packages/octicons.nix

{
  lib,
  fetchFromGitHub,
  stdenv,
  fontforge,
  writeText,
  useNerdfontsOffset ? true,
}: let
  pname = "octicons";
  version = "4.4.0";
  src = fetchFromGitHub {
    owner = "primer";
    repo = "octicons";
    rev = "v${version}";
    sha256 = "sha256-xhJRe5mO2YkqQggqZ1JHBYsJKQUSJA08crDvl22GSGg=";
  };

  script = writeText "octicons.py" ''
    import fontforge
    import json
    import itertools


    if ${
      if useNerdfontsOffset
      then "True"
      else "False"
    }:
      validRange = list(itertools.chain((0x2665, 0x26a1), range(0xF400, 0xF4A8), (0xF112, 0xF67C)))
      def codepointTransform(_):
        return validRange.pop(0)
    else:
      codepointTransform = lambda cp: cp

    offset = ${
      if useNerdfontsOffset
      then "0x0400"
      else "0"
    }

    with open("${src}/lib/font/codepoints.json") as f:
      codepoints = json.load(f)

    font = fontforge.font()

    for name, codepoint in sorted(codepoints.items(), key=lambda item: item[1]):
      transformed = codepointTransform(codepoint)
      print(name, hex(transformed))
      glyph = font.createChar(transformed)
      glyph.importOutlines(f"${src}/lib/svg/{name}.svg")

    font.familyname = "${pname}"
    font.fullname = "${pname}"
    font.fontname = "${pname}"

    font.generate("${pname}.ttf")
  '';
in
  stdenv.mkDerivation rec {
    inherit version src pname;

    buildPhase = ''
      fontforge \
        -lang py \
        -script ${script} \;
    '';

    installPhase = ''
      mkdir -p $out/bin $out/share/fonts/truetype
      mv ${pname}.ttf $out/share/fonts/truetype
      echo $out
    '';

    nativeBuildInputs = [fontforge];

    meta = with lib; {
      description = "GitHub's Octicons icon pack";
      homepage = "https://github.com/primer/octicons";
      license = licenses.mit;
      maintainers = with maintainers; [minion3665];
    };
  }