package libpod

import (
	"bufio"
	"bytes"
	"fmt"
	"io/ioutil"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"time"

	"github.com/containers/libpod/pkg/inspect"
	"github.com/coreos/go-systemd/dbus"
	"github.com/pkg/errors"
	"github.com/sirupsen/logrus"
)

// HealthCheckStatus represents the current state of a container
type HealthCheckStatus int

const (
	// HealthCheckSuccess means the health worked
	HealthCheckSuccess HealthCheckStatus = iota
	// HealthCheckFailure means the health ran and failed
	HealthCheckFailure HealthCheckStatus = iota
	// HealthCheckContainerStopped means the health check cannot
	// be run because the container is stopped
	HealthCheckContainerStopped HealthCheckStatus = iota
	// HealthCheckContainerNotFound means the container could
	// not be found in local store
	HealthCheckContainerNotFound HealthCheckStatus = iota
	// HealthCheckNotDefined means the container has no health
	// check defined in it
	HealthCheckNotDefined HealthCheckStatus = iota
	// HealthCheckInternalError means somes something failed obtaining or running
	// a given health check
	HealthCheckInternalError HealthCheckStatus = iota
	// HealthCheckDefined means the healthcheck was found on the container
	HealthCheckDefined HealthCheckStatus = iota

	// MaxHealthCheckNumberLogs is the maximum number of attempts we keep
	// in the healthcheck history file
	MaxHealthCheckNumberLogs int = 5
	// MaxHealthCheckLogLength in characters
	MaxHealthCheckLogLength = 500

	// HealthCheckHealthy describes a healthy container
	HealthCheckHealthy string = "healthy"
	// HealthCheckUnhealthy describes an unhealthy container
	HealthCheckUnhealthy string = "unhealthy"
	// HealthCheckStarting describes the time between when the container starts
	// and the start-period (time allowed for the container to start and application
	// to be running) expires.
	HealthCheckStarting string = "starting"
)

// hcWriteCloser allows us to use bufio as a WriteCloser
type hcWriteCloser struct {
	*bufio.Writer
}

// Used to add a closer to bufio
func (hcwc hcWriteCloser) Close() error {
	return nil
}

// HealthCheck verifies the state and validity of the healthcheck configuration
// on the container and then executes the healthcheck
func (r *Runtime) HealthCheck(name string) (HealthCheckStatus, error) {
	container, err := r.LookupContainer(name)
	if err != nil {
		return HealthCheckContainerNotFound, errors.Wrapf(err, "unable to lookup %s to perform a health check", name)
	}
	hcStatus, err := checkHealthCheckCanBeRun(container)
	if err == nil {
		return container.runHealthCheck()
	}
	return hcStatus, err
}

// runHealthCheck runs the health check as defined by the container
func (c *Container) runHealthCheck() (HealthCheckStatus, error) {
	var (
		newCommand    []string
		returnCode    int
		capture       bytes.Buffer
		inStartPeriod bool
	)
	hcStatus, err := checkHealthCheckCanBeRun(c)
	if err != nil {
		return hcStatus, err
	}
	hcCommand := c.HealthCheckConfig().Test
	if len(hcCommand) > 0 && hcCommand[0] == "CMD-SHELL" {
		newCommand = []string{"sh", "-c", strings.Join(hcCommand[1:], " ")}
	} else {
		newCommand = hcCommand
	}
	captureBuffer := bufio.NewWriter(&capture)
	hcw := hcWriteCloser{
		captureBuffer,
	}
	streams := new(AttachStreams)
	streams.OutputStream = hcw
	streams.ErrorStream = hcw
	streams.InputStream = os.Stdin
	streams.AttachOutput = true
	streams.AttachError = true
	streams.AttachInput = true

