Compare language codes in MessageContent::Choose()

If there is no exact match, compare language codes so that a more
generic match is preferred over just returning the English content.

This means that if a locale code is given, Choose() will also look for
the locale's language code (but will not match another locale with the
same language code), and if a language code is given, Choose() will also
look for a locale with that language code.

include/loot/metadata/message_content.h

@@ -37,7 +37,7 @@ class MessageContent {
 public:
   /**
    * The code for the default language assumed for message content, which is
-   * English.
+   * "en" (English).
    */
   LOOT_API static const std::string defaultLanguage;
 
@@ -73,7 +73,7 @@ public:
   /**
    * A less-than operator implemented with no semantics so that MessageContent
    * objects can be stored in sets.
-   * @returns True if this MessageContent is less than the given 
+   * @returns True if this MessageContent is less than the given
    *          MessageContent, false otherwise.
    */
   LOOT_API bool operator<(const MessageContent& rhs) const;
@@ -89,11 +89,26 @@ public:
    * @param  content
    *         The MessageContent objects to choose between.
    * @param  language
-   *         The language code for the preferred language to select. If no
-   *         message in the preferred language is present, the English
-   *         MessageContent will be returned.
-   * @return A MessageContent object. If the given vector is empty, a
-   *         default-constructed MessageContent is returned.
+   *         The locale or language code for the preferred language to select.
+   *         Locale codes are of the form <language code>_<country code>.
+   * @return A MessageContent object.
+   *
+   *         If the vector only contains a single element, that element is
+   *         returned.
+   *
+   *         If content with a language that exactly matches the given locale
+   *         or language code is present, that content is returned.
+   *
+   *         If a locale code is given and there is no exact match but content
+   *         for that locale's language is present, that content is returned.
+   *
+   *         If a language code is given and there is no exact match but content
+   *         for a locale in that langauge is present, that content is returned.
+   *
+   *         If no locale or language code matches are found and content in the
+   *         default language is present, that content is returned.
+   *
+   *         Otherwise, a default-constructed MessageContent is returned.
    */
   LOOT_API static MessageContent Choose(
       const std::vector<MessageContent> content,
@@ -111,9 +126,9 @@ private:
 LOOT_API bool operator!=(const MessageContent& lhs, const MessageContent& rhs);
 
 /**
- * Check if the first MessageContent object is greater than the second 
+ * Check if the first MessageContent object is greater than the second
  * MessageContent object.
- * @returns True if the second MessageContent object is less than the first 
+ * @returns True if the second MessageContent object is less than the first
  *          MessageContent object, false otherwise.
  */
 LOOT_API bool operator>(const MessageContent& lhs, const MessageContent& rhs);
@@ -121,13 +136,13 @@ LOOT_API bool operator>(const MessageContent& lhs, const MessageContent& rhs);
 /**
  * Check if the first MessageContent object is less than or equal to the second
  * MessageContent object.
- * @returns True if the first MessageContent object is not greater than the 
+ * @returns True if the first MessageContent object is not greater than the
  *          second MessageContent object, false otherwise.
  */
 LOOT_API bool operator<=(const MessageContent& lhs, const MessageContent& rhs);
 
 /**
- * Check if the first MessageContent object is greater than or equal to the 
+ * Check if the first MessageContent object is greater than or equal to the
  * second MessageContent object.
  * @returns True if the first MessageContent object is not less than the second
  *          MessageContent object, false otherwise.

src/api/metadata/message_content.cpp

@@ -24,6 +24,8 @@
 
 #include "loot/metadata/message_content.h"
 
+#include <optional>
+
 #include <boost/algorithm/string.hpp>
 
 namespace loot {
@@ -33,8 +35,7 @@ MessageContent::MessageContent() : language_(MessageContent::defaultLanguage) {}
 
 MessageContent::MessageContent(const std::string& text,
                                const std::string& language) :
-    text_(text),
-    language_(language) {}
+    text_(text), language_(language) {}
 
 std::string MessageContent::GetText() const { return text_; }
 
@@ -63,13 +64,39 @@ MessageContent MessageContent::Choose(const std::vector<MessageContent> content,
   else if (content.size() == 1)
     return content[0];
   else {
+    auto languageCode = language.substr(0, language.find("_"));
+    auto isCountryCodeGiven = languageCode.length() != language.length();
+
+    std::optional<MessageContent> matchedLanguage;
     MessageContent english;
     for (const auto& mc : content) {
-      if (mc.GetLanguage() == language) {
+      auto contentLanguage = mc.GetLanguage();
+
+      if (contentLanguage == language) {
         return mc;
-      } else if (mc.GetLanguage() == MessageContent::defaultLanguage)
-        english = mc;
+      } else if (!matchedLanguage.has_value()) {
+        if (isCountryCodeGiven && contentLanguage == languageCode) {
+          matchedLanguage = mc;
+        } else if (!isCountryCodeGiven) {
+          auto underscorePos = contentLanguage.find("_");
+          if (underscorePos != std::string::npos) {
+            auto contentLanguageCode = contentLanguage.substr(0, underscorePos);
+            if (contentLanguageCode == language) {
+              matchedLanguage = mc;
+            }
+          }
+        }
+
+        if (contentLanguage == MessageContent::defaultLanguage) {
+          english = mc;
+        }
+      }
     }
+
+    if (matchedLanguage.has_value()) {
+      return matchedLanguage.value();
+    }
+
     return english;
   }
 }

src/tests/api/internals/metadata/message_content_test.h

@@ -25,11 +25,10 @@ along with LOOT.  If not, see
 #ifndef LOOT_TESTS_API_INTERNALS_METADATA_MESSAGE_CONTENT_TEST
 #define LOOT_TESTS_API_INTERNALS_METADATA_MESSAGE_CONTENT_TEST
 
