plugins/pay: sort output payments in listpays

Changelog-Changed: `listpays` output is now ordered by the `created_at` timestamp.

plugins/pay.c

@@ -1,5 +1,6 @@
 #include <bitcoin/chainparams.h>
 #include <ccan/array_size/array_size.h>
+#include <ccan/asort/asort.h>
 #include <ccan/cast/cast.h>
 #include <ccan/crypto/siphash24/siphash24.h>
 #include <ccan/htable/htable_type.h>
@@ -1701,6 +1702,17 @@ static bool pay_mpp_eq(const struct pay_mpp *pm, const struct sha256 *payment_ha
 	return memcmp(pm->payment_hash, payment_hash, sizeof(struct sha256)) == 0;
 }
 
+static int cmp_pay_mpp(const struct pay_mpp *a,
+		       const struct pay_mpp *b,
+		       void *unused UNUSED)
+{
+	if (a->timestamp < b->timestamp)
+		return -1;
+	if (a->timestamp == b->timestamp)
+		return 0;
+	return 1;
+}
+
 HTABLE_DEFINE_TYPE(struct pay_mpp, pay_mpp_key, pay_mpp_hash, pay_mpp_eq,
 		   pay_map);
 
@@ -1796,6 +1808,7 @@ static struct command_result *listsendpays_done(struct command *cmd,
 	struct pay_map pay_map;
 	struct pay_map_iter it;
 	struct pay_mpp *pm;
+	struct pay_mpp *pays;
 
 	pay_map_init(&pay_map);
 
@@ -1864,17 +1877,26 @@ static struct command_result *listsendpays_done(struct command *cmd,
 		}
 	}
 
-	/* Now we've collapsed them, provide summary. */
-	ret = jsonrpc_stream_success(cmd);
-	json_array_start(ret, "pays");
 
+	pays = tal_arr(NULL, struct pay_mpp, pay_map_count(&pay_map));
+	i = 0;
 	for (pm = pay_map_first(&pay_map, &it);
 	     pm;
 	     pm = pay_map_next(&pay_map, &it)) {
-		add_new_entry(ret, buf, pm);
+		pays[i++] = *pm;
 	}
 	pay_map_clear(&pay_map);
 
+	asort(pays, tal_count(pays), cmp_pay_mpp, NULL);
+
+	/* Now we've collapsed and sorted them, provide summary. */
+	ret = jsonrpc_stream_success(cmd);
+	json_array_start(ret, "pays");
+
+	for (i = 0; i < tal_count(pays); i++)
+		add_new_entry(ret, buf, &pays[i]);
+	tal_free(pays);
+
 	json_array_end(ret);
 	return command_finished(cmd, ret);
 }