home-manager/modules/lib/gvariant.nix
2020-03-21 00:28:50 +01:00

142 lines
3.3 KiB
Nix

# A partial and basic implementation of GVariant formatted strings.
#
# Note, this API is not considered fully stable and it might therefore
# change in backwards incompatible ways without prior notice.
{ lib }:
with lib;
let
mkPrimitive = t: v: {
_type = "gvariant";
type = t;
value = v;
__toString = self: "@${self.type} ${toString self.value}";
};
type = {
arrayOf = t: "a${t}";
tupleOf = ts: "(${concatStrings ts})";
string = "s";
boolean = "b";
uchar = "y";
int16 = "n";
uint16 = "q";
int32 = "i";
uint32 = "u";
int64 = "x";
uint64 = "t";
double = "d";
};
# Returns the GVariant type of a given Nix value. If no type can be
# found for the value then the empty string is returned.
typeOf = v:
with type;
if builtins.isBool v then
boolean
else if builtins.isInt v then
int32
else if builtins.isFloat v then
double
else if builtins.isString v then
string
else if builtins.isList v then
let elemType = elemTypeOf v;
in if elemType == "" then "" else arrayOf elemType
else if builtins.isAttrs v && v ? type then
v.type
else
"";
elemTypeOf = vs:
if builtins.isList vs then
if vs == [ ] then "" else typeOf (head vs)
else
"";
in rec {
inherit type typeOf;
isArray = hasPrefix "a";
isTuple = hasPrefix "(";
# Returns the GVariant value that most closely matches the given Nix
# value. If no GVariant value can be found then `null` is returned.
#
# No support for dictionaries, maybe types, or variants.
mkValue = v:
if builtins.isBool v then
mkBoolean v
else if builtins.isInt v then
mkInt32 v
else if builtins.isFloat v then
mkDouble v
else if builtins.isString v then
mkString v
else if builtins.isList v then
if v == [ ] then mkArray type.string [ ] else mkArray (elemTypeOf v) v
else if builtins.isAttrs v && (v._type or "") == "gvariant" then
v
else
null;
mkArray = elemType: elems:
mkPrimitive (type.arrayOf elemType) (map mkValue elems) // {
__toString = self:
"@${self.type} [${concatMapStringsSep "," toString self.value}]";
};
mkEmptyArray = elemType: mkArray elemType [ ];
mkTuple = elems:
let
gvarElems = map mkValue elems;
tupleType = type.tupleOf (map (e: e.type) gvarElems);
in mkPrimitive tupleType gvarElems // {
__toString = self:
"@${self.type} (${concatMapStringsSep "," toString self.value})";
};
mkBoolean = v:
mkPrimitive type.boolean v // {
__toString = self: if self.value then "true" else "false";
};
mkString = v:
mkPrimitive type.string v // {
__toString = self: "'${escape [ "'" ] self.value}'";
};
mkObjectpath = v:
mkPrimitive type.string v // {
__toString = self: "objectpath '${escape [ "'" ] self.value}'";
};
mkUchar = mkPrimitive type.uchar;
mkInt16 = mkPrimitive type.int16;
mkUint16 = mkPrimitive type.uint16;
mkInt32 = v:
mkPrimitive type.int32 v // {
__toString = self: toString self.value;
};
mkUint32 = mkPrimitive type.uint32;
mkInt64 = mkPrimitive type.int64;
mkUint64 = mkPrimitive type.uint64;
mkDouble = v:
mkPrimitive type.double v // {
__toString = self: toString self.value;
};
}