fix(nonce): prevent computing nonces from incomplete chain data

[wcatz]

Summary

• Root cause: GetNonceForEpoch in full mode called ComputeEpochNonce during sync, when the DB only had blocks for epochs 208-222 plus live epoch 612. The 390-epoch gap produced a garbage nonce that got permanently cached.
• Fix: Check GetLastSyncedSlot vs the target epoch's end slot before computing locally. Falls through to Koios when sync is incomplete.
• Deleted the bad nonces and schedules from goduckbot_test DB already.

What changed

• GetNonceForEpoch now only computes from local chain data when sync has passed the target epoch
• When sync is incomplete, falls through to Koios (previously only used in lite mode)

Test plan

• go build && go vet && go test — all pass
• Deploy to test — verify nonces come from Koios during sync, then from local computation after sync completes

🤖 Generated with Claude Code

Summary by CodeRabbit

• Improvements

  • Enhanced nonce retrieval: uses local chain data only when fully synced, otherwise falls back to Koios; successful chain or Koios results are cached.
  • Improved logging for sync-vs-fallback scenarios to increase visibility.

• New Features

  • Commands now check sync status and will notify users when historical synchronization is in progress, delaying certain operations (e.g., leaderlog, nonce, validate, nextblock) until sync completes.

[coderabbitai]

📝 Walkthrough

Walkthrough

GetNonceForEpoch in nonce.go was changed to be sync-aware: it computes the epoch nonce from chain data only if the node has synced past the epoch end; otherwise it falls back to Koios. Sync state gating was added across command handlers and the indexer lifecycle to avoid running while historical sync is in progress.

Changes

Cohort / File(s)	Summary
Nonce sync-aware logic nonce.go	GetNonceForEpoch now checks last synced slot vs. epoch end; if fully synced it computes nonce from chain and caches it, otherwise falls back to Koios and caches Koios result. Logging updated to indicate sync-based fallback.
Indexer sync flag & gating main.go	Added historicalSyncDone int32 to Indexer, isSynced() helper, set flag for lite mode and at sync completion; leaderlog scheduling now skips while historical sync is incomplete.
Command handlers sync guard commands.go	Added requireSynced(m *telebot.Message) bool and applied it to several commands (Leaderlog, Nonce, Validate, NextBlock) to prevent execution during historical sync.

Sequence Diagram

sequenceDiagram
    participant Caller as Caller
    participant Indexer as Indexer / isSynced
    participant GetNonce as GetNonceForEpoch
    participant Chain as Chain Data Compute
    participant Koios as Koios Service
    participant DB as Nonce Cache (DB)

    Caller->>GetNonce: Request epoch nonce
    GetNonce->>Indexer: Check last synced slot / isSynced
    alt synced_slot >= epoch_end_slot
        GetNonce->>Chain: Compute nonce from chain data
        Chain-->>GetNonce: Computed nonce
        GetNonce->>DB: Cache nonce
        DB-->>GetNonce: Cached
        GetNonce-->>Caller: Return chain-derived nonce
    else not synced
        GetNonce->>Koios: Request nonce (fallback)
        Koios-->>GetNonce: Koios nonce
        GetNonce->>DB: Cache Koios nonce
        DB-->>GetNonce: Cached
        GetNonce-->>Caller: Return Koios nonce
    end

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Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• fix(nonce): run backfill after historical sync completes #60 — Closely related: also deals with nonce correctness around historical sync completion and Koios fallback timing.
• fix(nonce): remove wrong hardcoded epoch nonces #64 — Modifies nonce computation and fallback behavior in nonce.go, overlapping logic and caching changes.
• fix(nonce): add Koios verification fallback for backfill #61 — Adds Koios verification/substitution during backfill; touches the same nonce and fallback paths.

Poem

🐰 Hopping through slots with careful delight,

If sync's not complete, Koios keeps things right.
When chains are all caught up, compute and then store,
Cache the true nonce — then hop off once more.
A rabbit's small cheer for sync-aware lore! ✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'fix(nonce): prevent computing nonces from incomplete chain data' directly and clearly summarizes the main change: adding a guard to prevent nonce computation when chain data is incomplete.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch fix/nonce-incomplete-sync-guard

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