package driver

import (
	"context"
	"encoding/json"
	"fmt"
	"log"
	"os"
	"os/exec"
	"path/filepath"
	"regexp"
	"runtime"
	"strings"
	"time"

	"github.com/hashicorp/go-plugin"
	"github.com/hashicorp/nomad/client/config"
	"github.com/hashicorp/nomad/client/driver/executor"
	dstructs "github.com/hashicorp/nomad/client/driver/structs"
	"github.com/hashicorp/nomad/client/fingerprint"
	cstructs "github.com/hashicorp/nomad/client/structs"
	"github.com/hashicorp/nomad/helper/fields"
	"github.com/hashicorp/nomad/nomad/structs"
	"github.com/mitchellh/mapstructure"
)

var (
	reQemuVersion = regexp.MustCompile(`version (\d[\.\d+]+)`)
)

const (
	// The key populated in Node Attributes to indicate presence of the Qemu
	// driver
	qemuDriverAttr = "driver.qemu"
)

// QemuDriver is a driver for running images via Qemu
// We attempt to chose sane defaults for now, with more configuration available
// planned in the future
type QemuDriver struct {
	DriverContext
	fingerprint.StaticFingerprinter
}

type QemuDriverConfig struct {
	ImagePath   string           `mapstructure:"image_path"`
	Accelerator string           `mapstructure:"accelerator"`
	PortMap     []map[string]int `mapstructure:"port_map"` // A map of host port labels and to guest ports.
	Args        []string         `mapstructure:"args"`     // extra arguments to qemu executable
}

// qemuHandle is returned from Start/Open as a handle to the PID
type qemuHandle struct {
	pluginClient   *plugin.Client
	userPid        int
	executor       executor.Executor
	killTimeout    time.Duration
	maxKillTimeout time.Duration
	logger         *log.Logger
	version        string
	waitCh         chan *dstructs.WaitResult
	doneCh         chan struct{}
}

// NewQemuDriver is used to create a new exec driver
func NewQemuDriver(ctx *DriverContext) Driver {
	return &QemuDriver{DriverContext: *ctx}
}

// Validate is used to validate the driver configuration
func (d *QemuDriver) Validate(config map[string]interface{}) error {
	fd := &fields.FieldData{
		Raw: config,
		Schema: map[string]*fields.FieldSchema{
			"image_path": &fields.FieldSchema{
				Type:     fields.TypeString,
				Required: true,
			},
			"accelerator": &fields.FieldSchema{
				Type: fields.TypeString,
			},
			"port_map": &fields.FieldSchema{
				Type: fields.TypeArray,
			},
			"args": &fields.FieldSchema{
				Type: fields.TypeArray,
			},
		},
	}

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

	return nil
}

func (d *QemuDriver) Abilities() DriverAbilities {
	return DriverAbilities{
		SendSignals: false,
		Exec:        false,
	}
}

func (d *QemuDriver) FSIsolation() cstructs.FSIsolation {
	return cstructs.FSIsolationImage
}

func (d *QemuDriver) Fingerprint(cfg *config.Config, node *structs.Node) (bool, error) {
	bin := "qemu-system-x86_64"
	if runtime.GOOS == "windows" {
		// On windows, the "qemu-system-x86_64" command does not respond to the
		// version flag.
		bin = "qemu-img"
	}
	outBytes, err := exec.Command(bin, "--version").Output()
	if err != nil {
		delete(node.Attributes, qemuDriverAttr)
		return false, nil
	}
	out := strings.TrimSpace(string(outBytes))

	matches := reQemuVersion.FindStringSubmatch(out)
	if len(matches) != 2 {
		delete(node.Attributes, qemuDriverAttr)
		return false, fmt.Errorf("Unable to parse Qemu version string: %#v", matches)
	}

	node.Attributes[qemuDriverAttr] = "1"
	node.Attributes["driver.qemu.version"] = matches[1]
	return true, nil
}

func (d *QemuDriver) Prestart(*ExecContext, *structs.Task) (*PrestartResponse, error) {
	return nil, nil
}

// Run an existing Qemu image. Start() will pull down an existing, valid Qemu
// image and save it to the Drivers Allocation Dir
func (d *QemuDriver) Start(ctx *ExecContext, task *structs.Task) (DriverHandle, error) {
	var driverConfig QemuDriverConfig
	if err := mapstructure.WeakDecode(task.Config, &driverConfig); err != nil {
		return nil, err
	}

	if len(driverConfig.PortMap) > 1 {
		return nil, fmt.Errorf("Only one port_map block is allowed in the qemu driver config")
	}

