# WASM Support for foundation_nostd

## Overview

The `foundation_nostd` crate fully supports compilation to WebAssembly (WASM) targets, specifically `wasm32-unknown-unknown`. This enables the use of synchronization primitives in web environments.

## Building for WASM

### Prerequisites

Install the WASM target:
```bash
rustup target add wasm32-unknown-unknown
```

### Building

Build the library for WASM:
```bash
cargo build --package foundation_nostd --target wasm32-unknown-unknown --no-default-features
```

Or use the Makefile:
```bash
make build-wasm
```

### Testing

Build WASM tests (compile-time verification):
```bash
make test-wasm-build
```

**Note**: Runtime WASM testing requires `wasm-bindgen-test-runner` setup, which is not included in this basic configuration.

## WASM Limitations

### Threading

WASM has limited threading support:
- **Single-threaded**: By default, WASM runs in a single-threaded environment
- **No OS threads**: `std::thread::spawn()` is not available in `wasm32-unknown-unknown`
- **No parking**: Thread parking/unparking primitives don't exist

### CondVar Behavior in WASM

When compiled for WASM with `no_std`:
- **Spin-wait implementation**: Uses atomic operations with spin-waiting
- **Single-threaded safe**: All operations work correctly in single-threaded contexts
- **Timeout support**: `wait_timeout` functions work using WASM's timing APIs
- **Notify operations**: `notify_one()` and `notify_all()` are no-ops in single-threaded WASM but won't panic

## API Compatibility

All CondVar APIs are available in WASM:

| API | WASM Support | Notes |
|-----|--------------|-------|
| `CondVar::new()` | ✅ | Creates a new condition variable |
| `wait()` | ✅ | Single-threaded: returns immediately if no waiters |
| `wait_while()` | ✅ | Predicate-based waiting |
| `wait_timeout()` | ✅ | Uses WASM timing APIs |
| `wait_timeout_while()` | ✅ | Combines timeout and predicate |
| `notify_one()` | ✅ | No-op in single-threaded, but safe |
| `notify_all()` | ✅ | No-op in single-threaded, but safe |

## Example Usage in WASM

```rust
use foundation_nostd::primitives::{CondVar, CondVarMutex};
use std::time::Duration;

// Create a mutex and condvar
let mutex = CondVarMutex::new(false);
let condvar = CondVar::new();

// Lock and wait with timeout
let guard = mutex.lock().unwrap();
let (guard, result) = condvar
    .wait_timeout(guard, Duration::from_millis(100))
    .unwrap();

if result.timed_out() {
    // Timeout occurred (expected in single-threaded WASM)
}
```

## Testing Strategy for WASM

Since WASM runtime testing requires additional setup, the current testing strategy focuses on:

1. **Compile-time verification**: Ensure all code compiles for WASM target
2. **API compatibility**: Verify all APIs are available and callable
3. **Single-threaded correctness**: Test that operations work in single-threaded contexts
4. **Timeout accuracy**: Verify timeout durations work correctly

## Foundation Testing Crate

**Note**: The `foundation_testing` crate cannot be compiled for WASM because it depends on `criterion` (benchmarking), which requires `rayon` for parallelism. This is a fundamental limitation of the WASM target.

For WASM-specific testing, use:
- Unit tests in `foundation_nostd` (compile with `--target wasm32-unknown-unknown --tests`)
- Manual integration testing in web environments
- `wasm-bindgen-test` for browser-based testing (requires additional setup)

## Future Enhancements

Potential improvements for WASM support:

1. **wasm-bindgen-test integration**: Set up automated browser-based testing
2. **Web Workers support**: Test multi-threaded WASM with SharedArrayBuffer
3. **Performance benchmarks**: WASM-specific performance measurements
4. **Documentation examples**: Live code examples in web documentation

## Additional Resources

- [WebAssembly Threading Proposal](https://github.com/WebAssembly/threads)
- [wasm-bindgen Documentation](https://rustwasm.github.io/docs/wasm-bindgen/)
- [Rust WASM Book](https://rustwasm.github.io/docs/book/)

---

**Status**: WASM compilation and basic functionality verified ✅
