From 505d92bb06f6cd65d7f838b51e98f89cd5e47d3e Mon Sep 17 00:00:00 2001
From: Pavel Karpy <carpawell@nspcc.ru>
Date: Tue, 12 Oct 2021 19:04:48 +0300
Subject: [PATCH] [#873] morph/notary: Not `warn` at "low `till` value" notary
 deposit error

Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>
---
 pkg/morph/client/notary.go | 27 ++++++++++++++++++++++++---
 1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/pkg/morph/client/notary.go b/pkg/morph/client/notary.go
index 858ca374..bf30b101 100644
--- a/pkg/morph/client/notary.go
+++ b/pkg/morph/client/notary.go
@@ -186,7 +186,15 @@ func (c *Client) DepositNotary(amount fixedn.Fixed8, delta uint32) (res util.Uin
 		nil,
 	)
 	if err != nil {
-		return util.Uint256{}, fmt.Errorf("can't make notary deposit: %w", err)
+		if !tillShouldNotBeLessError(err) {
+			return util.Uint256{}, fmt.Errorf("can't make notary deposit: %w", err)
+		}
+
+		c.logger.Debug("notary deposit invoke failed due to low `till` value",
+			zap.Int64("amount", int64(amount)),
+			zap.Uint32("till", bc+delta))
+
+		return util.Uint256{}, nil
 	}
 
 	c.logger.Debug("notary deposit invoke",
@@ -704,8 +712,6 @@ func WithProxyContract(h util.Uint160) NotaryOption {
 	}
 }
 
-const alreadyOnChainErrorMessage = "already on chain"
-
 // Neo RPC node can return `core.ErrInvalidAttribute` error with
 // `conflicting transaction <> is already on chain` message. This
 // error is expected and ignored. As soon as main tx persisted on
@@ -713,9 +719,24 @@ const alreadyOnChainErrorMessage = "already on chain"
 // requires 5 out of 7 signatures to send main tx, thus last two
 // notary requests may be processed after main tx appeared on chain.
 func alreadyOnChainError(err error) bool {
+	const alreadyOnChainErrorMessage = "already on chain"
+
 	return strings.Contains(err.Error(), alreadyOnChainErrorMessage)
 }
 
+// Neo RPC node can return "`till` shouldn't be less then the
+// previous value <>" message. This error is expected and ignored.
+// This happens because previous `till` value could be bigger
+// than the current one due to significant epoch duration decrease.
+// Theoretically, balance should not run out so fast and such
+// errors are ignored(at least for now; there is #910 issue
+// for it).
+func tillShouldNotBeLessError(err error) bool {
+	const tillTooLowErrorMessage = "less then the previous value"
+
+	return strings.Contains(err.Error(), tillTooLowErrorMessage)
+}
+
 // CalculateNotaryDepositAmount calculates notary deposit amount
 // using the rule:
 //      IF notaryBalance < gasBalance * gasMul {