wallet: Add function to retrieve a watched transaction's blockheight

Signed-off-by: Christian Decker <decker.christian@gmail.com>

wallet/wallet.c

@@ -2201,3 +2201,20 @@ void wallet_transaction_add(struct wallet *w, const struct bitcoin_tx *tx,
 		db_exec_prepared(w->db, stmt);
 	}
 }
+
+u32 wallet_transaction_height(struct wallet *w, const struct bitcoin_txid *txid)
+{
+	u32 blockheight;
+	sqlite3_stmt *stmt = db_prepare(
+		w->db, "SELECT blockheight, txindex, rawtx FROM transactions WHERE id=?");
+	sqlite3_bind_sha256(stmt, 1, &txid->shad.sha);
+
+	if (sqlite3_step(stmt) != SQLITE_ROW) {
+		sqlite3_finalize(stmt);
+		return 0;
+	}
+
+	blockheight = sqlite3_column_int(stmt, 0);
+	sqlite3_finalize(stmt);
+	return blockheight;
+}

wallet/wallet.h

@@ -814,4 +814,10 @@ void wallet_utxoset_add(struct wallet *w, const struct bitcoin_tx *tx,
 void wallet_transaction_add(struct wallet *w, const struct bitcoin_tx *tx,
 			    const u32 blockheight, const u32 txindex);
 
+/**
+ * Get the confirmation height of a transaction we are watching by its
+ * txid. Returns 0 if the transaction was not part of any block.
+ */
+u32 wallet_transaction_height(struct wallet *w, const struct bitcoin_txid *txid);
+
 #endif /* LIGHTNING_WALLET_WALLET_H */