refactor(logging): separate logging from main (#2110)

src/logging.cpp

@@ -0,0 +1,73 @@
+/**
+ * @file src/logging.cpp
+ * @brief Logging implementation file for the Sunshine application.
+ */
+
+// standard includes
+#include <iostream>
+
+// lib includes
+#include <boost/log/attributes/clock.hpp>
+#include <boost/log/common.hpp>
+#include <boost/log/expressions.hpp>
+#include <boost/log/sinks.hpp>
+#include <boost/log/sources/severity_logger.hpp>
+
+// local includes
+#include "logging.h"
+
+using namespace std::literals;
+
+namespace bl = boost::log;
+
+boost::shared_ptr<boost::log::sinks::asynchronous_sink<boost::log::sinks::text_ostream_backend>> sink;
+
+bl::sources::severity_logger<int> verbose(0);  // Dominating output
+bl::sources::severity_logger<int> debug(1);  // Follow what is happening
+bl::sources::severity_logger<int> info(2);  // Should be informed about
+bl::sources::severity_logger<int> warning(3);  // Strange events
+bl::sources::severity_logger<int> error(4);  // Recoverable errors
+bl::sources::severity_logger<int> fatal(5);  // Unrecoverable errors
+
+/**
+ * @brief Flush the log.
+ *
+ * EXAMPLES:
+ * ```cpp
+ * log_flush();
+ * ```
+ */
+void
+log_flush() {
+  sink->flush();
+}
+
+/**
+ * @brief Print help to stdout.
+ * @param name The name of the program.
+ *
+ * EXAMPLES:
+ * ```cpp
+ * print_help("sunshine");
+ * ```
+ */
+void
+print_help(const char *name) {
+  std::cout
+    << "Usage: "sv << name << " [options] [/path/to/configuration_file] [--cmd]"sv << std::endl
+    << "    Any configurable option can be overwritten with: \"name=value\""sv << std::endl
+    << std::endl
+    << "    Note: The configuration will be created if it doesn't exist."sv << std::endl
+    << std::endl
+    << "    --help                    | print help"sv << std::endl
+    << "    --creds username password | set user credentials for the Web manager"sv << std::endl
+    << "    --version                 | print the version of sunshine"sv << std::endl
+    << std::endl
+    << "    flags"sv << std::endl
+    << "        -0 | Read PIN from stdin"sv << std::endl
+    << "        -1 | Do not load previously saved state and do retain any state after shutdown"sv << std::endl
+    << "           | Effectively starting as if for the first time without overwriting any pairings with your devices"sv << std::endl
+    << "        -2 | Force replacement of headers in video stream"sv << std::endl
+    << "        -p | Enable/Disable UPnP"sv << std::endl
+    << std::endl;
+}