refactor: add opt fee payer to revoke and approve instructions

[ananas-block]

1. Account index constants restructured: Renamed APPROVE_PAYER_IDX/REVOKE_PAYER_IDX to OWNER_IDX and added separate FEE_PAYER_IDX constants (Approve:
   owner=2, fee_payer=4; Revoke: owner=1, fee_payer=3) with system program placement documented
2. Generic function signatures expanded: Both handle_compressible_top_up and process_compressible_top_up now take three const generics (BASE_LEN, OWNER_IDX,
   FEE_PAYER_IDX) instead of two
3. Payer fallback logic implemented: Changed from direct owner lookup to optional fee_payer with owner fallback (fee_payer.or(authority_payer))
4. Documentation updated: Doc comments reflect new account layout with optional fee_payer and updated parameter descriptions

Summary by CodeRabbit

• Bug Fixes
  • Improved handling of owner and fee-payer account references in token approval and revocation flows, ensuring correct fee assignment and more reliable transactions.
• Documentation
  • Clarified instruction semantics for approve and revoke operations to reflect updated account roles.

[coderabbitai]

Caution

Review failed

The pull request is closed.

📝 Walkthrough

Walkthrough

Refactors approve/revoke instruction handling to separate an "owner" account and an optional "fee_payer" account. Constants and call sites were updated; handle_compressible_top_up and downstream calls now accept OWNER_IDX and FEE_PAYER_IDX, and payer selection uses fee_payer if present, otherwise owner. (≈38 added / 12 removed lines)

Changes

Cohort / File(s)	Summary
Approve Instruction Index Updates programs/compressed-token/program/src/ctoken/approve_revoke.rs	Replaced APPROVE_PAYER_IDX with APPROVE_OWNER_IDX (2) and APPROVE_FEE_PAYER_IDX (4). Updated process_ctoken_approve to call handle_compressible_top_up::<APPROVE_BASE_LEN, APPROVE_OWNER_IDX, APPROVE_FEE_PAYER_IDX>(...). Documentation comments adjusted.
Revoke Instruction Index Updates programs/compressed-token/program/src/ctoken/approve_revoke.rs	Replaced REVOKE_PAYER_IDX with REVOKE_OWNER_IDX (1) and REVOKE_FEE_PAYER_IDX (3). Updated process_ctoken_revoke to call handle_compressible_top_up::<REVOKE_BASE_LEN, REVOKE_OWNER_IDX, REVOKE_FEE_PAYER_IDX>(...). Documentation comments adjusted.
Top-up Processing Function Refactor programs/compressed-token/program/src/ctoken/approve_revoke.rs	Changed handle_compressible_top_up signature from (BASE_LEN, PAYER_IDX) to (BASE_LEN, OWNER_IDX, FEE_PAYER_IDX). Internal logic now resolves authority_payer (owner) and optional fee_payer; effective payer = fee_payer if present else owner. Updated nested calls and parameter docs accordingly.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~22 minutes

Possibly related PRs

• refactor: add opt fee payer to revoke and approve instructions #2306 — Applies the same refactor replacing a single payer index with OWNER_IDX and optional FEE_PAYER_IDX across related call sites.
• fix(programs): interpret max_top_up as units of 1,000 lamports (L-07) #2265 — Modifies the approve/revoke ctoken path (top-up logic) and may interact with the new owner/fee_payer index changes.

Suggested reviewers

• sergeytimoshin
• SwenSchaeferjohann

Poem

Owner and fee, a duo now true,
Indexes shifted, clearer view,
Calls updated, logic neat,
Fee first if present — owner keeps the seat,
Small refactor, tidy and new ✨

🚥 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 accurately describes the main change: adding an optional fee payer parameter to the revoke and approve instructions, which aligns with the refactoring of instruction data semantics and constant reindexing throughout the changeset.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 70.00%.

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✨ Finishing Touches

• 📝 Generate docstrings (stacked PR)
• 📝 Generate docstrings (commit on current branch)

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch jorrit/refactor-add-opt-fee-payer-to-revoke-approve

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[coderabbitai]

Actionable comments posted: 2

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.
Inline comments:
In `@programs/compressed-token/program/src/ctoken/approve_revoke.rs`:
- Around line 104-105: Doc comment for the account index constants is stale:
update the FEE_PAYER_IDX description near the OWNER_IDX/FEE_PAYER_IDX doc block
in approve_revoke.rs to read "(4 for approve, 3 for revoke)" (leave OWNER_IDX as
"2 for approve, 1 for revoke"); locate the doc comment that currently shows the
wrong values and replace only the FEE_PAYER_IDX tuple so the comment matches the
actual indexing used by handle_compressible_top_up and approve/revoke logic.
- Around line 75-76: The doc comment for FEE_PAYER_IDX has incorrect index
numbers; update the text to match the actual constants APPROVE_FEE_PAYER_IDX = 4
and REVOKE_FEE_PAYER_IDX = 3 (i.e. "4 for approve, 3 for revoke") so it no
longer mirrors the OWNER_IDX values and correctly documents the fee payer
account positions.