package watchers

import (
	"fmt"
	"os"
	"path/filepath"
	"sync"
	"time"

	"Moonshark/logger"
)

// Default debounce time between detected change and callback
const defaultDebounceTime = 300 * time.Millisecond

// FileChange represents a detected file change
type FileChange struct {
	Path      string
	IsNew     bool
	IsDeleted bool
}

// FileInfo stores minimal metadata about a file for change detection
type FileInfo struct {
	ModTime time.Time
}

// DirectoryWatcher watches a specific directory for changes
type DirectoryWatcher struct {
	// Directory to watch
	dir string

	// Map of file paths to their metadata
	files   map[string]FileInfo
	filesMu sync.RWMutex

	// Track changed files during a check cycle
	changedFiles []FileChange

	// Enhanced callback that receives changes (optional)
	enhancedCallback func([]FileChange) error

	// Configuration
	callback     func() error
	debounceTime time.Duration
	recursive    bool

	// Debounce timer
	debounceTimer *time.Timer
	debouncing    bool
	debounceMu    sync.Mutex

	// Error tracking
	consecutiveErrors int
	lastError         error
}

// DirectoryWatcherConfig contains configuration for a directory watcher
type DirectoryWatcherConfig struct {
	Dir              string                   // Directory to watch
	Callback         func() error             // Callback function to call when changes are detected
	DebounceTime     time.Duration            // Debounce time (0 means use default)
	Recursive        bool                     // Recursive watching (watch subdirectories)
	EnhancedCallback func([]FileChange) error // Enhanced callback that receives file changes
}

// scanDirectory builds the initial file list
func (w *DirectoryWatcher) scanDirectory() error {
	w.filesMu.Lock()
	defer w.filesMu.Unlock()

	w.files = make(map[string]FileInfo)

	return filepath.Walk(w.dir, func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return nil // Skip files with errors
		}

		if !w.recursive && info.IsDir() && path != w.dir {
			return filepath.SkipDir
		}

		w.files[path] = FileInfo{
			ModTime: info.ModTime(),
		}

		return nil
	})
}

// checkForChanges detects if any files have been added, modified, or deleted
func (w *DirectoryWatcher) checkForChanges() (bool, error) {
	w.filesMu.RLock()
	prevFileCount := len(w.files)
	w.filesMu.RUnlock()

	newFiles := make(map[string]FileInfo)
	changed := false
	w.changedFiles = nil // Reset changed files list

	err := filepath.Walk(w.dir, func(path string, info os.FileInfo, err error) error {
		// Skip errors
		if err != nil {
			return nil
		}

		if !w.recursive && info.IsDir() && path != w.dir {
			return filepath.SkipDir
		}

		currentInfo := FileInfo{
			ModTime: info.ModTime(),
		}
		newFiles[path] = currentInfo

		w.filesMu.RLock()
		prevInfo, exists := w.files[path]
		w.filesMu.RUnlock()

		if !exists {
			changed = true
			w.changedFiles = append(w.changedFiles, FileChange{
				Path:  path,
				IsNew: true,
			})
			w.logDebug("File added: %s", path)
		} else if currentInfo.ModTime != prevInfo.ModTime {
			changed = true
			w.changedFiles = append(w.changedFiles, FileChange{
				Path: path,
			})
			w.logDebug("File changed: %s", path)
		}

		return nil
	})

	// Only check for deleted files if needed
	if err == nil && (!changed && len(newFiles) != prevFileCount) {
		w.filesMu.RLock()
		for path := range w.files {
			if _, exists := newFiles[path]; !exists {
				changed = true
				w.changedFiles = append(w.changedFiles, FileChange{
					Path:      path,
					IsDeleted: true,
				})
				w.logDebug("File deleted: %s", path)
				break // We already know changes happened
			}
		}
		w.filesMu.RUnlock()
	}

	if changed {
		w.filesMu.Lock()
		w.files = newFiles
		w.filesMu.Unlock()
	}

	return changed, err
}

// notifyChange triggers the callback with debouncing
func (w *DirectoryWatcher) notifyChange() {
	w.debounceMu.Lock()
	defer w.debounceMu.Unlock()

	if w.debouncing {
		if w.debounceTimer != nil {
			w.debounceTimer.Stop()
		}
	} else {
		w.debouncing = true
	}

	// Make a copy of changed files to avoid race conditions
	changedFilesCopy := make([]FileChange, len(w.changedFiles))
	copy(changedFilesCopy, w.changedFiles)

	w.debounceTimer = time.AfterFunc(w.debounceTime, func() {
		var err error
		if w.enhancedCallback != nil {
			err = w.enhancedCallback(changedFilesCopy)
		} else if w.callback != nil {
			err = w.callback()
		}

		if err != nil {
			w.logError("Callback error: %v", err)
		}

		w.debounceMu.Lock()
		w.debouncing = false
		w.debounceMu.Unlock()
	})
}

// logDebug logs a debug message with the watcher's directory prefix
func (w *DirectoryWatcher) logDebug(format string, args ...any) {
	logger.Debugf("[Watcher] [%s] %s", w.dir, fmt.Sprintf(format, args...))
}

// logError logs an error message with the watcher's directory prefix
func (w *DirectoryWatcher) logError(format string, args ...any) {
	logger.Errorf("[Watcher] [%s] %s", w.dir, fmt.Sprintf(format, args...))
}

// GetDir gets the DirectoryWatcher's current directory
func (w *DirectoryWatcher) GetDir() string {
	return w.dir
}