use async_trait::async_trait;
use std::fmt::Debug;

use serde::de::DeserializeOwned;
use serde::Serialize;

use crate::aggregate::Aggregate;
use crate::event::EventEnvelope;

/// Each CQRS platform should have one or more `QueryProcessor`s where it will distribute committed
/// events, it is the responsibility of the `QueryProcessor` to update any interested
/// queries.
#[async_trait]
pub trait Query<A: Aggregate>: Send + Sync {
    /// Events will be dispatched here immediately after being committed for the downstream queries
    /// to be updated.
    async fn dispatch(&self, aggregate_id: &str, events: &[EventEnvelope<A>]);
}

/// A `Query` is a read element in a CQRS system. As events are emitted multiple downstream queries
/// are updated to reflect the current state of the system. A query may also be referred to as a
/// 'view', the concepts are identical but 'query' is used here to conform with CQRS nomenclature.
///
/// Queries are generally serialized for persistence, usually in a standard database, but a query
/// could also utilize messaging platform or other asynchronous, eventually-consistent systems.
pub trait View<A: Aggregate>: Debug + Default + Serialize + DeserializeOwned + Send + Sync {
    /// Each implemented query is responsible for updating its state based on events passed via
    /// this method.
    fn update(&mut self, event: &EventEnvelope<A>);
}