{ stdenv, fetchzip, lib
# To select only certain fonts, put a list of strings to `fonts`: every key in
# ./shas.nix is an optional font
, fonts ? [ ] }:

let
  # both of these files are generated via ./update.sh
  version = "version-20241013";
  fontsShas = import ./shas.nix;
  knownFonts = builtins.attrNames fontsShas;
  selectedFonts = if (fonts == [ ]) then
    knownFonts
  else
    let unknown = lib.subtractLists knownFonts fonts;
    in if (unknown != [ ]) then
      throw "Unknown font(s): ${lib.concatStringsSep " " unknown}"
    else
      fonts;

  # Filter the fonts by selectedFonts list
  filteredFonts =
    builtins.filter (fontName: builtins.elem fontName selectedFonts)
    (builtins.attrNames fontsShas);

  # Function to generate a list of srcs that look like
  #   [
  #   (fetchurl {
  #     name = "namezzxs"
  #     url = "";
  #     sha256 = "sha256-abc123...";
  #   })
  #   (fetchurl {
  #     name = "namezzxy"
  #     url = "";
  #     sha256 = "sha256-def456...";
  #   })
  # ]
  generateUrls = fontAttrs: fontName:
    builtins.map (variant:
      let sha = fontAttrs.${variant};
      in fetchzip {
        name = "${fontName}-${variant}";
        url = "https://smc.org.in/downloads/fonts/${fontName}/${variant}.zip";
        sha256 = sha;
        stripRoot = false;
      }) (builtins.attrNames fontAttrs);

  # Generate srcs for the filtered fonts
  srcs = builtins.concatLists
    (builtins.map (fontName: generateUrls fontsShas.${fontName} fontName)
      filteredFonts);

in stdenv.mkDerivation (finalAttrs: {
  inherit version;
  inherit srcs;
  pname = "smc-fonts";
  sourceRoot = ".";
  buildPhase = ''
    echo "selected fonts are ${toString selectedFonts}"
    ls *.otf *.ttf
  '';
  installPhase = ''
    find -name \*.otf -exec mkdir -p $out/share/fonts/opentype/SMCFonts \; -exec mv {} $out/share/fonts/opentype/SMCFonts \;
    find -name \*.ttf -exec mkdir -p $out/share/fonts/truetype/SMCFonts \; -exec mv {} $out/share/fonts/truetype/SMCFonts \;
  '';

  meta = with lib; {
    description = "SMC typefaces";
    longDescription = ''
      Swathanthra Malayalam Computing.
    '';
    homepage = "https://smc.org.in/";
    license = licenses.ofl;
    platforms = platforms.all;
    maintainers = with maintainers; [ aashiks ];
  };
})