speak-easy 0.1.2

use chrono::{DateTime, Utc};
use std::{fmt, time::SystemTime};
use tracing_core::{Event, Subscriber};
use tracing_subscriber::fmt::{
    format::{self, FormatEvent, FormatFields},
    FmtContext, FormattedFields,
};
use tracing_subscriber::registry::LookupSpan;

fn format_time(time: SystemTime) -> String {
    let datetime: DateTime<Utc> = time.into();
    datetime.format("%Y-%m-%d %H:%M:%S").to_string()
}

pub struct LogsFileFormatter;

impl<S, N> FormatEvent<S, N> for LogsFileFormatter
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 {
        // Format values from the event's's metadata:
        let metadata = event.metadata();
        let time = SystemTime::now();
        write!(
            &mut writer,
            "[{}] [{}] {}: ",
            format_time(time),
            metadata.level(),
            metadata.target()
        )?;

        // Format all the spans in the event's span context.
        if let Some(scope) = ctx.event_scope() {
            for span in scope.from_root() {
                write!(writer, "{}", span.name())?;

                // `FormattedFields` is a formatted representation of the span's
                // fields, which is stored in its extensions by the `fmt` layer's
                // `new_span` method. The fields will have been formatted
                // by the same field formatter that's provided to the event
                // formatter in the `FmtContext`.
                let ext = span.extensions();
                let fields = &ext
                    .get::<FormattedFields<N>>()
                    .expect("will never be `None`");

                // Skip formatting the fields if the span had no fields.
                if !fields.is_empty() {
                    write!(writer, "{{{}}}", fields)?;
                }
                write!(writer, ": ")?;
            }
        }

        // Write fields on the event
        ctx.field_format().format_fields(writer.by_ref(), event)?;

        writeln!(writer)
    }
}