# flake.nix - Nix-defined package and devel env for the Mercurial project.

#

# Copyright 2021-2023 Pacien TRAN-GIRARD <pacien.trangirard@pacien.net>

#

# This software may be used and distributed according to the terms of the

# GNU General Public License version 2 or any later version.

# Usage summary, from the root of this repository:

#

# Enter a shell with development tools:

#   nix develop 'hg+file:.?dir=contrib/nix'

#

# Running mercurial:

#   nix run 'hg+file:.?dir=contrib/nix' -- version

#

# Running the test suite in a sandbox:

#   nix build 'hg+file:.?dir=contrib/nix#mercurial-tests' -L

{

  inputs = {

    nixpkgs.url = "github:NixOS/nixpkgs/nixos-22.11";

    nixpkgs-black.url = "github:NixOS/nixpkgs/c7cb72b0";  # black 20.8b1

    # rust-overlay.url = "github:oxalica/rust-overlay";

    flake-utils.url = "github:numtide/flake-utils";

    flaky-utils.url = "git+https://cgit.pacien.net/libs/flaky-utils";

  };

  outputs = {

    self

  , nixpkgs

  , nixpkgs-black

  # , rust-overlay

  , flake-utils

  , flaky-utils

  }:

  flake-utils.lib.eachDefaultSystem (system:

  let

    # overlays = [ (import rust-overlay) ];

    pkgs = import nixpkgs { inherit system; };

    # We're in the contrib/nix sub-directory.

    src = ../..;

    # For snapshots, to satisfy extension minimum version requirements.

    dummyVersion = "99.99";

    pin = {

      # The test suite has issues with the latest/current versions of Python.

      # Use an older recommended version instead, matching the CI.

      python = pkgs.python39;

      # The project uses a pinned version (rust/clippy.toml) for compiling,

      # but uses formatter features from nightly.

      # TODO: make cargo use the formatter from nightly automatically

      #       (not supported by rustup/cargo yet? workaround?)

      # rustPlatform = pkgs.rust-bin.stable."1.61.0".default;

      # rustPlatformFormatter = pkgs.rust-bin.nightly."2023-04-20".default;

      # The CI uses an old version of the Black code formatter,

      # itself depending on old Python libraries.

      # The formatting rules have changed in more recent versions.

      inherit (import nixpkgs-black { inherit system; }) black;

    };

  in rec {

    apps.mercurial = apps.mercurial-rust;

    apps.default = apps.mercurial;

    apps.mercurial-c = flake-utils.lib.mkApp {

      drv = packages.mercurial-c;

    };

    apps.mercurial-rust = flake-utils.lib.mkApp {

      drv = packages.mercurial-rust;

    };

    packages.mercurial = packages.mercurial-rust;

    packages.default = packages.mercurial;

    packages.mercurial-c = pin.python.pkgs.buildPythonApplication {

      format = "other";

      pname = "mercurial";

      version = "SNAPSHOT";

      passthru.exePath = "/bin/hg";

      inherit src;

      postPatch = ''

        echo 'version = b"${toString dummyVersion}"' \

          > mercurial/__version__.py

        patchShebangs .

        for f in **/*.{py,c,t}; do

          # not only used in shebangs

          substituteAllInPlace "$f" '/bin/sh' '${pkgs.stdenv.shell}'

        done

      '';

      buildInputs = with pin.python.pkgs; [

        docutils

      ];

      nativeBuildInputs = with pkgs; [

        gettext

        installShellFiles

      ];

      makeFlags = [

        "PREFIX=$(out)"

      ];

      buildPhase = ''

        make local

      '';

      # Test suite is huge ; run on-demand in a separate package instead.

      doCheck = false;

    };

    packages.mercurial-rust = packages.mercurial-c.overrideAttrs (super: {

      cargoRoot = "rust";

      cargoDeps = pkgs.rustPlatform.importCargoLock {

        lockFile = "${src}/rust/Cargo.lock";

      };

      nativeBuildInputs = (super.nativeBuildInputs or []) ++ (

        with pkgs.rustPlatform; [

          cargoSetupHook

          rust.cargo

          rust.rustc

        ]

      );

      makeFlags = (super.makeFlags or []) ++ [

        "PURE=--rust"

      ];

    });

    packages.mercurial-tests = pkgs.stdenv.mkDerivation {

      pname = "mercurial-tests";

      version = "SNAPSHOT";

      inherit src;

      buildInputs = with pkgs; [

        pin.python

        pin.black

        unzip

        which

        sqlite

      ];

      postPatch = (packages.mercurial.postPatch or "") + ''

        # * paths emitted by our wrapped hg look like ..hg-wrapped-wrapped

        # * 'hg' is a wrapper; don't run using python directly

        for f in **/*.t; do

          substituteInPlace 2>/dev/null "$f" \

            --replace '*/hg:' '*/*hg*:' \

            --replace '"$PYTHON" "$BINDIR"/hg' '"$BINDIR"/hg'

        done

      '';

      buildPhase = ''

        export HGTEST_REAL_HG="${packages.mercurial}/bin/hg"

        export HGMODULEPOLICY="rust+c"

        export HGTESTFLAGS="--blacklist blacklists/nix"

        make check 2>&1 | tee "$out"

      '';

    };

    devShell = flaky-utils.lib.mkDevShell {

      inherit pkgs;

      tools = [

        pin.python

        pin.black

      ];

    };

  });

}