From 2beee27eb5803763a01f84d1d758a1d0200de143 Mon Sep 17 00:00:00 2001
From: Marcel Otto <marcelotto@gmx.de>
Date: Sun, 19 Dec 2021 01:39:31 +0100
Subject: [PATCH] Add :implicit_base option on the RDF.Turtle.Encoder

---
 CHANGELOG.md                             | 11 +++++++++
 lib/rdf/serializations/turtle_encoder.ex | 24 +++++++++++++-------
 test/unit/turtle_encoder_test.exs        | 29 +++++++++++++++++++++++-
 3 files changed, 55 insertions(+), 9 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 54b8a8d..c8a5cd5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,17 @@ This project adheres to [Semantic Versioning](http://semver.org/) and
 [Keep a CHANGELOG](http://keepachangelog.com).
 
 
+## Unreleased
+
+### Added
+
+- `:implicit_base` option on the `RDF.Turtle.Encoder` 
+
+
+[Compare v0.10.0...HEAD](https://github.com/rdf-elixir/rdf-ex/compare/v0.10.0...HEAD)
+
+
+
 ## 0.10.0 - 2021-12-13
 
 This release adds RDF-star support on the RDF data structures, the N-Triples, N-Quads, 
diff --git a/lib/rdf/serializations/turtle_encoder.ex b/lib/rdf/serializations/turtle_encoder.ex
index 167500b..6d5e5f6 100644
--- a/lib/rdf/serializations/turtle_encoder.ex
+++ b/lib/rdf/serializations/turtle_encoder.ex
@@ -9,13 +9,17 @@ defmodule RDF.Turtle.Encoder do
 
   ## Options
 
-  - `:base`: : Allows to specify the base URI to be used for a `@base` directive.
-    If not specified the one from the given graph is used or if there is also none
-    specified for the graph the `RDF.default_base_iri/0`.
   - `:prefixes`: Allows to specify the prefixes to be used as a `RDF.PrefixMap` or
     anything from which a `RDF.PrefixMap` can be created with `RDF.PrefixMap.new/1`.
     If not specified the ones from the given graph are used or if these are also not
     present the `RDF.default_prefixes/0`.
+  - `:base`: : Allows to specify the base URI to be used for a `@base` directive.
+    If not specified the one from the given graph is used or if there is also none
+    specified for the graph the `RDF.default_base_iri/0`.
+  - `:implicit_base`: This boolean flag allows to use a base URI to get relative IRIs
+    without embedding it explicitly in the content with a `@base` directive, so that
+    the URIs will be resolved according to the remaining strategy specified in
+    section 5.1 of [RFC3986](https://www.ietf.org/rfc/rfc3986.txt).
   - `:only`: Allows to specify which parts of a Turtle document should be generated.
     Possible values: `:base`, `:prefixes`, `:directives` (means the same as `[:base, :prefixes]`),
     `:triples` or a list with any combination of these values.
@@ -119,11 +123,15 @@ defmodule RDF.Turtle.Encoder do
   defp base_directive(nil, _), do: ""
 
   defp base_directive({_, base}, opts) do
-    indent(opts) <>
-      case Keyword.get(opts, :directive_style) do
-        :sparql -> "BASE <#{base}>"
-        _ -> "@base <#{base}> ."
-      end <> "\n\n"
+    if Keyword.get(opts, :implicit_base, false) do
+      ""
+    else
+      indent(opts) <>
+        case Keyword.get(opts, :directive_style) do
+          :sparql -> "BASE <#{base}>"
+          _ -> "@base <#{base}> ."
+        end <> "\n\n"
+    end
   end
 
   defp prefix_directive({prefix, ns}, opts) do
diff --git a/test/unit/turtle_encoder_test.exs b/test/unit/turtle_encoder_test.exs
index 4a761c2..947b457 100644
--- a/test/unit/turtle_encoder_test.exs
+++ b/test/unit/turtle_encoder_test.exs
@@ -131,7 +131,7 @@ defmodule RDF.Turtle.EncoderTest do
                """
     end
 
-    test "when a base IRI is given, it has used instead of the base IRI of the given graph" do
+    test "when a base IRI is given, it is used instead of the base IRI of the given graph" do
       assert Turtle.Encoder.encode!(
                Graph.new([{EX.S1, EX.p1(), EX.O1}],
                  prefixes: %{},
@@ -147,6 +147,33 @@ defmodule RDF.Turtle.EncoderTest do
                """
     end
 
+    test ":implicit_base option" do
+      assert Turtle.Encoder.encode!(
+               Graph.new([{EX.S1, EX.p1(), EX.O1}],
+                 prefixes: %{},
+                 base_iri: EX.other()
+               ),
+               base_iri: EX,
+               implicit_base: true
+             ) ==
+               """
+               <S1>
+                   <p1> <O1> .
+               """
+
+      assert Turtle.Encoder.encode!(
+               Graph.new([{EX.S1, EX.p1(), EX.O1}],
+                 prefixes: %{},
+                 base_iri: EX
+               ),
+               implicit_base: true
+             ) ==
+               """
+               <S1>
+                   <p1> <O1> .
+               """
+    end
+
     test "when no prefixes are given and no prefixes are in the given graph the default_prefixes are used" do
       assert Turtle.Encoder.encode!(Graph.new({EX.S, EX.p(), NS.XSD.string()})) ==
                """