infrastructure/lib/trivial.nix

rec {
  /* Fuses a list of attribute sets into a single attribute set.

     Example:
       x = [ { a = 1; } { b = 2; } ]
       fuseAttrs x
       => { a = 1; b = 2; }
  */
  fuseAttrs = builtins.foldl' (attrs: x: attrs // x) { };

  /* Maps then fuses a list of attribute sets into a single attribute set.

     Example:
       x = [ "a" "b" ]
       mapFuse (c: { ${c} = 42; }) x
       => { a = 42; b = 42; }
  */
  mapFuse = f: attrsList: fuseAttrs (builtins.map f attrsList);

  /* Equivalent of lib.singleton but for an attribute set.

     Example:
       singleAttr "a" 1
       => { a = 1; }
  */
  singleAttr = name: value: { ${name} = value; };

  mapSingleFuse = f: mapFuse (x: singleAttr x (f x));

  /* Creates a relative path as a string

     Example:
       mkRel /home/test/ "file.txt"
       => "/home/test/file.txt"
    */
  mkRel = path: file: path + "/${file}";

  compose = f: g: (x: g (f x));
}