nixos/fn.nix

{ lib }:
with builtins;
with lib;
rec {
  /**
    Shorthand for "if condition then a else b"

    # Type
    ```
    ifelse :: Bool -> Any -> Any -> Any
    ```

    # Arguments
    - [condition] A condition evaluating to a boolean
    - [a] Result if condition evaluates to true
    - [b] Result if condition evaluates to false

    # Example
    ```nix
    let
      myData = { val = "custom"; };
    in ifelse (myData ? val) myData.val "default"
    => "custom"
    ```
  */
  ifelse =
    condition: a: b:
    if condition then a else b;

  /**
    Value of PWD environment variable at evaluation time
  */
  cwd = builtins.getEnv "PWD";

  /**
    lst (string PATH) (string FILETYPE) (bool RETURNFULLPATH)
  */
  lst =
    {
      path ? cwd,
      fileType ? "regular",
      fullPath ? false,
    }:
    assert (builtins.isString path) || throw "Argument path needs to be a string.";
    (lists.forEach (attrNames (filterAttrs (n: v: v == fileType) (readDir path))) (
      v: ((optionalString fullPath "${path}/") + v)
    ));
  lsf = path: (lst { inherit path; });
  lsd =
    path:
    (lst {
      inherit path;
      fileType = "directory";
      fullPath = true;
    });
  lsfRec =
    path: fullPath:
    flatten (
      (map (nextPath: lsfRec nextPath fullPath) (lsd path))
      ++ (lst {
        inherit path fullPath;
      })
    );
  hasAttrs = aList: d: (map (a: (ifelse (isList a) (hasAttrByPath a d) (hasAttr a d))) aList);

  # Not sure how list operations are implemented in Nix
  # This might be a tad bit inefficient.
  # Sequentially checks elements of list (l) for condition (cond) and executes do on first match.
  /**
    Run lambda "(do element)" on the first element of list "l" where (cond element) returns true otherwise return false.

    # Type
    ```
    meetsConDo :: (any -> bool) -> (any -> any) -> [any] -> any
    ```

    # Arguments:
    - [cond] Condition  function
    - [do] Function to run on element if cond returns true
    - [list] List of elements

    # Example:
    ```nix
    meetsConDo (element: element >= 5) (element: element + 1) [ 4 2 0 5 1 ]
    => 6

    meetsConDo (element: element >= 5) (element: element + 1) [ 4 2 0 1 ]
    => false
    ```
  */
  meetsConDo =
    cond: do: list:
    let
      listLen = length list;
      meetsConDo' =
        currentIndex:
        ifelse (currentIndex == listLen) false (
          let
            head = elemAt list currentIndex;
          in
          ifelse (cond head) (do head) (meetsConDo' (currentIndex + 1))
        );
    in
    meetsConDo' 0;

  deps =
    p:
    ifelse (isAttrs p) (filter isAttrs (
      p.buildInputs ++ p.nativeBuildInputs ++ p.propagatedBuildInputs ++ p.propagatedNativeBuildInputs
    )) [ ];
  importFilter = l: filter (n: elem (nameFromURL (toString n) ".") l);
  depsRec =
    ld:
    ifelse (ld == [ ]) [ ] (
      (toList ld) ++ (depsRec (lists.unique (lists.flatten (map deps (toList ld)))))
    );
  isBroken =
    p:
    meetsConDo (s: ((hasAttrByPath s.path p) && (s.check (getAttrFromPath s.path p)))) (s: s.msg) [
      {
        path = [
          "meta"
          "broken"
        ];
        msg = warn "Package ${p.name} is marked as broken." true;
        check = m: m;
      }
      {
        path = [
          "meta"
          "knownVulnerabilities"
        ];
        msg = warn "Package ${p.name} has known Vulnerabilities.." true;
        check = m: m != [ ];
      }
      {
        path = [ "name" ];
        msg = warn "${p.name}: python2 is depricated." false;
        check = m: (strings.hasInfix "python2" m) || (strings.hasInfix "python-2" m);
      }
      # not sure if the following test creates false positives (AFAIK every derivation/package needs to have an outPath)
      # , definitely should catch all corner cases/everything that fails to evaluate.
      {
        path = [ "outPath" ];
        msg = warn "Package ${p.name} has no outPath" true;
        check = m: !(tryEval m).success;
      }
    ];
  depsBroken = p: lists.any (p: (isBroken p)) (deps p);
  # No more magic 🧙 here 😢
  # But at least it now (hopefully) checks ONLY dependencies (and all of them at that).
  depsBrokenRec =
    p: (meetsConDo (p: ifelse (depsBroken p) true (depsBrokenRec (deps p))) (p: true) (deps p));

  /**
    Helper function to generate secret definitions for sops-nix.

    # Type
    ```
    sopsHelper :: ()
    ```
    # Arguments
    # Examples
    ```nix
    sopsHelper (name: "services/nextcloud/${name}")
      [ "adminPass" "dbPass" ]
      { owner = "nextcloud"; group = "nextcloud"; }
    =>  {
          "services/nextcloud/adminPass" = {
            group = "nextcloud";
            owner = "nextcloud";
          };
          "services/nextcloud/dbPass" = {
            group = "nextcloud";
            owner = "nextcloud";
          };
        }

    sopsHelper (user: "users/${user}/publicKey")
      [ "alice" "bob" "eve" ]
      (user: { path = "/etc/ssh/authorized_keys.d/${user}"; mode = "444"; })
    =>  {
          "users/alice/publicKey" = {
            mode = "444";
            path = "/etc/ssh/authorized_keys.d/alice";
          };
          "users/bob/publicKey" = {
            mode = "444";
            path = "/etc/ssh/authorized_keys.d/bob";
          };
          "users/eve/publicKey" = {
            mode = "444";
            path = "/etc/ssh/authorized_keys.d/eve";
          };
        }
    ```
  */
  sopsHelper =
    template: names: options:
    let
      optionsIsFunction = (typeOf options) == "lambda";
    in
    listToAttrs (
      map (name: {
        name = template name;
        value = ifelse optionsIsFunction (options name) options;
      }) names
    );
  pkgFilter =
    ld:
    (filter (
      p:
      (ifelse (isBroken p) false (
        ifelse (depsBrokenRec p) (warn "Dependency of ${p.name} is marked as broken." false) true
      ))
    ) ld);
  makeOptionTypeList =
    path:
    (lists.forEach
      # get a list of all files ending in .nix in path
      (filter (hasSuffix ".nix") (lsfRec path true))
      # remove leading path and trailing ".nix", replace every slash with "::"
      (
        replaceStrings
          [
            "${path}/"
            "/"
            ".nix"
          ]
          [
            ""
            "::"
            ""
          ]
      )
    );
}