database_render/internal/template/hot_reload.go

package template

import (
	"log/slog"
	"os"
	"path/filepath"
	"time"

	"github.com/fsnotify/fsnotify"
)

// HotReloadWatcher watches template files for changes
type HotReloadWatcher struct {
	watcher    *fsnotify.Watcher
	loader     *TemplateLoader
	configPath string
	logger     *slog.Logger
	stopChan   chan struct{}
}

// NewHotReloadWatcher creates a new hot reload watcher
func NewHotReloadWatcher(loader *TemplateLoader, configPath string) (*HotReloadWatcher, error) {
	watcher, err := fsnotify.NewWatcher()
	if err != nil {
		return nil, err
	}

	return &HotReloadWatcher{
		watcher:    watcher,
		loader:     loader,
		configPath: configPath,
		logger:     slog.With("component", "hot_reload"),
		stopChan:   make(chan struct{}),
	}, nil
}

// Start starts watching template files for changes
func (hr *HotReloadWatcher) Start() error {
	// Watch template directories
	directories := []string{
		hr.configPath,
		filepath.Join(hr.configPath, "custom"),
		filepath.Join(hr.configPath, "builtin"),
		filepath.Join(hr.configPath, "custom", "_default"),
	}

	for _, dir := range directories {
		if err := hr.addDirectory(dir); err != nil {
			hr.logger.Warn("failed to watch directory", "dir", dir, "error", err)
			continue
		}
	}

	go hr.watch()

	hr.logger.Info("hot reload watcher started", "directories", directories)
	return nil
}

// addDirectory adds a directory and its subdirectories to the watcher
func (hr *HotReloadWatcher) addDirectory(dir string) error {
	return filepath.Walk(dir, func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return err
		}
		if info.IsDir() {
			return hr.watcher.Add(path)
		}
		return nil
	})
}

// watch watches for file changes and triggers reloads
func (hr *HotReloadWatcher) watch() {
	ticker := time.NewTicker(1 * time.Second)
	defer ticker.Stop()

	debounce := make(map[string]time.Time)

	for {
		select {
		case event := <-hr.watcher.Events:
			if event.Op&fsnotify.Write == fsnotify.Write || event.Op&fsnotify.Create == fsnotify.Create {
				// Debounce rapid file changes
				lastChange := debounce[event.Name]
				if time.Since(lastChange) > 100*time.Millisecond {
					debounce[event.Name] = time.Now()
					hr.handleFileChange(event.Name)
				}
			}
		case err := <-hr.watcher.Errors:
			if err != nil {
				hr.logger.Error("watcher error", "error", err)
			}
		case <-hr.stopChan:
			return
		case <-ticker.C:
			// Cleanup old debounce entries
			now := time.Now()
			for file, lastChange := range debounce {
				if now.Sub(lastChange) > 5*time.Second {
					delete(debounce, file)
				}
			}
		}
	}
}

// handleFileChange handles a file change event
func (hr *HotReloadWatcher) handleFileChange(filePath string) {
	ext := filepath.Ext(filePath)
	if ext != ".html" && ext != ".yaml" && ext != ".yml" {
		return
	}

	hr.logger.Info("detected file change", "file", filePath)

	// Reload templates
	hr.loader.ClearCache()

	// Notify clients via WebSocket or SSE
	hr.notifyClients()
}

// notifyClients notifies connected clients about template changes
func (hr *HotReloadWatcher) notifyClients() {
	// This could be extended to use WebSocket or Server-Sent Events
	// For now, just log the change
	hr.logger.Info("templates reloaded")
}

// Stop stops the hot reload watcher
func (hr *HotReloadWatcher) Stop() {
	close(hr.stopChan)
	hr.watcher.Close()
	hr.logger.Info("hot reload watcher stopped")
}

// AddTemplateDirectory adds a new template directory to watch
func (hr *HotReloadWatcher) AddTemplateDirectory(path string) error {
	return hr.addDirectory(path)
}

// RemoveTemplateDirectory removes a template directory from watch
func (hr *HotReloadWatcher) RemoveTemplateDirectory(path string) error {
	return hr.watcher.Remove(path)
}

// GetWatchedDirectories returns currently watched directories
func (hr *HotReloadWatcher) GetWatchedDirectories() []string {
	return hr.watcher.WatchList()
}

// IsWatching returns whether the watcher is active
func (hr *HotReloadWatcher) IsWatching() bool {
	select {
	case <-hr.stopChan:
		return false
	default:
		return true
	}
}

// ReloadTemplates triggers a manual template reload
func (hr *HotReloadWatcher) ReloadTemplates() {
	hr.loader.ClearCache()
	hr.logger.Info("templates manually reloaded")
}

// GetReloadStats returns hot reload statistics
func (hr *HotReloadWatcher) GetReloadStats() map[string]interface{} {
	watched := hr.GetWatchedDirectories()
	return map[string]interface{}{
		"watched_directories": len(watched),
		"watched_paths":       watched,
		"is_active":           hr.IsWatching(),
	}
}