separate out token replacer as a standalone function in preparation for #300

include/llmr/style/value.hpp

@@ -10,6 +10,12 @@ typedef util::variant<bool, int64_t, uint64_t, double, std::string> Value;
 
 std::string toString(const Value &value);
 
+inline std::string& operator+=(std::string& out, const Value& value) {
+    out += toString(value);
+    return out;
+}
+
+
 Value parseValue(pbf data);
 
 namespace util {

include/llmr/util/token.hpp

@@ -0,0 +1,49 @@
+#ifndef LLMR_UTIL_TOKEN
+#define LLMR_UTIL_TOKEN
+
+#ifdef __linux__
+#include <boost/regex.hpp>
+namespace regex_impl = boost;
+#else
+#include <regex>
+namespace regex_impl = std;
+#endif
+
+namespace llmr {
+namespace util {
+
+namespace detail {
+const regex_impl::regex tokenRegex("\\{\\{(\\w+)\\}\\}");
+const regex_impl::sregex_token_iterator tokensEnd = regex_impl::sregex_token_iterator();
+}
+
+template <typename Tokens>
+std::string replaceTokens(const std::string &source, const Tokens &tokens) {
+    std::string result;
+    result.reserve(source.size());
+
+    bool token = false;
+    for (auto token_it = regex_impl::sregex_token_iterator(source.begin(), source.end(),
+                                                           detail::tokenRegex, {-1, 1});
+         token_it != detail::tokensEnd; ++token_it, token = !token) {
+        if (!token_it->matched) {
+            continue;
+        }
+
+        if (token) {
+            const auto it_prop = tokens.find(token_it->str());
+            if (it_prop != tokens.end()) {
+                result += it_prop->second;
+            }
+        } else {
+            result += token_it->str();
+        }
+    }
+
+    return result;
+}
+
+} // end namespace util
+} // end namespace llmr
+
+#endif