//+build linux

package driver

import (
	"encoding/json"
	"fmt"
	"log"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"syscall"
	"time"

	"github.com/hashicorp/nomad/client/config"
	"github.com/hashicorp/nomad/client/fingerprint"
	"github.com/hashicorp/nomad/client/stats"
	"github.com/hashicorp/nomad/helper/fields"
	"github.com/hashicorp/nomad/nomad/structs"
	"github.com/mitchellh/mapstructure"

	dstructs "github.com/hashicorp/nomad/client/driver/structs"
	cstructs "github.com/hashicorp/nomad/client/structs"
	lxc "gopkg.in/lxc/go-lxc.v2"
)

const (
	containerMonitorIntv = 2 * time.Second
)

var (
	LXCMeasuredCpuStats = []string{"System Mode", "User Mode", "Percent"}
	LXCMeasuredMemStats = []string{"RSS", "Cache", "Swap", "Max Usage", "Kernel Usage", "Kernel Max Usage"}
)

// Add the lxc driver to the list of builtin drivers
func init() {
	BuiltinDrivers["lxc"] = NewLxcDriver
}

// LxcDriver allows users to run LXC Containers
type LxcDriver struct {
	DriverContext
	fingerprint.StaticFingerprinter
}

// LxcDriverConfig is the configuration of the LXC Container
type LxcDriverConfig struct {
	Template             string
	Distro               string
	Release              string
	Arch                 string
	ImageVariant         string   "mapstructure:`image_variant`"
	ImageServer          string   "mapstructure:`image_server`"
	GPGKeyID             string   "mapstructure:`gpg_key_id`"
	GPGKeyServer         string   "mapstructure:`gpg_key_server`"
	DisableGPGValidation bool     "mapstructure:`disable_gpg`"
	FlushCache           bool     "mapstructure:`flush_cache`"
	ForceCache           bool     "mapstructure:`force_cache`"
	TemplateArgs         []string "mapstructure:`template_args`"
}

// NewLxcDriver returns a new instance of the LXC driver
func NewLxcDriver(ctx *DriverContext) Driver {
	return &LxcDriver{DriverContext: *ctx}
}

// Validate validates the lxc driver configuration
func (d *LxcDriver) Validate(config map[string]interface{}) error {
	fd := &fields.FieldData{
		Raw: config,
		Schema: map[string]*fields.FieldSchema{
			"template": &fields.FieldSchema{
				Type:     fields.TypeString,
				Required: true,
			},
			"distro": &fields.FieldSchema{
				Type:     fields.TypeString,
				Required: false,
			},
			"release": &fields.FieldSchema{
				Type:     fields.TypeString,
				Required: false,
			},
			"arch": &fields.FieldSchema{
				Type:     fields.TypeString,
				Required: false,
			},
			"image_variant": &fields.FieldSchema{
				Type:     fields.TypeString,
				Required: false,
			},
			"image_server": &fields.FieldSchema{
				Type:     fields.TypeString,
				Required: false,
			},
			"gpg_key_id": &fields.FieldSchema{
				Type:     fields.TypeString,
				Required: false,
			},
			"gpg_key_server": &fields.FieldSchema{
				Type:     fields.TypeString,
				Required: false,
			},
			"disable_gpg": &fields.FieldSchema{
				Type:     fields.TypeString,
				Required: false,
			},
			"flush_cache": &fields.FieldSchema{
				Type:     fields.TypeString,
				Required: false,
			},
			"force_cache": &fields.FieldSchema{
				Type:     fields.TypeString,
				Required: false,
			},
			"template_args": &fields.FieldSchema{
				Type:     fields.TypeArray,
				Required: false,
			},
		},
	}

	if err := fd.Validate(); err != nil {
		return err
	}
	return nil
}

// Fingerprint fingerprints the lxc driver configuration
func (d *LxcDriver) Fingerprint(cfg *config.Config, node *structs.Node) (bool, error) {
	version := lxc.Version()
	if version == "" {
		return false, nil
	}
	node.Attributes["driver.lxc.version"] = version
	node.Attributes["driver.lxc"] = "1"
	return true, nil
}

// Start starts the LXC Driver
func (d *LxcDriver) Start(ctx *ExecContext, task *structs.Task) (DriverHandle, error) {
	var driverConfig LxcDriverConfig
	if err := mapstructure.WeakDecode(task.Config, &driverConfig); err != nil {
		return nil, err
	}
	lxcPath := lxc.DefaultConfigPath()
	if path := d.config.Read("lxc.path"); path != "" {
		lxcPath = path
	}

	containerName := fmt.Sprintf("%s-%s", task.Name, ctx.AllocID)
	c, err := lxc.NewContainer(containerName, lxcPath)
	if err != nil {
		return nil, fmt.Errorf("unable to create container: %v", err)
	}

