lightningd/invoice.c: Add timeout parameter to waitanyinvoice.

Fixes: #3192

Changelog-Added: `waitanyinvoice` now supports a `timeout` parameter, which when set will cause the command to fail when the timeout is reached; can set this to 0 to fail immediately if no new invoice has been paid yet.

common/jsonrpc_errors.h

@@ -52,5 +52,6 @@
 #define INVOICE_LABEL_ALREADY_EXISTS	900
 #define INVOICE_PREIMAGE_ALREADY_EXISTS	901
 #define INVOICE_HINTS_GAVE_NO_ROUTES	902
+#define INVOICE_WAIT_TIMED_OUT		904
 
 #endif /* LIGHTNING_COMMON_JSONRPC_ERRORS_H */

contrib/pyln-client/pyln/client/lightning.py

@@ -988,14 +988,18 @@ def stop(self):
         """
         return self.call("stop")
 
-    def waitanyinvoice(self, lastpay_index=None):
+    def waitanyinvoice(self, lastpay_index=None, timeout=None, **kwargs):
         """
         Wait for the next invoice to be paid, after {lastpay_index}
         (if supplied)
+        Fail after {timeout} seconds has passed without an invoice
+        being paid.
         """
         payload = {
-            "lastpay_index": lastpay_index
+            "lastpay_index": lastpay_index,
+            "timeout": timeout
         }
+        payload.update({k: v for k, v in kwargs.items()})
         return self.call("waitanyinvoice", payload)
 
     def waitblockheight(self, blockheight, timeout=None):

doc/lightning-waitanyinvoice.7.md

@@ -4,7 +4,7 @@ lightning-waitanyinvoice -- Command for waiting for payments
 SYNOPSIS
 --------
 
-**waitanyinvoice** \[*lastpay\_index*\]
+**waitanyinvoice** \[*lastpay\_index*\] \[*timeout*\]
 
 DESCRIPTION
 -----------
@@ -22,12 +22,25 @@ invoice when it gets paid. The first valid *pay\_index* is 1; specifying
 *lastpay\_index* of 0 equivalent to not specifying a *lastpay\_index*.
 Negative *lastpay\_index* is invalid.
 
+If *timeout* is specified, wait at most that number of seconds, which
+must be an integer.
+If the specified *timeout* is reached, this command will return with an
+error.
+You can specify this to 0 so that **waitanyinvoice** will return
+immediately with an error if no pending invoice is available yet.
+If unspecified, this command will wait indefinitely.
+
 RETURN VALUE
 ------------
 
 On success, an invoice description will be returned as per
 lightning-listinvoice(7): *complete* will always be *true*.
 
+Possible errors are:
+
+* 904.
+  The *timeout* was reached without an invoice being paid.
+
 AUTHOR
 ------
 

lightningd/invoice.c

@@ -16,6 +16,7 @@
 #include <common/overflows.h>
 #include <common/param.h>
 #include <common/pseudorand.h>
+#include <common/timeout.h>
 #include <common/utils.h>
 #include <errno.h>
 #include <gossipd/gen_gossip_wire.h>
@@ -102,6 +103,12 @@ static void wait_on_invoice(const struct invoice *invoice, void *cmd)
 	else
 		tell_waiter_deleted((struct command *) cmd);
 }
+static void wait_timed_out(struct command *cmd)
+{
+	was_pending(command_fail(cmd, INVOICE_WAIT_TIMED_OUT,
+				 "Timed out while waiting "
+				 "for invoice to be paid"));
+}
 
 /* We derive invoice secret using 1-way function from payment_preimage
  * (just a different one from the payment_hash!) */
@@ -1129,13 +1136,25 @@ static struct command_result *json_waitanyinvoice(struct command *cmd,
 						  const jsmntok_t *params)
 {
 	u64 *pay_index;
+	u64 *timeout;
 	struct wallet *wallet = cmd->ld->wallet;
 
 	if (!param(cmd, buffer, params,
 		   p_opt_def("lastpay_index", param_u64, &pay_index, 0),
+		   p_opt("timeout", &param_u64, &timeout),
 		   NULL))
 		return command_param_failed();
 
+	/*~ We allocate the timeout and the wallet-waitanyinvoice
+	 * in the cmd context, so whichever one manages to complete
+	 * the command first (and destroy the cmd context)
+	 * auto-cancels the other, is not tal amazing?
+	 */
+	if (timeout)
+		(void) new_reltimer(cmd->ld->timers, cmd,
+				    time_from_sec(*timeout),
+				    &wait_timed_out, cmd);
+
 	/* Set command as pending. We do not know if
 	 * wallet_invoice_waitany will return immediately
 	 * or not, so indicating pending is safest.  */
@@ -1155,7 +1174,8 @@ static const struct json_command waitanyinvoice_command = {
 	"waitanyinvoice",
 	"payment",
 	json_waitanyinvoice,
-	"Wait for the next invoice to be paid, after {lastpay_index} (if supplied)"
+	"Wait for the next invoice to be paid, after {lastpay_index} (if supplied).  "
+	"If {timeout} seconds is reached while waiting, fail with an error."
 };
 AUTODATA(json_command, &waitanyinvoice_command);