turul-a2a 0.1.17

A2A Protocol v1.0 server framework
Documentation 
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//! Durable event store trait for cross-instance streaming coordination.
//!
//! Per ADR-009: event store and task store MUST share the same backend.
//! A single storage instance implements both `A2aTaskStorage` and `A2aEventStore`.

use async_trait::async_trait;

use super::error::A2aStorageError;
use crate::streaming::StreamEvent;

/// Durable event store for streaming coordination.
///
/// Source of truth for task events. The in-process broker is a local
/// optimization for attached clients — this trait provides correctness.
///
/// Events are tenant-scoped and monotonically ordered per task.
#[async_trait]
pub trait A2aEventStore: Send + Sync {
    fn backend_name(&self) -> &'static str;

    /// Append an event for a task. Returns the assigned sequence number.
    /// The store assigns the sequence atomically.
    async fn append_event(
        &self,
        tenant: &str,
        task_id: &str,
        event: StreamEvent,
    ) -> Result<u64, A2aStorageError>;

    /// Get all events for a task after a given sequence number.
    /// Returns events in sequence order. Tenant-scoped.
    async fn get_events_after(
        &self,
        tenant: &str,
        task_id: &str,
        after_sequence: u64,
    ) -> Result<Vec<(u64, StreamEvent)>, A2aStorageError>;

    /// Get the latest event sequence number for a task.
    /// Returns 0 if no events exist. Tenant-scoped.
    async fn latest_sequence(&self, tenant: &str, task_id: &str) -> Result<u64, A2aStorageError>;

    /// Delete events older than the configured TTL.
    /// Returns count of deleted events.
    async fn cleanup_expired(&self) -> Result<u64, A2aStorageError>;
}