{ config, lib, ... }:

let
  cfg = config.disko;
in
{
  options.disko = {
    name = lib.mkOption {
      type = lib.types.str;
      example = "chaos";
      description = "Machine name used in eg zpool name.";
    };

    rootDisk = lib.mkOption {
      type = with lib.types; nullOr str;
      default = null;
      example = "/dev/sda";
      description = "Path of the root disk.";
    };

    enableCeph = lib.mkOption {
      type = lib.types.bool;
      default = true;
      description = "Wether to include a ceph on the root disk.";
    };

    enableLuks = lib.mkOption {
      type = lib.types.bool;
      default = true;
      description = "Wether to encrypt the root disk.";
    };

    enableZfs = lib.mkOption {
      type = lib.types.bool;
      default = true;
      description = "Wether to include a zfs on the root disk.";
    };
  };

  config = {
    assertions = [
      {
        assertion = cfg.enableCeph || cfg.enableZfs;
        message = "Must enable ceph or zfs!";
      }
      {
        assertion = cfg.enableCeph -> cfg.enableLuks;
        message = "Ceph requires Luks!";
      }
    ];

    disko = {
      devices =
        let
          rootSize = 200;
          zfs = {
            size = if (!cfg.enableCeph) then "100%FREE" else "${toString rootSize}GiB";
            content = {
              pool = cfg.name;
              type = "zfs";
            };
          };
        in
        lib.mkIf (cfg.rootDisk != "")
          {
            disk.${cfg.rootDisk} = {
              device = cfg.rootDisk;
              type = "disk";
              content = {
                type = "table";
                format = "gpt";
                partitions = lib.optional cfg.enableZfs
                  {
                    name = "ESP";
                    start = "1MiB";
                    end = "512MiB";
                    bootable = true;
                    content = {
                      type = "filesystem";
                      format = "vfat";
                      mountpoint = "/boot";
                    };
                  } ++ [
                  {
                    name = "root";
                    start = if cfg.enableZfs then "512MiB" else "1MiB";
                    end = "100%";
                    part-type = "primary";
                    content = lib.optionalAttrs cfg.enableLuks
                      {
                        type = "luks";
                        name = "crypt-${cfg.name}";
                        # TODO: add password, otherwise prompt opens
                        keyFile = "/$PWD/keyFile";
                        content = {
                          type = "lvm_pv";
                          vg = "lvm-${cfg.name}";
                        };
                      } // lib.optionalAttrs (!cfg.enableLuks) zfs.content;
                  }
                ];
              };
            };
          } // lib.optionalAttrs cfg.enableLuks {
          lvm_vg."lvm-${cfg.name}" = {
            type = "lvm_vg";
            lvs = lib.optionalAttrs cfg.enableCeph
              {
                # the header is 3650 byte long and substract an additional 446 byte for aligment
                # error messages:
                #   Volume group "lvm-chaos" has insufficient free space (51195 extents): 51200 required.
                #   Size is not a multiple of 512. Try using 40057405440 or 40057405952.
                ceph.size =
                  let
                    # convert GiB to bytes
                    rootSizeMiB = rootSize * 1024 * 1024 * 1024;
                    # convert back to MiB and allign to 4 MiB in the process
                    roundToMiB = "/1024/1024/4*4";
                    # substract 512 MiB for /boot and 20 MiB for luks+header+other
                    bootOther = "-512-20";
                  in
                  "$((($(lsblk /dev/sda --noheadings --nodeps --output SIZE --bytes)-${toString rootSizeMiB})${roundToMiB}${bootOther}))MiB";
              } // lib.optionalAttrs cfg.enableZfs { inherit zfs; };
          };
        } // {
          zpool."${cfg.name}" = {
            type = "zpool";
            mountpoint = null;
            mountRoot = "/mnt";
            rootFsOptions.acltype = "posixacl";
            options = {
              ashift = "12";
              autotrim = "on";
            };
            datasets =
              let
                dataset = mountpoint: {
                  options = {
                    canmount = "on";
                    compression = "zstd";
                    dnodesize = "auto";
                    normalization = "formD";
                    xattr = "sa";
                    inherit mountpoint;
                  };
                  type = "zfs_fs";
                };
              in
              {
                "data" = dataset "/";
                "data/etc" = dataset "/etc";
                "data/home" = dataset "/home";
                "data/var" = dataset "/var";
                # used by services.postgresqlBackup and later by restic
                "data/var/backup" = dataset "/var/backup";
                "data/var/lib" = dataset "/var/lib";
                "data/var/log" = dataset "/var/log";
                "nixos" = {
                  options = {
                    canmount = "off";
                    mountpoint = "none";
                  };
                  type = "zfs_fs";
                };
                "nixos/nix" = dataset "/nix";
                "nixos/nix/store" = {
                  options = {
                    atime = "off";
                    canmount = "on";
                    mountpoint = "/nix/store";
                  };
                  type = "zfs_fs";
                };
                "nixos/nix/var" = dataset "/nix/var";
                "reserved" = {
                  # zfs uses copy on write and requires some free space to delete files when the disk is completely filled
                  options = {
                    canmount = "off";
                    mountpoint = "none";
                    reservation = "5GiB";
                  };
                  type = "zfs_fs";
                };
              };
          };
        };
      # we use our own hardware-configuration.nix
      enableConfig = false;
    };
  };
}