#!/usr/bin/env bash
#
# Hook for updating local configuration on each pull. This will automatically put files in their
# right places, but will not enable or start any services automatically; this is left to the user.
#
# Move this to '.git/hooks/post-merge' to have to run automatically after every 'git pull' operation.
# The script assumes write access to host directories, and a CoreOS host. Don't run on other systems!

set -euo pipefail
shopt -s globstar

# Global configuration variables.
TEMP_CONFIG_PATH="$(git -C "$(dirname "$0")" rev-parse --show-toplevel)"
HOST_CONFIG_PATH="/etc/coreos-home-server"
SYSTEMD_CONFIG_PATH="/etc/systemd/system"

# Synchronize CoreOS home-server configuration for specific path.
function sync-coreos-config() {
    local hostdir="$1"
    local dirname="$(basename "$hostdir")"

    # Check if any remote configuration exists for the name given.
    if ! compgen -G "$TEMP_CONFIG_PATH"/*/"$dirname" > /dev/null; then
        printf "configuration not found, skipping.\n"
        return
    fi

    # Collect remote configuration files across base directories.
    for tmpdir in "$TEMP_CONFIG_PATH"/*/"$dirname"; do
        # Update timestamp for temporary file to match last commit time, in order to ensure correct partial updates.
        for f in "$tmpdir/"**; do
            # Skip directories, as updating their commit times will have all files within be synchronized.
            if test -d "$f"; then
                continue
            fi

            touch -t "$(cd "$tmpdir" && git log -n 1 --pretty=format:%cd --date=format-local:%Y%m%d%H%M.%S --date-order -- "$f")" -- "$f"
        done

        # Link source files into temporary destination directory.
        mkdir --parents "$TEMP_CONFIG_PATH/.tmp/$dirname"
        cp --archive --force --target-directory "$TEMP_CONFIG_PATH/.tmp/$dirname" "$tmpdir"/.
    done

    # Remove files that only exist in local configuration.
    for f in $(comm -23 <(cd "$hostdir"; find . | sort) <(cd "$TEMP_CONFIG_PATH/.tmp/$dirname"; find . | sort)); do
        # Don't delete environment files, as these are required for active services.
        if test "$(basename --suffix=.env "$f")" != "$(basename "$f")"; then
            continue
        fi

        rm --verbose --recursive --force "$(realpath --quiet "$hostdir/$f")"
    done

    # Copy files from temporary directory to host configuration directory.
    (cd "$TEMP_CONFIG_PATH/.tmp/$dirname" && cp --verbose --recursive --update --target-directory "$hostdir" -- *)
    printf "done.\n"
}

# Synchronize systemd service files from CoreOS home-server configuration.
function sync-systemd-services() {
    local buffer="" tmp

    # Copy service files if newer than destination.
    for src in "$HOST_CONFIG_PATH"/*/systemd/*; do
        tmp="$(cp --verbose --recursive --update --target-directory "$SYSTEMD_CONFIG_PATH" "$src")"
        if test -n "$tmp"; then buffer="${buffer}"$'\n'"${tmp}"; fi
    done

    printf "%s\ndone.\n" "$buffer"
    if test -n "$buffer"; then return 0; else return 1; fi
}

# Synchronize all existing CoreOS home-server configuration.
for hostdir in "$HOST_CONFIG_PATH"/*; do
    if test ! -d "$hostdir"; then
        continue
    fi

    printf "Synchronizing host configuration for '%s'... " "$hostdir"
    sync-coreos-config "$hostdir"
done

# Synchronize systemd services from local CoreOS home-server configuration.
printf "Synchronizing systemd service files... "
if sync-systemd-services; then
    printf "Reloading systemd daemon after service updates...\n"
    systemctl daemon-reload
fi