flakelight/default.nix

# flakelight -- Framework for simplifying flake setup
# Copyright (C) 2023 Archit Gupta <archit@accelbread.com>
# SPDX-License-Identifier: MIT

localInputs:
let
  inherit (builtins) isAttrs isPath readDir;
  inherit (localInputs.nixpkgs.lib) attrNames composeManyExtensions
    filter findFirst genAttrs getValues hasSuffix isFunction isList mapAttrs
    mapAttrsToList pathExists pipe removePrefix removeSuffix evalModules
    mkDefault mkOptionType singleton;
  inherit (localInputs.nixpkgs.lib.types) coercedTo functionTo listOf;

  builtinModules = mapAttrsToList (k: _: ./builtinModules + ("/" + k))
    (readDir ./builtinModules);

  mkFlake = src: root: (evalModules {
    specialArgs.modulesPath = ./builtinModules;
    modules = builtinModules ++ [
      { inputs.nixpkgs = mkDefault localInputs.nixpkgs; }
      { _module.args = { inherit src flakelight; }; }
      root
    ];
  }).config.outputs;

  flakelight = {
    inherit mkFlake supportedSystem importDir autoImport;

    types = {
      overlay = mkOptionType {
        name = "overlay";
        description = "nixpkgs overlay";
        descriptionClass = "noun";
        check = isFunction;
        merge = _: defs: composeManyExtensions (getValues defs);
      };

      packageDef = mkOptionType {
        name = "packageDef";
        description = "package definition";
        descriptionClass = "noun";
        check = isFunction;
      };

      path = mkOptionType {
        name = "path";
        description = "path";
        descriptionClass = "noun";
        check = isPath;
      };

      module = mkOptionType {
        name = "module";
        description = "module";
        descriptionClass = "noun";
        check = x: isPath x || isFunction x || isAttrs x;
        merge = _: defs: { imports = getValues defs; };
      };

      optListOf = elemType: coercedTo elemType singleton (listOf elemType);

      optFunctionTo = elemType: coercedTo elemType (x: _: x)
        (functionTo elemType);
    };
  };

  supportedSystem = { lib, stdenv, ... }:
    lib.meta.availableOn stdenv.hostPlatform;

  importDir = path: genAttrs
    (pipe (readDir path) [
      attrNames
      (filter (s: s != "default.nix"))
      (filter (hasSuffix ".nix"))
      (map (removeSuffix ".nix"))
      (map (removePrefix "_"))
    ])
    (p: import (path + (if pathExists
      (path + "/_${p}.nix") then "/_${p}.nix" else "/${p}.nix")));

  autoImport = dir: name:
    if isList name
    then findFirst (x: x != null) null (map (autoImport dir) name)
    else
      if pathExists (dir + "/${name}.nix")
      then import (dir + "/${name}.nix")
      else if pathExists (dir + "/${name}/default.nix")
      then import (dir + "/${name}")
      else if pathExists (dir + "/${name}")
      then importDir (dir + "/${name}")
      else null;

in
{
  lib = flakelight;
  __functor = _: mkFlake;
}