Convert relative img paths into absolute

Fixes #27

lib/readability.ex

@@ -62,7 +62,8 @@ defmodule Readability do
     replace_xml_version: ~r/<\?xml.*\?>/i,
     normalize: ~r/\s{2,}/,
     video: ~r/\/\/(www\.)?(dailymotion|youtube|youtube-nocookie|player\.vimeo)\.com/i,
-    protect_attrs: ~r/^(?!id|rel|for|summary|title|href|src|alt|srcdoc)/i
+    protect_attrs: ~r/^(?!id|rel|for|summary|title|href|src|alt|srcdoc)/i,
+    img_tag_src: ~r/(<img.*src=['"])([^'"]+)(['"][^>]*>)/Ui
   ]
 
   @markup_mimes ~r/^(application|text)\/[a-z\-_\.\+]+ml(;\s*charset=.*)?$/i
@@ -84,7 +85,9 @@ defmodule Readability do
 
     case is_response_markup(headers) do
       true ->
-        html_tree = Helper.normalize(raw)
+        html_tree =
+          raw
+          |> Helper.normalize(url: url)
 
         article_tree =
           html_tree

lib/readability/helper.ex

@@ -101,14 +101,54 @@ defmodule Readability.Helper do
   @doc """
   Normalize and Parse to html tree(tuple or list)) from binary html
   """
-  @spec normalize(binary) :: html_tree
-  def normalize(raw_html) do
+  @spec normalize(binary, list) :: html_tree
+  def normalize(raw_html, opts \\ []) do
     raw_html
     |> String.replace(Readability.regexes(:replace_xml_version), "")
     |> String.replace(Readability.regexes(:replace_brs), "</p><p>")
     |> String.replace(Readability.regexes(:replace_fonts), "<\1span>")
     |> String.replace(Readability.regexes(:normalize), " ")
+    |> transform_img_paths(opts[:url])
     |> Floki.parse()
     |> Floki.filter_out(:comment)
   end
+
+  # Turn relative `img` tag paths into absolute if possible
+  defp transform_img_paths(html_str, nil), do: html_str
+
+  defp transform_img_paths(html_str, url) do
+    Readability.regexes(:img_tag_src)
+    |> Regex.replace(html_str, &build_img_path(url, &1, &2, &3, &4))
+  end
+
+  defp build_img_path(url, _str, pre_src, src, post_src) do
+    new_src =
+      case URI.parse(src) do
+        %URI{host: nil} ->
+          base_url = base_url(url)
+          scrubbed_src = String.trim_leading(src, "/")
+
+          base_url <> "/" <> scrubbed_src
+
+        _ ->
+          src
+      end
+
+    pre_src <> new_src <> post_src
+  end
+
+  # Get the base url of a given url, including its scheme.
+  # E.g: both http://elixir-lang.org/guides and elixir-lang.org/guides
+  # would return http://elixir-lang.org
+  defp base_url(url) do
+    scheme_regex = ~r/^(https?:\/\/)?(.*)/i
+    path_regex = ~r/^([^\/]+)(.*)/i
+
+    url_without_scheme = Regex.replace(scheme_regex, url, "\\2")
+    base_url = Regex.replace(path_regex, url_without_scheme, "\\1")
+
+    scheme = URI.parse(url).scheme || "http"
+
+    scheme <> "://" <> base_url
+  end
 end

test/readability/helper_test.exs

@@ -11,10 +11,12 @@ defmodule Readability.HelperTest do
           <font>a</fond>
           <p>
             <font>abc</font>
+            <img src="https://example.org/images/foo.png">
           </p>
         </p>
         <p>
           <font>b</font>
+          <img class="img" src="/images/bar.png" alt="alt" />
         </p>
       </body>
     </html>
@@ -43,8 +45,30 @@ defmodule Readability.HelperTest do
     assert result == expected
   end
 
-  test "inner text lengt", %{html_tree: html_tree} do
+  test "inner text length", %{html_tree: html_tree} do
     result = html_tree |> Helper.text_length()
     assert result == 5
   end
+
+  test "transform img relative paths into absolute" do
+    foo_url = "https://example.org/images/foo.png"
+    bar_url_http = "http://example.org/images/bar.png"
+    bar_url_https = "https://example.org/images/bar.png"
+
+    result_without_scheme =
+      @sample
+      |> Helper.normalize(url: "example.org/blog/a-blog-post")
+      |> Floki.raw_html()
+
+    result_with_scheme =
+      @sample
+      |> Helper.normalize(url: "https://example.org/blog/a-blog-post")
+      |> Floki.raw_html()
+
+    assert result_without_scheme =~ foo_url
+    assert result_without_scheme =~ bar_url_http
+
+    assert result_with_scheme =~ foo_url
+    assert result_with_scheme =~ bar_url_https
+  end
 end