From 8c0a02916519872c3d6073de16c950d10da0b2f4 Mon Sep 17 00:00:00 2001
From: folex <0xdxdy@gmail.com>
Date: Mon, 26 Oct 2020 13:06:55 +0300
Subject: [PATCH] Pass log level & target to host log_utf8_string (#8)

---
 crates/main/src/lib.rs    |  4 ++-
 crates/main/src/logger.rs | 53 ++++++++++++++++++++++++++++-----------
 2 files changed, 42 insertions(+), 15 deletions(-)

diff --git a/crates/main/src/lib.rs b/crates/main/src/lib.rs
index 6ff74fc..dc20b08 100644
--- a/crates/main/src/lib.rs
+++ b/crates/main/src/lib.rs
@@ -54,7 +54,9 @@ pub(crate) fn log<S: AsRef<str>>(msg: S) {
     // logs will be printed only if debug feature is enabled
     #[cfg(feature = "debug")]
     {
+        let level = log::Level::Info as i32;
+        let target = 0i64;
         let msg = msg.as_ref();
-        logger::log_utf8_string(msg.as_ptr() as i32, msg.len() as i32);
+        logger::log_utf8_string(level, target, msg.as_ptr() as i32, msg.len() as i32);
     }
 }
diff --git a/crates/main/src/logger.rs b/crates/main/src/logger.rs
index 0c275fe..77fa4cf 100644
--- a/crates/main/src/logger.rs
+++ b/crates/main/src/logger.rs
@@ -64,6 +64,8 @@
 //! [`lazy_static::initialize()`]: https://docs.rs/lazy_static/1.3.0/lazy_static/fn.initialize.html
 //! [`backend app debugging`]: https://fluence.dev/docs/debugging
 
+use std::collections::HashMap;
+
 /// The Wasm Logger.
 ///
 /// This struct implements the [`Log`] trait from the [`log`] crate, which allows it to act as a
@@ -78,6 +80,7 @@
 /// [`init()`]: struct.WasmLogger.html#method.init
 pub struct WasmLogger {
     level: log::Level,
+    target_map: HashMap<&'static str, i64>,
 }
 
 #[allow(dead_code)]
@@ -98,12 +101,21 @@ impl WasmLogger {
     /// # }
     /// ```
     pub fn init_with_level(level: log::Level) -> Result<(), log::SetLoggerError> {
-        let logger = WasmLogger { level };
+        let logger = WasmLogger {
+            level,
+            target_map: <_>::default(),
+        };
         log::set_boxed_logger(Box::new(logger))?;
         log::set_max_level(level.to_level_filter());
         Ok(())
     }
 
+    /// Sets mapping between logging targets and numbers
+    /// Used to efficiently enable & disable logs per target on the host
+    pub fn with_target_map(&mut self, map: HashMap<&'static str, i64>) {
+        self.target_map = map;
+    }
+
     /// Initializes the global logger with a [`WasmLogger`] instance, sets
     /// `max_log_level` to `Level::Info`.
     ///
@@ -137,14 +149,14 @@ impl log::Log for WasmLogger {
             return;
         }
 
-        let log_msg = format!(
-            "{:<5} [{}] {}\n",
-            record.level().to_string(),
-            record.module_path().unwrap_or_default(),
-            record.args()
-        );
+        let level = record.metadata().level() as i32;
+        let target = *self
+            .target_map
+            .get(record.metadata().target())
+            .unwrap_or(&0);
+        let msg = record.args().to_string();
 
-        log_utf8_string(log_msg.as_ptr() as _, log_msg.len() as _);
+        log_utf8_string(level, target, msg.as_ptr() as _, msg.len() as _);
     }
 
     // in our case flushing is performed by the VM itself
@@ -153,17 +165,18 @@ impl log::Log for WasmLogger {
 }
 
 #[cfg(target_arch = "wasm32")]
-pub fn log_utf8_string(ptr: i32, size: i32) {
-    unsafe { log_utf8_string_impl(ptr, size) };
+pub fn log_utf8_string(level: i32, target: i64, msg_ptr: i32, msg_size: i32) {
+    unsafe { log_utf8_string_impl(level, target, msg_ptr, msg_size) };
 }
 
 #[cfg(not(target_arch = "wasm32"))]
-pub fn log_utf8_string(ptr: i32, size: i32) {
+pub fn log_utf8_string(level: i32, target: i64, msg_ptr: i32, msg_size: i32) {
     use std::str::from_utf8_unchecked;
     use core::slice::from_raw_parts;
 
-    let msg = unsafe { from_utf8_unchecked(from_raw_parts(ptr as _, size as _)) };
-    println!("{}", msg);
+    let level = level_from_i32(level);
+    let msg = unsafe { from_utf8_unchecked(from_raw_parts(msg_ptr as _, msg_size as _)) };
+    println!("[{}] {} {}", level, target, msg);
 }
 
 /// log_utf8_string should be provided directly by a host.
@@ -172,5 +185,17 @@ pub fn log_utf8_string(ptr: i32, size: i32) {
 extern "C" {
     // Writes a byte string of size bytes that starts from ptr to a logger
     #[link_name = "log_utf8_string"]
-    fn log_utf8_string_impl(ptr: i32, size: i32);
+    fn log_utf8_string_impl(level: i32, target: i64, msg_ptr: i32, msg_size: i32);
+}
+
+#[allow(dead_code)]
+fn level_from_i32(level: i32) -> log::Level {
+    match level {
+        1 => log::Level::Error,
+        2 => log::Level::Warn,
+        3 => log::Level::Info,
+        4 => log::Level::Debug,
+        5 => log::Level::Trace,
+        _ => log::Level::max(),
+    }
 }