# Copyright 2022 The TVL Contributors
# SPDX-License-Identifier: Apache-2.0

# This function header aims to provide compatibility between builds of
# Nixery taking place inside/outside of the TVL depot.
#
# In the future, Nixery will transition to using //nix/buildGo for its
# build system and this will need some major adaptations to support
# that.
{ depot ? { nix.readTree.drvTargets = x: x; }
, pkgs ? import <nixpkgs> { }
, preLaunch ? ""
, extraPackages ? [ ]
, maxLayers ? 20
, commitHash ? null
, ...
}@args:

with pkgs;

let
  inherit (pkgs) buildGoModule;

  # Avoid extracting this from git until we have a way to plumb
  # through revision numbers.
  nixery-commit-hash = "depot";

  # Go implementation of the Nixery server which implements the
  # container registry interface.
  #
  # Users should use the nixery-bin derivation below instead as it
  # provides the paths of files needed at runtime.
  nixery-server = buildGoModule rec {
    name = "nixery-server";
    src = ./.;
    doCheck = true;

    # Needs to be updated after every modification of go.mod/go.sum
    vendorSha256 = "1xnmyz2a5s5sck0fzhcz51nds4s80p0jw82dhkf4v2c4yzga83yk";

    buildFlagsArray = [
      "-ldflags=-s -w -X main.version=${nixery-commit-hash}"
    ];
  };
in
depot.nix.readTree.drvTargets rec {
  # Implementation of the Nix image building logic
  nixery-prepare-image = import ./prepare-image { inherit pkgs; };

  # Use mdBook to build a static asset page which Nixery can then
  # serve. This is primarily used for the public instance at
  # nixery.dev.
  nixery-book = callPackage ./docs { };

  # Wrapper script running the Nixery server with the above two data
  # dependencies configured.
  #
  # In most cases, this will be the derivation a user wants if they
  # are installing Nixery directly.
  nixery-bin = writeShellScriptBin "nixery" ''
    export WEB_DIR="${nixery-book}"
    export PATH="${nixery-prepare-image}/bin:$PATH"
    exec ${nixery-server}/bin/nixery
  '';

  nixery-popcount = callPackage ./popcount { };

  # Container image containing Nixery and Nix itself. This image can
  # be run on Kubernetes, published on AppEngine or whatever else is
  # desired.
  nixery-image =
    let
      # Wrapper script for the wrapper script (meta!) which configures
      # the container environment appropriately.
      #
      # Most importantly, sandboxing is disabled to avoid privilege
      # issues in containers.
      nixery-launch-script = writeShellScriptBin "nixery" ''
        set -e
        export PATH=${coreutils}/bin:$PATH
        export NIX_SSL_CERT_FILE=/etc/ssl/certs/ca-bundle.crt
        mkdir -p /tmp

        # Create the build user/group required by Nix
        echo 'nixbld:x:30000:nixbld' >> /etc/group
        echo 'nixbld:x:30000:30000:nixbld:/tmp:/bin/bash' >> /etc/passwd
        echo 'root:x:0:0:root:/root:/bin/bash' >> /etc/passwd
        echo 'root:x:0:' >> /etc/group

        # Disable sandboxing to avoid running into privilege issues
        mkdir -p /etc/nix
        echo 'sandbox = false' >> /etc/nix/nix.conf

        # In some cases users building their own image might want to
        # customise something on the inside (e.g. set up an environment
        # for keys or whatever).
        #
        # This can be achieved by setting a 'preLaunch' script.
        ${preLaunch}

        exec ${nixery-bin}/bin/nixery
      '';
    in
    dockerTools.buildLayeredImage {
      name = "nixery";
      config.Cmd = [ "${nixery-launch-script}/bin/nixery" ];

      inherit maxLayers;
      contents = [
        bashInteractive
        cacert
        coreutils
        git
        gnutar
        gzip
        iana-etc
        nix
        nixery-prepare-image
        nixery-launch-script
        openssh
        zlib
      ] ++ extraPackages;
    };
}