rillflow 0.1.0-alpha.5

use crate::{
    Result,
    events::{Event, EventEnvelope, Events, Expected},
};
use uuid::Uuid;

/// Minimal aggregate trait folded from event envelopes.
pub trait Aggregate: Sized {
    /// Construct a new empty aggregate.
    fn new() -> Self;
    /// Apply a single event envelope to mutate internal state.
    fn apply(&mut self, envelope: &EventEnvelope);
    /// Current aggregate version (number of applied stream events).
    fn version(&self) -> i32;
    /// Hydrate state from a snapshot body (optional; default no-op).
    fn hydrate(&mut self, _snapshot: &serde_json::Value) {}
}

/// Repository for loading and committing event-sourced aggregates.
pub struct AggregateRepository {
    events: Events,
    validator: Option<fn(&serde_json::Value) -> crate::Result<()>>,
}

impl AggregateRepository {
    pub fn new(events: Events) -> Self {
        Self {
            events,
            validator: None,
        }
    }

    pub fn with_validator(
        mut self,
        validator: fn(&serde_json::Value) -> crate::Result<()>,
    ) -> Self {
        self.validator = Some(validator);
        self
    }

    /// Load an aggregate by folding its stream envelopes in order.
    pub async fn load<A: Aggregate>(&self, stream_id: Uuid) -> Result<A> {
        let envelopes = self.events.read_stream_envelopes(stream_id).await?;
        let mut agg = A::new();
        for env in &envelopes {
            agg.apply(env);
        }
        Ok(agg)
    }

    /// Commit new events with explicit expected version.
    pub async fn commit(
        &self,
        stream_id: Uuid,
        expected: Expected,
        events: Vec<Event>,
    ) -> Result<()> {
        self.events.append_stream(stream_id, expected, events).await
    }

    /// Commit using the aggregate's current version as Expected::Exact(version).
    pub async fn commit_for_aggregate<A: Aggregate>(
        &self,
        stream_id: Uuid,
        aggregate: &A,
        events: Vec<Event>,
    ) -> Result<()> {
        self.commit(stream_id, Expected::Exact(aggregate.version()), events)
            .await
    }
}

impl AggregateRepository {
    /// Load an aggregate using a snapshot when available, then tail events.
    pub async fn load_with_snapshot<A: Aggregate>(&self, stream_id: Uuid) -> Result<A> {
        let snap: Option<(i32, serde_json::Value)> =
            sqlx::query_as("select version, body from snapshots where stream_id = $1")
                .bind(stream_id)
                .fetch_optional(&self.events.pool)
                .await?;

        let mut agg = A::new();
        let mut from_version = 0;
        if let Some((version, body)) = snap {
            agg.hydrate(&body);
            from_version = version;
        }

        let envelopes = self.events.read_stream_envelopes(stream_id).await?;
        for env in envelopes
            .into_iter()
            .filter(|e| e.stream_seq > from_version)
        {
            agg.apply(&env);
        }
        Ok(agg)
    }

    /// Commit events and optionally write a snapshot when threshold divides version.
    pub async fn commit_and_snapshot<A: Aggregate + serde::Serialize>(
        &self,
        stream_id: Uuid,
        aggregate: &A,
        events: Vec<Event>,
        snapshot_every: i32,
    ) -> Result<()> {
        let new_version = aggregate.version() + events.len() as i32;
        if let Some(v) = self.validator {
            let snapshot = serde_json::to_value(aggregate)?;
            v(&snapshot)?;
        }
        self.commit_for_aggregate(stream_id, aggregate, events)
            .await?;
        if new_version % snapshot_every == 0 {
            // Load latest state to snapshot the post-commit aggregate
            let latest: A = self.load(stream_id).await?;
            let body = serde_json::to_value(&latest)?;
            sqlx::query(
                r#"insert into snapshots(stream_id, version, body)
                    values ($1, $2, $3)
                    on conflict (stream_id) do update set version = excluded.version, body = excluded.body, created_at = now()"#,
            )
            .bind(stream_id)
            .bind(new_version)
            .bind(&body)
            .execute(&self.events.pool)
            .await?;
        }
        Ok(())
    }
}