-#include "loot/metadata/message_content.h"
-
 #include <gtest/gtest.h>
 
 #include "api/metadata/yaml/message_content.h"
+#include "loot/metadata/message_content.h"
 
 namespace loot {
 namespace test {
@@ -240,6 +239,98 @@ TEST(
   EXPECT_TRUE(content1 >= content2);
 }
 
+TEST(MessageContent,
+     chooseShouldReturnAnEmptyEnglishMessageIfTheVectorIsEmpty) {
+  auto content = MessageContent::Choose(std::vector<MessageContent>(), "fr");
+
+  EXPECT_EQ("en", content.GetLanguage());
+  EXPECT_EQ("", content.GetText());
+}
+
+TEST(MessageContent, chooseShouldReturnTheOnlyElementOfASingleElementVector) {
+  MessageContent content("test", "de");
+  auto chosen = MessageContent::Choose({MessageContent("test", "de")}, "fr");
+
+  EXPECT_EQ(content, chosen);
+}
+
+TEST(
+    MessageContent,
+    chooseShouldReturnAnEmptyEnglishMessageIfTheVectorHasNoEnglishOrMatchingLanguageContentWithTwoOrMoreElements) {
+  auto contents = {MessageContent("test1", "de"),
+                   MessageContent("test2", "fr")};
+  auto content = MessageContent::Choose(contents, "pt");
+
+  EXPECT_EQ("en", content.GetLanguage());
+  EXPECT_EQ("", content.GetText());
+}
+
+TEST(MessageContent,
+     chooseShouldReturnElementWithExactlyMatchingLocaleCodeIfPresent) {
+  auto contents = {MessageContent("test1", "en"),
+                   MessageContent("test2", "de"),
+                   MessageContent("test3", "pt"),
+                   MessageContent("test4", "pt_PT"),
+                   MessageContent("test5", "pt_BR")};
+  auto content = MessageContent::Choose(contents, "pt_BR");
+
+  EXPECT_EQ("pt_BR", content.GetLanguage());
+  EXPECT_EQ("test5", content.GetText());
+}
+
+TEST(
+    MessageContent,
+    chooseShouldReturnElementWithMatchingLanguageCodeIfExactlyMatchingLocaleCodeIsNotPresent) {
+  auto contents = {MessageContent("test1", "en"),
+                   MessageContent("test2", "de"),
+                   MessageContent("test3", "pt_PT"),
+                   MessageContent("test4", "pt")};
+  auto content = MessageContent::Choose(contents, "pt_BR");
+
+  EXPECT_EQ("pt", content.GetLanguage());
+  EXPECT_EQ("test4", content.GetText());
+}
+
+TEST(
+    MessageContent,
+    chooseShouldReturnElementWithEnLanguageCodeIfNoMatchingLanguageCodeIsPresent) {
+  auto contents = {MessageContent("test1", "en"),
+                   MessageContent("test2", "de"),
+                   MessageContent("test3", "pt_PT")};
+  auto content = MessageContent::Choose(contents, "pt_BR");
+
+  EXPECT_EQ("en", content.GetLanguage());
+  EXPECT_EQ("test1", content.GetText());
+}
+
+TEST(
+    MessageContent,
+    chooseShouldReturnElementWithExactlyMatchingLanguageCodeIfLanguageCodeIsGiven) {
+  auto contents = {
+      MessageContent("test1", "en"),
+      MessageContent("test2", "de"),
+      MessageContent("test3", "pt_BR"),
+      MessageContent("test4", "pt"),
+  };
+  auto content = MessageContent::Choose(contents, "pt");
+
+  EXPECT_EQ("pt", content.GetLanguage());
+  EXPECT_EQ("test4", content.GetText());
+}
+
+TEST(
+    MessageContent,
+    chooseShouldReturnFirstElementWithMatchingLanguageCodeIfLanguageCodeIsGivenAndNoExactMatchIsPresent) {
+  auto contents = {MessageContent("test1", "en"),
+                   MessageContent("test2", "de"),
+                   MessageContent("test3", "pt_PT"),
+                   MessageContent("test4", "pt_BR")};
+  auto content = MessageContent::Choose(contents, "pt");
+
+  EXPECT_EQ("pt_PT", content.GetLanguage());
+  EXPECT_EQ("test3", content.GetText());
+}
+
 TEST(MessageContent, emittingAsYamlShouldOutputDataCorrectly) {
   MessageContent content("content", french);
   YAML::Emitter emitter;