feat: Optimise log parsing logic

ampd/src/solana/mod.rs

@@ -94,18 +94,16 @@ where
     };
 
     // Check in the logs in a backward way the invocation comes from the gateway
-    if !event_comes_from_gateway(logs, desired_event_idx) {
-        error!("Event does not come from the gateway");
-        return Vote::NotFound;
-    }
-    // Check that the event index is in the logs
-    let Some(event_log) = logs.get(desired_event_idx) else {
-        error!("Event index is out of bounds");
-        return Vote::NotFound;
+    let log = match event_comes_from_gateway(logs, desired_event_idx) {
+        Ok(log) => log,
+        Err(err) => {
+            error!("Cannot find the gateway log: {}", err);
+            return Vote::NotFound;
+        }
     };
 
     // Second ensure we can parse the event
-    let event = match gateway_event_stack::parse_gateway_logs(event_log) {
+    let event = match gateway_event_stack::parse_gateway_logs(&log) {
         Ok(ev) => ev,
         Err(err) => {
             error!("Cannot parse the gateway log: {}", err);
@@ -122,27 +120,58 @@ where
 }
 
 // Check backward in the logs if the invocation comes from the gateway program,
-// skipping native program invocations
-fn event_comes_from_gateway(logs: &[String], desired_event_idx: usize) -> bool {
+// skipping native program invocations and returning the data log if the event comes from the gateway.
+// 
+// Example logs input (indexes are just for reference):
+// 
+// 1. Program gtwLjHAsfKAR6GWB4hzTUAA1w4SDdFMKamtGA5ttMEe invoke [1] 
+// 2. Program log: Instruction: Call Contract", 
+// 3. Program data: Y2FsbCBjb250cmFjdF9fXw== 6NGe5cm7PkXHz/g8V2VdRg0nU0l7R48x8lll4s0Clz0= xtlu5J3pLn7c4BhqnNSrP1wDZK/pQOJVCYbk6sroJhY= ZXRoZXJldW0= MHgwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDA2YzIwNjAzYzdiODc2NjgyYzEyMTczYmRlZjlhMWRjYTUyOGYxNGZk 8J+QqvCfkKrwn5Cq8J+Qqg==", 
+// 4. Program gtwLjHAsfKAR6GWB4hzTUAA1w4SDdFMKamtGA5ttMEe success"
+// 
+// In the above log example, this function would return the data log at 3, if and only if the event comes from the gateway,
+// which is determined by scanning log lines backwards till we find the pattern "Program <gateway_id> invoke" at 1 for the first time.
+// It will fail if it finds any other invocation before the gateway invocation, except for the system program. In that case it will omit it and
+// continue scanning.
+fn event_comes_from_gateway(
+    logs: &[String],
+    desired_event_idx: usize,
+) -> Result<&str, Box<dyn std::error::Error>> {
     let solana_gateway_id = axelar_solana_gateway::id().to_string();
     let system_program_id = solana_sdk::system_program::id().to_string();
 
-    for log in logs.iter().take(desired_event_idx).rev() {
-        let parts: Vec<&str> = log.split(' ').collect();
+    // From the logs, we take only the logs from the desired event index to the first log
+    let mut logs = logs
+        .iter()
+        .take(
+            desired_event_idx
+                .checked_add(1)
+                .expect("To add 1 to index count to get elem take"),
+        )
+        .rev(); // +1 because take() gets n elements, not index based.
 
-        if parts.len() < 3 && parts.len() > 4 {
-            continue;
-        }
-        if parts[0] == "Program" && parts[2] == "invoke" {
-            if parts[1] == system_program_id {
+    // This is the log that, if the event comes from the gateway, will contain the target data log
+    // It will be returned if the event comes from the gateway.
+    let data_log = logs.next().ok_or("Cannot find the first log")?;
+
+    for log in logs {
+        let mut parts = log.split(' ');
+
+        let program = parts.next().ok_or("Cannot find program log part")?;
+        let program_id = parts.next().ok_or("Cannot find program_id log part")?;
+        let action = parts.next().ok_or("Cannot find action log part")?;
+
+        if program == "Program" && action == "invoke" {
+            if program_id == system_program_id {
                 continue;
             }
-            if parts[1] == solana_gateway_id {
-                return true;
+            if program_id == solana_gateway_id {
+                // We return the data log to be processed by further functions if we confirm the log comes from the gateway
+                return Ok(data_log);
             } else {
                 break;
             }
         }
     }
-    false
+    Err("Log does not belong to the gateway program".into())
 }