Architecture

The package follows a simple fan-out model: a central logger distributes the same structured event to N independent destinations.

App (code)
    │
    ▼
StructureLogger
    │
    ▼
LogModel ──┬──► SimpleLineSink ──► stdout
           ├──► DefaultSink    ──► dart:developer
           └──► SinkSeq        ──► Seq server

Components

StructureLogger

Application entry point. Keeps an internal list of LogSink instances and, on each log() call, builds a LogModel and delivers it sequentially to every sink.

await logger.log(
  'Order {orderId} placed',
  level: LogLevel.info,
  data: {'orderId': 'A-42'},
);

LogModel

Represents a structured event with fields aligned to CLEF:

Field	CLEF key	Description
t	@t	ISO-8601 timestamp (auto-filled when empty)
mt	@mt	Message template with {placeholders}
level	@l	Level name (info, warning, …)
data	—	Structured properties bound to the template

LogSink

Minimal contract for output destinations:

abstract class LogSink {
  Future<void> write(LogModel event);
}

Any external integration (file, Firebase, Datadog, etc.) implements this interface.

Sink lifecycle

• Register: addSink(sink) — the sink receives all future events.
• Remove: removeSink(sink) — stops delivery.
• Dispose (Seq): SinkSeq.close() — releases the internal HTTP pool when no http.Client was injected.

Design notes

• Sequential per sink: each write() is awaited in order. This keeps usage simple, but slow sinks (HTTP) may delay the caller. A background queue is planned for future versions.
• Same event for all: there is no built-in level routing or filtering; implement that inside each sink if needed.