_:

final: _:
with final.lib;
rec {
  fishFile =
    { name
    , destination
    , content
    , checkPhase ? null
    }:
    final.writeTextFile {
      inherit name destination;
      executable = true;
      allowSubstitutes = true;
      preferLocalBuild = false;
      text = ''
        #!${getExe final.fish}

        ${content}
      '';

      checkPhase =
        if checkPhase == null then ''
          runHook preCheck
          ${getExe final.fish} -n "$target"
          runHook postCheck
        ''
        else checkPhase;
    };

  writeFishApplication =
    { name
    , text
    , completions ? null
    , runtimeInputs ? [ ]
    , checkPhase ? null
    }:
    let
      runtimeHeader = optionalString (runtimeInputs != [ ])
        ''export PATH="${makeBinPath runtimeInputs}:$PATH"'';

      script = fishFile {
        inherit checkPhase;
        name = "${name}_script";
        destination = "/bin/${name}";
        content = concatLines [ runtimeHeader text ];
      };
      completions_file = fishFile {
        inherit checkPhase;
        name = "${name}_completions";
        destination = "/share/fish/vendor_completions.d/${name}.fish";
        content = concatLines [ runtimeHeader completions ];
      };
    in
    final.symlinkJoin {
      inherit name;
      paths = [
        script
      ] ++ optional (completions != null) completions_file;
    };
}