended to be under the
  control of cobalt-git-deploy, and should be empty on the first run
  of cobalt-git-deploy.

  Note that cobalt-git-deploy will modify and delete files below
  STAGE-DIR.

- DEPLOY-DIR: The location of a symbolic link which will be updated
  to the rendered site. This location should either not exist, or
  already be a symbolic link, otherwise cobalt-git-deploy will fail.

  This is the directory you probably want to point the document root
  of your webserver to.

# Mode of operation

cobalt-git-deploy will alternatingly use the sub-directories `left`
and `right` of STAGE-DIR to check out the contents of the current
master branch of the bare git repository, which must exist in the
current working directory. It will then build the site in one of these
directories using cobalt. If successful, DEPLOY-DIR will be updated
with a symblic link pointing to generated `_site` directory.
EOF
}

while [ $# -ne 0 ]; do
    case "$1" in
        --help) help; exit 0 ;;
        -*) invalid_args ;;
        *) break ;;
    esac
done

if [ $# -ne 2 ]; then
    invalid_args
fi

STAGE_DIR_BASE="$1"
DEPLOY_DIR="$2"

mkdir -p "${STAGE_DIR_BASE}"
touch "${STAGE_DIR_BASE}/state"

STATE=$(cat "${STAGE_DIR_BASE}/state")

case "${STATE}" in
    "left")
        STATE="right"
        ;;
    "right")
        STATE="left"
        ;;
    *)
        echo "No previous state saved. First run?"
        STATE="left"
        ;;
esac


# See section 4.1 of http://gitolite.com/deploy.html
export GIT_WORK_TREE="${STAGE_DIR_BASE}/${STATE}"
export GIT_DIR="$(pwd)"

mkdir -p "${GIT_WORK_TREE}"

echo "Checking out master to ${GIT_WORK_TREE}"
git checkout --force master
git reset --hard HEAD
git clean -dxf

# Let cobalt build the website into ./_site/
echo "Building site"
cd ${GIT_WORK_TREE}
cobalt build

echo "Deploying site in ${DEPLOY_DIR}"
ln -s -f -n "${GIT_WORK_TREE}/_site" "${DEPLOY_DIR}"
# We successfully deployed the site
echo "${STATE}" > "${STAGE_DIR_BASE}/state"