rec {
  description = "";

  inputs = {
    nixpkgs.url = "nixpkgs"; # Use nixpkgs from system registry
    flake-utils.url = "github:numtide/flake-utils";
  };

  outputs = {
    self,
    nixpkgs,
    flake-utils,
  }:
  # Create a shell (and possibly package) for each possible system, not only x86_64-linux
    flake-utils.lib.eachDefaultSystem (system: let
      # =========================================================================================
      # Define pkgs/stdenvs
      # =========================================================================================
      pkgs = import nixpkgs {
        inherit system;
        config.allowUnfree = true;
        overlays = [];
      };

      inherit (pkgs) lib stdenv;

      # =========================================================================================
      # Define shell environment
      # =========================================================================================

      # Setup the shell when entering the "nix develop" environment (bash script).
      shellHook = let
        # Add project-local fish abbrs here
        abbrs = {};

        eraseAbbr = name: value: ''abbr --erase ${name} 2>/dev/null'';
        createAbbr = name: value: ''abbr -a ${name} "${value}"'';

        # This will be sourced by the global fish config if INIT_PROJECT_SHELL gets unset
        unloadProjectShell = pkgs.writers.writeFish "unload-shell.fish" ''
          echo "Unloading \"${description}\" environment..."

          ${builtins.concatStringsSep "\n" (lib.mapAttrsToList eraseAbbr abbrs)}
        '';

        # This will be sourced by the global fish config if INIT_PROJECT_SHELL gets set
        initProjectShell = pkgs.writers.writeFish "init-shell.fish" ''
          # Unload just in case, to not have redefinition errors
          source ${unloadProjectShell}

          echo "Sourcing \"${description}\" environment..."

          ${builtins.concatStringsSep "\n" (lib.mapAttrsToList createAbbr abbrs)}
        '';
      in
        builtins.concatStringsSep "\n" [
          # Launch into pure fish shell
          ''
            # Determine the project root, used e.g. in cmake scripts
            export FLAKE_PROJECT_ROOT="$(git rev-parse --show-toplevel)"

            # Can't do the "exec" with nix-direnv
            # - The "exec fish" would call direnv again => Infinite loop
            # - The shellHook is Bash/POSIX, so fish syntax doesn't work

            # Use this for "nix develop" without direnv
            # exec "$(type -p fish)" -C "source ${initProjectShell} && abbr -a menu '${pkgs.bat}/bin/bat "${initProjectShell}"'"

            # Use this for direnv without "nix develop"
            export INIT_PROJECT_SHELL="${initProjectShell}"
            export UNLOAD_PROJECT_SHELL="${unloadProjectShell}"
          ''
        ];

      # ===========================================================================================
      # Define custom dependencies
      # ===========================================================================================

      # ===========================================================================================
      # Specify dependencies
      # https://nixos.org/manual/nixpkgs/stable/#ssec-stdenv-dependencies-overview
      # Just for a "nix develop" shell, buildInputs can be used for everything.
      # ===========================================================================================

      # Add dependencies to nativeBuildInputs if they are executed during the build:
      # - Those which are needed on $PATH during the build, for example cmake and pkg-config
      # - Setup hooks, for example makeWrapper
      # - Interpreters needed by patchShebangs for build scripts (with the --build flag), which can be the case for e.g. perl
      nativeBuildInputs = with pkgs; [];

      # Add dependencies to buildInputs if they will end up copied or linked into the final output or otherwise used at runtime:
      # - Libraries used by compilers, for example zlib
      # - Interpreters needed by patchShebangs for scripts which are installed, which can be the case for e.g. perl
      buildInputs = with pkgs; [];
      # ===========================================================================================
      # Define buildable + installable packages
      # ===========================================================================================
    in rec {
      devShells = {
        # Provide default environment for "nix develop".
        # Other environments can be added below.
        default = pkgs.mkShell {
          inherit nativeBuildInputs buildInputs shellHook;
          name = description;

          # =========================================================================================
          # Define environment variables
          # =========================================================================================

          BIBINPUTS = "$PWD:$BIBINPUTS";
        };
      };
    });
}