	logrus.Debugf("executing health check command %s for %s", strings.Join(newCommand, " "), c.ID())
	timeStart := time.Now()
	hcResult := HealthCheckSuccess
	hcErr := c.Exec(false, false, []string{}, newCommand, "", "", streams, 0)
	if hcErr != nil {
		hcResult = HealthCheckFailure
		returnCode = 1
	}
	timeEnd := time.Now()
	if c.HealthCheckConfig().StartPeriod > 0 {
		// there is a start-period we need to honor; we add startPeriod to container start time
		startPeriodTime := c.state.StartedTime.Add(c.HealthCheckConfig().StartPeriod)
		if timeStart.Before(startPeriodTime) {
			// we are still in the start period, flip the inStartPeriod bool
			inStartPeriod = true
			logrus.Debugf("healthcheck for %s being run in start-period", c.ID())
		}
	}

	eventLog := capture.String()
	if len(eventLog) > MaxHealthCheckLogLength {
		eventLog = eventLog[:MaxHealthCheckLogLength]
	}

	if timeEnd.Sub(timeStart) > c.HealthCheckConfig().Timeout {
		returnCode = -1
		hcResult = HealthCheckFailure
		hcErr = errors.Errorf("healthcheck command exceeded timeout of %s", c.HealthCheckConfig().Timeout.String())
	}
	hcl := newHealthCheckLog(timeStart, timeEnd, returnCode, eventLog)
	if err := c.updateHealthCheckLog(hcl, inStartPeriod); err != nil {
		return hcResult, errors.Wrapf(err, "unable to update health check log %s for %s", c.healthCheckLogPath(), c.ID())
	}
	return hcResult, hcErr
}

func checkHealthCheckCanBeRun(c *Container) (HealthCheckStatus, error) {
	cstate, err := c.State()
	if err != nil {
		return HealthCheckInternalError, err
	}
	if cstate != ContainerStateRunning {
		return HealthCheckContainerStopped, errors.Errorf("container %s is not running", c.ID())
	}
	if !c.HasHealthCheck() {
		return HealthCheckNotDefined, errors.Errorf("container %s has no defined healthcheck", c.ID())
	}
	return HealthCheckDefined, nil
}

func newHealthCheckLog(start, end time.Time, exitCode int, log string) inspect.HealthCheckLog {
	return inspect.HealthCheckLog{
		Start:    start.Format(time.RFC3339Nano),
		End:      end.Format(time.RFC3339Nano),
		ExitCode: exitCode,
		Output:   log,
	}
}

// updatedHealthCheckStatus updates the health status of the container
// in the healthcheck log
func (c *Container) updateHealthStatus(status string) error {
	healthCheck, err := c.GetHealthCheckLog()
	if err != nil {
		return err
	}
	healthCheck.Status = status
	newResults, err := json.Marshal(healthCheck)
	if err != nil {
		return errors.Wrapf(err, "unable to marshall healthchecks for writing status")
	}
	return ioutil.WriteFile(c.healthCheckLogPath(), newResults, 0700)
}

// UpdateHealthCheckLog parses the health check results and writes the log
func (c *Container) updateHealthCheckLog(hcl inspect.HealthCheckLog, inStartPeriod bool) error {
	healthCheck, err := c.GetHealthCheckLog()
	if err != nil {
		return err
	}
	if hcl.ExitCode == 0 {
		//	set status to healthy, reset failing state to 0
		healthCheck.Status = HealthCheckHealthy
		healthCheck.FailingStreak = 0
	} else {
		if len(healthCheck.Status) < 1 {
			healthCheck.Status = HealthCheckHealthy
		}
		if !inStartPeriod {
			// increment failing streak
			healthCheck.FailingStreak = healthCheck.FailingStreak + 1
			// if failing streak > retries, then status to unhealthy
			if int(healthCheck.FailingStreak) >= c.HealthCheckConfig().Retries {
				healthCheck.Status = HealthCheckUnhealthy
			}
		}
	}
	healthCheck.Log = append(healthCheck.Log, hcl)
	if len(healthCheck.Log) > MaxHealthCheckNumberLogs {
		healthCheck.Log = healthCheck.Log[1:]
	}
	newResults, err := json.Marshal(healthCheck)
	if err != nil {
		return errors.Wrapf(err, "unable to marshall healthchecks for writing")
	}
	return ioutil.WriteFile(c.healthCheckLogPath(), newResults, 0700)
}

