core/lib/gvariant.nix

/*
  A partial and basic implementation of GVariant formatted strings.
  See [GVariant Format Strings](https://docs.gtk.org/glib/gvariant-format-strings.html) for details.

  :::{.warning}
  This API is not considered fully stable and it might therefore
  change in backwards incompatible ways without prior notice.
  :::
*/

# This file is based on https://github.com/nix-community/home-manager
# Copyright (c) 2017-2022 Home Manager contributors
{ lib }:

let
  inherit (lib)
    concatMapStringsSep
    concatStrings
    escape
    head
    replaceStrings
    ;

  mkPrimitive = t: v: {
    _type = "gvariant";
    type = t;
    value = v;
    __toString = self: "@${self.type} ${toString self.value}"; # https://docs.gtk.org/glib/gvariant-text.html
  };

  type = {
    arrayOf = t: "a${t}";
    maybeOf = t: "m${t}";
    tupleOf = ts: "(${concatStrings ts})";
    dictionaryEntryOf = nameType: valueType: "{${nameType}${valueType}}";
    string = "s";
    boolean = "b";
    uchar = "y";
    int16 = "n";
    uint16 = "q";
    int32 = "i";
    uint32 = "u";
    int64 = "x";
    uint64 = "t";
    double = "d";
    variant = "v";
  };

  /*
    Check if a value is a GVariant value

    Type:
      isGVariant :: Any -> Bool
  */
  isGVariant = v: v._type or "" == "gvariant";

in
rec {

  inherit type isGVariant;

  /*
    Returns the GVariant value that most closely matches the given Nix value.
    If no GVariant value can be found unambiguously then error is thrown.

    Type:
      mkValue :: Any -> gvariant
  */
  mkValue =
    v:
    if builtins.isBool v then
      mkBoolean v
    else if builtins.isFloat v then
      mkDouble v
    else if builtins.isString v then
      mkString v
    else if builtins.isList v then
      mkArray v
    else if isGVariant v then
      v
    else
      throw "The GVariant type of ${v} can't be inferred.";

  /*
    Returns the GVariant array from the given type of the elements and a Nix list.

    Type:
      mkArray :: [Any] -> gvariant

    Example:
      # Creating a string array
      lib.gvariant.mkArray [ "a" "b" "c" ]
  */
  mkArray =
    elems:
    let
      vs = map mkValue (lib.throwIf (elems == [ ]) "Please create empty array with mkEmptyArray." elems);
      elemType = lib.throwIfNot (lib.all (t: (head vs).type == t) (
        map (v: v.type) vs
      )) "Elements in a list should have same type." (head vs).type;
    in
    mkPrimitive (type.arrayOf elemType) vs
    // {
      __toString = self: "@${self.type} [${concatMapStringsSep "," toString self.value}]";
    };

  /*
    Returns the GVariant array from the given empty Nix list.

    Type:
      mkEmptyArray :: gvariant.type -> gvariant

    Example:
      # Creating an empty string array
      lib.gvariant.mkEmptyArray (lib.gvariant.type.string)
  */
  mkEmptyArray =
    elemType: mkPrimitive (type.arrayOf elemType) [ ] // { __toString = self: "@${self.type} []"; };

  /*
    Returns the GVariant variant from the given Nix value. Variants are containers
    of different GVariant type.

    Type:
      mkVariant :: Any -> gvariant

    Example:
      lib.gvariant.mkArray [
        (lib.gvariant.mkVariant "a string")
        (lib.gvariant.mkVariant (lib.gvariant.mkInt32 1))
      ]
  */
  mkVariant =
    elem:
    let
      gvarElem = mkValue elem;
    in
    mkPrimitive type.variant gvarElem // { __toString = self: "<${toString self.value}>"; };

  /*
    Returns the GVariant dictionary entry from the given key and value.

