feat: add optional latex block support

CHANGELOG.md

@@ -24,6 +24,7 @@ maddy uses [semver versioning](https://semver.org/).
 * ![**DEPRECATED**](https://img.shields.io/badge/-DEPRECATED-%23666) config flags `isEmphasizedParserEnabled` and `isHTMLWrappedInParagraph`
 * ![**ADDED**](https://img.shields.io/badge/-ADDED-%23099) config flag `enabledParsers` to en-/disable each parser separately
 * ![**ADDED**](https://img.shields.io/badge/-ADDED-%23099) class attribute to code blocks if there is text after the three backticks like ` ```cpp`
+* ![**ADDED**](https://img.shields.io/badge/-ADDED-%23099) optional support for latex blocks - it's off by default
 * ?
 
 ## version 1.1.2 2020-10-04

docs/definitions.md

@@ -376,3 +376,29 @@ becomes
 </table>
 ```
 table header and footer are optional
+
+## LaTeX(MathJax) block support
+
+To turn on the LaTeX support - which basically is only a
+[MathJax](https://www.mathjax.org/) support and makes sure, that formulas aren't
+internally checked for other parsers - it has to be enabled in config:
+
+```cpp
+std::shared_ptr<maddy::ParserConfig> config = std::make_shared<maddy::ParserConfig>();
+config->enabledParsers |= maddy::types::LATEX_BLOCK_PARSER;
+
+std::shared_ptr<maddy::Parser> parser = std::make_shared<maddy::Parser>(config);
+std::string htmlOutput = parser->Parse(markdownInput);
+```
+
+After this you can do the following in Markdown:
+
+```
+$$x = {-b \\pm \\sqrt{b^2-4ac} \\over 2a}.$$
+```
+
+Which results in
+
+```html
+$$x = {-b \\pm \\sqrt{b^2-4ac} \\over 2a}.$$\n
+```

include/maddy/latexblockparser.h

@@ -0,0 +1,135 @@
+/*
+ * This project is licensed under the MIT license. For more information see the
+ * LICENSE file.
+ */
+#pragma once
+
+// -----------------------------------------------------------------------------
+
+#include <functional>
+#include <string>
+#include <regex>
+
+#include "maddy/blockparser.h"
+
+// -----------------------------------------------------------------------------
+
+namespace maddy {
+
+// -----------------------------------------------------------------------------
+
+/**
+ * LatexBlockParser
+ *
+ * Support for https://www.mathjax.org/
+ * Be aware, that if you want to make MathJax work, you need also their
+ * JavaScript library added to your HTML code.
+ * maddy does not itself add that code to be more flexible in how you write your
+ * head and full body.
+ *
+ * From Markdown: `$$` surrounded text
+ *
+ * ```
+ *  $$some formula
+ *  $$
+ * ```
+ *
+ * To HTML:
+ *
+ * ```
+ * $$some formula
+ * $$
+ * ```
+ *
+ * @class
+ */
+class LatexBlockParser : public BlockParser
+{
+public:
+  /**
+   * ctor
+   *
+   * @method
+   * @param {std::function<void(std::string&)>} parseLineCallback
+   * @param {std::function<std::shared_ptr<BlockParser>(const std::string& line)>} getBlockParserForLineCallback
+   */
+   LatexBlockParser(
+    std::function<void(std::string&)> parseLineCallback,
+    std::function<std::shared_ptr<BlockParser>(const std::string& line)> getBlockParserForLineCallback
+  )
+    : BlockParser(parseLineCallback, getBlockParserForLineCallback)
+    , isStarted(false)
+    , isFinished(false)
+  {}
+
+  /**
+   * IsStartingLine
+   *
+   * If the line starts with two dollars, then it is a latex block.
+   *
+   * ```
+   *  $$
+   * ```
+   *
+   * @method
+   * @param {const std::string&} line
+   * @return {bool}
+   */
+  static bool
+  IsStartingLine(const std::string& line)
+  {
+    static std::regex re("^(?:\\$){2}(.*)$");
+    return std::regex_match(line, re);
+  }
+
+  /**
+   * IsFinished
+   *
+   * @method
+   * @return {bool}
+   */
+  bool
+  IsFinished() const override
+  {
+    return this->isFinished;
+  }
+
+protected:
+  bool
+  isInlineBlockAllowed() const override
+  {
+    return false;
+  }
+
+  bool
+  isLineParserAllowed() const override
+  {
+    return false;
+  }
+
+  void
+  parseBlock(std::string& line) override
+  {
+    if (!this->isStarted && line.substr(0, 2) == "$$")
+    {
+      this->isStarted = true;
+      this->isFinished = false;
+    }
+
+    if (this->isStarted && !this->isFinished && line.size() > 1 && line.substr(line.size() - 2, 2) == "$$")
