package driver

import (
	"errors"
	"fmt"
	"io/ioutil"
	"os"
	"strings"
	"syscall"
	"time"

	"github.com/mitchellh/go-ps"
	"github.com/chrislusf/seaweedfs/weed/util/log"
	"k8s.io/utils/mount"
)

func waitForProcess(p *os.Process, backoff int) error {
	if backoff == 20 {
		return fmt.Errorf("Timeout waiting for PID %v to end", p.Pid)
	}
	cmdLine, err := getCmdLine(p.Pid)
	if err != nil {
		log.Warnf("Error checking cmdline of PID %v, assuming it is dead: %s", p.Pid, err)
		return nil
	}
	if cmdLine == "" {
		// ignore defunct processes
		// TODO: debug why this happens in the first place
		// seems to only happen on k8s, not on local docker
		glog.Warning("Fuse process seems dead, returning")
		return nil
	}
	if err := p.Signal(syscall.Signal(0)); err != nil {
		log.Warnf("Fuse process does not seem active or we are unprivileged: %s", err)
		return nil
	}
	log.Infof("Fuse process with PID %v still active, waiting...", p.Pid)
	time.Sleep(time.Duration(backoff*100) * time.Millisecond)
	return waitForProcess(p, backoff+1)
}

func waitForMount(path string, timeout time.Duration) error {
	var elapsed time.Duration
	var interval = 10 * time.Millisecond
	for {
		notMount, err := mount.New("").IsLikelyNotMountPoint(path)
		if err != nil {
			return err
		}
		if !notMount {
			return nil
		}
		time.Sleep(interval)
		elapsed = elapsed + interval
		if elapsed >= timeout {
			return errors.New("Timeout waiting for mount")
		}
	}
}

func findFuseMountProcess(path string) (*os.Process, error) {
	processes, err := ps.Processes()
	if err != nil {
		return nil, err
	}
	for _, p := range processes {
		cmdLine, err := getCmdLine(p.Pid())
		if err != nil {
			log.Errorf("Unable to get cmdline of PID %v: %s", p.Pid(), err)
			continue
		}
		if strings.Contains(cmdLine, path) {
			log.Infof("Found matching pid %v on path %s", p.Pid(), path)
			return os.FindProcess(p.Pid())
		}
	}
	return nil, nil
}

func getCmdLine(pid int) (string, error) {
	cmdLineFile := fmt.Sprintf("/proc/%v/cmdline", pid)
	cmdLine, err := ioutil.ReadFile(cmdLineFile)
	if err != nil {
		return "", err
	}
	return string(cmdLine), nil
}