# Project notes for agents

## Project overview

Station is a persistent-world, RPG-style station simulation inspired by Space
Station 13, with singleplayer and multiplayer. It is built in Rust (edition
2024) with Bevy 0.19 (ECS), bevy_replicon + renet (networking), Rune
(scripting), rsn (data files) and Tiled (maps). Project documentation:
[README.md](README.md).

## Agent rules

- Never push changes unless explicitly told to.
- After changing files, run `cargo fmt --all`. Do not override project
  formatting configuration or invoke a formatter directly on individual files.
- Use conventional commits with the types `feat`, `fix`, `refactor`, `perf`,
  `test`, `docs`, `ci`, `build` and `chore`, scoped by crate or area where
  useful (`feat(server): ...`, `ci(gitea): ...`). Use `!` and a
  `BREAKING CHANGE:` footer for breaking API, save-format or protocol changes.
- End commit messages with a co-author trailer appropriate to the agent and
  product. For example:
  `Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>`.
- Inform the user about commits and other Git changes, including commit
  messages.
- Commit changes after each step unless the user says not to or a `.NOCOMMIT`
  file exists in the repository root.
  - Changes affecting compilation or tests may only be committed after
    `cargo clippy --workspace --all-targets -- -D warnings` and
    `cargo nextest run --workspace` pass.
  - Documentation, CI, editor, and deployment configuration changes do not
    require code checks; validate workflow YAML syntax.
  - Check the current branch before every commit.
- Commit formatting-only changes separately when formatting reformats code
  unrelated to the functional changes.
- Add user-visible changes to the `Unreleased` section of `CHANGELOG.md`
  (Keep a Changelog format).

## Repository structure

- `crates/game_core/`: shared data definitions (`data.rs`), ECS components,
  grid helpers, Tiled loader (`map.rs`) and network protocol (`protocol.rs`).
- `crates/game_server/`: authoritative simulation, Rune engine
  (`scripting.rs`), persistence, and the `game-server` dedicated server binary.
  Integration tests live in `crates/game_server/tests/`.
- `crates/game_client/`: the `game` binary: rendering, UI and input; embeds the
  server for singleplayer and hosting.
- `assets/data/`: item, recipe, building and skill definitions (`.rsn`).
- `assets/scripts/`: Rune scripts (`.rn`), referenced as `"module::function"`.
- `assets/maps/`, `assets/tilesets/`, `assets/sprites/`: Tiled maps and art.
- `tools/gen_placeholder_assets.py`: regenerates placeholder art and the
  example map (generated output is committed).
- `.github/workflows/`, `.gitea/workflows/`: CI for GitHub and Gitea.
- `.config/nextest.toml`: test runner configuration.

Keep `README.md` (run instructions, controls, data formats, script API, Tiled
conventions) in sync with API, configuration, and behavior changes.

## Architecture and constraints

- The server is authoritative. Clients only send protocol events (`Login`,
  `SetMoveDir`, `Interact`, `Craft`, ...) and render replicated state; never
  mutate game state from client code. Singleplayer runs the same server
  plugin in-process, so behavior must not depend on the mode.
- Game rules belong in data files or Rune scripts where possible; Rust code
  provides generic mechanics. Data references and script hooks are validated
  at load time.
- Protocol registration order in `game_core::protocol` must match between
  client and server; changing it breaks compatibility.
- Rune scripts stage changes in `ScriptState`; they are applied after the
  script returns, and a failing script has no effect. Ctx methods need
  `#[rune::function(keep)]`; script-facing numbers are integers.
- Save files (`persistence.rs`, `SAVE_VERSION`) are the source of truth for an
  existing world; the Tiled map only seeds new worlds. Changing saved types
  requires a version bump or a compatible migration.
- Characters are identified by name only (no authentication); renet uses
  unsecure authentication. Do not treat client input as trusted.
- Replicon builds its systems in `Plugin::finish`; headless tests must call
  `app.finish(); app.cleanup();` and update the app once more per round trip.
- Release builds of the client on Windows use the `windows` subsystem (no
  console output).

## Commands

```sh
cargo fmt --all
cargo build --workspace
cargo clippy --workspace --all-targets -- -D warnings
cargo nextest run --workspace
```

Run binaries with `cargo run` (client; `--host`, `--connect`) and
`cargo run -p game_server --bin game-server`. The Windows client can be
cross-built with `cargo build --release -p game_client --target
x86_64-pc-windows-gnu` (needs MinGW). Running the client requires a Vulkan or
GL capable GPU or a software driver such as lavapipe.

## Conventions

- Write comments for *why*, not *what*: invariants, non-obvious constraints, workarounds (with the reason or a link),
  and units/timebases where the type doesn't say. Never restate what the code does.
- Before committing, review every comment in your diff (`git diff`): delete those that restate the code or describe
  the change itself (e.g. "now uses X instead of Y"; that belongs in the commit message), and shorten the rest to one line where possible.
- Comment only code that needs clarification; keep comments short.
- Follow the repository's formatting, lint, error-handling, logging, and
  dependency-management conventions.
- Prefer existing helpers and patterns; keep changes focused and surface
  failures explicitly.
- Preserve existing line endings when editing files that use non-default line
  endings.
- Do not add tests in locations the project's normal test commands do not
  discover.

## Code reviews

For reviews of commits, branches, diffs, or specific files, report every
finding as an entry in a list with this shape:

- **Location:** `file:line` (use a range such as `file:120-146` when the
  finding spans several lines)
- **Category:** one of `Blocking`, `FYI`, or `Nit` (use another category, such
  as `Question`, only when none of those fit)
- **Comment:** the concrete issue or risk and, when claiming a defect, its
  failure scenario rather than only an abstract concern

Order findings by severity, with `Blocking` first. Use `Blocking` for defects,
unbounded resource use, or policy violations that must change before merge;
use `FYI` for design consequences and risks worth a conscious decision; use
`Nit` for style and cleanliness. Verify findings against the code and run the
relevant lint and test commands before reporting them. Say when a finding is a
possibility rather than a confirmed defect.