// HealthCheckLogPath returns the path for where the health check log is
func (c *Container) healthCheckLogPath() string {
	return filepath.Join(filepath.Dir(c.LogPath()), "healthcheck.log")
}

// GetHealthCheckLog returns HealthCheck results by reading the container's
// health check log file.  If the health check log file does not exist, then
// an empty healthcheck struct is returned
func (c *Container) GetHealthCheckLog() (inspect.HealthCheckResults, error) {
	var healthCheck inspect.HealthCheckResults
	if _, err := os.Stat(c.healthCheckLogPath()); os.IsNotExist(err) {
		return healthCheck, nil
	}
	b, err := ioutil.ReadFile(c.healthCheckLogPath())
	if err != nil {
		return healthCheck, errors.Wrapf(err, "failed to read health check log file %s", c.healthCheckLogPath())
	}
	if err := json.Unmarshal(b, &healthCheck); err != nil {
		return healthCheck, errors.Wrapf(err, "failed to unmarshal existing healthcheck results in %s", c.healthCheckLogPath())
	}
	return healthCheck, nil
}

// createTimer systemd timers for healthchecks of a container
func (c *Container) createTimer() error {
	if c.disableHealthCheckSystemd() {
		return nil
	}
	podman, err := os.Executable()
	if err != nil {
		return errors.Wrapf(err, "failed to get path for podman for a health check timer")
	}

	var cmd = []string{"--unit", fmt.Sprintf("%s", c.ID()), fmt.Sprintf("--on-unit-inactive=%s", c.HealthCheckConfig().Interval.String()), "--timer-property=AccuracySec=1s", podman, "healthcheck", "run", c.ID()}

	conn, err := dbus.NewSystemdConnection()
	if err != nil {
		return errors.Wrapf(err, "unable to get systemd connection to add healthchecks")
	}
	conn.Close()
	logrus.Debugf("creating systemd-transient files: %s %s", "systemd-run", cmd)
	systemdRun := exec.Command("systemd-run", cmd...)
	_, err = systemdRun.CombinedOutput()
	if err != nil {
		return err
	}
	return nil
}

// startTimer starts a systemd timer for the healthchecks
func (c *Container) startTimer() error {
	if c.disableHealthCheckSystemd() {
		return nil
	}
	conn, err := dbus.NewSystemdConnection()
	if err != nil {
		return errors.Wrapf(err, "unable to get systemd connection to start healthchecks")
	}
	defer conn.Close()
	_, err = conn.StartUnit(fmt.Sprintf("%s.service", c.ID()), "fail", nil)
	return err
}

// removeTimer removes the systemd timer and unit files
// for the container
func (c *Container) removeTimer() error {
	if c.disableHealthCheckSystemd() {
		return nil
	}
	conn, err := dbus.NewSystemdConnection()
	if err != nil {
		return errors.Wrapf(err, "unable to get systemd connection to remove healthchecks")
	}
	defer conn.Close()
	serviceFile := fmt.Sprintf("%s.timer", c.ID())
	_, err = conn.StopUnit(serviceFile, "fail", nil)
	return err
}

// HealthCheckStatus returns the current state of a container with a healthcheck
func (c *Container) HealthCheckStatus() (string, error) {
	if !c.HasHealthCheck() {
		return "", errors.Errorf("container %s has no defined healthcheck", c.ID())
	}
	results, err := c.GetHealthCheckLog()
	if err != nil {
		return "", errors.Wrapf(err, "unable to get healthcheck log for %s", c.ID())
	}
	return results.Status, nil
}

func (c *Container) disableHealthCheckSystemd() bool {
	if os.Getenv("DISABLE_HC_SYSTEMD") == "true" {
		return true
	}
	if c.config.HealthCheckConfig.Interval == 0 {
		return true
	}
	return false
}