From c5d5b3639dc6f52c0b6717aff05224d3475d28ae Mon Sep 17 00:00:00 2001
From: Lukasz Rubaszewski <117115317+lrubasze@users.noreply.github.com>
Date: Mon, 11 Nov 2024 19:02:10 +0100
Subject: [PATCH] Implement mempool/transaction endpoint

---
 .../src/mesh_api/conversions/common.rs        |  4 ++
 .../src/mesh_api/conversions/hashes.rs        | 17 ++++++++
 .../src/mesh_api/handlers/mempool.rs          | 40 +++++++++++++++++++
 .../mesh-api-server/src/mesh_api/server.rs    |  2 +-
 4 files changed, 62 insertions(+), 1 deletion(-)

diff --git a/core-rust/mesh-api-server/src/mesh_api/conversions/common.rs b/core-rust/mesh-api-server/src/mesh_api/conversions/common.rs
index 17279efa5b..1f1b8647b6 100644
--- a/core-rust/mesh-api-server/src/mesh_api/conversions/common.rs
+++ b/core-rust/mesh-api-server/src/mesh_api/conversions/common.rs
@@ -1,5 +1,9 @@
 use crate::prelude::*;
 
+pub fn from_hex<T: AsRef<[u8]>>(v: T) -> Result<Vec<u8>, ExtractionError> {
+    hex::decode(v).map_err(|_| ExtractionError::InvalidHex)
+}
+
 pub fn to_mesh_api_operation(
     mapping_context: &MappingContext,
     database: &StateManagerDatabase<impl ReadableRocks>,
diff --git a/core-rust/mesh-api-server/src/mesh_api/conversions/hashes.rs b/core-rust/mesh-api-server/src/mesh_api/conversions/hashes.rs
index 6d58bb07ba..6c9a848c39 100644
--- a/core-rust/mesh-api-server/src/mesh_api/conversions/hashes.rs
+++ b/core-rust/mesh-api-server/src/mesh_api/conversions/hashes.rs
@@ -9,3 +9,20 @@ pub fn to_api_transaction_hash_bech32m<T: IsTransactionHash>(
         .encode(hash)
         .map_err(|err| MappingError::InvalidTransactionHash { encode_error: err })
 }
+
+pub fn extract_transaction_intent_hash(
+    context: &ExtractionContext,
+    hash_str: String,
+) -> Result<TransactionIntentHash, ExtractionError> {
+    from_hex(&hash_str)
+        .ok()
+        .and_then(|bytes| Hash::try_from(bytes.as_slice()).ok())
+        .map(TransactionIntentHash::from_hash)
+        .or_else(|| {
+            context
+                .transaction_hash_decoder
+                .validate_and_decode(&hash_str)
+                .ok()
+        })
+        .ok_or(ExtractionError::InvalidHash)
+}
diff --git a/core-rust/mesh-api-server/src/mesh_api/handlers/mempool.rs b/core-rust/mesh-api-server/src/mesh_api/handlers/mempool.rs
index 3f5d122a94..6d5e04ee1b 100644
--- a/core-rust/mesh-api-server/src/mesh_api/handlers/mempool.rs
+++ b/core-rust/mesh-api-server/src/mesh_api/handlers/mempool.rs
@@ -20,3 +20,43 @@ pub(crate) async fn handle_mempool(
             .collect::<Result<Vec<_>, MappingError>>()?,
     )))
 }
+
+pub(crate) async fn handle_mempool_transaction(
+    state: State<MeshApiState>,
+    Json(request): Json<models::MempoolTransactionRequest>,
+) -> Result<Json<models::MempoolTransactionResponse>, ResponseError> {
+    assert_matching_network(&request.network_identifier, &state.network)?;
+
+    let extraction_context = ExtractionContext::new(&state.network);
+    let mapping_context = MappingContext::new(&state.network);
+    let mempool = state.state_manager.mempool.read();
+
+    let intent_hash = extract_transaction_intent_hash(
+        &extraction_context,
+        request.transaction_identifier.hash.clone(),
+    )
+    .map_err(|err| err.into_response_error("intent_hash"))?;
+
+    if mempool
+        .get_notarized_transaction_hashes_for_intent(&intent_hash)
+        .is_empty()
+    {
+        return Err(
+            ResponseError::from(ApiError::TransactionNotFound).with_details(format!(
+                "transaction {} not found in mempool transactions",
+                &request.transaction_identifier.hash
+            )),
+        );
+    }
+
+    // TODO:MESH prepare transaction estimates
+    let transaction = models::Transaction::new(
+        models::TransactionIdentifier::new(to_api_transaction_hash_bech32m(
+            &mapping_context,
+            &intent_hash,
+        )?),
+        vec![],
+    );
+
+    Ok(Json(models::MempoolTransactionResponse::new(transaction)))
+}
diff --git a/core-rust/mesh-api-server/src/mesh_api/server.rs b/core-rust/mesh-api-server/src/mesh_api/server.rs
index 946fa66034..21d0e0c291 100644
--- a/core-rust/mesh-api-server/src/mesh_api/server.rs
+++ b/core-rust/mesh-api-server/src/mesh_api/server.rs
@@ -109,7 +109,7 @@ pub async fn create_server<F>(
         .route("/block/transaction", post(handle_block_transaction))
         // TODO:MESH mempool
         .route("/mempool", post(handle_mempool))
-        .route("/mempool/transaction", post(handle_endpoint_todo))
+        .route("/mempool/transaction", post(handle_mempool_transaction))
         .route("/construction/derive", post(handle_endpoint_todo))
         .route("/construction/preprocess", post(handle_endpoint_todo))
         .route("/construction/metadata", post(handle_endpoint_todo))