make-aws-lambda-zip.nix

{ pkgs, flake }:

let
  buildLambda = cabalProject: executable:
    let
      exeComponent = flake.packages."${cabalProject}:exe:${executable}";
    in
      pkgs.runCommand executable { buildInputs = with pkgs; [ exeComponent glibc.bin patchelf zip ]; } ''
        # Copy the binary to `bootstrap`, which is what AWS Lambda expects:
        # https://docs.aws.amazon.com/lambda/latest/dg/runtimes-custom.html
        cp ${exeComponent}/bin/${executable} bootstrap

        # Copy the shared objects that our binary depends on to a subfolder `lib/`.
        mkdir lib
        cp $(ldd bootstrap | grep -F '=> /' | awk '{print $3}') lib/

        # Patch the binary to point the ELF interpreter and the run-time search
        # path to the shared objects we provide. Note that these paths are location
        # independent: as long as the binary is in the same directory as the folder
        # containing our shared objects, this will work.
        chmod +w bootstrap
        patchelf --set-interpreter ./lib/ld-linux-x86-64.so.2 --set-rpath ./lib --force-rpath bootstrap
        chmod -w bootstrap

        # Finally, we can zip up our binary and the subfolder holding our shared objects.
        # This zip file is the output artefact of this derivation and can be uploaded to AWS
        # Lambda as-is.
        mkdir $out
        zip -qr $out/${executable}.zip lib bootstrap
      '';
in
  buildLambda "haskell-aws-lambda-sam-nix" "haskell-aws-lambda-sam-nix"