added markdown metadata parsing

src/markdown.cpp

@@ -0,0 +1,43 @@
+#include "markdown.hpp"
+#include "utils.hpp"
+#include <fstream>
+#include <iostream>
+#include <map>
+#include <md4c-html.h>
+#include <optional>
+
+std::optional<Metadata> get_metadata(const std::string &FILE_PATH) {
+  std::fstream file(FILE_PATH);
+  std::string buffer;
+
+  if (!getline(file, buffer) || buffer != "---") {
+    std::cerr << "File " << FILE_PATH << "does not contain metadata."
+              << std::endl;
+    return std::nullopt;
+  }
+
+  std::map<std::string, std::string> metadata_map;
+
+  while (getline(file, buffer)) {
+    if (buffer == "---") {
+      break;
+    }
+    size_t colon_pos = buffer.find(":");
+
+    if (colon_pos == std::string::npos) {
+      std::cerr << "The line: \n"
+                << buffer << " does not contain a colon" << std::endl;
+    }
+
+    std::string key = buffer.substr(0, colon_pos);
+    trim(key);
+
+    std::string value = buffer.substr(colon_pos + 1);
+    trim(value);
+    metadata_map[key] = value;
+  }
+
+  return std::optional(Metadata{metadata_map["author"], metadata_map["date"],
+                                metadata_map["title"],
+                                convert_string_to_set(metadata_map["tags"])});
+}