{ lib, ... }:

let
  inherit (lib)
    all any attrNames concatMapStringsSep concatStringsSep const filter flip
    genid_uint31 hasSuffix head isInt isString length mergeOneOption mkOption
    mkOptionType optional optionalAttrs optionals range splitString
    stringLength substring test testString typeOf;
  inherit (lib.types)
    attrsOf bool either enum int lines listOf nullOr path str submodule;
in

rec {

  host = submodule ({ config, ... }: {
    options = {
      name = mkOption {
        type = label;
        default = config._module.args.name;
      };
      nets = mkOption {
        type = attrsOf net;
        default = {};
      };

      binary-cache.pubkey = mkOption {
        type = nullOr binary-cache-pubkey;
        default = null;
      };

      ci = mkOption {
        description = ''
          If true, then the host wants to be tested by some CI system.
          See ‹stockholm/krebs/2configs/buildbot-all.nix›
        '';
        type = bool;
        default = false;
      };

      external = mkOption {
        description = ''
          Whether the host is defined externally (in contrast to being defined
          in ‹stockholm›).  This is useful e.g. when legacy and/or adopted
          hosts should be part of retiolum or some other component.
        '';
        type = bool;
        default = false;
      };

      monitoring = mkOption {
        description = ''
          Whether the host should be monitored by monitoring tools like Prometheus.
        '';
        type = bool;
        default = false;
      };

      consul = mkOption {
        description = ''
          Whether the host is a member of the global consul network
        '';
        type = bool;
        default = false;
      };

      owner = mkOption {
        type = user;
      };

      extraZones = mkOption {
        default = {};
        # TODO: string is either MX, NS, A or AAAA
        type = attrsOf str;
      };

      secure = mkOption {
        type = bool;
        default = false;
        description = ''
          If true, then the host is capable of keeping secret information.

          TODO define minimum requirements for secure hosts
        '';
      };

      ssh.pubkey = mkOption {
        type = nullOr ssh-pubkey;
        default = null;
      };
      ssh.privkey = mkOption {
        type = nullOr ssh-privkey;
        default = null;
      };

      syncthing.id = mkOption {
        # TODO syncthing id type
        type = nullOr str;
        default = null;
      };
    };
  });

