lib.nix

# Copyright 2022-2023 TII (SSRC) and the Ghaf contributors
# Copyright 2020-2023 Pacman99 and the Digga Contributors
#
# SPDX-License-Identifier: MIT
# FlattenTree and rakeLeaves originate from
# https://github.com/divnix/digga
{inputs, ...}: let
  inherit (inputs) nixpkgs;
  # TODO REPLACE ME with hash pointed to by /run/current-system in built image
  ghaf-version = nixpkgs.lib.strings.fileContents ./.version;
in
  nixpkgs.lib.extend (lib: _:
    # some flake helpers
      (inputs.lib-extras.lib lib)
      # some utils for importing trees
      // rec {
        #
        # Ghaf versioning info
        #
        inherit ghaf-version;

        flattenTree =
          /*
          *
          Synopsis: flattenTree _tree_

          Flattens a _tree_ of the shape that is produced by rakeLeaves.

          Output Format:
          An attrset with names in the spirit of the Reverse DNS Notation form
          that fully preserve information about grouping from nesting.

          Example input:
          ```
          {
          a = {
          b = {
          c = <path>;
          };
          };
          }
          ```

          Example output:
          ```
          {
          "a.b.c" = <path>;
          }
          ```
          *
          */
          tree: let
            op = sum: path: val: let
              pathStr = builtins.concatStringsSep "." path; # dot-based reverse DNS notation
            in
              if builtins.isPath val
              then
                # builtins.trace "${toString val} is a path"
                (sum
                  // {
                    "${pathStr}" = val;
                  })
              else if builtins.isAttrs val
              then
                # builtins.trace "${builtins.toJSON val} is an attrset"
                # recurse into that attribute set
                (recurse sum path val)
              else
                # ignore that value
                # builtins.trace "${toString path} is something else"
                sum;

            recurse = sum: path: val:
              builtins.foldl'
              (sum: key: op sum (path ++ [key]) val.${key})
              sum
              (builtins.attrNames val);
          in
            recurse {} [] tree;

        rakeLeaves =
          /*
          *
          Synopsis: rakeLeaves _path_

          Recursively collect the nix files of _path_ into attrs.

          Output Format:
          An attribute set where all `.nix` files and directories with `default.nix` in them
          are mapped to keys that are either the file with .nix stripped or the folder name.
          All other directories are recursed further into nested attribute sets with the same format.

          Example file structure:
          ```
          ./core/default.nix
          ./base.nix
          ./main/dev.nix
          ./main/os/default.nix
          ```

          Example output:
          ```
          {
          core = ./core;
          base = base.nix;
          main = {
          dev = ./main/dev.nix;
          os = ./main/os;
          };
          }
          ```
          *
          */
          dirPath: let
            seive = file: type:
            # Only rake `.nix` files or directories
              (type == "regular" && lib.hasSuffix ".nix" file) || (type == "directory");

            collect = file: type: {
              name = lib.removeSuffix ".nix" file;
              value = let
                path = dirPath + "/${file}";
              in
                if
                  (type == "regular")
                  || (type == "directory" && builtins.pathExists (path + "/default.nix"))
                then path
                # recurse on directories that don't contain a `default.nix`
                else rakeLeaves path;
            };

            files = lib.filterAttrs seive (builtins.readDir dirPath);
          in
            lib.filterAttrs (_n: v: v != {}) (lib.mapAttrs' collect files);

        importLeaves =
          #
          # Create an import stanza by recursing a directory to find all default.nix and <file.nix>
          # files beneath withough manually having to list all the subsequent files.
          #
          path: builtins.attrValues (lib.mapAttrs (_: import) (rakeLeaves path));
      })