feat(IIO)!: BREAKING CHANGE - Callback-based message dispatch
## Breaking Change
IIO API redesigned from manual pull+if-forest to callback dispatch.
All modules must update their subscribe() calls to pass handlers.
### Before (OLD API)
```cpp
io->subscribe("input:mouse");
void process(...) {
while (io->hasMessages()) {
auto msg = io->pullMessage();
if (msg.topic == "input:mouse") {
handleMouse(msg);
} else if (msg.topic == "input:keyboard") {
handleKeyboard(msg);
}
}
}
```
### After (NEW API)
```cpp
io->subscribe("input:mouse", [this](const Message& msg) {
handleMouse(msg);
});
void process(...) {
while (io->hasMessages()) {
io->pullAndDispatch(); // Callbacks invoked automatically
}
}
```
## Changes
**Core API (include/grove/IIO.h)**
- Added: `using MessageHandler = std::function<void(const Message&)>`
- Changed: `subscribe()` now requires `MessageHandler` callback parameter
- Changed: `subscribeLowFreq()` now requires `MessageHandler` callback
- Removed: `pullMessage()`
- Added: `pullAndDispatch()` - pulls and auto-dispatches to handlers
**Implementation (src/IntraIO.cpp)**
- Store callbacks in `Subscription.handler`
- `pullAndDispatch()` matches topic against ALL subscriptions (not just first)
- Fixed: Regex pattern compilation supports both wildcards (*) and regex (.*)
- Performance: ~1000 msg/s throughput (unchanged from before)
**Files Updated**
- 31 test/module files migrated to callback API (via parallel agents)
- 8 documentation files updated (DEVELOPER_GUIDE, USER_GUIDE, module READMEs)
## Bugs Fixed During Migration
1. **pullAndDispatch() early return bug**: Was only calling FIRST matching handler
- Fix: Loop through ALL subscriptions, invoke all matching handlers
2. **Regex pattern compilation bug**: Pattern "player:.*" failed to match
- Fix: Detect ".*" in pattern → use as regex, otherwise escape and convert wildcards
## Testing
✅ test_11_io_system: PASSED (IIO pub/sub, pattern matching, batching)
✅ test_threaded_module_system: 6/6 PASSED
✅ test_threaded_stress: 5/5 PASSED (50 modules, 100x reload, concurrent ops)
✅ test_12_datanode: PASSED
✅ 10 TopicTree scenarios: 10/10 PASSED
✅ benchmark_e2e: ~1000 msg/s throughput
Total: 23+ tests passing
## Performance Impact
No performance regression from callback dispatch:
- IIO throughput: ~1000 msg/s (same as before)
- ThreadedModuleSystem: Speedup ~1.0x (barrier pattern expected)
## Migration Guide
For all modules using IIO:
1. Update subscribe() calls to include handler lambda
2. Replace pullMessage() loops with pullAndDispatch()
3. Move topic-specific logic from if-forest into callbacks
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
StillHammer
1b7703f07b