FHS Shell env for running rzup and cargo-risczero

risc0.nix

{
  description = "Dev shell with rzup and RISC Zero FHS compatibility";

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-24.05";
    flake-utils.url = "github:numtide/flake-utils";
  };

  outputs = {
    self,
    nixpkgs,
    flake-utils,
    ...
  }:
    flake-utils.lib.eachDefaultSystem (
      system: let
        pkgs = import nixpkgs {
          inherit system;
          config.allowUnfree = true;
        };

        rzupStartup = pkgs.writeShellScript "start-rzup-env" ''
          export HOME=$PWD/.risc0
          export RZUP_HOME=$HOME
          export PATH=$RZUP_HOME/bin:$PATH
          export RUSTUP_HOME=$PWD/.rustup
          export CARGO_HOME=$PWD/.cargo

          echo "rzup-env ready. rzup path: $RZUP_HOME/bin"

          if [ ! -x "$RZUP_HOME/bin/rzup" ]; then
            echo "rzup not found. Do you want to install it? (y/n)"
            read -r answer
            if [ "$answer" = "y" ]; then
              echo "Installing rzup to $HOME..."
              mkdir -p "$RZUP_HOME/bin"
              export HOME="$RZUP_HOME"
              curl -fsSL https://risc0.com/install | bash
            else
              echo "⚠️ Skipping rzup installation"
            fi
          fi

          exec ${pkgs.zsh}/bin/zsh -l
        '';

        # FHS user environment
        rzup-fhs = pkgs.buildFHSUserEnv {
          name = "rzup-env";
          targetPkgs = pkgs: [
            pkgs.glibc
            pkgs.bash
            pkgs.coreutils
            pkgs.curl
            pkgs.findutils
            pkgs.rustup
            pkgs.openssl
            pkgs.pkg-config
            pkgs.zsh
          ];
          runScript = rzupStartup;
        };
      in {
        devShells.default = pkgs.mkShell {
          buildInputs = with pkgs; [
            rustup
            curl
            bash
            zsh
            rzup-fhs
          ];

          shellHook = ''
            export RUSTUP_HOME=$PWD/.rustup
            export CARGO_HOME=$PWD/.cargo
            export PATH=$CARGO_HOME/bin:$PATH

            export RZUP_HOME=$PWD/.risc0
            export PATH=$RZUP_HOME/bin:$PATH
            export PATH=${rzup-fhs}/bin:$PATH

            export OPENSSL_DIR="${pkgs.openssl.dev}"
            export OPENSSL_LIB_DIR="${pkgs.openssl.out}/lib"
            export OPENSSL_INCLUDE_DIR="${pkgs.openssl.dev}/include"
            export PKG_CONFIG_PATH="${pkgs.openssl.dev}/lib/pkgconfig"


            echo "rzup path enabled: $RZUP_HOME/bin"
            echo "run 'rzup-env' for a full FHS shell with rzup + RISC Zero support"
            exec ${pkgs.zsh}/bin/zsh -l
          '';
        };

        # Optional: expose the FHS shell as an app (CLI-style)
        apps.${system}.rzup = {
          type = "app";
          program = "${rzup-fhs}/bin/rzup-env";
        };
      }
    );
}