# Adaptation of the MIT-licensed work on `sbt2nix` done by Charles O'Farrell

{ lib, fetchurl, stdenv }:
let
  defaultRepos = [
    "https://repo1.maven.org/maven2"
    "https://oss.sonatype.org/content/repositories/releases"
    "https://oss.sonatype.org/content/repositories/public"
    "https://repo.typesafe.com/typesafe/releases"
  ];
in

args@
{ # Example: "org.apache.httpcomponents"
  groupId
, # Example: "httpclient"
  artifactId
, # Example: "4.3.6"
  version
, # Example: "jdk11"
  classifier ? null
, # List of maven repositories from where to fetch the artifact.
  # Example: [ http://oss.sonatype.org/content/repositories/public ].
  repos ? defaultRepos
  # The `url` and `urls` parameters, if specified should point to the JAR
  # file and will take precedence over the `repos` parameter. Only one of `url`
  # and `urls` can be specified, not both.
, url ? ""
, urls ? []
, # The rest of the arguments are just forwarded to `fetchurl`.
  ...
}:

# only one of url and urls can be specified at a time.
assert (url == "") || (urls == []);
# if repos is empty, then url or urls must be specified.
assert (repos != []) || (url != "") || (urls != []);

let
  pname = (lib.replaceStrings [ "." ] [ "_" ] groupId) + "_" + (lib.replaceStrings [ "." ] [ "_" ] artifactId);
  suffix = lib.optionalString (classifier != null) "-${classifier}";
  filename = "${artifactId}-${version}${suffix}.jar";
  mkJarUrl = repoUrl:
    lib.concatStringsSep "/" [
      (lib.removeSuffix "/" repoUrl)
      (lib.replaceStrings ["."] ["/"] groupId)
      artifactId
      version
      filename
    ];
  urls_ =
    if url != "" then [url]
    else if urls != [] then urls
    else map mkJarUrl repos;
  jar =
    fetchurl (
      builtins.removeAttrs args [ "groupId" "artifactId" "version" "classifier" "repos" "url" ]
      // { urls = urls_; name = "${pname}-${version}.jar"; }
    );
in
  stdenv.mkDerivation {
    inherit pname version;
    dontUnpack = true;
    # By moving the jar to $out/share/java we make it discoverable by java
    # packages packages that mention this derivation in their buildInputs.
    installPhase = ''
      mkdir -p $out/share/java
      ln -s ${jar} $out/share/java/${filename}
    '';
    # We also add a `jar` attribute that can be used to easily obtain the path
    # to the downloaded jar file.
    passthru.jar = jar;
  }
