wallet: Add utxo_is_immature helper

common/utxo.c

@@ -73,3 +73,21 @@ size_t utxo_spend_weight(const struct utxo *utxo, size_t min_witness_weight)
 
 	return bitcoin_tx_input_weight(utxo->is_p2sh, wit_weight);
 }
+
+u32 utxo_is_immature(const struct utxo *utxo, u32 blockheight)
+{
+	if (utxo->is_in_coinbase) {
+		/* We got this from a block, it must have a known
+		 * blockheight. */
+		assert(utxo->blockheight);
+
+		if (blockheight < *utxo->blockheight + 100)
+			return *utxo->blockheight + 99 - blockheight;
+
+		else
+			return 0;
+	} else {
+		/* Non-coinbase outputs are always mature. */
+		return 0;
+	}
+}

common/utxo.h

@@ -83,4 +83,11 @@ struct utxo *fromwire_utxo(const tal_t *ctx, const u8 **ptr, size_t *max);
 
 /* Estimate of (signed) UTXO weight in transaction */
 size_t utxo_spend_weight(const struct utxo *utxo, size_t min_witness_weight);
+
+/**
+ * Determine how many blocks until a UTXO becomes mature.
+ *
+ * Returns 0 for non-coinbase outputs or the number of blocks to mature.
+ */
+u32 utxo_is_immature(const struct utxo *utxo, u32 blockheight);
 #endif /* LIGHTNING_COMMON_UTXO_H */

wallet/test/Makefile

@@ -26,6 +26,7 @@ WALLET_TEST_COMMON_OBJS :=			\
 	common/setup.o				\
 	common/timeout.o			\
 	common/utils.o				\
+	common/utxo.o				\
 	common/wireaddr.o			\
 	common/version.o			\
 	wallet/db_sqlite3_sqlgen.o		\

wallet/wallet.c

@@ -511,15 +511,9 @@ static bool deep_enough(u32 maxheight, const struct utxo *utxo,
 			return false;
 	}
 
-	/* If the utxo is a coinbase, we over-write the maxheight
-	 * to the coinbase maxheight (current - 99) */
-	if (utxo->is_in_coinbase) {
-		/* Nothing is spendable the first 100 blocks */
-		if (current_blockheight < 100)
-			return false;
-		if (maxheight > current_blockheight - 99)
-			maxheight = current_blockheight - 99;
-	}
+	bool immature = utxo_is_immature(utxo, current_blockheight);
+	if (immature)
+		return false;
 
 	/* If we require confirmations check that we have a
 	 * confirmation height and that it is below the required

wallet/walletrpc.c

@@ -272,11 +272,11 @@ static void json_add_utxo(struct json_stream *response,
 	if (utxo->spendheight)
 		json_add_string(response, "status", "spent");
 	else if (utxo->blockheight) {
-		if (utxo->is_in_coinbase
-		    && *utxo->blockheight + 99 > current_height) {
-			json_add_string(response, "status", "immature");
-		} else
-			json_add_string(response, "status", "confirmed");
+		json_add_string(response, "status",
+				utxo_is_immature(utxo, current_height)
+				    ? "immature"
+				    : "confirmed");
+
 		json_add_num(response, "blockheight", *utxo->blockheight);
 	} else
 		json_add_string(response, "status", "unconfirmed");