{ lib ? import <nixpkgs/lib> }:
with lib;
with builtins;

let

  helper.find-device = device:
    let
      environment = helper.device-id device;
    in
    # DEVICE points already to /dev/disk, so we don't handle it via /dev/disk/by-path
    if hasPrefix "/dev/disk" device then
      "${environment}='${device}'"
    else ''
      ${environment}=$(for x in $(find /dev/disk/{by-path,by-id}/); do
        dev=$x
        if [ "$(readlink -f $x)" = "$(readlink -f '${device}')" ]; then
          target=$dev
          break
        fi
      done
      if test -z ''${target+x}; then
        echo 'unable to find path of disk: ${device}, bailing out' >&2
        exit 1
      else
        echo $target
      fi)
    '';

  helper.device-id = device: "DEVICE${builtins.substring 0 5 (builtins.hashString "sha1" device)}";

  config-f = q: x: config.${x.type} q x;

  config.filesystem = q: x: {
    fileSystems.${x.mountpoint} = {
      device = q.device;
      fsType = x.format;
      ${if x ? options then "options" else null} = x.options;
    };
  };

  config.zfs_filesystem = q: x: {
    fileSystems.${x.mountpoint} = {
      device = q.device;
      fsType = "zfs";
    };
  };

  config.devices = q: x:
    foldl' recursiveUpdate { } (mapAttrsToList (name: config-f { device = "/dev/${name}"; }) x.content);

  config.luks = q: x: {
    boot.initrd.luks.devices.${x.name}.device = q.device;
  } // config-f { device = "/dev/mapper/${x.name}"; } x.content;

  config.lvm_lv = q: x:
    config-f { device = "/dev/${q.vgname}/${q.name}"; } x.content;

  config.lvm_vg = q: x:
    foldl' recursiveUpdate { } (mapAttrsToList (name: config-f { inherit name; vgname = x.name; }) x.lvs);

  config.noop = q: x: { };

  config.partition = q: x:
    config-f { device = q.device + toString q.index; } x.content;

  config.table = q: x:
    foldl' recursiveUpdate { } (imap (index: config-f (q // { inherit index; })) x.partitions);


  create-f = q: x: create.${x.type} q x;

  create.btrfs = q: x: ''
    mkfs.btrfs ${q.device}
    ${lib.optionalString (!isNull x.subvolumes or null) ''
      MNTPOINT=$(mktemp -d)
      (
        mount ${q.device} "$MNTPOINT"
        trap 'umount $MNTPOINT; rm -rf $MNTPOINT' EXIT
        ${concatMapStringsSep "\n" (subvolume: "btrfs subvolume create \"$MNTPOINT\"/${subvolume}") x.subvolumes}
      )
    ''}
  '';

  create.filesystem = q: x: ''
    mkfs.${x.format} \
      ${lib.optionalString (!isNull x.extraArgs or null) x.extraArgs} \
      ${q.device}
  '';

  create.devices = q: x:
    let
      raid-devices = lib.filterAttrs (_: dev: dev.type == "mdadm" || dev.type == "zpool" || dev.type == "lvm_vg") x.content;
      other-devices = lib.filterAttrs (_: dev: dev.type != "mdadm" && dev.type != "zpool" && dev.type != "lvm_vg") x.content;
    in
    ''
      ${concatStrings (mapAttrsToList (name: create-f { device = "/dev/${name}"; }) other-devices)}
      ${concatStrings (mapAttrsToList (name: create-f { device = "/dev/${name}"; name = name; }) raid-devices)}
    '';

  create.mdraid = q: x: ''
    RAIDDEVICES_N_${x.name}=$((''${RAIDDEVICES_N_${x.name}:-0}+1))
    RAIDDEVICES_${x.name}="''${RAIDDEVICES_${x.name}:-}${q.device} "
  '';

  create.mdadm = q: x: ''
    echo 'y' | mdadm --create /dev/md/${q.name} --level=${toString x.level or 1} --raid-devices=''${RAIDDEVICES_N_${q.name}} ''${RAIDDEVICES_${q.name}}
    udevadm trigger --subsystem-match=block; udevadm settle
    ${create-f { device = "/dev/md/${q.name}"; } x.content}
  '';

