crates/adapters/postgres/src/engagement.rs

@@ -0,0 +1,83 @@
+use crate::db_error::IntoDbResult;
+use async_trait::async_trait;
+use domain::{
+    errors::DomainError,
+    models::feed::{EngagementStats, ViewerContext},
+    ports::EngagementRepository,
+    value_objects::{ThoughtId, UserId},
+};
+use sqlx::PgPool;
+use std::collections::HashMap;
+
+pub struct PgEngagementRepository {
+    pool: PgPool,
+}
+
+impl PgEngagementRepository {
+    pub fn new(pool: PgPool) -> Self {
+        Self { pool }
+    }
+}
+
+#[async_trait]
+impl EngagementRepository for PgEngagementRepository {
+    async fn get_for_thoughts(
+        &self,
+        thought_ids: &[ThoughtId],
+        viewer_id: Option<&UserId>,
+    ) -> Result<HashMap<ThoughtId, (EngagementStats, Option<ViewerContext>)>, DomainError> {
+        if thought_ids.is_empty() {
+            return Ok(HashMap::new());
+        }
+
+        #[derive(sqlx::FromRow)]
+        struct Row {
+            thought_id: uuid::Uuid,
+            like_count: i64,
+            boost_count: i64,
+            reply_count: i64,
+            liked_by_viewer: bool,
+            boosted_by_viewer: bool,
+        }
+
+        let ids: Vec<uuid::Uuid> = thought_ids.iter().map(|t| t.as_uuid()).collect();
+        let viewer_uuid: Option<uuid::Uuid> = viewer_id.map(|v| v.as_uuid());
+
+        let rows = sqlx::query_as::<_, Row>(
+            "SELECT
+                t.id AS thought_id,
+                COUNT(DISTINCT l.user_id) AS like_count,
+                COUNT(DISTINCT b.user_id) AS boost_count,
+                COUNT(DISTINCT r.id) AS reply_count,
+                COALESCE(BOOL_OR(l.user_id = $2), false) AS liked_by_viewer,
+                COALESCE(BOOL_OR(b.user_id = $2), false) AS boosted_by_viewer
+             FROM thoughts t
+             LEFT JOIN likes l ON l.thought_id = t.id
+             LEFT JOIN boosts b ON b.thought_id = t.id
+             LEFT JOIN thoughts r ON r.in_reply_to_id = t.id
+             WHERE t.id = ANY($1)
+             GROUP BY t.id",
+        )
+        .bind(&ids[..])
+        .bind(viewer_uuid)
+        .fetch_all(&self.pool)
+        .await
+        .into_domain()?;
+
+        let mut result = HashMap::new();
+        for row in rows {
+            let tid = ThoughtId::from_uuid(row.thought_id);
+            let stats = EngagementStats {
+                like_count: row.like_count,
+                boost_count: row.boost_count,
+                reply_count: row.reply_count,
+            };
+            let viewer = viewer_id.map(|_| ViewerContext {
+                liked: row.liked_by_viewer,
+                boosted: row.boosted_by_viewer,
+            });
+            result.insert(tid, (stats, viewer));
+        }
+        Ok(result)
+    }
+}

crates/adapters/postgres/src/lib.rs

@@ -1,4 +1,5 @@
 pub mod activitypub;
+pub mod engagement;
 pub mod api_key;
 pub mod block;
 pub mod boost;