Add regex for title text version of links

* Add regex for title text version of links

Original parser matched:
  [name](http:://link)

Add match for:
  [name](http:://link "title text")

* Add tests and improve regex's
* Several new tests in test_maddy_linkparser.cpp  (Some with paths for future improvement, and one to ensure an overzealous future update doesn't disallow actually-used special characters like o-umlaut).
* URLs now ignore leading/trailing spaces.
* URLs now don't match on internal spaces or quotes.
* Small grammar fix in CONTRIBUTING.md
* Updated changelog.

tests/maddy/test_maddy_linkparser.cpp

@@ -37,14 +37,47 @@ TEST(MADDY_LINKPARSER, ItReplacesMarkdownWithLinks)
   ASSERT_EQ(expected, text);
 }
 
+TEST(MADDY_LINKPARSER, ItReplacesMarkdownWithSpacesAfterLink)
+{
+  std::string text =
+    "Some text [Link Title](http://example.com    ) bla [Link "
+    "Title](http://example.com)";
+  std::string expected =
+    "Some text <a href=\"http://example.com\">Link Title</a> bla <a "
+    "href=\"http://example.com\">Link Title</a>";
+  auto linkParser = std::make_shared<maddy::LinkParser>();
+
+  linkParser->Parse(text);
+
+  ASSERT_EQ(expected, text);
+}
+
+TEST(MADDY_LINKPARSER, ItHandlesURLsWithOfficiallyIllegalCharacters)
+{
+  // Some links in the real world have characters that are not
+  // 'official' characters that are supposedly allowed in URLs.
+  std::string text =
+    "Wikipedia's [Möbius strip]"
+    "(https://en.wikipedia.org/wiki/Möbius_strip) link.";
+  std::string expected =
+    "Wikipedia's <a "
+    "href=\"https://en.wikipedia.org/wiki/Möbius_strip\">"
+    "Möbius strip</a> link.";
+  auto linkParser = std::make_shared<maddy::LinkParser>();
+
+  linkParser->Parse(text);
+
+  ASSERT_EQ(expected, text);
+}
+
 TEST(
   MADDY_LINKPARSER, ItReplacesMarkdownProperlyEvenWithMultipleParenthesisInLine
 )
 {
   std::string text =
-    "(This is a [link](/ABC/some file) (the URL will include this).)";
+    "(This is a [link](/ABC/some_file) (the URL will not include this).)";
   std::string expected =
-    "(This is a <a href=\"/ABC/some file\">link</a> (the URL will include "
+    "(This is a <a href=\"/ABC/some_file\">link</a> (the URL will not include "
     "this).)";
   auto linkParser = std::make_shared<maddy::LinkParser>();
 
@@ -53,6 +86,99 @@ TEST(
   ASSERT_EQ(expected, text);
 }
 
+TEST(MADDY_LINKPARSER, ItDoesntReplaceMarkdownWithSpaceInURL)
+{
+  // Spaces are not allowed in URLs, so don't match them.
+  std::string text = "This is an invalid [link](/ABC/some file)";
+  std::string expected = "This is an invalid [link](/ABC/some file)";
+  auto linkParser = std::make_shared<maddy::LinkParser>();
+
+  linkParser->Parse(text);
+
+  ASSERT_EQ(expected, text);
+}
+
+TEST(MADDY_LINKPARSER, ItReplacesMarkdownWithTitleText)
+{
+  std::string text = "Link to [name](http:://example.com \"title text\")";
+  std::string expected =
+    "Link to <a href=\"http:://example.com\" title=\"title text\">name</a>";
+  auto linkParser = std::make_shared<maddy::LinkParser>();
+
+  linkParser->Parse(text);
+
+  ASSERT_EQ(expected, text);
+}
+
+TEST(MADDY_LINKPARSER, ItReplacesMarkdownWithSpacesWithTitleText)
+{
+  std::string text = "Link to [name](http:://example.com     \"title text\")";
+  std::string expected =
+    "Link to <a href=\"http:://example.com\" title=\"title text\">name</a>";
+  auto linkParser = std::make_shared<maddy::LinkParser>();
+
+  linkParser->Parse(text);
+
+  ASSERT_EQ(expected, text);
+}
+
+TEST(MADDY_LINKPARSER, ItReplacesMarkdownWithMoreSpacesWithTitleText)
+{
+  std::string text =
+    "Link to [name](http:://example.com     \"title text\"    )";
+  std::string expected =
+    "Link to <a href=\"http:://example.com\" title=\"title text\">name</a>";
+  auto linkParser = std::make_shared<maddy::LinkParser>();
+
+  linkParser->Parse(text);
+
+  ASSERT_EQ(expected, text);
+}
+
+TEST(MADDY_LINKPARSER, ItReplacesMarkdownWithParentheticalText)
+{
+  std::string text = "Link to [name](http:://example.com \"title (text)\")";
+  std::string expected =
+    "Link to <a href=\"http:://example.com\" title=\"title (text)\">name</a>";
+  auto linkParser = std::make_shared<maddy::LinkParser>();
+
+  linkParser->Parse(text);
+
+  ASSERT_EQ(expected, text);
+}
+
+TEST(MADDY_LINKPARSER, ItDoesntReplaceMarkdownWithTooManyQuotes)
+{
+  // If you have too many quotation marks, don't match:
+  std::string text =
+    "This is an invalid [link](/ABC/some_file \"title \" text \")";
+  std::string expected =
+    "This is an invalid [link](/ABC/some_file \"title \" text \")";
+  auto linkParser = std::make_shared<maddy::LinkParser>();
+
+  linkParser->Parse(text);
+
+  ASSERT_EQ(expected, text);
+}
+
+TEST(MADDY_LINKPARSER, ItDoesntReplaceMarkdownWithQuoteInLink)
+{
+  // This is actually legal markdown, but hard to parse with regexes;
+  // See disabled 'ItReplacesMarkdownWithQuoteInLink' below.
+  //
+  // For now, don't try to translate it; it would produce invalid HTML.
+
+  std::string text = "Some text [Link Title](http://example.com/\"foo ) bla.";
+  std::string current_expected =
+    "Some text [Link Title](http://example.com/\"foo ) bla.";
+  std::string correct_expected =
+    "Some text <a href=\"http://example.com/%22foo\">Link Title</a> bla.";
+  auto linkParser = std::make_shared<maddy::LinkParser>();
+
+  linkParser->Parse(text);
+
+  ASSERT_EQ(current_expected, text);
+}
 // -----------------------------------------------------------------------------
 
 class DISABLED_MADDY_LINKPARSER : public ::testing::Test
@@ -70,3 +196,17 @@ TEST_F(DISABLED_MADDY_LINKPARSER, ItReplacesNoImageMarkdownWithLinks)
 
   ASSERT_EQ(expected, text);
 }
+
+TEST(DISABLED_MADDY_LINKPARSER, ItReplacesMarkdownWithQuoteInLink)
+{
+  // This is legal markdown, but hard to parse with regexes; dropping it
+  // here for a future update.
+  std::string text = "Some text [Link Title](http://example.com/\"foo ) bla.";
+  std::string expected =
+    "Some text <a href=\"http://example.com/%22foo\">Link Title</a> bla.";
+  auto linkParser = std::make_shared<maddy::LinkParser>();
+
+  linkParser->Parse(text);
+
+  ASSERT_EQ(expected, text);
+}