	// TODO make them driver configuration
	c.SetVerbosity(lxc.Verbose)
	c.SetLogLevel(lxc.TRACE)

	logFile := filepath.Join(ctx.AllocDir.LogDir(), fmt.Sprintf("%v-lxc.log", task.Name))
	c.SetLogFile(logFile)

	options := lxc.TemplateOptions{
		Template:             driverConfig.Template,
		Distro:               driverConfig.Distro,
		Release:              driverConfig.Release,
		Arch:                 driverConfig.Arch,
		FlushCache:           driverConfig.FlushCache,
		DisableGPGValidation: driverConfig.DisableGPGValidation,
	}

	if err := c.Create(options); err != nil {
		return nil, fmt.Errorf("unable to create container: %v", err)
	}
	if err := c.Start(); err != nil {
		return nil, fmt.Errorf("unable to start container: %v", err)
	}
	// Set the resource limits
	if err := c.SetMemoryLimit(lxc.ByteSize(task.Resources.MemoryMB) * lxc.MB); err != nil {
		return nil, fmt.Errorf("unable to set memory limits: %v", err)
	}
	if err := c.SetCgroupItem("cpu.shares", strconv.Itoa(task.Resources.CPU)); err != nil {
		return nil, fmt.Errorf("unable to set cpu shares: %v", err)
	}

	handle := lxcDriverHandle{
		container:      c,
		initPid:        c.InitPid(),
		lxcPath:        lxcPath,
		logger:         d.logger,
		killTimeout:    GetKillTimeout(task.KillTimeout, d.DriverContext.config.MaxKillTimeout),
		maxKillTimeout: d.DriverContext.config.MaxKillTimeout,
		totalCpuStats:  stats.NewCpuStats(),
		userCpuStats:   stats.NewCpuStats(),
		systemCpuStats: stats.NewCpuStats(),
		waitCh:         make(chan *dstructs.WaitResult, 1),
		doneCh:         make(chan bool, 1),
	}

	go handle.run()

	return &handle, nil
}

// Open opena the driver to monitor an existing LXC container
func (d *LxcDriver) Open(ctx *ExecContext, handleID string) (DriverHandle, error) {
	pid := &lxcPID{}
	if err := json.Unmarshal([]byte(handleID), pid); err != nil {
		return nil, fmt.Errorf("Failed to parse handle '%s': %v", handleID, err)
	}

	var container *lxc.Container
	containers := lxc.Containers(pid.LxcPath)
	for _, c := range containers {
		if c.Name() == pid.ContainerName {
			container = &c
			break
		}
	}

	if container == nil {
		return nil, fmt.Errorf("container %v not found", pid.ContainerName)
	}

	handle := lxcDriverHandle{
		container:      container,
		initPid:        container.InitPid(),
		lxcPath:        pid.LxcPath,
		logger:         d.logger,
		killTimeout:    pid.KillTimeout,
		maxKillTimeout: d.DriverContext.config.MaxKillTimeout,
		totalCpuStats:  stats.NewCpuStats(),
		userCpuStats:   stats.NewCpuStats(),
		systemCpuStats: stats.NewCpuStats(),
		waitCh:         make(chan *dstructs.WaitResult, 1),
		doneCh:         make(chan bool, 1),
	}
	go handle.run()

	return &handle, nil
}

// lxcDriverHandle allows controlling the lifecycle of an lxc container
type lxcDriverHandle struct {
	container *lxc.Container
	initPid   int
	lxcPath   string

	logger *log.Logger

	killTimeout    time.Duration
	maxKillTimeout time.Duration

	totalCpuStats  *stats.CpuStats
	userCpuStats   *stats.CpuStats
	systemCpuStats *stats.CpuStats

	waitCh chan *dstructs.WaitResult
	doneCh chan bool
}

type lxcPID struct {
	ContainerName string
	InitPid       int
	LxcPath       string
	KillTimeout   time.Duration
}

func (h *lxcDriverHandle) ID() string {
	pid := lxcPID{
		ContainerName: h.container.Name(),
		InitPid:       h.initPid,
		LxcPath:       h.lxcPath,
		KillTimeout:   h.killTimeout,
	}
	data, err := json.Marshal(pid)
	if err != nil {
		h.logger.Printf("[ERR] driver.lxc: failed to marshal lxc PID to JSON: %v", err)
	}
	return string(data)
}

