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//! Janus-Kafka
//!
//! Kafka adapter for Janus.
#![warn(
    missing_debug_implementations,
    missing_docs,
    rust_2018_idioms,
    unreachable_pub
)]
#![cfg_attr(doc_cfg, feature(doc_cfg))]

mod error;
mod publisher;
#[cfg(feature = "serde1")]
mod serde;
mod subscriber;

use std::future::Future;

use futures_util::stream::TryStreamExt;
use janus::{AckHandler, AckMessage, Message};

pub use crate::error::{KafkaError, OffsetError};
pub use crate::publisher::{
    KafkaPublisher, KafkaPublisherStatus, PublisherAcker, PublisherConfig, PublisherMessage,
};
pub use crate::subscriber::{
    KafkaSubscriber, KafkaSubscriberStatus, Offset, SubscriberAcker, SubscriberConfig,
};

#[cfg(feature = "tokio-rt")]
#[cfg_attr(doc_cfg, doc(cfg(feature = "tokio-rt")))]
pub use rdkafka::util::TokioRuntime;

#[cfg(feature = "instrumented")]
#[cfg_attr(doc_cfg, doc(cfg(feature = "instrumented")))]
pub use prometheus::{opts, Opts};

/// Message extension methods for Kafka messages
pub trait MessageExt: Message {
    /// The topic of the message.
    fn topic(&self) -> &str;

    /// The key the message is partitioned against.
    fn key(&self) -> Option<&str>;
}

impl<M: MessageExt> MessageExt for AckMessage<M> {
    fn topic(&self) -> &str {
        self.message().topic()
    }

    fn key(&self) -> Option<&str> {
        self.message().key()
    }
}

/// Awaits each future returned by the publisher ack handler.
pub async fn noop_publisher_ack_handler<M, A>(mut handler: A) -> Result<(), A::Error>
where
    M: MessageExt,
    A: AckHandler,
    <A as janus::AckHandler>::Output: Future<Output = Result<M, (M, A::Error)>>,
{
    while let Some(fut) = handler.try_next().await? {
        fut.await.map(|_| ()).map_err(|(_, e)| e)?;
    }
    Ok(())
}

/// Acknowledges each ack, if the result variant is an error, the error is propagated.
pub async fn noop_subscriber_ack_handler<M, A>(mut handler: A) -> Result<(), KafkaError>
where
    M: MessageExt,
    A: AckHandler<Output = Result<M, (M, KafkaError)>, Error = KafkaError>,
{
    while let Some(res) = handler.try_next().await? {
        res.map(|_| ()).map_err(|(_, e)| e)?;
    }
    Ok(())
}

/// Awaits each future returned by the ack handler and increments a metric.
/// A convenience function to continuously processes acks until an error is
/// encountered.
#[cfg(feature = "instrumented")]
#[cfg_attr(doc_cfg, doc(cfg(feature = "instrumented")))]
pub async fn instrumented_publisher_ack_handler<M, A>(
    mut handler: A,
    opts: prometheus::Opts,
) -> Result<(), A::Error>
where
    M: MessageExt,
    A: AckHandler,
    <A as janus::AckHandler>::Output: Future<Output = Result<M, (M, A::Error)>>,
{
    let counter = prometheus::register_counter_vec!(opts, &["status", "topic"]).unwrap();

    while let Some(fut) = handler.try_next().await? {
        fut.await
            .map(|m| {
                counter.with_label_values(&["success", m.topic()]).inc();
                ()
            })
            .map_err(|(m, e)| {
                counter.with_label_values(&["error", m.topic()]).inc();
                e
            })?;
    }
    Ok(())
}

/// For each ack increments a metric depending on the variant in the result.
/// A convenience function to continuously processes acks until an error is
/// encountered.
#[cfg(feature = "instrumented")]
#[cfg_attr(doc_cfg, doc(cfg(feature = "instrumented")))]
pub async fn instrumented_subscriber_ack_handler<M, A>(
    mut handler: A,
    opts: prometheus::Opts,
) -> Result<(), KafkaError>
where
    M: MessageExt,
    A: AckHandler<Output = Result<M, (M, KafkaError)>, Error = KafkaError>,
{
    let counter = prometheus::register_counter_vec!(opts, &["status", "topic"]).unwrap();

    while let Some(res) = handler.try_next().await? {
        res.map(|m| {
            counter.with_label_values(&["success", m.topic()]).inc();
            ()
        })
        .map_err(|(m, e)| {
            counter.with_label_values(&["error", m.topic()]).inc();
            e
        })?
    }
    Ok(())
}