el/engram/engrams/engram-server/src/routes/sync.rs

/// Sync routes — peer delta exchange and peer registry.
///
/// All routes under /sync require Authorization: Bearer {api_key}.
///
/// GET  /sync/delta?since={ms}&peer_id={uuid}  — generate delta for caller
/// POST /sync/push                              — receive delta from peer
/// POST /sync/peers                            — register a new peer
/// GET  /sync/peers                            — list peers
/// DELETE /sync/peers/{id}                     — remove peer
use axum::{
    extract::{Path, Query, State},
    http::StatusCode,
    Json,
};
use engram_core::types::MemoryTier;
use engram_sync::{Peer, SyncDelta};
use serde::Deserialize;
use std::sync::Arc;
use uuid::Uuid;

use crate::state::AppState;

// ── GET /sync/delta ───────────────────────────────────────────────────────────

#[derive(Deserialize)]
pub struct DeltaParams {
    pub since: Option<i64>,
    pub peer_id: Option<Uuid>,
}

pub async fn get_delta(
    State(state): State<Arc<AppState>>,
    Query(params): Query<DeltaParams>,
) -> Result<Json<SyncDelta>, StatusCode> {
    let since = params.since.unwrap_or(0);

    // Determine which tiers to expose based on caller's peer_id
    let tiers: Vec<MemoryTier> = {
        let engine = state.sync_engine.lock().await;
        if let Some(peer_id) = params.peer_id {
            if let Some(peer) = engine.get_peer(peer_id) {
                if peer.trusted {
                    peer.sync_tiers.clone()
                } else {
                    vec![MemoryTier::Semantic]
                }
            } else {
                vec![MemoryTier::Semantic]
            }
        } else {
            vec![MemoryTier::Semantic]
        }
        // engine lock released here
    };

    let engine = state.sync_engine.lock().await;
    let delta = engine
        .generate_delta(since, &tiers)
        .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;

    Ok(Json(delta))
}

// ── POST /sync/push ───────────────────────────────────────────────────────────

pub async fn push_delta(
    State(state): State<Arc<AppState>>,
    Json(delta): Json<SyncDelta>,
) -> Result<StatusCode, StatusCode> {
    // Accepted tiers for incoming pushes (Semantic and Procedural by default)
    let accepted_tiers = vec![MemoryTier::Semantic, MemoryTier::Procedural];

    // Apply the delta using the DB handle directly (no async needed)
    let db = state.db.lock().map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;

    // Tombstones
    for id in &delta.tombstones {
        let _ = db.delete_node(*id);
    }

    // Nodes
    for node in delta.nodes {
        if !accepted_tiers.contains(&node.tier) {
            continue;
        }
        if db.get_node(node.id).map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?.is_some() {
            continue;
        }
        db.put_node(node).map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;
    }

    // Edges
    for edge in delta.edges {
        let from_ok = db.get_node(edge.from_id)
            .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?
            .is_some();
        let to_ok = db.get_node(edge.to_id)
            .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?
            .is_some();
        if from_ok && to_ok {
            let _ = db.put_edge(edge);
        }
    }

    Ok(StatusCode::OK)
}

// ── Peer registry ─────────────────────────────────────────────────────────────

pub async fn list_peers(
    State(state): State<Arc<AppState>>,
) -> Result<Json<Vec<Peer>>, StatusCode> {
    let engine = state.sync_engine.lock().await;
    Ok(Json(engine.list_peers().to_vec()))
}

pub async fn register_peer(
    State(state): State<Arc<AppState>>,
    Json(peer): Json<Peer>,
) -> Result<StatusCode, StatusCode> {
    let mut engine = state.sync_engine.lock().await;
    engine.add_peer(peer);
    Ok(StatusCode::CREATED)
}

pub async fn delete_peer(
    State(state): State<Arc<AppState>>,
    Path(id): Path<Uuid>,
) -> Result<StatusCode, StatusCode> {
    let mut engine = state.sync_engine.lock().await;
    engine.remove_peer(id);
    Ok(StatusCode::NO_CONTENT)
}