	// Get the image source
	vmPath := driverConfig.ImagePath
	if vmPath == "" {
		return nil, fmt.Errorf("image_path must be set")
	}
	vmID := filepath.Base(vmPath)

	// Parse configuration arguments
	// Create the base arguments
	accelerator := "tcg"
	if driverConfig.Accelerator != "" {
		accelerator = driverConfig.Accelerator
	}
	// TODO: Check a lower bounds, e.g. the default 128 of Qemu
	mem := fmt.Sprintf("%dM", task.Resources.MemoryMB)

	absPath, err := GetAbsolutePath("qemu-system-x86_64")
	if err != nil {
		return nil, err
	}

	args := []string{
		absPath,
		"-machine", "type=pc,accel=" + accelerator,
		"-name", vmID,
		"-m", mem,
		"-drive", "file=" + vmPath,
		"-nographic",
	}

	// Add pass through arguments to qemu executable. A user can specify
	// these arguments in driver task configuration. These arguments are
	// passed directly to the qemu driver as command line options.
	// For example, args = [ "-nodefconfig", "-nodefaults" ]
	// This will allow a VM with embedded configuration to boot successfully.
	args = append(args, driverConfig.Args...)

	// Check the Resources required Networks to add port mappings. If no resources
	// are required, we assume the VM is a purely compute job and does not require
	// the outside world to be able to reach it. VMs ran without port mappings can
	// still reach out to the world, but without port mappings it is effectively
	// firewalled
	protocols := []string{"udp", "tcp"}
	if len(task.Resources.Networks) > 0 && len(driverConfig.PortMap) == 1 {
		// Loop through the port map and construct the hostfwd string, to map
		// reserved ports to the ports listenting in the VM
		// Ex: hostfwd=tcp::22000-:22,hostfwd=tcp::80-:8080
		var forwarding []string
		taskPorts := task.Resources.Networks[0].MapLabelToValues(nil)
		for label, guest := range driverConfig.PortMap[0] {
			host, ok := taskPorts[label]
			if !ok {
				return nil, fmt.Errorf("Unknown port label %q", label)
			}

			for _, p := range protocols {
				forwarding = append(forwarding, fmt.Sprintf("hostfwd=%s::%d-:%d", p, host, guest))
			}
		}

		if len(forwarding) != 0 {
			args = append(args,
				"-netdev",
				fmt.Sprintf("user,id=user.0,%s", strings.Join(forwarding, ",")),
				"-device", "virtio-net,netdev=user.0",
			)
		}
	}

	// If using KVM, add optimization args
	if accelerator == "kvm" {
		args = append(args,
			"-enable-kvm",
			"-cpu", "host",
			// Do we have cores information available to the Driver?
			// "-smp", fmt.Sprintf("%d", cores),
		)
	}

	d.logger.Printf("[DEBUG] Starting QemuVM command: %q", strings.Join(args, " "))
	pluginLogFile := filepath.Join(ctx.TaskDir.Dir, "executor.out")
	executorConfig := &dstructs.ExecutorConfig{
		LogFile:  pluginLogFile,
		LogLevel: d.config.LogLevel,
	}

	exec, pluginClient, err := createExecutor(d.config.LogOutput, d.config, executorConfig)
	if err != nil {
		return nil, err
	}
	executorCtx := &executor.ExecutorContext{
		TaskEnv: ctx.TaskEnv,
		Driver:  "qemu",
		AllocID: d.DriverContext.allocID,
		Task:    task,
		TaskDir: ctx.TaskDir.Dir,
		LogDir:  ctx.TaskDir.LogDir,
	}
	if err := exec.SetContext(executorCtx); err != nil {
		pluginClient.Kill()
		return nil, fmt.Errorf("failed to set executor context: %v", err)
	}

	execCmd := &executor.ExecCommand{
		Cmd:  args[0],
		Args: args[1:],
		User: task.User,
	}
	ps, err := exec.LaunchCmd(execCmd)
	if err != nil {
		pluginClient.Kill()
		return nil, err
	}
	d.logger.Printf("[INFO] Started new QemuVM: %s", vmID)

