Replace logging API

Allow clients to provide a callback function that the LOOT API will use
when logging. This provides more flexibility than the previous choice of
outputting to an exclusive file or the console.

include/loot/api.h

@@ -25,6 +25,7 @@
 #ifndef LOOT_API_H
 #define LOOT_API_H
 
+#include <functional>
 #include <string>
 #include <memory>
 
@@ -36,7 +37,7 @@
 #include "loot/exception/file_access_error.h"
 #include "loot/exception/git_state_error.h"
 #include "loot/enum/game_type.h"
-#include "loot/enum/log_verbosity.h"
+#include "loot/enum/log_level.h"
 #include "loot/loot_version.h"
 
 namespace loot {
@@ -47,21 +48,14 @@ namespace loot {
 /**@{*/
 
 /**
- * @brief Set the API's logging verbosity.
- * @details The default is ``LogVerbosity::off``.
- * @param verbosity
- *        The logging verbosity to set.
+ * @brief Set the callback function that is called when logging.
+ * @details If this function is not called, the default behaviour is to 
+ *          print messages to the console.
+ * @param callback
+ *        The function called when logging. The first parameter is the
+ *        level of the message being logged, and the second is the message.
  */
-LOOT_API void SetLoggingVerbosity(LogVerbosity verbosity);
-
-/**
- * @brief Set the file path that logging statements are written to.
- * @details If no file is set the default behaviour is to print logging
- *          statements to the console.
- * @param path
- *        The log file path.
- */
-LOOT_API void SetLogFile(const std::string& path);
+LOOT_API void SetLoggingCallback(std::function<void(LogLevel, const char*)> callback);
 
 /**@}*/
 /**********************************************************************//**

include/loot/enum/log_level.h

@@ -22,20 +22,23 @@ along with LOOT.  If not, see
 <https://www.gnu.org/licenses/>.
 */
 
-#ifndef LOOT_LOG_VERBOSITY
-#define LOOT_LOG_VERBOSITY
+#ifndef LOOT_LOG_LEVEL
+#define LOOT_LOG_LEVEL
 
 /**
  * The namespace used by the LOOT API.
  */
 namespace loot {
 /**
- * @brief Codes used to specify different levels of API logging verbosity.
+ * @brief Codes used to specify different levels of API logging.
  */
-enum struct LogVerbosity : unsigned int {
-  off,
-  warning,
+enum struct LogLevel : unsigned int {
   trace,
+  debug,
+  info,
+  warning,
+  error,
+  fatal
 };
 }