//! Custom tracing layer that captures log events and broadcasts them to SSE clients.

use chrono::Utc;
use serde::Serialize;
use std::collections::VecDeque;
use std::sync::{Arc, Mutex};
use tokio::sync::broadcast;
use tracing::Event;
use tracing_subscriber::Layer;

/// A single structured log line sent to SSE clients.
#[derive(Debug, Clone, Serialize)]
pub struct LogLine {
    pub level: String,
    pub target: String,
    pub message: String,
    pub timestamp: String,
}

/// Tracing layer that fans log events out to a broadcast channel + ring buffer.
pub struct AppLogLayer {
    tx: broadcast::Sender<LogLine>,
    history: Arc<Mutex<VecDeque<LogLine>>>,
}

impl AppLogLayer {
    pub fn new(
        tx: broadcast::Sender<LogLine>,
        history: Arc<Mutex<VecDeque<LogLine>>>,
    ) -> Self {
        Self { tx, history }
    }
}

impl<S: tracing::Subscriber> Layer<S> for AppLogLayer {
    fn on_event(&self, event: &Event<'_>, _ctx: tracing_subscriber::layer::Context<'_, S>) {
        let mut visitor = MsgVisitor(String::new());
        event.record(&mut visitor);

        let line = LogLine {
            level: event.metadata().level().to_string(),
            target: event.metadata().target().to_string(),
            message: visitor.0,
            timestamp: Utc::now().to_rfc3339(),
        };

        if let Ok(mut history) = self.history.lock() {
            if history.len() >= 200 {
                history.pop_front();
            }
            history.push_back(line.clone());
        }

        let _ = self.tx.send(line);
    }
}

struct MsgVisitor(String);

impl tracing::field::Visit for MsgVisitor {
    fn record_str(&mut self, field: &tracing::field::Field, value: &str) {
        if field.name() == "message" {
            self.0 = value.to_owned();
        }
    }

    fn record_debug(&mut self, field: &tracing::field::Field, value: &dyn std::fmt::Debug) {
        if field.name() == "message" {
            self.0 = format!("{value:?}");
        }
    }
}