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//! This module provides the functionality for subscribing to the logs stream and delivering it to
//! the external consumers through the [`tokio::sync::broadcast`] channel.

use once_cell::sync::Lazy;
use tokio::sync::broadcast;
use tracing::Subscriber;
use tracing_subscriber::Layer;

/// Channel to deliver logs.
static LOGS: Lazy<broadcast::Sender<Vec<u8>>> = Lazy::new(|| {
    let (tx, _) = broadcast::channel(2000);
    tx
});

/// Returns the [`tokio::sync::broadcast::Receiver`] part of logs subscriber.
pub fn receiver() -> broadcast::Receiver<Vec<u8>> {
    LOGS.subscribe()
}

/// Writer for the logs out to the [`tokio::sync::broadcast`] channel.
struct LogsWriter;

impl std::io::Write for LogsWriter {
    fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
        let tx = &*LOGS;
        let buf_len = buf.len();
        tx.send(buf.to_vec()).ok();
        Ok(buf_len)
    }

    fn flush(&mut self) -> std::io::Result<()> {
        Ok(())
    }
}

/// Returns the dashbaord subscriber.
pub(crate) fn dashboard_subscriber<S>() -> impl Layer<S> + Send + Sync
where
    S: Subscriber + for<'a> tracing_subscriber::registry::LookupSpan<'a>,
{
    tracing_subscriber::fmt::layer()
        .with_writer(|| LogsWriter)
        .with_target(true)
        .with_ansi(true)
        .compact()
}