#!/usr/bin/env bash

# Exit immediately if a command exits with a non-zero status
set -e

function show_usage() {
    echo "Usage:"
    echo "  $0 [--dry-run] backup <archive_name.tgz>"
    echo "  $0 [--dry-run] restore <archive_name.tgz> <target_home_directory> <target_username>"
    echo ""
    echo "Options:"
    echo "  --dry-run    Show what would be copied/extracted without making any actual changes."
    echo ""
    echo "Example:"
    echo "  $0 --dry-run backup /tmp/my_gnome_setup.tgz"
    echo "  sudo $0 restore /tmp/my_gnome_setup.tgz /home/guest guest"
    exit 1
}

# Check for dry-run flag
DRY_RUN=0
if [[ "$1" == "--dry-run" ]]; then
    DRY_RUN=1
    shift
fi

if [ "$#" -lt 2 ]; then
    show_usage
fi

ACTION="$1"
ARCHIVE="$2"

# Define the exact paths we care about (relative to the home directory)
GNOME_PATHS=(
    ".config/monitors.xml"
    ".config/mimeapps.list"
    ".config/gtk-3.0"
    ".config/gtk-4.0"
    ".config/fontconfig"
    ".config/user-dirs.dirs"
    ".config/autostart"
    ".local/share/gnome-shell/extensions"
    ".local/share/backgrounds"
    ".local/share/fonts"
    ".local/share/themes"
    ".local/share/icons"
    ".themes"
    ".icons"
    ".fonts"
)

if [ "$ACTION" == "backup" ]; then
    if [ "$DRY_RUN" -eq 1 ]; then
        echo "==> [DRY RUN] Starting GNOME backup simulation..."
        echo "--> [DRY RUN] Would dump dconf database to dconf_backup.ini"
        echo "--> [DRY RUN] Would copy the following paths from $HOME:"
        
        for path in "${GNOME_PATHS[@]}"; do
            if [ -e "$HOME/$path" ]; then
                echo "    [DRY RUN] MATCH: $path"
            else
                echo "    [DRY RUN] MISSING (Skipping): $path"
            fi
        done
        
        echo "--> [DRY RUN] Would aggressively scrub any 'keyrings' directories."
        echo "--> [DRY RUN] Would compress all matched files to: $ARCHIVE"
        echo "==> [DRY RUN] Backup simulation complete. No files were actually touched."
        exit 0
    fi

    echo "==> Starting GNOME backup..."
    
    # Create a staging area in /tmp
    STAGING_DIR="/tmp/gnome_backup_$$"
    mkdir -p "$STAGING_DIR"

    echo "--> Dumping dconf database..."
    dconf dump / > "$STAGING_DIR/dconf_backup.ini"

    echo "--> Gathering visual assets and system configs..."
    for path in "${GNOME_PATHS[@]}"; do
        if [ -e "$HOME/$path" ]; then
            # Create the parent directory structure in the staging area
            mkdir -p "$STAGING_DIR/$(dirname "$path")"
            # Copy the files over, preserving their structure
            cp -a "$HOME/$path" "$STAGING_DIR/$(dirname "$path")/"
            echo "    Saved: $path"
        fi
    done

    echo "--> Scrubbing keyrings and password data..."
    # Explicitly find and annihilate any keyrings that managed to sneak into the staging area
    find "$STAGING_DIR" -type d \( -name "keyrings" -o -name "kwalletd" \) -exec rm -rf {} + 2>/dev/null || true

    echo "--> Compressing to $ARCHIVE..."
    # Pack it all up from the staging directory
    tar -czf "$ARCHIVE" -C "$STAGING_DIR" .
    
    # Clean up the bloody mess in /tmp
    rm -rf "$STAGING_DIR"
    
    echo "==> Backup complete! Your setup is safe at $ARCHIVE"

elif [ "$ACTION" == "restore" ]; then
    TARGET_DIR="$3"
    TARGET_USER="$4"
    
    if [ -z "$TARGET_DIR" ] || [ ! -d "$TARGET_DIR" ]; then
        echo "Error: You must provide a valid target directory."
        show_usage
    fi

    if [ -z "$TARGET_USER" ]; then
        echo "Error: You must provide the exact target username as the 4th argument."
        show_usage
    fi

    # We need root to properly chown the files to the new user
    if [ "$EUID" -ne 0 ] && [ "$DRY_RUN" -eq 0 ]; then
        echo "Warning: You must run the 'restore' command with sudo,"
        echo "otherwise fixing the file ownership for the new profile will fail."
        exit 1
    fi

