//! Custom log formatter that includes source file and line for WARN/ERROR events.

use std::fmt;
use tracing::{Event, Level, Subscriber};
use tracing_subscriber::fmt::format::{self, FormatEvent, FormatFields};
use tracing_subscriber::fmt::FmtContext;
use tracing_subscriber::registry::LookupSpan;

/// Event formatter that appends `[file:line]` to WARN and ERROR log lines.
///
/// INFO, DEBUG, and TRACE events use the default format without source location.
pub struct ErrorLocationFormat;

impl<S, N> FormatEvent<S, N> for ErrorLocationFormat
where
    S: Subscriber + for<'a> LookupSpan<'a>,
    N: for<'a> FormatFields<'a> + 'static,
{
    fn format_event(
        &self,
        ctx: &FmtContext<'_, S, N>,
        mut writer: format::Writer<'_>,
        event: &Event<'_>,
    ) -> fmt::Result {
        let metadata = event.metadata();
        let level = metadata.level();
        let timestamp = chrono::Utc::now().format("%Y-%m-%dT%H:%M:%S%.6fZ");

        // Write: timestamp + level + target
        write!(writer, "{} {:>5} {}", timestamp, level, metadata.target())?;

        // Append [file:line] for WARN and ERROR only
        if *level <= Level::WARN {
            if let (Some(file), Some(line)) = (metadata.file(), metadata.line()) {
                write!(writer, " [{}:{}]", file, line)?;
            }
        }

        write!(writer, ": ")?;

        // Write the event fields (message, structured fields)
        ctx.format_fields(writer.by_ref(), event)?;

        writeln!(writer)
    }
}