package main

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

	"github.com/fsnotify/fsnotify"
)

// TODO flesh out event handling with an eye towards eventual sampling

func initHomeWatcher() (*fsnotify.Watcher, error) {
	fmt.Fprintf(os.Stderr, "setting up home watcher...\n")
	watcher, err := fsnotify.NewWatcher()
	if err != nil {
		return nil, err
	}

	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("/home", username)
		addHome(watcher, home)
	}

	return watcher, nil
}

func addHome(watcher *fsnotify.Watcher, homePath string) error {
	fileCount := 0
	filepath.Walk(homePath, 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 = watcher.Add(path)
		if err != nil && err.Error() != "permission denied" && err.Error() != "no such file or directory" {
			fmt.Printf("%#v\n", err)
			fmt.Println("Died at ", fileCount)
			fmt.Printf("%#v\n", info)
			panic(err.Error())
		} else {
			fmt.Fprintf(os.Stderr, "watching %s\n", path)
		}
		return nil
	})

	return nil
}

func watchHomes(watcher *fsnotify.Watcher) {
	fmt.Fprintf(os.Stderr, "starting poll\n")
	for {
		select {
		case event, ok := <-watcher.Events:
			if !ok {
				return
			}
			log.Println("event:", event)
			if event.Op&fsnotify.Write == fsnotify.Write {
				log.Println("modified file:", event.Name)
			}
		case err, ok := <-watcher.Errors:
			if !ok {
				return
			}
			log.Println("error:", err)
		}
	}
}

func cli(args []string) int {
	fmt.Fprintf(os.Stderr, "starting\n")
	watcher, err := initHomeWatcher()
	fmt.Fprintf(os.Stderr, "watcher initialized\n")
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to create watcher: %w\n", err)
		return 1
	}
	defer watcher.Close()

	// TODO have an event bus to write to
	// TODO what is this done for do i need this done
	done := make(chan bool)
	go watchHomes(watcher)
	<-done

	return 0
}

func main() {
	os.Exit(cli(os.Args))
}