gradle2nix/maven-repo.nix

{
  lib,
  stdenv,
  fetchurl,
  symlinkJoin,
}:

{
  # Path to the lockfile generated by gradle2nix (e.g. gradle.lock).
  lockFile,
  pname ? "project",
  version ? null,
  # Override functions which fetch dependency artifacts.
  # Keys in this set are URL schemes such as "https" or "s3".
  # Values are functions which take a dependency in the form
  # `{ urls, hash }` and fetch into the Nix store. For example:
  #
  #   {
  #     s3 = { name, urls, hash }: fetchs3 {
  #       s3url = builtins.head urls;
  #       # TODO This doesn't work without patching fetchs3 to accept SRI hashes
  #       inherit name hash;
  #       region = "us-west-2";
  #       credentials = {
  #         access_key_id = "foo";
  #         secret_access_key = "bar";
  #       };
  #     };
  #   }
  fetchers ? { },
  # Overlays for dependencies in the offline Maven repository.
  #
  # Acceps an attrset of dependencies (usually parsed from 'lockFile'), and produces an attrset
  # containing dependencies to merge into the final set.
  #
  # The attrset is of the form:
  #
  #   {
  #      "${group}:${module}:${version}" = <derivation>;
  #      # ...
  #   }
  #
  # A dependency derivation unpacks multiple source files into a single Maven-style directory named
  # "${out}/${groupPath}/${module}/${version}/", where 'groupPath' is the dependency group ID with dot
  # characters ('.') replaced by the path separator ('/').
  #
  # Examples:
  #
  # 1. Add or replace a dependency with a single JAR file:
  #
  #    (_: {
  #      "com.squareup.okio:okio:3.9.0" = fetchurl {
  #        url = "https://repo.maven.apache.org/maven2/com/squareup/okio/okio/3.9.0/okio-3.9.0.jar";
  #        hash = "...";
  #        downloadToTemmp = true;
  #        postFetch = "install -Dt $out/com/squareup/okio/okio/3.9.0/ $downloadedFile"
  #      };
  #    })
  #
  # 2. Remove a dependency entirely:
  #
  #    # This works because the result is filtered for values that are derivations.
  #    (_: {
  #      "org.apache.log4j:core:2.23.1" = null;
  #    })
  overlays ? [ ],
}:

let

  inherit (builtins)
    attrValues
    elemAt
    filter
    fromJSON
    getAttr
    head
    length
    mapAttrs
    replaceStrings
    ;

  inherit (lib) mapAttrsToList readFile;

  inherit (lib.strings) sanitizeDerivationName;

  toCoordinates =
    id:
    let
      coords = builtins.split ":" id;

      parseVersion =
        version:
        let
          parts = builtins.split ":" version;
          base = elemAt parts 0;
        in
        if length parts >= 2 then
          let
            snapshot = elemAt parts 2;
          in
          replaceStrings [ "-SNAPSHOT" ] [ "-${snapshot}" ] base
        else
          base;
    in
    rec {
      group = elemAt coords 0;
      module = elemAt coords 2;
      version = elemAt coords 4;
      uniqueVersion = parseVersion version;
    };

  fetchers' = {
    http = fetchurl;
    https = fetchurl;
  } // fetchers;

  fetch =
    name:
    { url, hash }:
    let
      scheme = head (builtins.match "([a-z0-9+.-]+)://.*" url);
      fetch' = getAttr scheme fetchers';
    in
    fetch' { inherit url hash; };

  mkModule =
    id: artifacts:
    let
      coords = toCoordinates id;
      modulePath = "${replaceStrings [ "." ] [ "/" ] coords.group}/${coords.module}/${coords.version}";
    in
    stdenv.mkDerivation {
      pname = sanitizeDerivationName "${coords.group}-${coords.module}";
      version = coords.uniqueVersion;

      srcs = mapAttrsToList fetch artifacts;

      dontPatch = true;
      dontConfigure = true;
      dontBuild = true;
      dontFixup = true;
      dontInstall = true;

      preUnpack = ''
        mkdir -p "$out/${modulePath}"
      '';

      unpackCmd = ''
        cp "$curSrc" "$out/${modulePath}/$(stripHash "$curSrc")"
      '';

      sourceRoot = ".";

      preferLocalBuild = true;
      allowSubstitutes = false;
    };

  # Intermediate dependency spec.
  #
  # We want to allow overriding dependencies via the 'dependencies' function,
  # so we pass an intermediate set that maps each Maven coordinate to the
  # derivation created with 'mkModule'. This allows users extra flexibility
  # to do things like patching native libraries with patchelf or replacing
  # artifacts entirely.
  lockedDependencies =
    final:
    if lockFile == null then
      { }
    else
      let
        lockedDependencySpecs = fromJSON (readFile lockFile);
      in
      mapAttrs mkModule lockedDependencySpecs;

  finalDependencies =
    let
      composedExtension = lib.composeManyExtensions overlays;
      extended = lib.extends composedExtension lockedDependencies;
      fixed = lib.fix extended;
    in
    filter lib.isDerivation (attrValues fixed);

  offlineRepo = symlinkJoin {
    name = if version != null then "${pname}-${version}-gradle-repo" else "${pname}-gradle-repo";
    paths = finalDependencies;
  };
in
offlineRepo