#!/bin/sh

set -u

VERSION="21.10"

show_version() {
    cat <<END
evocommit version ${VERSION}

Copyright 2021 Evolix <info@evolix.fr>,
               Jérémy Lecour <jlecour@evolix.fr>
               and others.

evocommit comes with ABSOLUTELY NO WARRANTY.  This is free software,
and you are welcome to redistribute it under certain conditions.
See the GNU General Public Licence for details.
END
}

show_help() {
    cat <<END
evocommit helps properly committing changes in a repository

END
    show_usage
}
show_usage() {
    cat <<END
Usage: evocommit --repository /path/to/repository --message "add new host"

Options
     --repository PATH   set the path for the repository
     --message MESSAGE   set the commit message
 -V, --version           print version number
 -v, --verbose           increase verbosity
 -n, --dry-run           actions are not executed
     --help              print this message and exit
     --version           print version and exit
END
}

syslog() {
    if [ -x "${LOGGER_BIN}" ]; then
        ${LOGGER_BIN} -t "evocommit" "$1"
    fi
}
get_system() {
    uname -s
}
is_repository_readonly() {
    if [ "$(get_system)" = "OpenBSD" ]; then
        partition=$(stat -f '%Sd' $1)
        mount | grep "${partition}" | grep -q "read-only"
    elif command -v findmnt >/dev/null; then
        mountpoint=$(stat -c '%m' $1)
        findmnt "${mountpoint}" --noheadings --output OPTIONS -O ro
    else
        grep /usr /proc/mounts | grep -E '\bro\b'
    fi
}
remount_repository_readwrite() {
    if [ "$(get_system)" = "OpenBSD" ]; then
        partition=$(stat -f '%Sd' $1)
        mount -u -w /dev/${partition} 2>/dev/null
    else
        mountpoint=$(stat -c '%m' $1)
        mount -o remount,rw ${mountpoint}
        syslog "Re-mount ${mountpoint} as read-write to commit in repository $1"
    fi
}
remount_repository_readonly() {
    if [ "$(get_system)" = "OpenBSD" ]; then
        partition=$(stat -f '%Sd' $1)
        mount -u -r /dev/${partition} 2>/dev/null
    else
        mountpoint=$(stat -c '%m' $1)
        mount -o remount,ro ${mountpoint} 2>/dev/null
        syslog "Re-mount ${mountpoint} as read-only after commit to repository $1"
    fi
}
is_dry_run() {
    test "${DRY_RUN}" = "1"
}
main() {

    lock="${GIT_DIR}/index.lock"
    if [ -f "${lock}" ]; then
        limit=$(date +"%s" -d "now - 1 hour")
        updated_at=$(stat -c "%Y" "${lock}")
        if [ "$updated_at" -lt "$limit" ]; then
            rm -f "${lock}"
        fi
    fi

    git_status=$(${GIT_BIN} status --porcelain)

    if [ -n "${git_status}" ]; then
        if is_dry_run; then
            ${GIT_BIN} status
        else
            readonly_orig=0
            # remount mount point read-write if currently readonly
            if is_repository_readonly "${REPOSITORY}"; then
                readonly_orig=1;
                remount_repository_readwrite "${REPOSITORY}";
            fi
            author=$(logname)
            email=$(git config --get user.email)
            email=${email:-"${author}@evolix.net"}
            # commit changes
            ${GIT_BIN} add --all
            ${GIT_BIN} commit --message "${MESSAGE}" --author "${author} <${email}>" --quiet
            # remount mount point read-only if it was before
            if [ ${readonly_orig} -eq 1 ]; then
                remount_repository_readonly "${REPOSITORY}"
            fi
        fi
    fi

    unset GIT_DIR
    unset GIT_WORK_TREE
}
# Parse options
# based on https://gist.github.com/deshion/10d3cb5f88a21671e17a
while :; do
    case ${1:-''} in
        -h|-\?|--help)
            show_help
            exit 0
            ;;
        -V|--version)
            show_version
            exit 0
            ;;
        --message)
            # message options, with value speparated by space
            if [ -n "$2" ]; then
                MESSAGE=$2
                shift
            else
                printf 'ERROR: "--message" requires a non-empty option argument.\n' >&2
                exit 1
            fi
            ;;
        --message=?*)
            # message options, with value speparated by =
            MESSAGE=${1#*=}
            ;;
        --message=)
            # message options, without value
            printf 'ERROR: "--message" requires a non-empty option argument.\n' >&2
            exit 1
            ;;
        --repository)
            # repository options, with value speparated by space
            if [ -n "$2" ]; then
                REPOSITORY=$2
                shift
            else
                printf 'ERROR: "--repository" requires a non-empty option argument.\n' >&2
                exit 1
            fi
            ;;
        --repository=?*)
            # repository options, with value speparated by =
            REPOSITORY=${1#*=}
            ;;
        --repository=)
            # repository options, without value
            printf 'ERROR: "--repository" requires a non-empty option argument.\n' >&2
            exit 1
            ;;
        -n|--dry-run)
            # disable actual commands
            DRY_RUN=1
            ;;
        -v|--verbose)
            # print verbose information
            VERBOSE=1
            ;;
        --)
            # End of all options.
            shift
            break
            ;;
        -?*|[[:alnum:]]*)
            # ignore unknown options
            printf 'WARN: Unknown option (ignored): %s\n' "$1" >&2
            ;;
        *)
            # Default case: If no more options then break out of the loop.
            break
            ;;
    esac

    shift
done

if [ -z "${MESSAGE}" ]; then
    echo "Error: missing message parameter" >&2
    show_usage
    exit 1
fi
if [ -z "${REPOSITORY}" ]; then
    echo "Error: missing repository parameter" >&2
    show_usage
    exit 1
fi
DRY_RUN=${DRY_RUN:-0}
VERBOSE=${VERBOSE:-0}

GIT_BIN=$(command -v git)
readonly GIT_BIN

LOGGER_BIN=$(command -v logger)
readonly LOGGER_BIN

export GIT_DIR="${REPOSITORY}/.git"
export GIT_WORK_TREE="${REPOSITORY}"

if [ -d "${GIT_DIR}" ]; then
    main
else
    echo "There is no Git repository in '${REPOSITORY}'" >&2
    exit 1
fi