  create.luks = q: x: ''
    cryptsetup -q luksFormat ${q.device} ${if builtins.hasAttr "keyfile" x then x.keyfile else ""} ${toString (x.extraArgs or [])}
    cryptsetup luksOpen ${q.device} ${x.name} ${if builtins.hasAttr "keyfile" x then "--key-file " + x.keyfile else ""}
    ${create-f { device = "/dev/mapper/${x.name}"; } x.content}
  '';

  create.lvm_pv = q: x: ''
    pvcreate ${q.device}
    LVMDEVICES_${x.vg}="''${LVMDEVICES_${x.vg}:-}${q.device} "
  '';

  create.lvm_lv = q: x: ''
    lvcreate \
      ${if hasInfix "%" x.size then "-l" else "-L"} ${x.size} \
      -n ${q.name} \
      ${lib.optionalString (!isNull x.lvm_type or null) "--type=${x.lvm_type}"} \
      ${lib.optionalString (!isNull x.extraArgs or null) x.extraArgs} \
      ${q.vgname}
    ${create-f { device = "/dev/${q.vgname}/${q.name}"; } x.content}
  '';

  create.lvm_vg = q: x: ''
    vgcreate ${q.name} $LVMDEVICES_${q.name}
    ${concatStrings (mapAttrsToList (name: create-f { inherit name; vgname = q.name; }) x.lvs)}
  '';

  create.noop = q: x: "";

  create.partition = q: x:
    let
      env = helper.device-id q.device;
    in
    ''
      parted -s "''${${env}}" mkpart ${x.part-type} ${x.fs-type or ""} ${x.start} ${x.end}
      # ensure /dev/disk/by-path/..-partN exists before continuing
      udevadm trigger --subsystem-match=block; udevadm settle
      ${optionalString (x.bootable or false) ''
        parted -s "''${${env}}" set ${toString q.index} boot on
      ''}
      ${concatMapStringsSep "" (flag: ''
        parted -s "''${${env}}" set ${toString q.index} ${flag} on
      '') (x.flags or [])}
      ${create-f { device = "\"\${${env}}\"-part" + toString q.index; } x.content}
    '';

  create.table = q: x: ''
    ${helper.find-device q.device}
    parted -s "''${${helper.device-id q.device}}" mklabel ${x.format}
    ${concatStrings (imap (index: create-f (q // { inherit index; })) x.partitions)}
  '';

  create.zfs = q: x: ''
    ZFSDEVICES_${x.pool}="''${ZFSDEVICES_${x.pool}:-}${q.device} "
  '';

  create.zfs_filesystem = q: x: ''
    zfs create ${q.pool}/${x.name} \
      ${lib.optionalString (isAttrs x.options or null) (concatStringsSep " " (mapAttrsToList (n: v: "-o ${n}=${v}") x.options))}
  '';

  create.zfs_volume = q: x: ''
    zfs create ${q.pool}/${x.name} \
      -V ${x.size} \
      ${lib.optionalString (isAttrs x.options or null) (concatStringsSep " " (mapAttrsToList (n: v: "-o ${n}=${v}") x.options))}
    udevadm trigger --subsystem-match=block; udevadm settle
    ${create-f { device = "/dev/zvol/${q.pool}/${x.name}"; } x.content}
  '';

  create.zpool = q: x: ''
    zpool create ${q.name} \
      ${lib.optionalString (!isNull (x.mode or null) && x.mode != "stripe") x.mode} \
      ${lib.optionalString (isAttrs x.options or null) (concatStringsSep " " (mapAttrsToList (n: v: "-o ${n}=${v}") x.options))} \
      ${lib.optionalString (isAttrs x.rootFsOptions or null) (concatStringsSep " " (mapAttrsToList (n: v: "-O ${n}=${v}") x.rootFsOptions))} \
      ''${ZFSDEVICES_${q.name}}
    ${concatMapStrings (create-f (q // { pool = q.name; })) x.datasets}
  '';


  mount-f = q: x: mount.${x.type} q x;

