flake.nix

{
  # inputs.nixpkgs.url = "github:NixOS/nixpkgs?rev=3d58e3a31ee55554fe26650bb59db7d6d0e97625";
  # inputs.nixpkgs.url = "github:NixOS/nixpkgs?rev=fd83da2b640e05c6dd14fad4b741714b069ae0d7";
  inputs.nixpkgs.url = "github:NixOS/nixpkgs";
  # inputs.nixpkgs.url = "github:NixOS/nixpkgs?ref=nixos-22.05";
  # inputs.nixpkgs.url = "github:NixOS/nixpkgs?ref=nixos-22.11";
  # inputs.mach-nix.url = "github:DavHau/mach-nix";

  outputs =
    { self
    , nixpkgs
    # , mach-nix
    }:
    let
      native-pkgs = import nixpkgs {
        system = "x86_64-linux";
        config = {
          allowUnfree = true;
          android_sdk.accept_license = true;
        };
      };
      cross-pkgs = native-pkgs.pkgsCross.aarch64-android;

      platformVersion = "31";
      cmakeVersion = "3.10.2";
      buildToolsVersion = "30.0.0";
      # Check out pkgs/development/mobile/androidenv/repo.json for
      # nixpkgs-supported versions.
      ndkVersion = "23.0.7123448-rc1";
      androidComposition = native-pkgs.callPackage ../android.nix {
        inherit cmakeVersion buildToolsVersion platformVersion ndkVersion;
      };

      # mach-nix' = native-pkgs.callPackage mach-nix {
      #   python = "python3Minimal";
      # };

    in {
      devShells.x86_64-linux.default = native-pkgs.mkShell rec {
        BUILD_PYTHON = "${native-pkgs.python3}/bin/python";
        HOST_PYTHON = "${cross-pkgs.python3Minimal}/bin/python";
        ANDROIDSDK = "${androidComposition.androidsdk}/libexec/android-sdk";
        ANDROIDNDK = "${ANDROIDSDK}/ndk-bundle";
        CROSSENV_WHEEL = native-pkgs.fetchurl {
          url = "https://files.pythonhosted.org/packages/46/11/8bdda7df08c5d7566a518bb422e305f11980d2be1d1ca9b3fb6806097762/crossenv-1.3.0-py3-none-any.whl";
          sha256 = "sha256-bdkjYJChMU+810cd8MN5/b82KCsMzQJ7WPoayKTwRyE=";
        };

        nativeBuildInputs = [
          # expose ffi header and library so we can build cffi, itself used by
          # various other Python packages
          cross-pkgs.libffi
        ];

        setupCrossEnv = ''
          # Create a virtualenv with software we can run on the build system.
          $BUILD_PYTHON -m venv build-env

          # Put crossenv into that build environment so we can use it to
          # manage the cross build.
          ./build-env/bin/pip install crossenv

          # Create a cross build environment with crossenv.  It doesn't find
          # CC on its own, so help it out.  Also tell it where a Python
          # configured for the host system can be found, so it can extra more
          # details from it.
          ./build-env/bin/python -m crossenv --cc $CC $HOST_PYTHON ./cross-env

          # Activate the cross build environment for interactive use.
          . ./cross-env/bin/activate
        '';

        shellHook = ''
          # Point at the compiler that can build for the host platform.  This
          # seems like a plausible choice but it doesn't actually match the
          # compiler used to build the host Python so maybe it is wrong.
          export CC="${ANDROIDNDK}/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android${platformVersion}-clang"

          # Let cffi build find ffi.h
          export CFLAGS=$NIX_CFLAGS_COMPILE
          # Let cffi build find libffi.so
          export LDFLAGS=$NIX_LDFLAGS
        '';
      };
    };
}