add previous slot info field

catalyst-gateway/bin/src/event_db/follower.rs

@@ -62,7 +62,7 @@ impl EventDB {
         let rows = conn
             .query(
                 include_str!(
-                    "../../../event-db/queries/follower/select_slot_index_by_datetime/current_slot_no.sql"
+                    "../../../event-db/queries/follower/select_slot_index_by_datetime/current_slot_info.sql"
                 ),
                 &[&network, &date_time],
             )
@@ -78,6 +78,38 @@ impl EventDB {
         Ok((slot_number, block_hash, block_time))
     }
 
+    /// Get previous slot info for the provided date-time and network
+    pub(crate) async fn previous_slot_info(
+        &self, date_time: DateTime, network: Network,
+    ) -> Result<(SlotNumber, BlockHash, DateTime), Error> {
+        let conn = self.pool.get().await?;
+
+        let network = match network {
+            Network::Mainnet => "mainnet".to_string(),
+            Network::Preview => "preview".to_string(),
+            Network::Preprod => "preprod".to_string(),
+            Network::Testnet => "testnet".to_string(),
+        };
+
+        let rows = conn
+                .query(
+                    include_str!(
+                        "../../../event-db/queries/follower/select_slot_index_by_datetime/previous_slot_info.sql"
+                    ),
+                    &[&network, &date_time],
+                )
+                .await?;
+
+        let Some(row) = rows.first() else {
+            return Err(Error::NotFound);
+        };
+
+        let slot_number: SlotNumber = row.try_get("slot_no")?;
+        let block_hash = hex::encode(row.try_get::<_, Vec<u8>>("block_hash")?);
+        let block_time = row.try_get("block_time")?;
+        Ok((slot_number, block_hash, block_time))
+    }
+
     /// Get next slot info for the provided date-time and network
     pub(crate) async fn next_slot_info(
         &self, date_time: DateTime, network: Network,
@@ -94,7 +126,7 @@ impl EventDB {
         let rows = conn
             .query(
                 include_str!(
-                    "../../../event-db/queries/follower/select_slot_index_by_datetime/next_slot_no.sql"
+                    "../../../event-db/queries/follower/select_slot_index_by_datetime/next_slot_info.sql"
                 ),
                 &[&network, &date_time],
             )

catalyst-gateway/bin/src/service/api/cardano/date_time_to_slot_number_get.rs

@@ -68,6 +68,21 @@ pub(crate) async fn endpoint(
         Err(err) => return server_error_response!("{err}"),
     };
 
+    let previous = match event_db
+        .previous_slot_info(date_time, network.clone().into())
+        .await
+    {
+        Ok((slot_number, block_hash, block_time)) => {
+            Some(Slot {
+                slot_number,
+                block_hash,
+                block_time,
+            })
+        },
+        Err(DBError::NotFound) => None,
+        Err(err) => return server_error_response!("{err}"),
+    };
+
     let next = match event_db.next_slot_info(date_time, network.into()).await {
         Ok((slot_number, block_hash, block_time)) => {
             Some(Slot {
@@ -80,5 +95,9 @@ pub(crate) async fn endpoint(
         Err(err) => return server_error_response!("{err}"),
     };
 
-    T200(OK(Json(SlotInfo { current, next })))
+    T200(OK(Json(SlotInfo {
+        previous,
+        current,
+        next,
+    })))
 }

catalyst-gateway/bin/src/service/common/objects/cardano/slot_info.rs

@@ -38,6 +38,9 @@ impl Example for Slot {
 #[derive(Object)]
 #[oai(example = true)]
 pub(crate) struct SlotInfo {
+    /// Previous slot info.
+    pub(crate) previous: Option<Slot>,
+
     /// Current slot info.
     pub(crate) current: Option<Slot>,
 
@@ -48,6 +51,7 @@ pub(crate) struct SlotInfo {
 impl Example for SlotInfo {
     fn example() -> Self {
         Self {
+            previous: Some(Slot::example()),
             current: Some(Slot::example()),
             next: Some(Slot::example()),
         }

catalyst-gateway/event-db/queries/follower/select_slot_index_by_datetime/current_slot_info.sql

@@ -0,0 +1,14 @@
+SELECT
+  cardano_slot_index.slot_no,
+  cardano_slot_index.block_hash,
+  cardano_slot_index.block_time
+
+FROM cardano_slot_index
+
+WHERE
+  cardano_slot_index.network = $1
+  AND cardano_slot_index.block_time = $2
+
+ORDER by cardano_slot_index.slot_no DESC
+
+LIMIT 1;