# nixos-config - My current NixOS configuration
#
# Copyright (C) 2025 Benedikt Peetz <benedikt.peetz@b-peetz.de>
# SPDX-License-Identifier: GPL-3.0-or-later
#
# This file is part of my nixos-config.
#
# You should have received a copy of the License along with this program.
# If not, see <https://www.gnu.org/licenses/gpl-3.0.txt>.
{
  config,
  lib,
  pkgs,
  modules,
  ...
}: let
  cfg = config.soispha.disks;
  defaultMountOptions = [
    "compress-force=zstd:15" # This saves disk space, at a performance cost
    "noatime" # should have some performance upsides, and I don't use it anyways
    "lazytime" # make time changes in memory
  ];
in {
  options.soispha.disks = {
    enable = lib.mkEnableOption "disk setup with disko";

    disk = lib.mkOption {
      type = lib.types.path;
      example = lib.literalExpression "/dev/disk/by-uuid/0442cb6d-f13a-4635-b487-fa76189774c5";
      description = "The disk used for installing the OS.";
    };

    ssd = lib.mkEnableOption "ssd specific improvements, like trim";

    swap = {
      ram_size = lib.mkOption {
        type = lib.types.str;
        example = lib.literalExpression "16G";
        description = "The size of the ram (translates to the swapfile size)";
      };
    };
  };

  imports = [
    modules.disko.nixosModules.default
  ];

  config = lib.mkIf cfg.enable {
    systemd = lib.recursiveUpdate (import ./hibernate.nix {inherit pkgs;}) (import ./fstrim.nix {inherit pkgs lib cfg;});

    services.btrfs.autoScrub = {
      enable = true;
      fileSystems = ["/srv" "/nix"];
      interval = "monthly";
    };

    disko.devices = {
      disk = {
        main = {
          device = cfg.disk;
          content = {
            type = "gpt";
            partitions = {
              ESP = {
                # 2GiB plus 512MiB for tails ISO and normal boot stuff
                size = "2600M";

                type = "EF00";
                content = {
                  type = "filesystem";
                  format = "vfat";
                  mountpoint = "/boot";
                  mountOptions = ["umask=0077"];
                };
              };

              nix = {
                size = "30G";
                content = {
                  type = "luks";
                  name = "nixos-store";
                  extraOpenArgs = ["--allow-discards"];
                  content = {
                    type = "btrfs";
                    extraArgs = ["-f" "--label nixos-store"]; # Override existing partitions
                    mountpoint = "/nix";
                    mountOptions = defaultMountOptions;
                  };
                };
              };

              root = {
                size = "100%";
                content = {
                  type = "luks";
                  name = "nixos-root";
                  extraOpenArgs = ["--allow-discards"];
                  content = {
                    type = "btrfs";
                    extraArgs = ["-f" "--label nixos-root"]; # Override existing partitions
                    subvolumes = {
                      "persistent-storage" = {
                        mountpoint = "/srv";
                        mountOptions = defaultMountOptions;
                      };
                      "persistent-storage@snapshots" = {
                        mountpoint = "/srv/.snapshots";
                        mountOptions = defaultMountOptions;
                      };
                      "swap" = {
                        mountpoint = "/swap";
                        mountOptions = [
                          "noatime" # should have some performance upsides, and I don't use it anyways
                          "lazytime" # make time changes in memory
                        ];
                        swap = {
                          swapfile = {
                            priority = -1; # lower than zramSwap, just in case
                            size = cfg.swap.ram_size;
                          };
                        };
                      };
                    };
                  };
                };
              };
            };
          };
        };
      };
      nodev = {
        "/" = {
          fsType = "tmpfs";
          mountOptions = ["defaults" "size=25%" "mode=0755"];
        };
        "/tmp" = {
          fsType = "tmpfs";
          mountOptions = ["defaults" "size=50%" "mode=0755"];
        };
        "/nix/var/nix/b" = {
          fsType = "tmpfs";
          mountOptions = [
            "defaults"
            "noswap" # Otherwise, we might run into io-based slowdowns
            "size=80%"
            "mode=0755"
          ];
        };
      };
    };
    fileSystems = {
      "/nix" = {
        neededForBoot = true;
      };
      "/srv" = {
        neededForBoot = true;
      };
      "/swap" = {
        neededForBoot = true;
      };
    };
    zramSwap = {
      enable = true;
      priority = 10; # needs to be higher than hardware-swap
    };
    boot = {
      kernelParams = [
        "zswap.enabled=0" # zswap and zram are not really compatible
      ];
    };
  };
}