package clientinfo

import (
	"os"
	"sync"

	"github.com/fsnotify/fsnotify"
	"github.com/jaytaylor/go-hostsfile"

	"github.com/Control-D-Inc/ctrld"
)

// hostsFile provides client discovery functionality using system hosts file.
type hostsFile struct {
	watcher *fsnotify.Watcher
	mu      sync.Mutex
	m       map[string][]string
}

// init performs initialization works, which is necessary before hostsFile can be fully operated.
func (hf *hostsFile) init() error {
	watcher, err := fsnotify.NewWatcher()
	if err != nil {
		return err
	}
	hf.watcher = watcher
	if err := hf.watcher.Add(hostsfile.HostsPath); err != nil {
		return err
	}
	m, err := hostsfile.ParseHosts(hostsfile.ReadHostsFile())
	if err != nil {
		return err
	}
	hf.mu.Lock()
	hf.m = m
	hf.mu.Unlock()
	return nil
}

// refresh reloads hosts file entries.
func (hf *hostsFile) refresh() error {
	m, err := hostsfile.ParseHosts(hostsfile.ReadHostsFile())
	if err != nil {
		return err
	}
	hf.mu.Lock()
	hf.m = m
	hf.mu.Unlock()
	return nil
}

// watchChanges watches and updates hosts file data if any changes happens.
func (hf *hostsFile) watchChanges() {
	if hf.watcher == nil {
		return
	}
	for {
		select {
		case event, ok := <-hf.watcher.Events:
			if !ok {
				return
			}
			if event.Has(fsnotify.Write) || event.Has(fsnotify.Rename) || event.Has(fsnotify.Chmod) || event.Has(fsnotify.Remove) {
				if err := hf.refresh(); err != nil && !os.IsNotExist(err) {
					ctrld.ProxyLogger.Load().Err(err).Msg("hosts file changed but failed to update client info")
				}
			}
		case err, ok := <-hf.watcher.Errors:
			if !ok {
				return
			}
			ctrld.ProxyLogger.Load().Err(err).Msg("could not watch client info file")
		}
	}

}

// LookupHostnameByIP returns hostname for given IP from current hosts file entries.
func (hf *hostsFile) LookupHostnameByIP(ip string) string {
	hf.mu.Lock()
	defer hf.mu.Unlock()
	if names := hf.m[ip]; len(names) > 0 {
		return normalizeHostname(names[0])
	}
	return ""
}

// LookupHostnameByMac returns hostname for given Mac from current hosts file entries.
func (hf *hostsFile) LookupHostnameByMac(mac string) string {
	return ""
}

// String returns human-readable format of hostsFile.
func (hf *hostsFile) String() string {
	return "hosts"
}