Add logging controls to the API

Control verbosity and choose a file to output to.

CMakeLists.txt

@@ -200,6 +200,7 @@ set (LOOT_API_HEADERS "${CMAKE_SOURCE_DIR}/include/loot/api.h"
                       "${CMAKE_SOURCE_DIR}/include/loot/exception/git_state_error.h"
                       "${CMAKE_SOURCE_DIR}/include/loot/enum/game_type.h"
                       "${CMAKE_SOURCE_DIR}/include/loot/enum/language_code.h"
+                      "${CMAKE_SOURCE_DIR}/include/loot/enum/log_verbosity.h"
                       "${CMAKE_SOURCE_DIR}/include/loot/enum/message_type.h"
                       "${CMAKE_SOURCE_DIR}/include/loot/enum/plugin_cleanliness.h"
                       "${CMAKE_SOURCE_DIR}/include/loot/game_interface.h"

include/loot/api.h

@@ -37,9 +37,33 @@
 #include "loot/exception/game_detection_error.h"
 #include "loot/exception/git_state_error.h"
 #include "loot/enum/game_type.h"
+#include "loot/enum/log_verbosity.h"
 #include "loot/loot_version.h"
 
 namespace loot {
+/**@}*/
+/**********************************************************************//**
+ *  @name Logging Functions
+ *************************************************************************/
+/**@{*/
+
+/**
+ * @brief Set the API's logging verbosity.
+ * @details The default is ``LogVerbosity::off``.
+ * @param verbosity
+ *        The logging verbosity to set.
+ */
+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);
+
 /**@}*/
 /**********************************************************************//**
  *  @name Version Functions

include/loot/enum/log_verbosity.h

@@ -0,0 +1,48 @@
+/*  LOOT
+
+A load order optimisation tool for Oblivion, Skyrim, Fallout 3 and
+Fallout: New Vegas.
+
+Copyright (C) 2012-2016    WrinklyNinja
+
+This file is part of LOOT.
+
+LOOT is free software: you can redistribute
+it and/or modify it under the terms of the GNU General Public License
+as published by the Free Software Foundation, either version 3 of
+the License, or (at your option) any later version.
+
+LOOT is distributed in the hope that it will
+be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with LOOT.  If not, see
+<https://www.gnu.org/licenses/>.
+*/
+
+#ifndef LOOT_LOG_VERBOSITY
+#define LOOT_LOG_VERBOSITY
+
+/**
+ * The namespace used by the LOOT API.
+ */
+namespace loot {
+/**
+ * @brief Codes used to specify the preferred language for messages when
+ *        evaluating masterlists and userlists.
+ * @details If a message is not available in the preferred language, its English
+ *          string will be used. Note that messages with only one language
+ *          string are assumed to be written in English, but this cannot be
+ *          guaranteed (any violations should be reported as bugs so that they
+ *          can be fixed).
+ */
+enum struct LogVerbosity : unsigned int {
+  off,
+  warning,
+  trace,
+};
+}
+
+#endif

src/api/api.cpp

@@ -26,6 +26,11 @@
 
 #include <boost/filesystem.hpp>
 #include <boost/log/core.hpp>
+#include <boost/log/expressions.hpp>
+#include <boost/log/support/date_time.hpp>
+#include <boost/log/trivial.hpp>
+#include <boost/log/utility/setup/common_attributes.hpp>
+#include <boost/log/utility/setup/file.hpp>
 
 #include "api/game/game.h"
 
@@ -39,6 +44,40 @@ std::string ResolvePath(const std::string& path) {
   return fs::read_symlink(path).string();
 }
 
+LOOT_API void SetLoggingVerbosity(LogVerbosity verbosity) {
+  switch (verbosity) {
+  case LogVerbosity::off:
+    boost::log::core::get()->set_logging_enabled(false);
+    break;
+  case LogVerbosity::warning:
+    boost::log::core::get()->set_filter(boost::log::trivial::severity > boost::log::trivial::warning);
+    boost::log::core::get()->set_logging_enabled(true);
+    break;
+  case LogVerbosity::trace:
+    boost::log::core::get()->reset_filter();
+    boost::log::core::get()->set_logging_enabled(true);
+    break;
+  }
+}
+
+LOOT_API void SetLogFile(const std::string& path) {
+  // Set the locale to get UTF-8 conversions working correctly.
+  std::locale::global(boost::locale::generator().generate(""));
+  boost::filesystem::path::imbue(std::locale());
+
+  boost::log::add_file_log(
+    boost::log::keywords::file_name = path,
+    boost::log::keywords::auto_flush = true,
+    boost::log::keywords::format = (
+      boost::log::expressions::stream
+      << "[" << boost::log::expressions::format_date_time< boost::posix_time::ptime >("TimeStamp", "%H:%M:%S") << "]"
+      << " [" << boost::log::trivial::severity << "]: "
+      << boost::log::expressions::smessage
+      )
+  );
+  boost::log::add_common_attributes();
+}
+
 LOOT_API bool IsCompatible(const unsigned int versionMajor, const unsigned int versionMinor, const unsigned int versionPatch) {
   if (versionMajor > 0)
     return versionMajor == loot::LootVersion::major;
@@ -53,9 +92,6 @@ LOOT_API std::shared_ptr<GameInterface> CreateGameHandle(const GameType game,
   std::locale::global(boost::locale::generator().generate(""));
   boost::filesystem::path::imbue(std::locale());
 
-  //Disable logging or else stdout will get overrun.
-  boost::log::core::get()->set_logging_enabled(false);
-
   // Check for valid paths.
   const std::string resolvedGamePath = ResolvePath(gamePath);
   if (!gamePath.empty() && !fs::is_directory(resolvedGamePath))