package watchers

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

	"git.sharkk.net/Sky/Moonshark/core/logger"
	"git.sharkk.net/Sky/Moonshark/core/runner"
)

const (
	defaultPollInterval = 1 * time.Second
	defaultDebounceTime = 300 * time.Millisecond
)

// FileInfo stores metadata about a file for change detection
type FileInfo struct {
	ModTime time.Time
	Size    int64
	IsDir   bool
}

// FileWatcher watches a single directory for changes
type FileWatcher struct {
	dir           string
	callback      func() error
	log           *logger.Logger
	files         map[string]FileInfo
	done          chan struct{}
	ticker        *time.Ticker
	debounceTime  time.Duration
	debouncing    bool
	debounceTimer *time.Timer
	debounceMu    sync.Mutex
	filesMu       sync.RWMutex
	wg            sync.WaitGroup
}

// Registry for Lua runners to notify about .lua file changes
var (
	luaRunners   = make([]*runner.LuaRunner, 0)
	runnersMutex sync.RWMutex
)

// NewFileWatcher creates a new file watcher for a directory
func NewFileWatcher(dir string, callback func() error, log *logger.Logger) (*FileWatcher, error) {
	w := &FileWatcher{
		dir:          dir,
		callback:     callback,
		log:          log,
		files:        make(map[string]FileInfo),
		done:         make(chan struct{}),
		debounceTime: defaultDebounceTime,
	}

	// Perform initial scan
	if err := w.scanDirectory(); err != nil {
		return nil, err
	}

	// Start the watcher
	w.ticker = time.NewTicker(defaultPollInterval)
	w.wg.Add(1)
	go w.watchLoop()

	log.Info("Started watching directory: %s", dir)
	return w, nil
}

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

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

	return filepath.Walk(w.dir, func(path string, info os.FileInfo, err error) error {
		if err != nil {
			w.log.Warning("[Watcher] [%s] Error accessing path %s: %v", w.dir, path, err)
			return nil // Continue with other files
		}

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

		return nil
	})
}

// watchLoop is the polling loop that checks for changes
func (w *FileWatcher) watchLoop() {
	defer w.wg.Done()

	w.log.Debug("[Watcher] [%s] Starting watch loop", w.dir)

	for {
		select {
		case <-w.ticker.C:
			changedFiles, err := w.checkForChanges()
			if err != nil {
				w.log.Error("[Watcher] [%s] Error checking for changes: %v", w.dir, err)
				continue
			}

			if len(changedFiles) > 0 {
				w.log.Debug("[Watcher] [%s] Detected %d changed files", w.dir, len(changedFiles))

				// Notify Lua runners about .lua file changes
				for _, file := range changedFiles {
					if strings.HasSuffix(file, ".lua") {
						w.notifyLuaRunners(file)
					}
				}

				// Trigger the callback with debouncing
				w.triggerCallback()
			}

		case <-w.done:
			w.log.Debug("[Watcher] [%s] Watch loop stopped", w.dir)
			return
		}
	}
}

// checkForChanges detects file changes and returns a list of changed files
func (w *FileWatcher) checkForChanges() ([]string, error) {
	changedFiles := []string{}

	// Get current state
	currentFiles := make(map[string]FileInfo)

	err := filepath.Walk(w.dir, func(path string, info os.FileInfo, err error) error {
		if err != nil {
			// File might have been deleted between directory read and stat
			return nil
		}

		currentFiles[path] = FileInfo{
			ModTime: info.ModTime(),
			Size:    info.Size(),
			IsDir:   info.IsDir(),
		}

		return nil
	})

	if err != nil {
		return changedFiles, fmt.Errorf("error walking directory: %w", err)
	}

	// Compare with previous state
	w.filesMu.RLock()
	previousFiles := w.files
	w.filesMu.RUnlock()

	// Check for new or modified files
	for path, currentInfo := range currentFiles {
		prevInfo, exists := previousFiles[path]

		if !exists {
			// New file
			w.log.Debug("[Watcher] [%s] New file: %s", w.dir, path)
			changedFiles = append(changedFiles, path)
		} else if currentInfo.ModTime != prevInfo.ModTime || currentInfo.Size != prevInfo.Size {
			// Modified file
			w.log.Debug("[Watcher] [%s] Modified file: %s", w.dir, path)
			changedFiles = append(changedFiles, path)
		}
	}

	// Check for deleted files
	for path, info := range previousFiles {
		if _, exists := currentFiles[path]; !exists {
			// File deleted
			w.log.Debug("[Watcher] [%s] Deleted file: %s", w.dir, path)
			if !info.IsDir { // Only add files, not directories
				changedFiles = append(changedFiles, path)
			}
		}
	}

	// Update internal file list if changes were found
	if len(changedFiles) > 0 {
		w.filesMu.Lock()
		w.files = currentFiles
		w.filesMu.Unlock()
	}

	return changedFiles, nil
}

// triggerCallback executes the callback with debouncing
func (w *FileWatcher) triggerCallback() {
	w.debounceMu.Lock()
	defer w.debounceMu.Unlock()

	w.log.Debug("[Watcher] [%s] Preparing to trigger callback", w.dir)

	if w.debouncing {
		// Reset timer if already debouncing
		if w.debounceTimer != nil {
			w.log.Debug("[Watcher] [%s] Resetting existing debounce timer", w.dir)
			w.debounceTimer.Stop()
		}
	} else {
		w.log.Debug("[Watcher] [%s] Starting debounce timer (%v)", w.dir, w.debounceTime)
		w.debouncing = true
	}

	w.debounceTimer = time.AfterFunc(w.debounceTime, func() {
		w.log.Debug("[Watcher] [%s] Executing callback", w.dir)

		if err := w.callback(); err != nil {
			w.log.Error("[Watcher] [%s] Callback error: %v", w.dir, err)
		} else {
			w.log.Debug("[Watcher] [%s] Callback executed successfully", w.dir)
		}

		// Reset debouncing state
		w.debounceMu.Lock()
		w.debouncing = false
		w.debounceMu.Unlock()
	})
}

// Close stops the file watcher
func (w *FileWatcher) Close() error {
	w.log.Debug("[Watcher] [%s] Stopping watcher", w.dir)
	close(w.done)
	if w.ticker != nil {
		w.ticker.Stop()
	}
	w.wg.Wait()
	return nil
}

// notifyLuaRunners notifies all registered Lua runners about a .lua file change
func (w *FileWatcher) notifyLuaRunners(file string) {
	runnersMutex.RLock()
	defer runnersMutex.RUnlock()

	for _, r := range luaRunners {
		w.log.Debug("[Watcher] [%s] Notifying Lua runner about change to %s", w.dir, file)
		r.NotifyFileChanged(file)
	}
}