XC-194: Add check_transaction_query method to Bitcoin checker

rs/bitcoin/checker/btc_checker_canister.did

@@ -91,6 +91,11 @@ service : (CheckArg) -> {
     // Same as check_transaction, but taking the transaction id argument as a string.
     check_transaction_str: (CheckTransactionStrArgs) -> (CheckTransactionResponse);
 
+    // Same as check_transaction, but query method, hence it does not perform any HTTP
+    // outcalls to fetch the required information.
+    // IMPORTANT: this endpoint is meant as a debugging tool and is not guaranteed to be backwards-compatible.
+    check_transaction_query: (CheckTransactionStrArgs) -> (CheckTransactionResponse) query;
+
     // Return `Passed` if the given Bitcoin address passes the Bitcoin checker, or `Failed` otherwise.
     // May throw error (trap) if the given address is malformed or not a mainnet address.
     check_address: (CheckAddressArgs) -> (CheckAddressResponse) query;

rs/bitcoin/checker/src/main.rs

@@ -14,7 +14,9 @@ use ic_cdk::api::call::RejectionCode;
 use ic_cdk::api::management_canister::http_request::{HttpResponse, TransformArgs};
 use std::cell::RefCell;
 use std::collections::BTreeMap;
+use std::convert::Infallible;
 use std::fmt;
+use std::future::Future;
 use std::str::FromStr;
 
 mod dashboard;
@@ -23,6 +25,7 @@ mod logs;
 mod providers;
 mod state;
 
+use crate::state::FetchedTx;
 use fetch::{FetchEnv, FetchResult, TryFetchResult};
 use logs::{Log, LogEntry, Priority, DEBUG, WARN};
 use state::{get_config, set_config, Config, FetchGuardError, HttpGetTxError};
@@ -105,8 +108,7 @@ fn check_address(args: CheckAddressArgs) -> CheckAddressResponse {
 /// together with a text description.
 #[ic_cdk::update]
 async fn check_transaction(args: CheckTransactionArgs) -> CheckTransactionResponse {
-    check_transaction_with(|| Txid::try_from(args.txid.as_ref()).map_err(|err| err.to_string()))
-        .await
+    check_transaction_with(|| check_transaction_txid(args)).await
 }
 
 #[ic_cdk::update]
@@ -116,6 +118,21 @@ async fn check_transaction_str(args: CheckTransactionStrArgs) -> CheckTransactio
         .await
 }
 
+/// Performs the same checks as the `check_transaction` method, but since no cycles are available,
+/// it only returns `Passed` if the transaction information is already available. If the transaction
+/// inputs need to be fetched, it will return `NotEnoughCycles`.
+#[ic_cdk::query]
+async fn check_transaction_query(args: CheckTransactionArgs) -> CheckTransactionResponse {
+    match check_transaction_txid(args) {
+        Ok(txid) => check_transaction_inputs(txid).await,
+        Err(err) => CheckTransactionIrrecoverableError::InvalidTransactionId(err).into(),
+    }
+}
+
+fn check_transaction_txid(args: CheckTransactionArgs) -> Result<Txid, String> {
+    Txid::try_from(args.txid.as_ref()).map_err(|err| err.to_string())
+}
+
 async fn check_transaction_with<F: FnOnce() -> Result<Txid, String>>(
     get_txid: F,
 ) -> CheckTransactionResponse {