//! Per-project event buffer and `GET /api/events` HTTP endpoint.
//!
//! The gateway polls `/api/events?since={ts_ms}` on each registered project
//! server to aggregate cross-project pipeline notifications into a single
//! gateway chat channel.  Each project server buffers up to 500 events in
//! memory and serves them via this endpoint.
//!
//! Domain logic lives in `service::events`; this module is a thin HTTP
//! adapter: extract query params → call service → shape response.

#[cfg(test)]
pub use crate::service::events::StoredEvent;
pub use crate::service::events::{EventBuffer, subscribe_to_watcher};
// MAX_BUFFER_SIZE is used in tests via `use super::*`.
#[cfg(test)]
pub use crate::service::events::MAX_BUFFER_SIZE;

use poem::web::{Data, Query};
use poem::{Response, handler, http::StatusCode};
use serde::Deserialize;

/// Query parameters for `GET /api/events`.
#[derive(Deserialize)]
pub struct EventsQuery {
    /// Return only events with `timestamp_ms` strictly greater than this value.
    /// Defaults to `0` (return all buffered events).
    #[serde(default)]
    pub since: u64,
}

/// `GET /api/events?since={ts_ms}`
///
/// Returns a JSON array of [`StoredEvent`] objects recorded after `since` ms.
/// The gateway polls this endpoint on each registered project server to build
/// an aggregated cross-project notification stream.
#[handler]
pub fn events_handler(
    Query(params): Query<EventsQuery>,
    Data(buffer): Data<&EventBuffer>,
) -> Response {
    let events = crate::service::events::events_since(buffer, params.since);
    let body = serde_json::to_vec(&events).unwrap_or_else(|_| b"[]".to_vec());
    Response::builder()
        .status(StatusCode::OK)
        .header(poem::http::header::CONTENT_TYPE, "application/json")
        .body(body)
}

#[cfg(test)]
mod tests {
    use super::*;
    use tokio::sync::broadcast;

    #[test]
    fn event_buffer_push_and_retrieve() {
        let buf = EventBuffer::new();
        buf.push(StoredEvent::MergeFailure {
            story_id: "42_story_x".to_string(),
            reason: "conflict".to_string(),
            timestamp_ms: 1000,
        });
        buf.push(StoredEvent::StoryBlocked {
            story_id: "43_story_y".to_string(),
            reason: "retry limit".to_string(),
            timestamp_ms: 2000,
        });

        let all = buf.events_since(0);
        assert_eq!(all.len(), 2);

        let after_1000 = buf.events_since(1000);
        assert_eq!(after_1000.len(), 1);
        assert!(matches!(after_1000[0], StoredEvent::StoryBlocked { .. }));
    }

    #[test]
    fn event_buffer_evicts_oldest_when_full() {
        let buf = EventBuffer::new();
        for i in 0..MAX_BUFFER_SIZE + 1 {
            buf.push(StoredEvent::MergeFailure {
                story_id: format!("{i}_story_x"),
                reason: "x".to_string(),
                timestamp_ms: i as u64,
            });
        }
        // Buffer must not exceed MAX_BUFFER_SIZE.
        assert_eq!(buf.events_since(0).len(), MAX_BUFFER_SIZE);
        // Oldest entry (timestamp_ms == 0) should have been evicted.
        assert!(buf.events_since(0).iter().all(|e| e.timestamp_ms() > 0));
    }

    #[test]
    fn stage_transition_timestamp_ms_accessor() {
        let e = StoredEvent::StageTransition {
            story_id: "1".to_string(),
            from_stage: "2_current".to_string(),
            to_stage: "3_qa".to_string(),
            timestamp_ms: 9999,
        };
        assert_eq!(e.timestamp_ms(), 9999);
    }

    #[tokio::test]
    async fn subscribe_to_watcher_stores_work_item_with_from_stage() {
        let buf = EventBuffer::new();
        let (tx, rx) = broadcast::channel(16);

        subscribe_to_watcher(buf.clone(), rx);

        tx.send(crate::io::watcher::WatcherEvent::WorkItem {
            stage: "3_qa".to_string(),
            item_id: "42_story_foo".to_string(),
            action: "qa".to_string(),
            commit_msg: "huskies: qa 42_story_foo".to_string(),
            from_stage: Some("2_current".to_string()),
        })
        .unwrap();

        tokio::time::sleep(std::time::Duration::from_millis(50)).await;

        let events = buf.events_since(0);
        assert_eq!(events.len(), 1);
        assert!(matches!(events[0], StoredEvent::StageTransition { .. }));
        if let StoredEvent::StageTransition {
            ref story_id,
            ref from_stage,
            ref to_stage,
            ..
        } = events[0]
        {
            assert_eq!(story_id, "42_story_foo");
            assert_eq!(from_stage, "2_current");
            assert_eq!(to_stage, "3_qa");
        }
    }

    #[tokio::test]
    async fn subscribe_to_watcher_ignores_work_item_without_from_stage() {
        let buf = EventBuffer::new();
        let (tx, rx) = broadcast::channel(16);

        subscribe_to_watcher(buf.clone(), rx);

        // Synthetic event: no from_stage.
        tx.send(crate::io::watcher::WatcherEvent::WorkItem {
            stage: "2_current".to_string(),
            item_id: "99_story_syn".to_string(),
            action: "start".to_string(),
            commit_msg: "huskies: start 99_story_syn".to_string(),
            from_stage: None,
        })
        .unwrap();

        tokio::time::sleep(std::time::Duration::from_millis(50)).await;

        assert_eq!(buf.events_since(0).len(), 0);
    }

    #[tokio::test]
    async fn subscribe_to_watcher_stores_merge_failure() {
        let buf = EventBuffer::new();
        let (tx, rx) = broadcast::channel(16);

        subscribe_to_watcher(buf.clone(), rx);

        tx.send(crate::io::watcher::WatcherEvent::MergeFailure {
            story_id: "42_story_foo".to_string(),
            reason: "merge conflict".to_string(),
        })
        .unwrap();

        tokio::time::sleep(std::time::Duration::from_millis(50)).await;

        let events = buf.events_since(0);
        assert_eq!(events.len(), 1);
        assert!(matches!(events[0], StoredEvent::MergeFailure { .. }));
    }

    #[tokio::test]
    async fn subscribe_to_watcher_stores_story_blocked() {
        let buf = EventBuffer::new();
        let (tx, rx) = broadcast::channel(16);

        subscribe_to_watcher(buf.clone(), rx);

        tx.send(crate::io::watcher::WatcherEvent::StoryBlocked {
            story_id: "43_story_bar".to_string(),
            reason: "retry limit exceeded".to_string(),
        })
        .unwrap();

        tokio::time::sleep(std::time::Duration::from_millis(50)).await;

        let events = buf.events_since(0);
        assert_eq!(events.len(), 1);
        assert!(matches!(events[0], StoredEvent::StoryBlocked { .. }));
    }
}