# Hot-Reload Dev Script Design (dev.sh)

## 1. Overview

`dev.sh` is a development script that starts all backend microservices with file-watching hot-reload. When any `.go` file changes in a service's directory, only that specific service is recompiled and restarted.

## 2. Architecture

```
dev.sh
├── Load .env (same as start.sh)
├── Start all services in dependency order (background)
└── Run multiple concurrent file watchers (background)
    ├── watcher(gateway)        → monitors gateway/         → restart gateway
    ├── watcher(userService)    → monitors services/userService/    → restart userService
    ├── watcher(assetService)   → monitors services/assetService/   → restart assetService
    ├── watcher(socialService)  → monitors services/socialService/  → restart socialService
    ├── watcher(galleryService) → monitors services/galleryService/ → restart galleryService
    └── watcher(activityService) → monitors services/activityService/ → restart activityService
```

## 3. Service Startup Order

Same as `start.sh`:
1. userService (port 20000)
2. assetService (port 20003)
3. socialService (port 20002)
4. galleryService (port 20004)
5. activityService (port 20005)
6. gateway (port 8080)

## 4. Watcher Behavior

For each service:
- **Monitor**: `<service_dir>/**/*.go`
- **Trigger**: Any `.go` file create/modify/write event
- **Debounce**: 300ms cooldown — after a restart is triggered, ignore further events for 300ms to avoid rapid successive rebuilds.
- **Action** (executed inside service's own module directory, matching `start.sh`):
  1. Recompile: `cd <service_dir> && go build -o <binary> .`
  2. **Build-failure safety**: If build fails, log the error and keep the old process running
  3. Only after successful build: kill the running service process
  4. Restart with same arguments as `start.sh`
  5. Log the event to console (cyan color)

## 5. Dependencies

- **Mac**: `fswatch` (install via `brew install fswatch`)
- **Linux**: `inotifywait` (install via package manager)

If the required tool is not installed, the script prints a clear installation instruction and exits.

## 6. Signal Handling

- `Ctrl+C` / SIGINT / SIGTERM: Use a `trap` to catch signals — stop all services and watchers, then exit
- On exit: Kill all service processes and watcher processes in reverse startup order (gateway first, then services)

## 7. Logging

- Each service logs to `/tmp/<service_name>.log` (same as start.sh)
- Console output shows which file changed and which service was restarted
- Hot-reload events are printed in distinct color (cyan)

## 8. File Structure

```
backend/
├── dev.sh          # Main dev script (new)
└── start.sh        # Production start script (existing)
```

## 9. Edge Cases

- **Build failure**: Old process keeps running; error is logged to console and `/tmp/<service>.log`
- **Watched directory missing**: Script exits with error if monitored directory does not exist
- **Tool not found**: Script prints installation instructions and exits
- **Rapid file changes**: 300ms debounce prevents immediate successive rebuilds; each batch of changes triggers at most one restart

## 10. No Changes to Existing Files

`dev.sh` does not modify any existing files. It only reads `start.sh` for reference and adds a new file.