  mount.filesystem = q: x: {
    fs.${x.mountpoint} = ''
      if ! findmnt ${q.device} "/mnt${x.mountpoint}" > /dev/null 2>&1; then
        mount ${q.device} "/mnt${x.mountpoint}" \
        -o X-mount.mkdir \
        ${lib.optionalString (isList x.mountOptions or null) (concatStringsSep " " x.mountOptions)}
      fi
    '';
  };

  mount.zfs_filesystem = q: x:
    optionalAttrs ((x.options.mountpoint or "") != "none")
      (mount.filesystem (q // { device = q.dataset; }) (x // { mountOptions = [
        (lib.optionalString ((x.options.mountpoint or "") != "legacy") "-o zfsutil")
        "-t zfs"
      ]; }));

  mount.btrfs = mount.filesystem;

  mount.devices = q: x:
    let
      z = foldl' recursiveUpdate { } (mapAttrsToList (name: mount-f { device = "/dev/${name}"; inherit name; }) x.content);
      # attrValues returns values sorted by name.  This is important, because it
      # ensures that "/" is processed before "/foo" etc.
    in
    ''
      ${optionalString (hasAttr "table" z) (concatStringsSep "\n" (attrValues z.table))}
      ${optionalString (hasAttr "luks" z) (concatStringsSep "\n" (attrValues z.luks))}
      ${optionalString (hasAttr "lvm" z) (concatStringsSep "\n" (attrValues z.lvm))}
      ${optionalString (hasAttr "zpool" z) (concatStringsSep "\n" (attrValues z.zpool))}
      ${optionalString (hasAttr "zfs" z) (concatStringsSep "\n" (attrValues z.zfs))}
      ${optionalString (hasAttr "fs" z) (concatStringsSep "\n" (attrValues z.fs))}
    '';

  mount.luks = q: x: (
    recursiveUpdate
      (mount-f { device = "/dev/mapper/${x.name}"; } x.content)
      {
        luks.${q.device} = ''
          cryptsetup status ${x.name} >/dev/null 2>/dev/null || cryptsetup luksOpen ${q.device} ${x.name} ${if builtins.hasAttr "keyfile" x then "--key-file " + x.keyfile else ""}
        '';
      }
  );

  mount.lvm_lv = q: x:
    mount-f { device = "/dev/${q.vgname}/${q.name}"; } x.content;

  mount.lvm_vg = q: x: (
    recursiveUpdate
      (foldl' recursiveUpdate { } (mapAttrsToList (name: mount-f { inherit name; vgname = q.name; }) x.lvs))
      {
        lvm.${q.device} = ''
          vgchange -a y
        '';
      }
  );

  mount.lvm_pv = mount.noop;

  mount.noop = q: x: { };

  mount.mdadm = q: x:
    mount-f { device = "/dev/md/${q.name}"; } x.content;
  mount.mdraid = mount.noop;

  mount.partition = q: x:
    mount-f { device = "\"\${${q.device}}\"-part" + toString q.index; } x.content;

  mount.table = q: x: (
    recursiveUpdate
      (foldl' recursiveUpdate { } (imap (index: mount-f (q // { inherit index; device = helper.device-id q.device; })) x.partitions))
      { table.${q.device} = helper.find-device q.device; }
  );

  mount.zfs = mount.noop;

  mount.zpool = q: x:
    let
      datasets = [{
        inherit (q) name;
        type = "zfs_filesystem";
        dataset = q.name;
        mountpoint = x.mountpoint or "/${q.name}";
        options = q.rootFsOptions or { };
      }] ++ x.datasets;
    in
    recursiveUpdate
      (foldl' recursiveUpdate { }
        (
          (map
            (x: mount-f
              ({
                dataset = x.dataset or "${q.name}/${x.name}";
                mountpoint = x.mountpoint or "/${q.name}/${x.name}";
              } // q)
              x)
            datasets)
        )
      )
      {
        zpool.${q.device} = ''
          zpool list '${q.name}' >/dev/null 2>/dev/null || zpool import '${q.name}'
        '';
      };

  mount.zfs_volume = q: x:
    mount-f { device = "/dev/zvol/${q.dataset}"; } x.content;

in
{
  config = config-f { };
  create = cfg: ''
    set -efux
    ${create-f {} cfg}
  '';
  mount = cfg: ''
    set -efux
    ${mount-f {} cfg}
  '';

}