    # Deduce the primary group for the target user (usually matches the username)
    TARGET_GROUP=$(id -gn "$TARGET_USER" 2>/dev/null || echo "$TARGET_USER")

    if [ "$DRY_RUN" -eq 1 ]; then
        echo "==> [DRY RUN] Starting GNOME restore simulation to $TARGET_DIR..."
        
        if [ ! -f "$ARCHIVE" ]; then
            echo "Error: Backup archive $ARCHIVE does not exist. Cannot simulate restore."
            exit 1
        fi

        echo "--> [DRY RUN] Target user explicitly set to: $TARGET_USER:$TARGET_GROUP"
        echo "--> [DRY RUN] Would extract the following contents from $ARCHIVE to $TARGET_DIR:"
        tar -tf "$ARCHIVE" | sed 's/^/    [DRY RUN] /'
        
        echo "--> [DRY RUN] Would exclude 'keyrings' and 'dconf_backup.ini' from file sync."
        echo "--> [DRY RUN] Would scaffold standard XDG user directories (Desktop, Downloads, etc.)"
        echo "--> [DRY RUN] Would run a blanket chown on $TARGET_DIR to $TARGET_USER:$TARGET_GROUP"
        echo "--> [DRY RUN] Would deploy helper script $TARGET_DIR/load_gnome_settings.sh"
        echo "==> [DRY RUN] Restore simulation complete. No files were actually deployed or altered."
        exit 0
    fi

    echo "==> Starting GNOME restore to $TARGET_DIR..."

    STAGING_DIR="/tmp/gnome_restore_$$"
    mkdir -p "$STAGING_DIR"

    echo "--> Extracting archive..."
    tar -xzf "$ARCHIVE" -C "$STAGING_DIR"

    echo "--> Deploying files into $TARGET_DIR..."
    # Copy everything EXCEPT the dconf dump and any leftover keyrings into the target directory
    rsync -a "$STAGING_DIR/" "$TARGET_DIR/" --exclude "dconf_backup.ini" --exclude "keyrings" --exclude "kwalletd"

    echo "--> Scaffolding standard XDG user directories..."
    # Create the empty default folders so GNOME doesn't shit a brick
    for dir in Desktop Documents Downloads Music Pictures Public Templates Videos; do
        mkdir -p "$TARGET_DIR/$dir"
    done

    echo "--> Ensuring .cache/dconf exists..."
    # Pre-create the dconf cache directory so the helper script never throws a 'Permission denied'
    mkdir -p "$TARGET_DIR/.cache/dconf"

    echo "--> Running a blanket ownership fix across the entire home directory to $TARGET_USER:$TARGET_GROUP..."
    # Force absolute ownership of every single file and folder in the home directory to the new user
    chown -R "$TARGET_USER:$TARGET_GROUP" "$TARGET_DIR"

    echo "--> Prepping the headless dconf restore script..."
    DCONF_SCRIPT="$TARGET_DIR/load_gnome_settings.sh"
    cp "$STAGING_DIR/dconf_backup.ini" "$TARGET_DIR/"
    
    cat << 'EOF' > "$DCONF_SCRIPT"
#!/usr/bin/env bash
echo "Loading GNOME settings into dconf..."

# If there is no active display/Wayland session, we spawn a temporary headless D-Bus
# so dconf can write the local database file without throwing a fit.
if [ -z "$DBUS_SESSION_BUS_ADDRESS" ]; then
    echo "No graphical D-Bus session detected. Firing up a headless session..."
    dbus-run-session dconf load / < "$HOME/dconf_backup.ini"
else
    dconf load / < "$HOME/dconf_backup.ini"
fi

echo "Done! You can safely delete this script and dconf_backup.ini."
EOF

    chmod +x "$DCONF_SCRIPT"
    chown "$TARGET_USER:$TARGET_GROUP" "$DCONF_SCRIPT" "$TARGET_DIR/dconf_backup.ini"

    # Clean up /tmp
    rm -rf "$STAGING_DIR"

    echo "==> Files restored successfully!"
    echo "====================================================================="
    echo "IMPORTANT: Log into the new profile ($TARGET_USER) or switch to a TTY."
    echo "Run: ./load_gnome_settings.sh"
    echo "====================================================================="

else
    echo "Error: Invalid action. Use 'backup' or 'restore'."
    show_usage
fi