depot/pkgs/development/lua-modules/lib.nix

{
  pkgs,
  lib,
  lua,
}:
let
  inherit (lib.generators) toLua;
  requiredLuaModules =
    drvs:
    let
      modules = lib.filter hasLuaModule drvs;
    in
    lib.unique ([ lua ] ++ modules ++ lib.concatLists (lib.catAttrs "requiredLuaModules" modules));
  # Check whether a derivation provides a lua module.
  hasLuaModule = drv: drv ? luaModule;

  # Use this to override the arguments passed to buildLuarocksPackage
  overrideLuarocks =
    drv: f:
    (drv.override (
      args:
      args
      // {
        buildLuarocksPackage = drv: (args.buildLuarocksPackage drv).override f;
      }
    ))
    // {
      overrideScope = scope: overrideLuarocks (drv.overrideScope scope) f;
    };

in
rec {
  inherit overrideLuarocks;
  inherit hasLuaModule requiredLuaModules;

  luaPathList = [
    "share/lua/${lua.luaversion}/?.lua"
    "share/lua/${lua.luaversion}/?/init.lua"
  ];
  luaCPathList = [
    "lib/lua/${lua.luaversion}/?.so"
  ];

  # generate paths without a prefix
  luaPathRelStr = lib.concatStringsSep ";" luaPathList;
  luaCPathRelStr = lib.concatStringsSep ";" luaCPathList;

  # generate LUA_(C)PATH value for a specific derivation, i.e., with absolute paths
  genLuaPathAbsStr = drv: lib.concatMapStringsSep ";" (x: "${drv}/${x}") luaPathList;
  genLuaCPathAbsStr = drv: lib.concatMapStringsSep ";" (x: "${drv}/${x}") luaCPathList;

  # Generate a LUA_PATH with absolute paths
  # genLuaPathAbs = drv:
  #   lib.concatStringsSep ";" (map (x: "${drv}/x") luaPathList);

  luaAtLeast = lib.versionAtLeast lua.luaversion;
  luaOlder = lib.versionOlder lua.luaversion;
  isLua51 = (lib.versions.majorMinor lua.version) == "5.1";
  isLua52 = (lib.versions.majorMinor lua.version) == "5.2";
  isLua53 = lua.luaversion == "5.3";
  isLuaJIT = lib.getName lua == "luajit";

  /*
    generates the relative path towards the folder where
    seems stable even when using  lua_modules_path = ""

    Example:
     getDataFolder luaPackages.stdlib
     => stdlib-41.2.2-1-rocks/stdlib/41.2.2-1/doc
  */
  getDataFolder = drv: "${drv.pname}-${drv.version}-rocks/${drv.pname}/${drv.version}";

  /*
    Convert derivation to a lua module.
    so that luaRequireModules can be run later
  */
  toLuaModule =
    drv:
    drv.overrideAttrs (oldAttrs: {
      # Use passthru in order to prevent rebuilds when possible.
      passthru = (oldAttrs.passthru or { }) // {
        luaModule = lua;
        requiredLuaModules = requiredLuaModules drv.propagatedBuildInputs;
      };
    });

  /*
    generate a luarocks config conforming to:
    https://github.com/luarocks/luarocks/wiki/Config-file-format

    The config lists folders where to find lua dependencies

    Example:
      generateLuarocksConfig {
        externalDeps = [ { name = "CRYPTO"; dep = pkgs.openssl; } ];
        rocksSubdir = "subdir";
      };

    Type:
       generateLuarocksConfig :: AttrSet -> String
  */
  generateLuarocksConfig =
    {
      externalDeps ? [ ],
      # a list of lua derivations
      requiredLuaRocks ? [ ],
      ...
    }@args:
    let
      rocksTrees = lib.imap0 (i: dep: {
        name = "dep-${toString i}";
        root = "${dep}";
        # packages built by buildLuaPackage or luarocks doesn't contain rocksSubdir
        # hence a default here
        rocks_dir =
          if dep ? rocksSubdir then "${dep}/${dep.rocksSubdir}" else "${dep.pname}-${dep.version}-rocks";
      }) requiredLuaRocks;

      # Explicitly point luarocks to the relevant locations for multiple-output
      # derivations that are external dependencies, to work around an issue it has
      # (https://github.com/luarocks/luarocks/issues/766)
      depVariables = zipAttrsWithLast (
        lib.lists.map (
          { name, dep }:
          {
            "${name}_INCDIR" = "${lib.getDev dep}/include";
            "${name}_LIBDIR" = "${lib.getLib dep}/lib";
            "${name}_BINDIR" = "${lib.getBin dep}/bin";
          }
        ) externalDeps'
      );
      zipAttrsWithLast = lib.attrsets.zipAttrsWith (name: lib.lists.last);

      # example externalDeps': [ { name = "CRYPTO"; dep = pkgs.openssl; } ]
      externalDeps' = lib.filter (dep: !lib.isDerivation dep) externalDeps;

      externalDepsDirs = map (x: builtins.toString x) (lib.filter (lib.isDerivation) externalDeps);

      generatedConfig = (
        {

          # first tree is the default target where new rocks are installed,
          # any other trees in the list are treated as additional sources of installed rocks for matching dependencies.
          rocks_trees = (
            [
              {
                name = "current";
                root = "${placeholder "out"}";
                rocks_dir = "current";
              }
            ]
            ++ rocksTrees
          );
        }
        // lib.optionalAttrs lua.pkgs.isLuaJIT {
          # Luajit provides some additional functionality built-in; this exposes
          # that to luarock's dependency system
          rocks_provided = {
            jit = "${lua.luaversion}-1";
            ffi = "${lua.luaversion}-1";
            luaffi = "${lua.luaversion}-1";
            bit = "${lua.luaversion}-1";
          };
        }
        // {
          # For single-output external dependencies
          external_deps_dirs = externalDepsDirs;
          # Some needed machinery to handle multiple-output external dependencies,
          # as per https://github.com/luarocks/luarocks/issues/766
          variables = depVariables;
        }
        // removeAttrs args [
          "requiredLuaRocks"
          "externalDeps"
        ]
      );
    in
    generatedConfig;
}