#!/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 path="$1"

    # Search for configuration in any of the local configuration sub-directories.
    for dir in "$TEMP_CONFIG_PATH"/config/*/"$(basename "$path")"; do
        if test ! -d "$dir"; then
            printf "configuration not found, skipping\n"
            return
        fi

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

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

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

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

        # Copy files from temporary directory to host configuration directory.
        cp --verbose --recursive --update --target-directory "$path" "$dir"/*
        printf "done\n"
    done
}

# 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")"
        buffer="${buffer}${tmp}"
    done

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

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

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