use tracing_opentelemetry::OpenTelemetryLayer;
use tracing_subscriber::{
    filter::{EnvFilter, LevelFilter},
    prelude::*,
};

/// Initialize logging and OpenTelemetry tracing and exporter.
///
/// Logging can be configured using `RUST_LOG` environment variable.
///
/// OpenTelemetry is configured with OTLP/HTTP exporter. It picks up
/// configuration from environment variables. For example, to change the
/// destination, set `OTEL_EXPORTER_OTLP_ENDPOINT=http://jaeger:4318`.
/// See <https://opentelemetry.io/docs/reference/specification/sdk-environment-variables>
pub async fn init() -> anyhow::Result<LoggingGuard> {
    let env_filter = EnvFilter::builder()
        .with_default_directive(LevelFilter::INFO.into())
        .from_env_lossy();

    let fmt_layer = tracing_subscriber::fmt::layer()
        .with_ansi(false)
        .with_writer(std::io::stderr)
        .with_target(false);

    let otlp_layer = tracing_utils::init_tracing("proxy")
        .await
        .map(OpenTelemetryLayer::new);

    tracing_subscriber::registry()
        .with(env_filter)
        .with(otlp_layer)
        .with(fmt_layer)
        .try_init()?;

    Ok(LoggingGuard)
}

pub struct LoggingGuard;

impl Drop for LoggingGuard {
    fn drop(&mut self) {
        // Shutdown trace pipeline gracefully, so that it has a chance to send any
        // pending traces before we exit.
        tracing::info!("shutting down the tracing machinery");
        tracing_utils::shutdown_tracing();
    }
}