refactor: remove slot empty endpoint from crisp server

[cedoor]

Closes #1155

Summary by CodeRabbit

• Breaking Changes

  • Removed the dedicated slot-empty check endpoint; consumers must treat missing ciphertext as empty.
  • Slot index queries now return signed values and indicate empty slots (e.g., -1) instead of reverting.

• API Updates

  • Ciphertext fetches now return nullable/undefined when absent instead of throwing.
  • SDK now always requests previous ciphertext (removes pre-checks) to preserve request patterns.

• Tests

  • Updated mocks to cover 404 (not found) responses for previous ciphertext.

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2 Skipped Deployments

Project	Deployment	Actions	Updated (UTC)
crisp	Skipped		Mar 5, 2026 2:17pm
enclave-docs	Skipped		Mar 5, 2026 2:17pm

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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Review profile: CHILL

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Run ID: e075e350-1344-445d-b551-2f8e2f24ea66

📥 Commits

Reviewing files that changed from the base of the PR and between e1b4565 and 4bedc82.

📒 Files selected for processing (1)

• examples/CRISP/server/Dockerfile

✅ Files skipped from review due to trivial changes (1)

• examples/CRISP/server/Dockerfile

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📝 Walkthrough

Walkthrough

This PR removes the separate slot-empty API and changes slot lookup semantics: getSlotIndex now returns a signed integer (-1 indicates empty) and the SDK/server treat missing previous ciphertext as undefined (404) instead of calling an extra emptiness endpoint.

Changes

Cohort / File(s)	Summary
Contract & EVM bindings examples/CRISP/packages/crisp-contracts/contracts/CRISPProgram.sol, examples/CRISP/crates/evm_helpers/src/lib.rs	getSlotIndex changed from unsigned to signed return (int40 / int256) so empty slots map to -1; removed isSlotEmptyByAddress. Rust binding updated to return Option<u64> and use I256.
SDK constants & state examples/CRISP/packages/crisp-sdk/src/constants.ts, examples/CRISP/packages/crisp-sdk/src/state.ts, examples/CRISP/packages/crisp-sdk/README.md	Removed CRISP_SERVER_IS_SLOT_EMPTY_ENDPOINT and getIsSlotEmpty export. getPreviousCiphertext signature changed to `Uint8Array
SDK logic & tests examples/CRISP/packages/crisp-sdk/src/sdk.ts, examples/CRISP/packages/crisp-sdk/tests/vote.test.ts	Vote proof functions now unconditionally call getPreviousCiphertext() (no emptiness check). Tests updated to mock 404/200 responses. Added doc note that previous ciphertext isn't used in proof but is fetched to hide vote type.
Server models & routes examples/CRISP/server/src/server/models.rs, examples/CRISP/server/src/server/routes/state.rs	Removed IsSlotEmptyRequest/IsSlotEmptyResponse types and the /isSlotEmpty route. handle_get_previous_ciphertext updated to handle Option<u64> and return 404 when index is None.
Misc (build) examples/CRISP/server/Dockerfile	Bumped ARG RUST_VERSION from 1.86.0 to 1.88.0 in Dockerfile.

Sequence Diagram(s)

sequenceDiagram
    participant Client as Client SDK
    participant Server as CRISP Server
    participant Contract as CRISPProgram Contract

    rect rgba(100,150,200,0.5)
    Note over Client,Contract: Previous Flow (with isSlotEmpty)
    Client->>Server: isSlotEmpty(e3Id, address)
    Server->>Contract: getSlotIndex(e3Id, address)
    Contract-->>Server: uint40 (reverts if empty)
    Server-->>Client: {is_empty: bool}
    alt slot not empty
        Client->>Server: getPreviousCiphertext(e3Id, address)
        Server->>Contract: getSlotIndex(e3Id, address)
        Contract-->>Server: uint40
        Server-->>Client: Uint8Array
    end
    end

    rect rgba(150,200,100,0.5)
    Note over Client,Contract: New Flow (direct call)
    Client->>Server: getPreviousCiphertext(e3Id, address)
    Server->>Contract: getSlotIndex(e3Id, address)
    Contract-->>Server: int40 (-1 if empty)
    alt slot exists
        Server-->>Client: Uint8Array
    else slot empty
        Server-->>Client: 404 / undefined
    end
    end

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Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• refactor: simplify crisp sdk api #1135: Similar API consolidation—removes isSlotEmpty and makes previousCiphertext optional in the SDK/server paths.
• feat: get previous ciphertext from server [skip-line-limit] #1109: Related changes to getSlotIndex and surrounding server/SDK contract interactions.
• chore: check vote is zero for masking #938: Changes around CRISP SDK masking/vote flows that touch previous ciphertext handling.

