# CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

## Build, Test, and Development Commands

### Core workflows
- **Build library**: `cargo build` (debug) or `cargo build --release` (optimized)
- **Build FFI shared library**: `cargo build --release --features ffi` (generates C header via cbindgen)
- **Run tests**: `cargo test` (all tests) or `cargo test --test <name>` (single integration test file)
- **Run examples**: `cargo run --example usage`, `cargo run --example patient`, `cargo run --example tracing_demo`
- **Run demo monitor**: `cargo run --example demo_app --features demo-monitor`
- **Benchmarks**: `cargo bench` (runs Criterion benchmarks; results in `target/criterion/`)
- **Format code**: `cargo fmt --all` (run before committing)
- **Lint**: `cargo clippy --all-targets -- -D warnings` (enforce before committing)

### Packaging binary distributions
- **Linux/macOS**: Run `../scripts/package.sh [target-triple]` from `medicallib_rust/`
- **Windows**: Run `..\scripts\package.ps1 [target-triple]` from `medicallib_rust\`
- Artifacts placed in `medicallib_rust/dist/` as both `.tar.gz` and `.zip`

## Architecture Overview

### Core structure
- **`src/lib.rs`**: Crate facade re-exporting public API (`Patient`, `Organ`, types, errors)
- **`src/types.rs`**: Domain types (`Blood`, `BloodPressure`, `OrganType`, `VitalSign`)
- **`src/error.rs`**: `MedicalError` enum using `thiserror`
- **`src/patient.rs`**: `Patient` struct orchestrating `Vec<Box<dyn Organ>>` with inter-organ signal routing
- **`src/organs/mod.rs`**: `Organ` trait and `OrganInfo`; per-organ modules (heart, lungs, brain, etc.)
- **`src/ekg/mod.rs`**: EKG monitoring system with configurable leads
- **`src/ffi.rs`**: C-compatible FFI layer (feature `ffi`); header auto-generated to `ffi/medicallib.h` by `build.rs` using cbindgen

### Organ system
- Each organ module implements the `Organ` trait (`id()`, `organ_type()`, `update(dt)`, `summary()`, `as_any()`, `as_any_mut()`)
- `Patient` owns organs as trait objects, calls `update()` each tick, and routes signals between organs
- Inter-organ communication examples:
  - Lungs SpO2 → Heart rate adjustment
  - Kidneys GFR → Bladder volume accumulation
  - Brain autonomic signals → Heart rate variability and respiratory drive
  - Bloodstream perfusion → multiple organ metabolic states

### FFI boundary
- **Opaque handle**: `MLPatient` pointer to boxed `Patient`
- **Functions**: `ml_patient_new/free/update`, `ml_patient_summary`, `ml_patient_organ_summary`, `medicallib_bmi`
- **Memory**: All returned strings allocated by Rust must be freed via `ml_string_free`
- **Build script**: `build.rs` runs cbindgen when `--features ffi` is enabled, updates `ffi/medicallib.h` if changed
- **Validation**: Any change to `src/ffi.rs` must be tested against `examples/c/ffi_example.c`

### Testing and benchmarks
- **Integration tests**: `tests/` directory (e.g., `tests/patient.rs`, `tests/ffi.rs`)
- **Benchmarks**: `benches/heart.rs` uses Criterion; compare results across runs for performance regressions
- **Unit tests**: In-module `#[cfg(test)]` blocks for focused invariants

## Important Development Notes

### When modifying FFI
1. Edit `src/ffi.rs`
2. Run `cargo build --features ffi` to regenerate `ffi/medicallib.h` via cbindgen
3. Verify C example still compiles: `gcc -o ffi_example examples/c/ffi_example.c -L target/release -lmedicallib_rust`
4. Update `cbindgen.toml` only if header generation settings need adjustment

### Adding new organs
1. Create module in `src/organs/<organ_name>.rs`
2. Define struct implementing `Organ` trait
3. Add module declaration and public re-export in `src/organs/mod.rs`
4. Update `Patient` signal structs and `couple_organs()` method if inter-organ communication needed
5. Add corresponding `OrganType` variant in `src/types.rs`
6. Update FFI constants in `src/ffi.rs` if organ needs FFI exposure

### Cargo features
- **`serde`**: Enables serialization on public types
- **`ffi`**: Exposes C ABI; triggers cbindgen in `build.rs`
- **`demo-monitor`**: Required for `demo_app` example with colorized dashboard

### CI workflows
- GitHub Actions: `.github/workflows/ci.yml`
- Gitea Actions: `.gitea/workflows/ci.yml`
- Both run tests, clippy, formatting checks, and cross-platform builds

## Key Patterns

### Patient simulation loop
```rust
let mut patient = Patient::new("case-01")?.initialize_default();
loop {
    patient.update(dt_seconds);
    let summary = patient.patient_summary();
    // Process vitals...
}
```

### Accessing specific organ
```rust
let heart = patient.find_organ_typed::<Heart>()?;
println!("HR: {}", heart.heart_rate_bpm());
```

### Inter-organ signals
Patient's `couple_organs()` method reads state from one organ (e.g., `Lungs::spo2_pct()`) and injects it into another (e.g., `Heart::receive_spo2_signal()`). Add new signal fields to the internal `*Signals` structs in `patient.rs` when coupling new organ interactions.