    Type:
      mkDictionaryEntry :: String -> Any -> gvariant

    Example:
      # A dictionary describing an Epiphany’s search provider
      [
        (lib.gvariant.mkDictionaryEntry "url" (lib.gvariant.mkVariant "https://duckduckgo.com/?q=%s&t=epiphany"))
        (lib.gvariant.mkDictionaryEntry "bang" (lib.gvariant.mkVariant "!d"))
        (lib.gvariant.mkDictionaryEntry "name" (lib.gvariant.mkVariant "DuckDuckGo"))
      ]
  */
  mkDictionaryEntry =
    # The key of the entry
    name:
    # The value of the entry
    value:
    let
      name' = mkValue name;
      value' = mkValue value;
      dictionaryType = type.dictionaryEntryOf name'.type value'.type;
    in
    mkPrimitive dictionaryType { inherit name value; }
    // {
      __toString = self: "@${self.type} {${name'},${value'}}";
    };

  /*
    Returns the GVariant maybe from the given element type.

    Type:
      mkMaybe :: gvariant.type -> Any -> gvariant
  */
  mkMaybe =
    elemType: elem:
    mkPrimitive (type.maybeOf elemType) elem
    // {
      __toString =
        self: if self.value == null then "@${self.type} nothing" else "just ${toString self.value}";
    };

  /*
    Returns the GVariant nothing from the given element type.

    Type:
      mkNothing :: gvariant.type -> gvariant
  */
  mkNothing = elemType: mkMaybe elemType null;

  /*
    Returns the GVariant just from the given Nix value.

    Type:
      mkJust :: Any -> gvariant
  */
  mkJust =
    elem:
    let
      gvarElem = mkValue elem;
    in
    mkMaybe gvarElem.type gvarElem;

  /*
    Returns the GVariant tuple from the given Nix list.

    Type:
      mkTuple :: [Any] -> gvariant
  */
  mkTuple =
    elems:
    let
      gvarElems = map mkValue elems;
      tupleType = type.tupleOf (map (e: e.type) gvarElems);
    in
    mkPrimitive tupleType gvarElems
    // {
      __toString = self: "@${self.type} (${concatMapStringsSep "," toString self.value})";
    };

  /*
    Returns the GVariant boolean from the given Nix bool value.

    Type:
      mkBoolean :: Bool -> gvariant
  */
  mkBoolean =
    v: mkPrimitive type.boolean v // { __toString = self: if self.value then "true" else "false"; };

  /*
    Returns the GVariant string from the given Nix string value.

    Type:
      mkString :: String -> gvariant
  */
  mkString =
    v:
    let
      sanitize =
        s:
        replaceStrings [ "\n" ] [ "\\n" ] (
          escape [
            "'"
            "\\"
          ] s
        );
    in
    mkPrimitive type.string v // { __toString = self: "'${sanitize self.value}'"; };

  /*
    Returns the GVariant object path from the given Nix string value.

    Type:
      mkObjectpath :: String -> gvariant
  */
  mkObjectpath =
    v: mkPrimitive type.string v // { __toString = self: "objectpath '${escape [ "'" ] self.value}'"; };

  /*
    Returns the GVariant uchar from the given Nix int value.

    Type:
      mkUchar :: Int -> gvariant
  */
  mkUchar = mkPrimitive type.uchar;

  /*
    Returns the GVariant int16 from the given Nix int value.

    Type:
      mkInt16 :: Int -> gvariant
  */
  mkInt16 = mkPrimitive type.int16;

  /*
    Returns the GVariant uint16 from the given Nix int value.

    Type:
      mkUint16 :: Int -> gvariant
  */
  mkUint16 = mkPrimitive type.uint16;

  /*
    Returns the GVariant int32 from the given Nix int value.

    Type:
      mkInt32 :: Int -> gvariant
  */
  mkInt32 = v: mkPrimitive type.int32 v // { __toString = self: toString self.value; };

  /*
    Returns the GVariant uint32 from the given Nix int value.

    Type:
      mkUint32 :: Int -> gvariant
  */
  mkUint32 = mkPrimitive type.uint32;

  /*
    Returns the GVariant int64 from the given Nix int value.

    Type:
      mkInt64 :: Int -> gvariant
  */
  mkInt64 = mkPrimitive type.int64;

  /*
    Returns the GVariant uint64 from the given Nix int value.

    Type:
      mkUint64 :: Int -> gvariant
  */
  mkUint64 = mkPrimitive type.uint64;

  /*
    Returns the GVariant double from the given Nix float value.

    Type:
      mkDouble :: Float -> gvariant
  */
  mkDouble = v: mkPrimitive type.double v // { __toString = self: toString self.value; };
}