  net = submodule ({ config, ... }: {
    options = {
      name = mkOption {
        type = label;
        default = config._module.args.name;
      };
      via = mkOption {
        type =
          # XXX break infinite recursion when generating manuals
          if config._module.args.name == "‹name›" then
            mkOptionType {
              name = "‹net›";
            }
          else
            nullOr net;
        default = null;
      };
      addrs = mkOption {
        type = listOf (either addr str);
        default =
          optional (config.ip4 != null) config.ip4.addr ++
          optional (config.ip6 != null) config.ip6.addr;
      };
      aliases = mkOption {
        # TODO nonEmptyListOf hostname
        type = listOf hostname;
        default = [];
      };
      mac = mkOption {
        type = nullOr str;
        default = null;
      };
      ip4 = mkOption {
        type = nullOr (submodule (ip4: {
          options = {
            addr = mkOption {
              type = addr4;
            };
            prefix = mkOption ({
              type = cidr4;
            } // {
              retiolum.default = "10.243.0.0/16";
              wiregrill.default = "10.244.0.0/16";
            }.${config._module.args.name} or {
              default = "${ip4.config.addr}/32";
            });
            prefixLength = mkOption ({
              type = uint;
            } // {
              retiolum.default = 16;
              wiregrill.default = 16;
            }.${config._module.args.name} or {
              default = 32;
            });
          };
        }));
        default = null;
      };
      ip6 = mkOption {
        type = nullOr (submodule (ip6: {
          options = {
            addr = mkOption {
              type = addr6;
              apply = lib.normalize-ip6-addr;
            };
            prefix = mkOption ({
              type = cidr6;
            } // {
              retiolum.default = "42:0::/32";
              wiregrill.default = "42:1::/32";
            }.${config._module.args.name} or {
              default = "${ip6.config.addr}/128";
            });
            prefixLength = mkOption ({
              type = uint;
            } // {
              retiolum.default = 32;
              wiregrill.default = 32;
            }.${config._module.args.name} or {
              default = 128;
            });
          };
        }));
        default = null;
      };
      ssh = mkOption {
        type = submodule {
          options = {
            port = mkOption {
              type = int;
              default = 22;
            };
          };
        };
        default = {};
      };
      tinc = mkOption {
        type = let net = config; in nullOr (submodule ({ config, ... }: {
          options = {
            config = mkOption {
              type = str;
              default = concatStringsSep "\n" (
                (optionals (net.via != null)
                  (map (a: "Address = ${a} ${toString config.port}") net.via.addrs))
                ++
                (map (a: "Subnet = ${a}") net.addrs)
                ++
                (map (a: "Subnet = ${a}") config.subnets)
                ++
                [config.extraConfig]
                ++
                [config.pubkey]
                ++
                optional (config.pubkey_ed25519 != null) ''
                  Ed25519PublicKey = ${config.pubkey_ed25519}
                ''
                ++
                optional (config.weight != null) "Weight = ${toString config.weight}"
              );
              defaultText = ''
                Address = ‹addr› ‹port› # for each ‹net.via.addrs›
                Subnet = ‹addr› # for each ‹net.addrs›
                ‹extraConfig›
                ‹pubkey›
              '';
            };
            pubkey = mkOption {
              type = tinc-pubkey;
            };
            pubkey_ed25519 = mkOption {
              type = nullOr tinc-pubkey;
              default = null;
            };
            extraConfig = mkOption {
              description = "Extra Configuration to be appended to the hosts file";
              default = "";
              type = lines;
            };
            port = mkOption {
              type = int;
              description = "tinc port to use to connect to host";
              default = 655;
            };
            subnets = mkOption {
              type = listOf cidr;
              description = "tinc subnets";
              default = [];
            };
            weight = mkOption {
              type = nullOr int;
              description = ''
                global tinc weight (latency in ms) of this particular node.
                can be set to some high value to make it unprobable to be used as router.
                if set to null, tinc will autogenerate the value based on latency.
              '';
              default = if net.via != null then null else 300;
            };
          };
        }));
        default = null;
      };
      wireguard = mkOption {
        type = nullOr (submodule ({ config, ... }: {
          options = {
            port = mkOption {
              type = int;
              description = "tinc port to use to connect to host";
              default = 51820;
            };
            pubkey = mkOption {
              type = wireguard-pubkey;
            };
            subnets = mkOption {
              type = listOf cidr;
              description = ''
                wireguard subnets,
                this defines how routing behaves for hosts that can't reach each other.
              '';
              default = [];
            };
          };
        }));
        default = null;
      };
    };
  });

  boundedInt = min: max: mkOptionType {
    name = "bounded integer";
    check = x: isInt x && min <= x && x <= max;
    merge = mergeOneOption;
  };

  lowerBoundedInt = min: mkOptionType {
    name = "lower bounded integer";
    check = x: isInt x && min <= x;
    merge = mergeOneOption;
  };

  positive = mkOptionType {
    inherit (lowerBoundedInt 1) check;
    name = "positive integer";
    merge = mergeOneOption;
  };

  uint = mkOptionType {
    inherit (lowerBoundedInt 0) check;
    name = "unsigned integer";
    merge = mergeOneOption;
  };

  secret-file = submodule ({ config, ... }: {
    options = {
      name = mkOption {
        type = pathname;
        default = config._module.args.name;
      };
      path = mkOption {
        type = absolute-pathname;
        default = "/run/keys/${config.name}";
        defaultText = "/run/keys/‹name›";
      };
      mode = mkOption {
        type = file-mode;
        default = "0400";
      };
      owner = mkOption {
        type = user;
      };
      group-name = mkOption {
        type = str;
        default = "root";
      };
      service = mkOption {
        type = systemd.unit-name;
        default = "secret-${lib.systemd.encodeName config.name}.service";
        defaultText = "secret-‹name›.service";
      };
      source-path = mkOption {
        type = str;
        default = toString <secrets> + "/${config.name}";
        defaultText = "‹secrets/‹name››";
      };
    };
  });


