[doublegate]

Summary

Implements T-81-003's full stated scope, behind a new cheats flag:

• Decode: a new rustysnes_core::cheat module decodes SNES Game Genie codes (XXXX-XXXX, 9 characters including the dash, the 16-character alphabet DF4709156BC8A23E) and Pro Action Replay codes (8 hex digits, AAAAAADD — 6 hex-digit address, 2 hex-digit value, no scrambling) into a plain 24-bit CPU-bus (address, value) patch. Ported from bsnes's CheatEditor::decodeSNES (ref-proj/bsnes/bsnes/target-bsnes/tools/cheat-editor.cpp) and cross-checked bit-for-bit against Mesen2's independent CheatManager::ConvertFromSnesGameGenie/ConvertFromSnesProActionReplay — both codebases compute an identical address/value for any given code. Unit tests decode real commercial codes drawn from Mesen2's shipped CheatDb.Snes.json as an external-oracle check.
• Application: unlike NES's Game Genie (PRG-ROM read interception), neither SNES format supports a compare byte and neither needs LoROM/HiROM bank translation in the decoder — that stays the Bus's job. A decoded patch is applied by poking WRAM directly via Bus::poke_wram (the same bank/mirror-aware accessor T-81-002's scripting/movie work already built), applied every real frame before it runs. A cheat is host-applied external input (docs/adr/0004), not emulated hardware — with cheats off, or no entries enabled, nothing executes and the determinism contract is untouched.
• Frontend: a Tools → Cheats… window (add/enable/disable/remove codes, shows the decoded address=value), gated #[cfg(feature = "cheats")]. Unlike scripting's mlua, cheat decoding is pure computation with no platform constraint, so this works on native and wasm32 both — verified via clippy on both wasm-winit and wasm-canvas.
• In-memory only for this pass (no per-ROM disk persistence yet) — matches the frontend's own quick-save slot's current in-memory-only maturity level; an honest, documented scope cut, not a silent gap.

Test plan

• cargo test --workspace (357 tests, incl. 8 new rustysnes_core::cheat unit tests against real commercial-code oracles, 4 new rustysnes-frontend::cheats unit tests)
• cargo clippy --workspace --all-targets -- -D warnings
• cargo clippy -p rustysnes-frontend --all-targets --features cheats -- -D warnings and --features cheats,scripting
• cargo clippy -p rustysnes-frontend --target wasm32-unknown-unknown --no-default-features --features wasm-winit,cheats --lib -- -D warnings and wasm-canvas,cheats
• cargo build -p rustysnes-core --target thumbv7em-none-eabihf --no-default-features (no_std gate)
• cargo fmt --check
• RUSTDOCFLAGS="-D warnings" cargo doc --workspace --no-deps and -p rustysnes-frontend --features cheats,scripting
• With cheats off, full default-feature workspace build/test/clippy/fmt/doc verified unaffected

🤖 Generated with Claude Code

[gemini-code-assist]

Code Review

This pull request introduces Game Genie and Pro Action Replay cheat-code support under a new cheats feature flag, adding a decoding module in rustysnes-core and a dedicated UI window in the frontend to manage and apply patches. The review feedback highlights a critical correctness issue: Game Genie codes target ROM addresses rather than WRAM, meaning applying them via poke_wram will have no effect; instead, read operations should be intercepted. Additionally, the reviewer suggests avoiding heap allocations and double passes during decoding, resolving a potential lossy truncation in character casting, preserving specific parsing errors during format dispatch, and suffixing egui widget labels with unique IDs to prevent ID clashes in the cheat list.

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[Copilot]

Pull request overview

Adds SNES cheat-code support (Game Genie + Pro Action Replay) to RustySNES, introducing a core decoder and a feature-gated frontend UI + per-frame WRAM patch application, with accompanying documentation/changelog updates.

Changes:

• Add rustysnes-core::cheat with Game Genie / Pro Action Replay decoding + unit tests.
• Add rustysnes-frontend cheats feature: in-session cheat list, Tools → Cheats… UI, and per-frame Bus::poke_wram application.
• Update sprint tracking, docs/STATUS.md, and CHANGELOG.md to reflect T-81-003 completion and feature details.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
to-dos/phase-8-reach/sprint-1-instrumentation.md	Marks T-81-003 acceptance criteria and sprint checklist as completed with implementation notes.
docs/STATUS.md	Updates frontend status to mention the new cheats feature and where it lives.
crates/rustysnes-frontend/src/ui_shell.rs	Adds Cheats window state and renders a new Cheats UI entry under Tools.
crates/rustysnes-frontend/src/lib.rs	Feature-gates and exports the new cheats module.
crates/rustysnes-frontend/src/cheats.rs	Implements cheat entry parsing/storage and per-frame WRAM application, plus tests.
crates/rustysnes-frontend/src/app.rs	Stores cheat list in Active and applies enabled cheats before each emulated frame.
crates/rustysnes-frontend/Cargo.toml	Introduces the cheats feature flag for the frontend.
crates/rustysnes-core/src/lib.rs	Exposes the new cheat module from core.
crates/rustysnes-core/src/cheat.rs	Implements the decoders + tests for Game Genie and Pro Action Replay.
CHANGELOG.md	Documents the new cheats feature for the upcoming release entry.