Suggested reviewers

• ctrlc03
• 0xjei

Poem

🐰 One less hop to check the nest,
The slot now answers -1 at rest.
No extra call, the path is lean,
Ciphertext shows if a vote has been seen.
🥕 Hooray — the code runs clean!

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The PR title accurately summarizes the primary change: removing the slot empty endpoint from the CRISP server and SDK, which aligns with the main objective of eliminating unnecessary isSlotEmpty calls.
Linked Issues check	✅ Passed	The PR successfully addresses all requirements from issue #1155: eliminates isSlotEmpty calls [multiple files], makes getPreviousCiphertext return undefined for empty slots, and adds documentation to generateVoteProof explaining why it still calls the server API.
Out of Scope Changes check	✅ Passed	The Rust version bump in Dockerfile (1.86.0 to 1.88.0) is justified by the commit message as fixing a cargo-chef compatibility issue. While supporting, this change is tangentially related to the primary refactoring objective.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch refactor/crisp-server-calls

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[coderabbitai]

🧹 Nitpick comments (1)

examples/CRISP/crates/evm_helpers/src/lib.rs (1)

25-25: Align ABI return width: Solidity declares int40, binding declares int256.

The contract's getSlotIndex function returns int40 (line 244 in CRISPProgram.sol), but the Rust binding declares int256 (line 25). This works via ABI sign-extension, but explicitly matching the return type widths or documenting the intentional widening will reduce maintenance risk and improve code clarity.

The negative sentinel handling (lines 143–147) correctly interprets negative values as empty slots, so the current implementation is functionally sound.

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@examples/CRISP/crates/evm_helpers/src/lib.rs` at line 25, The generated
binding for function getSlotIndex currently declares the return as int256 while
the Solidity contract (CRISPProgram.sol) returns int40; update the ABI/binding
declaration for getSlotIndex to match the contract's return width (int40) so the
binding signature and generated types align, or if you intentionally widen to
256 bits, add a clear comment in the binding next to getSlotIndex explaining the
deliberate sign-extension widening and why negative sentinel handling remains
valid (refer to getSlotIndex and the sentinel logic in CRISPProgram.sol).

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Nitpick comments:
In `@examples/CRISP/crates/evm_helpers/src/lib.rs`:
- Line 25: The generated binding for function getSlotIndex currently declares
the return as int256 while the Solidity contract (CRISPProgram.sol) returns
int40; update the ABI/binding declaration for getSlotIndex to match the
contract's return width (int40) so the binding signature and generated types
align, or if you intentionally widen to 256 bits, add a clear comment in the
binding next to getSlotIndex explaining the deliberate sign-extension widening
and why negative sentinel handling remains valid (refer to getSlotIndex and the
sentinel logic in CRISPProgram.sol).

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: d7442819-5132-4dc3-b415-5a61de12a527

📥 Commits

Reviewing files that changed from the base of the PR and between c7167ec and e1b4565.

📒 Files selected for processing (9)

• examples/CRISP/crates/evm_helpers/src/lib.rs
• examples/CRISP/packages/crisp-contracts/contracts/CRISPProgram.sol
• examples/CRISP/packages/crisp-sdk/README.md
• examples/CRISP/packages/crisp-sdk/src/constants.ts
• examples/CRISP/packages/crisp-sdk/src/sdk.ts
• examples/CRISP/packages/crisp-sdk/src/state.ts
• examples/CRISP/packages/crisp-sdk/tests/vote.test.ts
• examples/CRISP/server/src/server/models.rs
• examples/CRISP/server/src/server/routes/state.rs

💤 Files with no reviewable changes (2)

• examples/CRISP/packages/crisp-sdk/src/constants.ts
• examples/CRISP/server/src/server/models.rs

[ctrlc03]

Thanks