  source = submodule ({ config, ... }: {
    options = {
      type = let
        known-types = attrNames source-types;
        type-candidates = filter (k: config.${k} != null) known-types;
      in mkOption {
        default = if length type-candidates == 1
                    then head type-candidates
                    else throw "cannot determine type";
        type = enum known-types;
      };
      file = mkOption {
        apply = x:
          if absolute-pathname.check x
            then { path = x; }
            else x;
        default = null;
        type = nullOr (either absolute-pathname source-types.file);
      };
      git = mkOption {
        default = null;
        type = nullOr source-types.git;
      };
      pass = mkOption {
        default = null;
        type = nullOr source-types.pass;
      };
      pipe = mkOption {
        apply = x:
          if absolute-pathname.check x
            then { command = x; }
            else x;
        default = null;
        type = nullOr (either absolute-pathname source-types.pipe);
      };
      symlink = mkOption {
        type = nullOr (either pathname source-types.symlink);
        default = null;
        apply = x:
          if pathname.check x
            then { target = x; }
            else x;
      };
    };
  });

  source-types = {
    file = submodule {
      options = {
        path = mkOption {
          type = absolute-pathname;
        };
      };
    };
    git = submodule {
      options = {
        ref = mkOption {
          type = str; # TODO types.git.ref
        };
        url = mkOption {
          type = str; # TODO types.git.url
        };
      };
    };
    pass = submodule {
      options = {
        dir = mkOption {
          type = absolute-pathname;
        };
        name = mkOption {
          type = pathname; # TODO relative-pathname
        };
      };
    };
    pipe = submodule {
      options = {
        command = mkOption {
          type = absolute-pathname;
        };
      };
    };
    symlink = submodule {
      options = {
        target = mkOption {
          type = pathname; # TODO relative-pathname
        };
      };
    };

  };

  suffixed-str = suffs:
    mkOptionType {
      name = "string suffixed by ${concatStringsSep ", " suffs}";
      check = x: isString x && any (flip hasSuffix x) suffs;
      merge = mergeOneOption;
    };

  user = submodule ({ config, ... }: {
    options = {
      home = mkOption {
        type = absolute-pathname;
        default = "/home/${config.name}";
        defaultText = "/home/‹name›";
      };
      mail = mkOption {
        type = nullOr str;
        default = null;
      };
      name = mkOption {
        type = username;
        default = config._module.args.name;
      };
      pgp.pubkeys = mkOption {
        type = attrsOf pgp-pubkey;
        default = {};
        description = ''
          Set of user's PGP public keys.

          Modules supporting PGP may use well-known key names to define
          default values for options, in which case the well-known name
          should be documented in the respective option's description.
        '';
      };
      pubkey = mkOption {
        type = nullOr ssh-pubkey;
        default = null;
      };
      uid = mkOption {
        type = int;
        default = genid_uint31 config.name;
        defaultText = "genid_uint31 ‹name›";
      };
    };
  });
  group = submodule ({ config, ... }: {
    options = {
      name = mkOption {
        type = username;
        default = config._module.args.name;
        defaultText = "genid_uint31 ‹name›";
      };
      gid = mkOption {
        type = int;
        default = genid_uint31 config.name;
        defaultText = "genid_uint31 ‹name›";
      };
    };
  });

  addr = either addr4 addr6;
  addr4 = mkOptionType {
    name = "IPv4 address";
    check = let
      IPv4address = let d = "([1-9]?[0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])"; in
        concatMapStringsSep "." (const d) (range 1 4);
    in
      test IPv4address;
    merge = mergeOneOption;
  };
  addr6 = mkOptionType {
    name = "IPv6 address";
    check = let
      # TODO check IPv6 address harder
      IPv6address = "[0-9a-f.:]+";
    in
      test IPv6address;
    merge = mergeOneOption;
  };

  cidr = either cidr4 cidr6;
  cidr4 = mkOptionType {
    name = "CIDRv4 address";
    check = let
      CIDRv4address = let d = "([1-9]?[0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])"; in
        concatMapStringsSep "." (const d) (range 1 4) + "(/([1-2]?[0-9]|3[0-2]))?";
    in
      test CIDRv4address;
    merge = mergeOneOption;
  };
  cidr6 = mkOptionType {
    name = "CIDRv6 address";
    check = let
      # TODO check IPv6 address harder
      CIDRv6address = "[0-9a-f.:]+(/([0-9][0-9]?|1[0-2][0-8]))?";
    in
      test CIDRv6address;
    merge = mergeOneOption;
  };

