feat: logs filter (#95)

tutorial/tutorial_0_introduction.cpp

@@ -40,8 +40,30 @@
 /// operation fails, they print a useful error message to `stderr` and return
 /// `1`. Successful tutorials print progress to `stdout` and return `0`.
 ///
-/// The `stdout` stream can be noisy because logs from the wrapped C binding
-/// are also included. This is tracked in [issue #79](https://github.com/logos-co/logos-libp2p-module/issues/79).
+/// ## Controlling libp2p Logs
+///
+/// The wrapped libp2p binding can emit runtime logs. Tutorials set the log
+/// level to `LogLevel::Fatal` by default so `stdout` only shows the tutorial's
+/// own progress messages during normal runs. Choose another level such as
+/// `LogLevel::Info`, `LogLevel::Debug`, or `LogLevel::Trace` when you need more
+/// detail while debugging:
+///
+/// ```cpp
+/// setLogLevel(LogLevel::Debug);
+/// // ... or
+/// Libp2pModuleImpl::setLogLevel(LogLevel::Debug);
+/// ```
+///
+/// Log levels are inclusive minimum thresholds: `LogLevel::Trace` emits trace
+/// and above, `LogLevel::Debug` emits debug and above, and so on.
+/// `LogLevel::None` is the lowest threshold, so it emits all logs; it does not
+/// disable logging. Use `LogLevel::Fatal` for the quietest built-in threshold.
+///
+/// In your own application, `LogLevel::Error` is often a useful default. 
+/// It keeps normal output quiet while still surfacing conditions
+/// that may indicate libp2p is misbehaving or that your integration code needs an
+/// adjustment. Some error logs describe remote-peer behavior, retries, or
+/// recoverable internal state, so they may not require any action from your side.
 ///
 /// ## Convert JSON Values Explicitly
 ///
@@ -79,6 +101,9 @@ int main()
 {
     printf("=== Tutorial 0: Introduction and Common Patterns ===\n\n");
 
+    // Silence logs from wrapped library.
+    setLogLevel(LogLevel::Fatal);
+
 /// ## Step 1: Create and start a node
 ///
 /// Even the first real operation returns a result. Check it before moving on.
@@ -166,3 +191,17 @@ int main()
 /// ```bash
 /// nix --extra-experimental-features 'nix-command flakes' develop --command ./tutorial/build_tutorials.sh
 /// ```
+
+/// ## Exercise: Enable libp2p debug logs
+///
+/// Change this tutorial's log level from `LogLevel::None` to
+/// `LogLevel::Debug`:
+///
+/// ```cpp
+/// setLogLevel(LogLevel::Debug);
+/// ```
+///
+/// Compile the tutorial binaries again, using the same command from above.
+///
+/// Run tutorial 0 again. You should now see libp2p debug logs in `stdout`
+/// alongside the tutorial's own progress messages.