{ pkgs, src, baseName }:
let
  nixfmt = import (builtins.fetchTarball
    "https://github.com/serokell/nixfmt/archive/master.tar.gz") { };
in rec {
  baseTask = pkgs.stdenv.mkDerivation {
    name = "${baseName}-task";
    src = src;
    buildInputs = [ ];
    phases = "unpackPhase buildPhase";
    buildPhase = ''
      echo "ERROR: base task buildPhase not overriden."
      exit 1
    '';
  };
  shellcheck = ignoredFindPattern:
    baseTask.overrideAttrs (baseAttrs: rec {
      name = "${baseAttrs.name}-shellcheck";
      buildInputs = baseAttrs.buildInputs ++ [ pkgs.shellcheck ];
      ignoredPattern =
        if ignoredFindPattern == null then "" else ignoredFindPattern;
      buildPhase = ''
        find . -type f \( -name '*.sh' -and -regextype egrep ! -regex '${ignoredPattern}' \) -print0 | xargs -0 shellcheck -x
        touch $out
      '';
    });
  formatNix = baseTask.overrideAttrs (baseAttrs: {
    name = "${baseAttrs.name}-nixfmt";
    buildInputs = baseAttrs.buildInputs ++ [ nixfmt ];
    buildPhase = ''
      format() {
        nix_file="$1"
        diff <(nixfmt < "$nix_file") "$nix_file" || {
          echo "The $nix_file is unformatted. To fix it, run:"
          echo "  nixfmt $nix_file"
          exit 1
        }
      }
      export -f format
      find . -type f -name '*.nix' -print0 | xargs -0 -I{} bash -c "format {}" \;
      touch $out
    '';
  });
  fixme = ignoredFiles:
    baseTask.overrideAttrs (baseAttrs: rec {
      name = "${baseAttrs.name}-fixme";
      buildInputs = baseAttrs.buildInputs ++ [ pkgs.ag ];
      ignoredPattern = pkgs.lib.fold (a: b: " --ignore ${a} ${b}") ""
        (if ignoredFiles == null then [
          "utils.nix"
          "TODOs.org"
        ] else
          ignoredFiles);
      buildPhase = ''
        ag FIXME ${ignoredPattern} || {
          touch $out
          exit 0
        }
        echo "  Found dangling FIXME markers on the project."
        echo "  You should write them down properly on TODOs.org."
        exit 1
      '';
    });
  readmeOrg = title:
    baseTask.overrideAttrs (baseAttrs: {
      name = "${baseAttrs.name}-readme-docs";
      buildInputs = [ pkgs.pandoc ];
      buildPhase = ''
        pandoc README.org -o $out --css docs/README.css --to=html5 --self-contained --metadata title="${title}"
      '';
    });
  test = testDerivations:
    baseTask.overrideAttrs (baseAttrs: {
      name = "${baseAttrs.name}-test";
      buildPhase = ''
        echo "Ran tests for:"
        for d in ${builtins.toString testDerivations}; do
          echo "  $d"
        done
        echo "All tests passed!"
        touch $out
      '';
    });
  shellEnvironmentBuild = shellBuildInputs:
    baseTask.overrideAttrs (baseAttrs: {
      name = "${baseAttrs.name}-shell-build-inputs";
      buildPhase = ''
        echo "Can build shell environment for shellBuildInputs!"
        echo noop > $out
      '';
    });
  shellEnvironment = shellBuildInputs:
    pkgs.mkShell {
      name = "${baseName}-shell";
      buildInputs = shellBuildInputs;
    };
  overwritingPublishScript = { docsDerivation, overwrite ? true }:
    pkgs.writeShellScriptBin "publish.sh" ''
      set -euo pipefail
      OUT_DOCS="${docsDerivation}"
      ${
        if overwrite then "" else "# "
      }${pkgs.openssh}/bin/ssh -o StrictHostKeyChecking=no "$SERVER_URL" rm -rf "$DOCS_SERVER_PATH/*"
      ${pkgs.rsync}/bin/rsync -avzP                                   \
                              --rsh="ssh -o StrictHostKeyChecking=no" \
                              "$OUT_DOCS/"                            \
                              "$SERVER_URL:$DOCS_SERVER_PATH"
    '';
}