nixos/hardware/filesystem.nix

{ config, lib, pkgs, modulesPath, hostname, ... }:

let
rootDisk = "/dev/disk/by-partlabel/disk-${hostname}-root";
bootDisk = "/dev/disk/by-partlabel/disk-${hostname}-ESP";
in

{
    boot.initrd.supportedFilesystems = [ "btrfs" ];

    boot.initrd.systemd.services.rollback-root = {
        description = "Rollback btrfs root subvolume";
        wantedBy = [ "initrd.target" ];
        after = [ "systemd-cryptsetup@.service" ];
        before = [ "sysroot.mount" ];
        unitConfig.DefaultDependencies = "no";
        serviceConfig.Type = "oneshot";
        script = ''
            mkdir -p /btrfs_tmp
            mount ${rootDisk} /btrfs_tmp

            # Ensure the old_roots directory exists
            mkdir -p /btrfs_tmp/old_roots

            if [[ -e /btrfs_tmp/root ]]; then
                timestamp=$(date +%Y-%m-%d_%H-%M-%S)
                mv /btrfs_tmp/root "/btrfs_tmp/old_roots/$timestamp"
            fi

            delete_subvolume_recursively() {
                IFS=$'\n'
                for i in $(btrfs subvolume list -o "$1" | cut -f 9 -d ' '); do
                    delete_subvolume_recursively "/btrfs_tmp/$i"
                done
                btrfs subvolume delete "$1"
            }

            for i in $(find /btrfs_tmp/old_roots/ -maxdepth 1 -mtime +7); do
                # Don't delete the old_roots directory itself
                if [[ "$i" == "/btrfs_tmp/old_roots/" ]]; then continue; fi
                delete_subvolume_recursively "$i"
            done

            btrfs subvolume create /btrfs_tmp/root
            umount /btrfs_tmp
        '';
    };

    # fileSystems."/" = {
    #     device = rootDisk;
    #     fsType = "btrfs";
    #     options = [ "subvol=root" ];
    # };
    #
    # fileSystems."/persist" = {
    #     device = rootDisk;
    #     neededForBoot = true;
    #     fsType = "btrfs";
    #     options = [ "subvol=persist" ];
    # };
    #
    # fileSystems."/nix" = {
    #     device = rootDisk;
    #     neededForBoot = true;
    #     fsType = "btrfs";
    #     options = [ "subvol=nix" ];
    # };
    #
    # fileSystems."/boot" = {
    #     device = bootDisk;
    #     fsType = "vfat";
    #     options = [ "fmask=0022" "dmask=0022" "umask=0077" ];
    # };
    #
    # swapDevices = [ {
    #     device = "/.swapvol/swapfile";
    # } ];

    fileSystems."/persist".neededForBoot = true;
    fileSystems."/nix".neededForBoot = true;
}