{ 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
  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 = "Malayalam typefaces made by smc.org.in";
    longDescription = ''
      Swathanthra Malayalam Computing (SMC) is a free software collective engaged in the development, localization, standardization and popularization of various Free and Open Source Software in the Malayalam language. This derivation builds all fonts made by SMC.
    '';
    homepage = "https://smc.org.in/";
    license = licenses.ofl;
    platforms = platforms.all;
    maintainers = with maintainers; [ aashiks ];
  };
})