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fix: carry cumulative factors across round gaps (fixes CRF reset from #249) #2

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fix: carry cumulative factors across round gaps (fixes CRF reset from #249) #2

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45 changes: 33 additions & 12 deletions utils/helpers.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -62,23 +62,44 @@ export function createOrLoadPool(roundId: string, transcoderAddress: string): Po
pool.delegate = transcoderAddress;
pool.fees = ZERO_BD;

// Propagate cumulative factors from the previous round's pool so every
// pool has valid factors even if the transcoder misses reward() or has
// no fees in a round. This mirrors the contract's latestCumulativeFactorsPool.
let prevRoundNum = integerFromString(roundId).minus(ONE_BI);
let prevPool = Pool.load(
makePoolId(transcoderAddress, prevRoundNum.toString())
);
if (prevPool) {
pool.cumulativeRewardFactor = prevPool.cumulativeRewardFactor;
pool.cumulativeFeeFactor = prevPool.cumulativeFeeFactor;
let transcoder = Transcoder.load(transcoderAddress);

// Propagate cumulative factors from the most recent EXISTING pool so they
// never reset to base across a round gap. Normally that is the previous
// round's pool, but when the transcoder was inactive — or newRound's
// non-deterministic enumeration skipped it (see #249) — the previous
// round's pool can be missing for several rounds. Walk back to the most
// recent pool that exists, bounded below by lastRewardRound (which is
// guaranteed to have a pool with valid factors). This mirrors the
// contract's latestCumulativeFactorsPool.
//
// Only checking round-1 (the previous behavior) left the factors at 0
// whenever that single pool was missing, and reward() then reset the
// cumulative reward factor to base (10^27) — corrupting the stake of every
// delegator whose last claim predated the gap.
let sourcePool: Pool | null = null;
if (transcoder != null && transcoder.lastRewardRound != null) {
let cursor = integerFromString(roundId).minus(ONE_BI);
let floor = integerFromString(transcoder.lastRewardRound!);
while (cursor.ge(floor)) {
let candidate = Pool.load(
makePoolId(transcoderAddress, cursor.toString())
);
if (candidate != null) {
sourcePool = candidate;
break;
}
cursor = cursor.minus(ONE_BI);
}
}
if (sourcePool != null) {
pool.cumulativeRewardFactor = sourcePool.cumulativeRewardFactor;
pool.cumulativeFeeFactor = sourcePool.cumulativeFeeFactor;
} else {
pool.cumulativeRewardFactor = ZERO_BI;
pool.cumulativeFeeFactor = ZERO_BI;
}

let transcoder = Transcoder.load(transcoderAddress);

if (transcoder) {
pool.totalStake = transcoder.totalStake;
pool.rewardCut = transcoder.rewardCut;
Expand Down