Reproducible development environment and preparation for publishing NGS into nix package manager to increase adoption

.envrc

@@ -0,0 +1,2 @@
+use flake
+

.gitignore

@@ -21,3 +21,6 @@ pcre_constants.include
 junk
 
 .vagrant/
+
+.direnv/
+result

flake.nix

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+{
+  description = "NGS - Next Generation Shell";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs =
+    {
+      self,
+      nixpkgs,
+      flake-utils,
+    }:
+    flake-utils.lib.eachDefaultSystem (
+      system:
+      let
+        pkgs = nixpkgs.legacyPackages.${system};
+
+        # Local source filter - exclude build artifacts
+        localSrc = builtins.path {
+          path = ./.;
+          name = "ngs-source";
+          filter =
+            path: type:
+            let
+              baseName = baseNameOf path;
+            in
+            !(baseName == "build" || baseName == "result" || baseName == ".git" || baseName == ".direnv");
+        };
+
+        # For local development, override the package to use local source
+        ngs = (pkgs.callPackage ./package.nix { }).overrideAttrs (oldAttrs: {
+          src = localSrc;
+          version = oldAttrs.version + "-dev";
+        });
+      in
+      {
+        packages = {
+          default = ngs;
+          ngs = ngs;
+        };
+
+        devShells.default = pkgs.mkShell {
+          inputsFrom = [ ngs ];
+
+          packages =
+            with pkgs;
+            [
+              # Development tools
+              gdb
+              clang-tools # clangd, clang-format
+            ]
+            ++ lib.optionals stdenv.isLinux [
+              valgrind
+              strace
+            ];
+
+          shellHook = ''
+            echo "╔══════════════════════════════════════════════════════════╗"
+            echo "║           NGS Development Environment                    ║"
+            echo "╠══════════════════════════════════════════════════════════╣"
+            echo "║ Build:    cmake -B build && cmake --build build          ║"
+            echo "║ Test:     cd build && ctest --output-on-failure          ║"
+            echo "║ Run:      NGS_PATH=lib ./build/ngs                       ║"
+            echo "║ Package:  nix build                                      ║"
+            echo "╚══════════════════════════════════════════════════════════╝"
+          '';
+        };
+
+        # For nix fmt
+        formatter = pkgs.nixpkgs-fmt;
+      }
+    );
+}

package.nix

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+{
+  lib,
+  stdenv,
+  fetchFromGitHub,
+  fetchurl,
+  cmake,
+  pkg-config,
+  pandoc,
+  gawk,
+  makeWrapper,
+  boehmgc,
+  json_c,
+  libffi,
+  pcre,
+  # Darwin-specific: GNU sed is required for build scripts
+  gnused,
+}:
+
+stdenv.mkDerivation (finalAttrs: {
+  pname = "ngs";
+  version = "0.2.17";
+
+  src = fetchFromGitHub {
+    owner = "ngs-lang";
+    repo = "ngs";
+    rev = "v${finalAttrs.version}";
+    hash = "sha256-j7OAXHADc2LlabKxVgYiKeDDtLttDVIavhQZSGyPGlE=";
+  };
+
+  # NGS requires peg 0.1.18 specifically due to custom patches in build-scripts/
+  # The build scripts patch the leg output for location tracking, and this
+  # patching is not compatible with newer peg versions (0.1.20+).
+  # CMake will download and build peg 0.1.18 automatically when leg is not found.
+  pegSrc = fetchurl {
+    url = "https://www.piumarta.com/software/peg/peg-0.1.18.tar.gz";
+    hash = "sha256-IBk73Wc/x0h6OJN+KX//CKpzdRtjOghqwow7NIkPkIQ=";
+  };
+
+  nativeBuildInputs =
+    [
+      cmake
+      pkg-config
+      pandoc
+      gawk
+      makeWrapper
+    ]
+    ++ lib.optionals stdenv.isDarwin [
+      gnused
+    ];
+
+  buildInputs = [
+    boehmgc
+    json_c
+    libffi
+    pcre
+  ];
+
+  # The build scripts require GNU sed; on Darwin we need to ensure it's found
+  # Also pre-populate the peg source to avoid network access during build
+  preConfigure =
+    ''
+      # Create the external project download directory
+      mkdir -p build/leg-prefix/src
+
+      # Copy peg source to where CMake ExternalProject expects it
+      cp ${finalAttrs.pegSrc} build/leg-prefix/src/peg-0.1.18.tar.gz
+    ''
+    + lib.optionalString stdenv.isDarwin ''
+      export PATH="${gnused}/bin:$PATH"
+    '';
+
+  cmakeFlags = [
+    "-DBUILD_MAN=ON"
+  ];
+
+  # Set NGS_PATH so the installed binary can find the standard library
+  postInstall = ''
+    wrapProgram $out/bin/ngs \
+      --set NGS_PATH $out/lib/ngs
+  '';
+
+  meta = with lib; {
+    description = "Next Generation Shell - a powerful programming language and shell designed for Ops";
+    longDescription = ''
+      NGS is a unique combination of select features borrowed from other
+      languages and original features. NGS was built from the ground up
+      focusing on daily systems engineering tasks.
+
+      One way to think about NGS is bash plus data structures plus better
+      syntax and error handling. Scripting AWS is much easier with NGS,
+      there is a Declarative Primitives style library for that.
+    '';
+    homepage = "https://ngs-lang.org/";
+    changelog = "https://github.com/ngs-lang/ngs/blob/v${finalAttrs.version}/CHANGELOG.md";
+    license = licenses.gpl3Only;
+    maintainers = with maintainers; [ ];
+    mainProgram = "ngs";
+    platforms = platforms.unix;
+  };
+})