install.sh

#!/usr/bin/env bash

set -euo pipefail

SOURCE_DIR="$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" && pwd)"

APT_HOOK="/etc/apt/apt.conf.d/80snapper"
BACKUP_DIR="/var/backups/dpkg-pre-post-snapper"
APT_HOOK_BACKUP="${BACKUP_DIR}/80snapper.original"
LEGACY_APT_HOOK_BACKUP="${APT_HOOK}.original"
SCRIPT_DIR="/opt/snapper/bin"
SCRIPT_PATH="${SCRIPT_DIR}/dpkg-pre-post-snapper.sh"

if [[ $EUID -ne 0 ]]; then
    echo "Error: Run this installer with sudo." >&2
    exit 1
fi

for command in apt-get dpkg; do
    if ! command -v "$command" >/dev/null 2>&1; then
        echo "Error: Required package tool not found: $command" >&2
        echo "This installer requires an APT/dpkg-based system." >&2
        echo "Nothing was changed." >&2
        exit 1
    fi
done

if [[ ! -d /etc/apt/apt.conf.d ]]; then
    echo "Error: Required APT configuration directory not found: /etc/apt/apt.conf.d" >&2
    echo "Nothing was changed." >&2
    exit 1
fi

for file in \
    "${SOURCE_DIR}/80snapper" \
    "${SOURCE_DIR}/dpkg-pre-post-snapper.sh"
do
    if [[ ! -f "$file" ]]; then
        echo "Error: Required file not found: $file" >&2
        exit 1
    fi
done

install -d -m 0755 -o root -g root "$BACKUP_DIR"

if [[ -e "$LEGACY_APT_HOOK_BACKUP" ]]; then
    if [[ ! -e "$APT_HOOK_BACKUP" ]]; then
        mv "$LEGACY_APT_HOOK_BACKUP" "$APT_HOOK_BACKUP"
    elif cmp -s "$LEGACY_APT_HOOK_BACKUP" "$APT_HOOK_BACKUP"; then
        rm "$LEGACY_APT_HOOK_BACKUP"
    else
        echo "Error: Conflicting APT hook backups exist:" >&2
        echo "  $LEGACY_APT_HOOK_BACKUP" >&2
        echo "  $APT_HOOK_BACKUP" >&2
        echo "Resolve them manually, then rerun the installer." >&2
        exit 1
    fi
fi

if [[ -e "$APT_HOOK" && ! -e "$APT_HOOK_BACKUP" ]]; then
    cp -a "$APT_HOOK" "$APT_HOOK_BACKUP"
fi

if [[ -e "$APT_HOOK_BACKUP" ]]; then
    chmod 0644 "$APT_HOOK_BACKUP"
fi

install -d -m 0755 -o root -g root "$SCRIPT_DIR"

install -m 0755 -o root -g root \
    "${SOURCE_DIR}/dpkg-pre-post-snapper.sh" \
    "$SCRIPT_PATH"

install -m 0644 -o root -g root \
    "${SOURCE_DIR}/80snapper" \
    "$APT_HOOK"

echo "dpkg-pre-post-snapper installed successfully."
echo "APT hook: $APT_HOOK"
echo "Script: $SCRIPT_PATH"

if [[ -e "$APT_HOOK_BACKUP" ]]; then
    echo "Original APT hook backup: $APT_HOOK_BACKUP"
fi