✨ Add config-driven logger builder and queue observability

bitlogger/BitLogger_test.mbt

@@ -29,3 +29,117 @@ test "child logger composes target path" {
     .child("worker")
   inspect(logger.target, content="app.worker")
 }
+
+test "logger config parser reads core options" {
+  let config = parse_logger_config_text(
+    "{\"min_level\":\"debug\",\"target\":\"service\",\"timestamp\":true}",
+  )
+  inspect(config.min_level.label(), content="DEBUG")
+  inspect(config.target, content="service")
+  inspect(config.timestamp, content="true")
+}
+
+test "logger config parser reads formatter and queue options" {
+  let config = parse_logger_config_text(
+    "{\"sink\":{\"kind\":\"text_console\",\"text_formatter\":{\"separator\":\" | \",\"show_timestamp\":false}},\"queue\":{\"max_pending\":32,\"overflow\":\"DropOldest\"}}",
+  )
+  inspect(match config.sink.kind {
+    SinkKind::TextConsole => "TextConsole"
+    _ => "other"
+  }, content="TextConsole")
+  inspect(config.sink.text_formatter.separator, content=" | ")
+  inspect(config.sink.text_formatter.show_timestamp, content="false")
+  match config.queue {
+    Some(queue) => {
+      inspect(queue.max_pending, content="32")
+      inspect(match queue.overflow {
+        QueueOverflowPolicy::DropNewest => "DropNewest"
+        QueueOverflowPolicy::DropOldest => "DropOldest"
+      }, content="DropOldest")
+    }
+    None => inspect(false, content="true")
+  }
+}
+
+test "logger config stringify roundtrips stable fields" {
+  let text = stringify_logger_config(
+    LoggerConfig::new(
+      min_level=Level::Warn,
+      target="api",
+      timestamp=true,
+      sink=SinkConfig::new(
+        kind=SinkKind::TextConsole,
+        text_formatter=TextFormatterConfig::new(
+          show_timestamp=false,
+          show_level=true,
+          show_target=true,
+          show_fields=true,
+          separator=" | ",
+          field_separator=",",
+        ),
+      ),
+      queue=Some(QueueConfig::new(8, overflow=QueueOverflowPolicy::DropNewest)),
+    ),
+  )
+  let config = parse_logger_config_text(text)
+  inspect(config.min_level.label(), content="WARN")
+  inspect(config.target, content="api")
+  inspect(config.timestamp, content="true")
+  inspect(config.sink.text_formatter.separator, content=" | ")
+}
+
+test "build logger from config supports queued text console" {
+  let logger = build_logger(
+    LoggerConfig::new(
+      min_level=Level::Debug,
+      target="config.runtime",
+      timestamp=true,
+      sink=SinkConfig::new(
+        kind=SinkKind::TextConsole,
+        text_formatter=TextFormatterConfig::new(show_timestamp=false, separator=" | "),
+      ),
+      queue=Some(QueueConfig::new(2, overflow=QueueOverflowPolicy::DropOldest)),
+    ),
+  )
+  logger.info("one")
+  logger.info("two")
+  logger.info("three")
+  inspect(logger.pending_count(), content="2")
+  inspect(logger.flush(), content="2")
+}
+
+test "configured logger drain supports partial queue draining" {
+  let logger = build_logger(
+    LoggerConfig::new(
+      min_level=Level::Info,
+      target="config.partial",
+      sink=SinkConfig::new(kind=SinkKind::Console),
+      queue=Some(QueueConfig::new(4, overflow=QueueOverflowPolicy::DropNewest)),
+    ),
+  )
+  logger.info("one")
+  logger.info("two")
+  logger.info("three")
+  inspect(logger.pending_count(), content="3")
+  inspect(logger.drain(max_items=2), content="2")
+  inspect(logger.pending_count(), content="1")
+  inspect(logger.flush(), content="1")
+}
+
+test "configured logger reports dropped_count for bounded queue" {
+  let logger = build_logger(
+    LoggerConfig::new(
+      min_level=Level::Info,
+      target="config.drop",
+      sink=SinkConfig::new(kind=SinkKind::TextConsole),
+      queue=Some(QueueConfig::new(2, overflow=QueueOverflowPolicy::DropOldest)),
+    ),
+  )
+  logger.info("one")
+  logger.info("two")
+  logger.info("three")
+  logger.info("four")
+  inspect(logger.pending_count(), content="2")
+  inspect(logger.dropped_count(), content="2")
+  inspect(logger.flush(), content="2")
+}