package watcher

import (
	"fmt"
	"io/fs"
	"os"
	"path/filepath"
	"slices"

	"github.com/fsnotify/fsnotify"

	"alin.ovh/erl/ignore"
)

type Event fsnotify.Event

type Watcher interface {
	AddRecursive(pathname string) error
	Monitor() (<-chan Event, <-chan error)
	WatchList() []string
	Remove(pathname string) error
	Close() error
}

// FSWatcher implements the Watcher interface using fsnotify.
type FSWatcher struct {
	watcher fsnotify.Watcher
	filter  ignore.Filter
}

type Options struct {
	Filter ignore.Filter
}

var IgnoredDirs = []string{
	".git",
}

func New(options Options) (*FSWatcher, error) {
	watcher, err := fsnotify.NewWatcher()
	if err != nil {
		return nil, fmt.Errorf("failed to create watcher: %v", err)
	}

	return &FSWatcher{
		watcher: *watcher,
		filter:  options.Filter,
	}, nil
}

func (w *FSWatcher) AddRecursive(pathname string) error {
	stat, err := os.Stat(pathname)
	if err != nil {
		return fmt.Errorf("failed to stat %s: %v", pathname, err)
	}
	if !stat.IsDir() {
		pathname = filepath.Dir(pathname)
	}

	return w.addDirRecursive(pathname)
}

func (w *FSWatcher) Remove(pathname string) error {
	return w.watcher.Remove(pathname)
}

func (w *FSWatcher) Monitor() (<-chan Event, <-chan error) {
	events := make(chan Event)
	errors := make(chan error)

	go func() {
		for {
			select {
			case event, ok := <-w.watcher.Events:
				if ok && event.Name != "" && !w.filter.Ignored(event.Name) {
					events <- Event(event)
				}
			case err := <-w.watcher.Errors:
				errors <- err
			}
		}
	}()

	return events, errors
}

func (w *FSWatcher) WatchList() []string {
	return w.watcher.WatchList()
}

func (w *FSWatcher) Close() error {
	return w.watcher.Close()
}

func (w *FSWatcher) addDirRecursive(dir string) error {
	err := filepath.Walk(dir, func(path string, entry fs.FileInfo, err error) error {
		if err != nil {
			return err
		}

		if entry.IsDir() {
			if slices.Contains(IgnoredDirs, entry.Name()) || w.filter.Ignored(path) {
				return fs.SkipDir
			}

			err = w.watcher.Add(path)
			if err != nil {
				return fmt.Errorf("failed to add directory to watcher: %v", err)
			}
		}

		return nil
	})
	if err != nil {
		return fmt.Errorf("failed to walk directory: %v", err)
	}

	return nil
}