basic reorg protection

(cherry picked from commit e3696ed73c2012f20205b98099f397ad799fcff4)

src/node.rs

@@ -4,13 +4,14 @@ use grin_api::json_rpc::{build_request, Request, Response};
 use grin_api::{client, LocatedTxKernel};
 use grin_api::{OutputPrintable, OutputType, Tip};
 use grin_core::consensus::COINBASE_MATURITY;
-use grin_core::core::{Input, OutputFeatures, Transaction};
+use grin_core::core::{Committed, Input, OutputFeatures, Transaction};
 use grin_util::ToHex;
 
 use async_trait::async_trait;
 use serde_json::json;
 use std::net::SocketAddr;
 use std::sync::Arc;
+use grin_core::core::hash::Hash;
 use thiserror::Error;
 
 #[async_trait]
@@ -21,8 +22,8 @@ pub trait GrinNode: Send + Sync {
 		output_commit: &Commitment,
 	) -> Result<Option<OutputPrintable>, NodeError>;
 
-	/// Gets the height of the chain tip
-	async fn async_get_chain_height(&self) -> Result<u64, NodeError>;
+    /// Gets the height and hash of the chain tip
+    async fn async_get_chain_tip(&self) -> Result<(u64, Hash), NodeError>;
 
 	/// Posts a transaction to the grin node
 	async fn async_post_tx(&self, tx: &Transaction) -> Result<(), NodeError>;
@@ -108,6 +109,23 @@ pub async fn async_build_input(
 	Ok(None)
 }
 
+pub async fn async_is_tx_valid(node: &Arc<dyn GrinNode>, tx: &Transaction) -> Result<bool, NodeError> {
+    let next_block_height = node.async_get_chain_tip().await?.0 + 1;
+    for input_commit in &tx.inputs_committed() {
+        if !async_is_spendable(&node, &input_commit, next_block_height).await? {
+            return Ok(false);
+        }
+    }
+
+    for output_commit in &tx.outputs_committed() {
+        if async_is_unspent(&node, &output_commit).await? {
+            return Ok(false);
+        }
+    }
+
+    Ok(true)
+}
+
 /// HTTP (JSON-RPC) implementation of the 'GrinNode' trait
 #[derive(Clone)]
 pub struct HttpGrinNode {
@@ -176,7 +194,7 @@ impl GrinNode for HttpGrinNode {
 		Ok(Some(outputs[0].clone()))
 	}
 
-	async fn async_get_chain_height(&self) -> Result<u64, NodeError> {
+    async fn async_get_chain_tip(&self) -> Result<(u64, Hash), NodeError> {
 		let params = json!([]);
 		let tip_json = self
 			.async_send_request::<serde_json::Value>("get_tip", &params)
@@ -184,7 +202,7 @@ impl GrinNode for HttpGrinNode {
 		let tip =
 			serde_json::from_value::<Tip>(tip_json).map_err(NodeError::DecodeResponseError)?;
 
-		Ok(tip.height)
+        Ok((tip.height, Hash::from_hex(tip.last_block_pushed.as_str()).unwrap()))
 	}
 
 	async fn async_post_tx(&self, tx: &Transaction) -> Result<(), NodeError> {
@@ -226,6 +244,7 @@ pub mod mock {
 	use grin_onion::crypto::secp::Commitment;
 	use std::collections::HashMap;
 	use std::sync::RwLock;
+    use grin_core::core::hash::Hash;
 
 	/// Implementation of 'GrinNode' trait that mocks a grin node instance.
 	/// Use only for testing purposes.
@@ -299,8 +318,8 @@ pub mod mock {
 			Ok(None)
 		}
 
-		async fn async_get_chain_height(&self) -> Result<u64, NodeError> {
-			Ok(100)
+        async fn async_get_chain_tip(&self) -> Result<(u64, Hash), NodeError> {
+            Ok((100, Hash::default()))
 		}
 
 		async fn async_post_tx(&self, tx: &Transaction) -> Result<(), NodeError> {