rotate log files (#2283)

Fixes #1228 (wow only took 1 year)

common/log/log.cpp

@@ -108,9 +108,28 @@ void log_print(const char* message) {
 }
 }  // namespace internal
 
+// how many extra log files for a single program should be kept?
+constexpr int LOG_ROTATE_MAX = 5;
+
 void set_file(const std::string& filename) {
   ASSERT(!gLogger.fp);
   file_util::create_dir_if_needed_for_file(filename);
+
+  // rotate files. log.txt is the current one, log.1.txt is the previous one, etc.
+  auto as_path = fs::path(filename);
+  auto stem = as_path.stem().string();
+  auto ext = as_path.extension().string();
+  auto dir = as_path.parent_path();
+  for (int i = LOG_ROTATE_MAX; i-- > 0;) {
+    auto src_name = i != 0 ? fmt::format("{}.{}{}", stem, i, ext) : fmt::format("{}{}", stem, ext);
+    auto src_path = dir / src_name;
+    if (file_util::file_exists(src_path.string())) {
+      auto dst_name = fmt::format("{}.{}{}", stem, i + 1, ext);
+      auto dst_path = dir / dst_name;
+      file_util::copy_file(src_path, dst_path);
+    }
+  }
+
   gLogger.fp = file_util::open_file(filename.c_str(), "w");
   ASSERT(gLogger.fp);
 }

common/util/FileUtil.cpp

@@ -584,4 +584,13 @@ std::vector<fs::path> find_directories_in_dir(const fs::path& base_dir) {
   return dirs;
 }
 
+void copy_file(const fs::path& src, const fs::path& dst) {
+  if (src == dst) {
+    lg::error("Failed to copy_file {}, source and destination are the same\n", src.string());
+    throw std::runtime_error("Failed to copy_file");
+  }
+  auto data = read_binary_file(src);
+  write_binary_file(dst, data.data(), data.size());
+}
+
 }  // namespace file_util

common/util/FileUtil.h

@@ -63,4 +63,6 @@ std::vector<u8> decompress_dgo(const std::vector<u8>& data_in);
 FILE* open_file(const fs::path& path, const std::string& mode);
 std::vector<fs::path> find_files_recursively(const fs::path& base_dir, const std::regex& pattern);
 std::vector<fs::path> find_directories_in_dir(const fs::path& base_dir);
+// writes the contents of one file to another
+void copy_file(const fs::path& src, const fs::path& dst);
 }  // namespace file_util