package main

import (
	"bufio"
	"bytes"
	"fmt"
	"log"
	"os"
	"os/exec"
	"path"
	"path/filepath"
	"regexp"
	"strings"

	"github.com/fsnotify/fsnotify"
)

type Watcher interface {
	AddDirectory(string) error
	Watch()
	Close()
	Root() string
}

type HomeWatcher struct {
	watcher *fsnotify.Watcher
	root    string
	raw     chan Event
}

func NewHomeWatcher(rawEvents chan Event) (Watcher, error) {
	watcher, err := fsnotify.NewWatcher()
	if err != nil {
		return nil, err
	}

	hw := &HomeWatcher{
		watcher: watcher,
		root:    "/home",
		raw:     rawEvents,
	}

	out, err := exec.Command("sh", "-c", "stats | jq .active_users[] | tr -d '\"'").Output()
	if err != nil {
		return nil, fmt.Errorf("failed to call and process stats: %w", err)
	}

	scanner := bufio.NewScanner(bytes.NewReader(out))
	for scanner.Scan() {
		username := strings.TrimSpace(scanner.Text())
		home := filepath.Join(hw.Root(), username)
		if err := hw.AddDirectory(home); err != nil {
			return nil, err
		}
	}

	return hw, nil
}

func (hw *HomeWatcher) AddDirectory(path string) error {
	fileCount := 0
	filepath.Walk(path, func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return nil
		}
		if info.IsDir() && strings.HasPrefix(info.Name(), ".") {
			return filepath.SkipDir
		}
		fileCount++
		if info.Mode()&os.ModeSymlink != 0 {
			return nil
		}

		err = hw.watcher.Add(path)
		if err != nil && err.Error() != "permission denied" && err.Error() != "no such file or directory" {
			return fmt.Errorf("died at file %d. info: %#v error: %w\n", fileCount, info, err)
		}

		log.Printf("watching %s\n", path)
		return nil
	})

	return nil
}

func (hw *HomeWatcher) Root() string {
	return hw.root
}

func (hw *HomeWatcher) Close() {
	hw.watcher.Close()
}

func (hw *HomeWatcher) Watch() {
	unre := regexp.MustCompile("^/home/([^/]+)/.*$")
	for {
		select {
		case event, ok := <-hw.watcher.Events:
			if !ok {
				return
			}
			matches := unre.FindStringSubmatch(event.Name)
			if matches == nil {
				log.Printf("could not extract username: %s\n", event)
			}
			un := matches[1]
			hw.raw <- Event{
				Username: un,
				Type:     eventHomeActivity,
				Flavor:   fmt.Sprintf("%s is knocking about in %s", un, path.Dir(event.Name)),
			}
			// event.Name is filepath
			log.Println("event:", event)
			fmt.Printf("DBG %#v\n", event)
			if event.Op&fsnotify.Write == fsnotify.Write {
				log.Println("modified file:", event.Name)
			}
		case err, ok := <-hw.watcher.Errors:
			if !ok {
				return
			}
			log.Println("error:", err)
		}
	}
}