	// Create and Return Handle
	maxKill := d.DriverContext.config.MaxKillTimeout
	h := &qemuHandle{
		pluginClient:   pluginClient,
		executor:       exec,
		userPid:        ps.Pid,
		killTimeout:    GetKillTimeout(task.KillTimeout, maxKill),
		maxKillTimeout: maxKill,
		version:        d.config.Version,
		logger:         d.logger,
		doneCh:         make(chan struct{}),
		waitCh:         make(chan *dstructs.WaitResult, 1),
	}
	go h.run()
	return h, nil
}

type qemuId struct {
	Version        string
	KillTimeout    time.Duration
	MaxKillTimeout time.Duration
	UserPid        int
	PluginConfig   *PluginReattachConfig
}

func (d *QemuDriver) Open(ctx *ExecContext, handleID string) (DriverHandle, error) {
	id := &qemuId{}
	if err := json.Unmarshal([]byte(handleID), id); err != nil {
		return nil, fmt.Errorf("Failed to parse handle '%s': %v", handleID, err)
	}

	pluginConfig := &plugin.ClientConfig{
		Reattach: id.PluginConfig.PluginConfig(),
	}

	exec, pluginClient, err := createExecutorWithConfig(pluginConfig, d.config.LogOutput)
	if err != nil {
		d.logger.Println("[ERR] driver.qemu: error connecting to plugin so destroying plugin pid and user pid")
		if e := destroyPlugin(id.PluginConfig.Pid, id.UserPid); e != nil {
			d.logger.Printf("[ERR] driver.qemu: error destroying plugin and userpid: %v", e)
		}
		return nil, fmt.Errorf("error connecting to plugin: %v", err)
	}

	ver, _ := exec.Version()
	d.logger.Printf("[DEBUG] driver.qemu: version of executor: %v", ver.Version)
	// Return a driver handle
	h := &qemuHandle{
		pluginClient:   pluginClient,
		executor:       exec,
		userPid:        id.UserPid,
		logger:         d.logger,
		killTimeout:    id.KillTimeout,
		maxKillTimeout: id.MaxKillTimeout,
		version:        id.Version,
		doneCh:         make(chan struct{}),
		waitCh:         make(chan *dstructs.WaitResult, 1),
	}
	go h.run()
	return h, nil
}

func (d *QemuDriver) Cleanup(*ExecContext, *CreatedResources) error { return nil }

func (h *qemuHandle) ID() string {
	id := qemuId{
		Version:        h.version,
		KillTimeout:    h.killTimeout,
		MaxKillTimeout: h.maxKillTimeout,
		PluginConfig:   NewPluginReattachConfig(h.pluginClient.ReattachConfig()),
		UserPid:        h.userPid,
	}

	data, err := json.Marshal(id)
	if err != nil {
		h.logger.Printf("[ERR] driver.qemu: failed to marshal ID to JSON: %s", err)
	}
	return string(data)
}

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

func (h *qemuHandle) Update(task *structs.Task) error {
	// Store the updated kill timeout.
	h.killTimeout = GetKillTimeout(task.KillTimeout, h.maxKillTimeout)
	h.executor.UpdateTask(task)

	// Update is not possible
	return nil
}

func (h *qemuHandle) Exec(ctx context.Context, cmd string, args []string) ([]byte, int, error) {
	return nil, 0, fmt.Errorf("Qemu driver can't execute commands")
}

func (h *qemuHandle) Signal(s os.Signal) error {
	return fmt.Errorf("Qemu driver can't send signals")
}

// TODO: allow a 'shutdown_command' that can be executed over a ssh connection
// to the VM
func (h *qemuHandle) Kill() error {
	if err := h.executor.ShutDown(); err != nil {
		if h.pluginClient.Exited() {
			return nil
		}
		return fmt.Errorf("executor Shutdown failed: %v", err)
	}

	select {
	case <-h.doneCh:
		return nil
	case <-time.After(h.killTimeout):
		if h.pluginClient.Exited() {
			return nil
		}
		if err := h.executor.Exit(); err != nil {
			return fmt.Errorf("executor Exit failed: %v", err)
		}

		return nil
	}
}

func (h *qemuHandle) Stats() (*cstructs.TaskResourceUsage, error) {
	return h.executor.Stats()
}

func (h *qemuHandle) run() {
	ps, werr := h.executor.Wait()
	if ps.ExitCode == 0 && werr != nil {
		if e := killProcess(h.userPid); e != nil {
			h.logger.Printf("[ERR] driver.qemu: error killing user process: %v", e)
		}
	}
	close(h.doneCh)

	// Exit the executor
	h.executor.Exit()
	h.pluginClient.Kill()

	// Send the results
	h.waitCh <- &dstructs.WaitResult{ExitCode: ps.ExitCode, Signal: ps.Signal, Err: werr}
	close(h.waitCh)
}