+    {
+      this->isFinished = true;
+      this->isStarted = false;
+    }
+
+    line += "\n";
+  }
+
+private:
+  bool isStarted;
+  bool isFinished;
+}; // class LatexBlockParser
+
+// -----------------------------------------------------------------------------
+
+} // namespace maddy

include/maddy/parser.h

@@ -18,6 +18,7 @@
 #include "maddy/headlineparser.h"
 #include "maddy/horizontallineparser.h"
 #include "maddy/htmlparser.h"
+#include "maddy/latexblockparser.h"
 #include "maddy/orderedlistparser.h"
 #include "maddy/paragraphparser.h"
 #include "maddy/quoteparser.h"
@@ -259,6 +260,17 @@ private:
         nullptr
       );
     }
+    else if (
+      this->config &&
+      (this->config->enabledParsers & maddy::types::LATEX_BLOCK_PARSER) != 0 &&
+      maddy::LatexBlockParser::IsStartingLine(line)
+    )
+    {
+      parser = std::make_shared<LatexBlockParser>(
+        nullptr,
+        nullptr
+      );
+    }
     else if (
       (
         !this->config ||

include/maddy/parserconfig.h

@@ -41,9 +41,10 @@ enum PARSER_TYPE : uint32_t
   STRONG_PARSER            = 0b1000000000000000,
   TABLE_PARSER             = 0b10000000000000000,
   UNORDERED_LIST_PARSER    = 0b100000000000000000,
+  LATEX_BLOCK_PARSER       = 0b1000000000000000000,
 
-  DEFAULT                  = 0b111111111110111111,
-  ALL                      = 0b111111111111111111,
+  DEFAULT                  = 0b0111111111110111111,
+  ALL                      = 0b1111111111111111111,
 };
 
 } // namespace types

tests/maddy/test_maddy_latexblockparser.cpp

@@ -0,0 +1,102 @@
+/*
+ * This project is licensed under the MIT license. For more information see the
+ * LICENSE file.
+ */
+#include <memory>
+
+#include "gmock/gmock.h"
+
+#include "maddy/latexblockparser.h"
+
+// -----------------------------------------------------------------------------
+
+class MADDY_LATEXBLOCKPARSER : public ::testing::Test
+{
+protected:
+  std::shared_ptr<maddy::LatexBlockParser> lbParser;
+
+  void
+  SetUp() override
+  {
+    this->lbParser = std::make_shared<maddy::LatexBlockParser>(
+      nullptr,
+      nullptr
+    );
+  }
+};
+
+// -----------------------------------------------------------------------------
+
+TEST_F(MADDY_LATEXBLOCKPARSER, IsStartingLineReturnsTrueWhenFacedWithTwoDollars)
+{
+  ASSERT_TRUE(maddy::LatexBlockParser::IsStartingLine("$$"));
+}
+
+TEST_F(MADDY_LATEXBLOCKPARSER, IsFinishedReturnsFalseInTheBeginning)
+{
+  ASSERT_FALSE(lbParser->IsFinished());
+}
+
+TEST_F(MADDY_LATEXBLOCKPARSER, ItReplacesOneLineMarkdownWithALatexBlock)
+{
+  std::vector<std::string> markdown = {
+    "$$x = {-b \\pm \\sqrt{b^2-4ac} \\over 2a}.$$"
+  };
+
+  std::string expected = "$$x = {-b \\pm \\sqrt{b^2-4ac} \\over 2a}.$$\n";
+
+  for (std::string md : markdown)
+  {
+    lbParser->AddLine(md);
+  }
+  ASSERT_TRUE(lbParser->IsFinished());
+
+  std::stringstream& output(lbParser->GetResult());
+  const std::string& outputString = output.str();
+
+  ASSERT_EQ(expected, outputString);
+}
+
+TEST_F(MADDY_LATEXBLOCKPARSER, ItReplacesABlockMarkdownWithALatexBlock)
+{
+  std::vector<std::string> markdown = {
+    "$$",
+    "x = {-b \\pm \\sqrt{b^2-4ac} \\over 2a}.",
+    "$$"
+  };
+
+  std::string expected = "$$\nx = {-b \\pm \\sqrt{b^2-4ac} \\over 2a}.\n$$\n";
+
+  for (std::string md : markdown)
+  {
+    lbParser->AddLine(md);
+  }
+  ASSERT_TRUE(lbParser->IsFinished());
+
+  std::stringstream& output(lbParser->GetResult());
+  const std::string& outputString = output.str();
+
+  ASSERT_EQ(expected, outputString);
+}
+
+TEST_F(MADDY_LATEXBLOCKPARSER, ItReplacesAMultilineBlockMarkdownWithALatexBlock)
+{
+  std::vector<std::string> markdown = {
+    "$$",
+    "x = {-b \\pm \\sqrt{b^2-4ac}",
+    "\\over 2a}.$$"
+  };
+
+  std::string expected = "$$\nx = {-b \\pm \\sqrt{b^2-4ac}\n\\over 2a}.$$\n";
+
+  for (std::string md : markdown)
+  {
+    lbParser->AddLine(md);
+  }
+  ASSERT_TRUE(lbParser->IsFinished());
+
+  std::stringstream& output(lbParser->GetResult());
+  const std::string& outputString = output.str();
+
+  ASSERT_EQ(expected, outputString);
+}