Determine log level dynamically

The log level can now be set by environment variable `XWIM_LOGLEVEL`.
Alternatively a default log level per build type (determined by NDEBUG flag) is
used.

README.md

@@ -116,7 +116,7 @@ likely move to GitHub as it's main repository.
 
 If you want to contribute, you can either issue a pull request on it's Github
 mirror (will be cherry picked into the main repository) or send patches to
-`dev [at] friedl [dot] net`.
+dev[at]friedl[dot]net.
 
 If you are interested in a long-term co-maintainership you can also drop me a
 mail for an account on https://git.friedl.net.

src/main.cpp

@@ -1,5 +1,4 @@
 #include <spdlog/common.h>
-#include <spdlog/spdlog.h>
 namespace logger = spdlog;
 
 #include <iostream>
@@ -7,12 +6,13 @@ namespace logger = spdlog;
 #include <string>
 #include <list>
 
+#include "util/log.hpp"
 #include "archive.hpp"
 #include "spec.hpp"
 #include "fileformats.hpp"
 
 int main(int argc, char** argv) {
-  logger::set_level(logger::level::trace);
+  xwim::log::init();
 
   try {
     std::filesystem::path filepath{argv[1]};

src/meson.build

@@ -2,13 +2,8 @@ xwim_src = ['main.cpp',
             'archive.cpp',
             'archive_sys.cpp']
 
-xwim_inc = ['archive.hpp',
-            'spec.hpp',
-            'archive_sys.hpp',
-            'fileformats.hpp']
-
 xwim_libs = [dependency('libarchive', required: true),
              dependency('fmt', required: true),
              dependency('spdlog', required: true)]
 
-executable('xwim', xwim_src, xwim_inc, dependencies: xwim_libs)
+executable('xwim', xwim_src, dependencies: xwim_libs)

src/util/log.hpp

@@ -0,0 +1,79 @@
+#pragma once
+
+#include <spdlog/common.h>
+#include <spdlog/spdlog.h>
+#include <cstdlib>
+
+#ifdef NDEBUG
+#define XWIM_LOGLEVEL SPDLOG_LEVEL_ERROR
+#else
+#define XWIM_LOGLEVEL SPDLOG_LEVEL_DEBUG
+#endif
+
+namespace xwim {
+namespace log {
+
+/**
+ * Get log level from XWIM_LOGLEVEL environment variable.
+ * For valid values see SPDLOG_LEVEL_NAMES in spdlog/common.h
+ *
+ * @returns spdlog::level::level_enum::off if no valid XWIM_LOGLEVEL defined
+ */
+spdlog::level::level_enum _init_from_env() {
+  char* env_lvl = std::getenv("XWIM_LOGLEVEL");
+  if (!env_lvl) {
+    return spdlog::level::level_enum::off;
+  }
+
+  spdlog::level::level_enum lvl = spdlog::level::from_str(env_lvl);
+
+  //`::from_str` returns `off` if no match found
+  if (spdlog::level::level_enum::off == lvl) {
+    spdlog::debug("No environment definition for log level");  // uses default
+                                                               // logger/level
+  }
+
+  return lvl;
+};
+
+/**
+ * Get log level from compile time definition.
+ *
+ * @return spdlog::level::level_enum::error for release builds (-DNDEBUG)
+ *         spdlog::level::level_enum::debug for debug builds
+ */
+spdlog::level::level_enum _init_from_compile() {
+  return static_cast<spdlog::level::level_enum>(XWIM_LOGLEVEL);
+}
+
+/**
+ * Determine the log level from various sources at runtime.
+ *
+ * The log level is determined from sources in the following order (first
+ * wins):
+ * 1. The `level` argument
+ * 2. The XWIM_LOGLEVEL environment variable
+ * 3. The default for the build type (-DNDEBUG)
+ *      -> ERROR for release builds
+ *      -> DEBUG for debug builds
+ *
+ * The determined level is then set for the default logger via
+ * `spdlog::set_level`.
+ */
+void init(spdlog::level::level_enum level = spdlog::level::level_enum::off) {
+  if (spdlog::level::level_enum::off != level) {
+    spdlog::set_level(level);
+    return;
+  }
+
+  level = _init_from_env();
+  if (spdlog::level::level_enum::off != level) {
+    spdlog::set_level(level);
+    return;
+  }
+
+  return spdlog::set_level(_init_from_compile());
+}
+
+}  // namespace log
+}  // namespace xwim