nixpkgs/pkgs/games/openra_2019/default.nix

/*
  This file defines all OpenRA packages under `openraPackages`,
   e.g. the OpenRA release engine can be found at `openraPackages.engines.release` (see `engines.nix`),
   or the out-of-tree mod "Combined Arms" can be found at `openraPackages.mods.ca` (see `mods.nix`).
   The `openra` package is just an alias to `openraPackages.engines.release`,
   and just provides the mods included in the source code of the engine.
   Additional engines or mods can be added with `openraPackages.buildOpenRAEngine` (function around `engine.nix`)
   and `openraPackages.buildOpenRAMod` (function around `mod.nix`), respectively.
*/
{ pkgs, lib }:

let
  /*
    Building an engine or out-of-tree mod is very similar,
     but different enough not to be able to build them with the same package definition,
     so instaed we define what is common between them in a separate file.

     Although `callPackage` could be used, it would require undoing `makeOverridable`,
     because `common.nix` does not define a package, but just an attribute set,
     which is directly passed as part of the argument to the engines and mods `callPackage`,
     so either the attributes added by `makeOverridable` have to be removed
     or the engine and mod package definitions will need to add `...` to the argument list.
  */
  common =
    let
      f = import ./common.nix;
      fArgs = lib.functionArgs f;
    in
    f (
      builtins.intersectAttrs fArgs pkgs
      // {
        lua = pkgs.lua5_1;
      }
    );

  /*
    Building a set of engines or mods requires some dependencies as well,
     so the sets will actually be defined as a function instead,
     requiring the dependencies and returning the actual set.

     Not all dependencies for defining a engine or mod set are shared,
     so additional arguments can be passed as well.

     The builders for engines and mods allow to delay specifying the name,
     by returning a function that expects a name, which we use, in this case,
     to base the name on the attribute name instead, preventing the need to specify the name twice
     if the attribute name and engine/mod name are equal.
  */
  callWithName = name: value: if lib.isFunction value then value name else value;
  buildOpenRASet =
    f: args:
    pkgs.recurseIntoAttrs (
      lib.mapAttrs callWithName (
        f (
          {
            inherit (pkgs) fetchFromGitHub;
            postFetch = ''
              sed -i 's/curl/curl --insecure/g' $out/thirdparty/{fetch-thirdparty-deps,noget}.sh
              $out/thirdparty/fetch-thirdparty-deps.sh
            '';
          }
          // args
        )
      )
    );

in
pkgs.recurseIntoAttrs rec {
  # The whole attribute set is destructered to ensure those (and only those) attributes are given
  # and to provide defaults for those that are optional.
  buildOpenRAEngine =
    {
      name ? null,
      version,
      description,
      homepage,
      mods,
      src,
    }@engine:
    # Allow specifying the name at a later point if no name has been given.
    let
      builder =
        name:
        pkgs.callPackage ./engine.nix (
          common
          // {
            engine = engine // {
              inherit name;
            };
          }
        );
    in
    if name == null then builder else builder name;

  # See `buildOpenRAEngine`.
  buildOpenRAMod =
    {
      name ? null,
      version,
      title,
      description,
      homepage,
      src,
      engine,
      assetsError ? "",
    }@mod:
    (
      {
        version,
        mods ? [ ],
        src,
      }@engine:
      let
        builder =
          name:
          pkgs.callPackage ./mod.nix (
            common
            // {
              mod = mod // {
                inherit name assetsError;
              };
              engine = engine // {
                inherit mods;
              };
            }
          );
      in
      if name == null then builder else builder name
    )
      engine;

  # See `buildOpenRASet`.
  engines = buildOpenRASet (import ./engines.nix) { inherit buildOpenRAEngine; };
  mods = buildOpenRASet (import ./mods.nix) { inherit buildOpenRAMod; };
}