Sync the SNS rewards status logic calculation with the backend (#5766)

# Motivation

The logic for SNS reward status calculation is outdated on the front
end. Although we haven’t received error reports recently, after
discussing with a backend developer, it was suggested to sync the logic.


Presumably, the backend fixes led to the related code changes:

**1. SNS list_proposals reward status filtering does not exclude old
SNS-1 proposals.**

There is a new field is reward_event_end_timestamp_seconds. Older
proposals do not populate this field, since they predate it.
Currently, the correct way to determine whether a proposal is associated
with a reward event is to look at both the new field, as well as the old
one, to wit reward_event_round.

[Added
here.](https://github.com/dfinity/nns-dapp/pull/5766/files#diff-bc794365fb0826c7ec5cc7d9ab15121c6bc9630e990e7bd8751b8b84273601b6R304-R305)

See more in [NNS1-2588](https://dfinity.atlassian.net/browse/NNS1-2588).

**2. NNS proposal votes should not be able to be registered after the
proposal deadline.**

dfinity/ic@9587cc9#diff-0da5ccadff83a3bb673833b806280c8032311d143120522fa59b6e202d7216f9R902

A voter can still cast a ballot in the time between which a proposal’s
deadline is over and the time where the proposal is settled.
This is not expected. It should be checked whether a proposal still
accepts votes (with the method accepts_vote) before a neuron’s vote is
cast.

And the logic from the `accepts_vote` function was added
[here](https://github.com/dfinity/nns-dapp/pull/5766/files#diff-bc794365fb0826c7ec5cc7d9ab15121c6bc9630e990e7bd8751b8b84273601b6R312-R313).

See more in [NNS1-959](https://dfinity.atlassian.net/browse/NNS1-959).

# Changes

- Update the logic and the reference url to the backend code.

# Tests

- Unit test updated.

# Todos

- [ ] Add entry to changelog (if necessary).
Not necessary.

[NNS1-2588]:
https://dfinity.atlassian.net/browse/NNS1-2588?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ

[NNS1-959]:
https://dfinity.atlassian.net/browse/NNS1-959?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ

frontend/src/lib/utils/sns-proposals.utils.ts

@@ -35,7 +35,12 @@ import {
   SnsProposalRewardStatus,
   type SnsPercentage,
 } from "@dfinity/sns";
-import { fromDefinedNullable, fromNullable, isNullish } from "@dfinity/utils";
+import {
+  fromDefinedNullable,
+  fromNullable,
+  isNullish,
+  nonNullish,
+} from "@dfinity/utils";
 import { get } from "svelte/store";
 import { nowInSeconds } from "./date.utils";
 import { keyOfOptional } from "./utils";
@@ -282,7 +287,7 @@ export const snsDecisionStatus = (
 /**
  * Returns the status of a proposal based on the data.
  *
- * Reference: https://github.com/dfinity/ic/blob/226ab04e0984367da356bbe27c90447863d33a27/rs/sns/governance/src/proposal.rs#L735
+ * Reference: https://github.com/dfinity/ic/blob/bc2c84c5e3dc14bedb7ef9bbe231748886a34a29/rs/sns/governance/src/proposal.rs#L1692-L1706
  *
  * @param {SnsProposalData} proposal
  * @returns {SnsProposalRewardStatus}
@@ -291,18 +296,22 @@ export const snsRewardStatus = ({
   reward_event_round,
   wait_for_quiet_state,
   is_eligible_for_rewards,
+  reward_event_end_timestamp_seconds,
+  proposal_creation_timestamp_seconds,
+  initial_voting_period_seconds,
 }: SnsProposalData): SnsProposalRewardStatus => {
-  if (reward_event_round > 0n) {
+  if (
+    nonNullish(fromNullable(reward_event_end_timestamp_seconds)) ||
+    reward_event_round > 0n
+  ) {
     return SnsProposalRewardStatus.PROPOSAL_REWARD_STATUS_SETTLED;
   }
 
   const now = nowInSeconds();
   const deadline =
-    fromNullable(wait_for_quiet_state)?.current_deadline_timestamp_seconds;
-  if (!deadline) {
-    // Reference: https://github.com/dfinity/ic/blob/226ab04e0984367da356bbe27c90447863d33a27/rs/sns/governance/src/proposal.rs#L760
-    throw new Error("Proposal must have a wait_for_quiet_state.");
-  }
+    fromNullable(wait_for_quiet_state)?.current_deadline_timestamp_seconds ??
+    proposal_creation_timestamp_seconds + initial_voting_period_seconds;
+
   if (now < deadline) {
     return SnsProposalRewardStatus.PROPOSAL_REWARD_STATUS_ACCEPT_VOTES;
   }

frontend/src/tests/lib/utils/sns-proposals.utils.spec.ts

@@ -155,6 +155,17 @@ describe("sns-proposals utils", () => {
       );
     });
 
+    it("should return SETTLED based on reward event end timestamp", () => {
+      const proposal: SnsProposalData = {
+        ...mockSnsProposal,
+        reward_event_round: 0n,
+        reward_event_end_timestamp_seconds: [0n],
+      };
+      expect(snsRewardStatus(proposal)).toBe(
+        SnsProposalRewardStatus.PROPOSAL_REWARD_STATUS_SETTLED
+      );
+    });
+
     it("should return ACCEPT_VOTES", () => {
       const now = BigInt(nowInSeconds());
       const proposal: SnsProposalData = {
@@ -171,6 +182,20 @@ describe("sns-proposals utils", () => {
       );
     });
 
+    it("should return ACCEPT_VOTES w/o current_deadline_timestamp_seconds ", () => {
+      const now = BigInt(nowInSeconds());
+      const proposal: SnsProposalData = {
+        ...mockSnsProposal,
+        reward_event_round: 0n,
+        wait_for_quiet_state: [],
+        proposal_creation_timestamp_seconds: now,
+        initial_voting_period_seconds: 100n,
+      };
+      expect(snsRewardStatus(proposal)).toBe(
+        SnsProposalRewardStatus.PROPOSAL_REWARD_STATUS_ACCEPT_VOTES
+      );
+    });
+
     it("should return READY_TO_SETTLE", () => {
       const now = BigInt(nowInSeconds());
       const proposal: SnsProposalData = {