  binary-cache-pubkey = str;

  pgp-pubkey = str;

  sitemap.entry = submodule ({ config, ... }: {
    options = {
      desc = mkOption {
        default = null;
        type = nullOr str;
      };
      href = mkOption {
        ${if testString "https?://.*" config._module.args.name
          then "default" else null} = config._module.args.name;
        type = nullOr str; # TODO nullOr uri?
      };
    };
  });

  ssh-pubkey = str;
  ssh-privkey = submodule {
    options = {
      bits = mkOption {
        type = nullOr (enum ["4096"]);
        default = null;
      };
      path = mkOption {
        type = either path str;
        apply = x: {
          path = toString x;
          string = x;
        }.${typeOf x};
      };
      type = mkOption {
        type = enum ["rsa" "ed25519"];
        default = "ed25519";
      };
    };
  };

  tinc-pubkey = str;

  krebs.file-location = submodule {
    options = {
      # TODO user
      host = mkOption {
        type = host;
      };
      # TODO merge with ssl.privkey.path
      path = mkOption {
        type = either path str;
        apply = x: {
          path = toString x;
          string = x;
        }.${typeOf x};
      };
    };
  };

  file-mode = mkOptionType {
    name = "file mode";
    check = test "[0-7]{4}";
    merge = mergeOneOption;
  };

  haskell.conid = mkOptionType {
    name = "Haskell constructor identifier";
    check = test "[[:upper:]][[:lower:]_[:upper:]0-9']*";
    merge = mergeOneOption;
  };

  haskell.modid = mkOptionType {
    name = "Haskell module identifier";
    check = x: isString x && all haskell.conid.check (splitString "." x);
    merge = mergeOneOption;
  };

  systemd.unit-name = mkOptionType {
    name = "systemd unit name";
    check = x:
      test "^[0-9A-Za-z:_.\\-]+@?\\.(service|socket|device|mount|automount|swap|target|path|timer|slice|scope)$" x &&
      stringLength x <= 256;
    merge = mergeOneOption;
  };

  # RFC952, B. Lexical grammar, <hname>
  hostname = mkOptionType {
    name = "hostname";
    check = x: isString x && all label.check (splitString "." x);
    merge = mergeOneOption;
  };

  # RFC952, B. Lexical grammar, <name>
  # RFC1123, 2.1  Host Names and Numbers
  label = mkOptionType {
    name = "label";
    # TODO case-insensitive labels
    check = test "[0-9A-Za-z]([0-9A-Za-z-]*[0-9A-Za-z])?";
    merge = mergeOneOption;
  };

  # POSIX.1‐2017, 3.190 Group Name
  groupname = mkOptionType {
    name = "POSIX group name";
    check = filename.check;
    merge = mergeOneOption;
  };

  # POSIX.1‐2017, 3.281 Portable Filename
  filename = mkOptionType {
    name = "POSIX portable filename";
    check = test "[0-9A-Za-z._][0-9A-Za-z._-]*";
    merge = mergeOneOption;
  };

  # POSIX.1‐2017, 3.2 Absolute Pathname
  absolute-pathname = mkOptionType {
    name = "POSIX absolute pathname";
    check = x: isString x && substring 0 1 x == "/" && pathname.check x;
    merge = mergeOneOption;
  };

  # POSIX.1-2017, 3.271 Pathname
  pathname = mkOptionType {
    name = "POSIX pathname";
    check = x:
      let
        # The filter is used to normalize paths, i.e. to remove duplicated and
        # trailing slashes.  It also removes leading slashes, thus we have to
        # check for "/" explicitly below.
        xs = filter (s: stringLength s > 0) (splitString "/" x);
      in
        isString x && (x == "/" || (length xs > 0 && all filename.check xs));
    merge = mergeOneOption;
  };

  # POSIX.1-2017, 3.216 Login Name
  username = mkOptionType {
    name = "POSIX login name";
    check = filename.check;
    merge = mergeOneOption;
  };

  wireguard-pubkey = str;
}