func (h *lxcDriverHandle) WaitCh() chan *dstructs.WaitResult {
	return h.waitCh
}

func (h *lxcDriverHandle) Update(task *structs.Task) error {
	h.killTimeout = GetKillTimeout(task.KillTimeout, h.killTimeout)
	return nil
}

func (h *lxcDriverHandle) Kill() error {
	h.logger.Printf("[INFO] driver.lxc: shutting down container %q", h.container.Name())
	if err := h.container.Shutdown(h.killTimeout); err != nil {
		h.logger.Printf("[INFO] driver.lxc: shutting down container %q failed: %v", h.container.Name(), err)
		if err := h.container.Stop(); err != nil {
			h.logger.Printf("[ERR] driver.lxc: error stopping container %q: %v", h.container.Name(), err)
		}
	}
	close(h.doneCh)
	return nil
}

func (h *lxcDriverHandle) Stats() (*cstructs.TaskResourceUsage, error) {
	cpuStats, err := h.container.CPUStats()
	if err != nil {
		return nil, nil
	}
	total, err := h.container.CPUTime()
	if err != nil {
		return nil, nil
	}

	t := time.Now()

	// Get the cpu stats
	system := cpuStats["system"]
	user := cpuStats["user"]
	cs := &cstructs.CpuStats{
		SystemMode: h.systemCpuStats.Percent(float64(system)),
		UserMode:   h.systemCpuStats.Percent(float64(user)),
		Percent:    h.totalCpuStats.Percent(float64(total)),
		TotalTicks: float64(user + system),
		Measured:   LXCMeasuredCpuStats,
	}

	// Get the Memory Stats
	memData := map[string]uint64{
		"rss":   0,
		"cache": 0,
		"swap":  0,
	}
	rawMemStats := h.container.CgroupItem("memory.stat")
	for _, rawMemStat := range rawMemStats {
		key, val, err := keysToVal(rawMemStat)
		if err != nil {
			h.logger.Printf("[ERR] driver.lxc: error getting stat for key %q: %v", key, err)
			continue
		}
		if _, ok := memData[key]; ok {
			memData[key] = val

		}
	}
	ms := &cstructs.MemoryStats{
		RSS:      memData["rss"],
		Cache:    memData["cache"],
		Swap:     memData["swap"],
		Measured: LXCMeasuredMemStats,
	}

	mu := h.container.CgroupItem("memory.max_usage_in_bytes")
	for _, rawMemMaxUsage := range mu {
		val, err := strconv.ParseUint(rawMemMaxUsage, 10, 64)
		if err != nil {
			h.logger.Printf("[ERR] driver.lxc: unable to get max memory usage: %v", err)
			continue
		}
		ms.MaxUsage = val
	}
	ku := h.container.CgroupItem("memory.kmem.usage_in_bytes")
	for _, rawKernelUsage := range ku {
		val, err := strconv.ParseUint(rawKernelUsage, 10, 64)
		if err != nil {
			h.logger.Printf("[ERR] driver.lxc: unable to get kernel memory usage: %v", err)
			continue
		}
		ms.KernelUsage = val
	}

	mku := h.container.CgroupItem("memory.kmem.max_usage_in_bytes")
	for _, rawMaxKernelUsage := range mku {
		val, err := strconv.ParseUint(rawMaxKernelUsage, 10, 64)
		if err != nil {
			h.logger.Printf("[ERR] driver.lxc: unable to get max kernel memory usage: %v", err)
			continue
		}
		ms.KernelMaxUsage = val
	}

	taskResUsage := cstructs.TaskResourceUsage{
		ResourceUsage: &cstructs.ResourceUsage{
			CpuStats:    cs,
			MemoryStats: ms,
		},
		Timestamp: t.UTC().UnixNano(),
	}

	return &taskResUsage, nil
}

func (h *lxcDriverHandle) run() {
	defer close(h.waitCh)
	timer := time.NewTimer(containerMonitorIntv)
	for {
		select {
		case <-timer.C:
			process, err := os.FindProcess(h.initPid)
			if err != nil {
				h.waitCh <- &dstructs.WaitResult{Err: err}
				return
			}
			if err := process.Signal(syscall.Signal(0)); err != nil {
				h.waitCh <- &dstructs.WaitResult{}
				return
			}
			timer.Reset(containerMonitorIntv)
		case <-h.doneCh:
			h.waitCh <- &dstructs.WaitResult{}
			return
		}
	}
}

func keysToVal(line string) (string, uint64, error) {
	tokens := strings.Split(line, " ")
	key := tokens[0]
	val, err := strconv.ParseUint(tokens[1], 10, 64)
	return key, val, err
}