package java

import (
	"context"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"runtime"
	"syscall"
	"time"

	"github.com/hashicorp/consul-template/signals"
	"github.com/hashicorp/go-hclog"
	"github.com/hashicorp/go-plugin"
	"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/drivers/shared/eventer"
	"github.com/hashicorp/nomad/plugins/base"
	"github.com/hashicorp/nomad/plugins/drivers"
	"github.com/hashicorp/nomad/plugins/drivers/utils"
	"github.com/hashicorp/nomad/plugins/shared"
	"github.com/hashicorp/nomad/plugins/shared/hclspec"
	"github.com/hashicorp/nomad/plugins/shared/loader"
)

const (
	// pluginName is the name of the plugin
	pluginName = "java"

	// fingerprintPeriod is the interval at which the driver will send fingerprint responses
	fingerprintPeriod = 30 * time.Second

	// The key populated in Node Attributes to indicate presence of the Java driver
	driverAttr        = "driver.java"
	driverVersionAttr = "driver.java.version"
)

var (
	// PluginID is the java plugin metadata registered in the plugin
	// catalog.
	PluginID = loader.PluginID{
		Name:       pluginName,
		PluginType: base.PluginTypeDriver,
	}

	// PluginConfig is the java driver factory function registered in the
	// plugin catalog.
	PluginConfig = &loader.InternalPluginConfig{
		Config:  map[string]interface{}{},
		Factory: func(l hclog.Logger) interface{} { return NewDriver(l) },
	}

	// pluginInfo is the response returned for the PluginInfo RPC
	pluginInfo = &base.PluginInfoResponse{
		Type:             base.PluginTypeDriver,
		PluginApiVersion: "0.0.1",
		PluginVersion:    "0.1.0",
		Name:             pluginName,
	}

	// configSpec is the hcl specification returned by the ConfigSchema RPC
	configSpec = hclspec.NewObject(map[string]*hclspec.Spec{})

	// taskConfigSpec is the hcl specification for the driver config section of
	// a taskConfig within a job. It is returned in the TaskConfigSchema RPC
	taskConfigSpec = hclspec.NewObject(map[string]*hclspec.Spec{
		// It's required for either `class` or `jar_path` to be set,
		// but that's not expressable in hclspec.  Marking both as optional
		// and setting checking explicitly later
		"class":       hclspec.NewAttr("class", "string", false),
		"class_path":  hclspec.NewAttr("class_path", "string", false),
		"jar_path":    hclspec.NewAttr("jar_path", "string", false),
		"jvm_options": hclspec.NewAttr("jvm_options", "list(string)", false),
		"args":        hclspec.NewAttr("args", "list(string)", false),
	})

	// capabilities is returned by the Capabilities RPC and indicates what
	// optional features this driver supports
	capabilities = &drivers.Capabilities{
		SendSignals: false,
		Exec:        false,
		FSIsolation: cstructs.FSIsolationNone,
	}

	_ drivers.DriverPlugin = (*Driver)(nil)
)

func init() {
	if runtime.GOOS == "linux" {
		capabilities.FSIsolation = cstructs.FSIsolationChroot
	}
}

// TaskConfig is the driver configuration of a taskConfig within a job
type TaskConfig struct {
	Class     string   `codec:"class"`
	ClassPath string   `codec:"class_path"`
	JarPath   string   `codec:"jar_path"`
	JvmOpts   []string `codec:"jvm_options"`
	Args      []string `codec:"args"` // extra arguments to java executable
}

// TaskState is the state which is encoded in the handle returned in
// StartTask. This information is needed to rebuild the taskConfig state and handler
// during recovery.
type TaskState struct {
	ReattachConfig *shared.ReattachConfig
	TaskConfig     *drivers.TaskConfig
	Pid            int
	StartedAt      time.Time
}

// Driver is a driver for running images via Java
type Driver struct {
	// eventer is used to handle multiplexing of TaskEvents calls such that an
	// event can be broadcast to all callers
	eventer *eventer.Eventer

	// tasks is the in memory datastore mapping taskIDs to taskHandle
	tasks *taskStore

	// ctx is the context for the driver. It is passed to other subsystems to
	// coordinate shutdown
	ctx context.Context

	// nomadConf is the client agent's configuration
	nomadConfig *base.ClientDriverConfig

	// signalShutdown is called when the driver is shutting down and cancels the
	// ctx passed to any subsystems
	signalShutdown context.CancelFunc

	// logger will log to the Nomad agent
	logger hclog.Logger
}

func NewDriver(logger hclog.Logger) drivers.DriverPlugin {
	ctx, cancel := context.WithCancel(context.Background())
	logger = logger.Named(pluginName)
	return &Driver{
		eventer:        eventer.NewEventer(ctx, logger),
		tasks:          newTaskStore(),
		ctx:            ctx,
		signalShutdown: cancel,
		logger:         logger,
	}
}

func (d *Driver) PluginInfo() (*base.PluginInfoResponse, error) {
	return pluginInfo, nil
}

func (d *Driver) ConfigSchema() (*hclspec.Spec, error) {
	return configSpec, nil
}

func (d *Driver) SetConfig(_ []byte, cfg *base.ClientAgentConfig) error {
	if cfg != nil {
		d.nomadConfig = cfg.Driver
	}
	return nil
}

func (d *Driver) TaskConfigSchema() (*hclspec.Spec, error) {
	return taskConfigSpec, nil
}

func (d *Driver) Capabilities() (*drivers.Capabilities, error) {
	return capabilities, nil
}

func (d *Driver) Fingerprint(ctx context.Context) (<-chan *drivers.Fingerprint, error) {
	ch := make(chan *drivers.Fingerprint)
	go d.handleFingerprint(ctx, ch)
	return ch, nil
}

func (d *Driver) handleFingerprint(ctx context.Context, ch chan *drivers.Fingerprint) {
	ticker := time.NewTimer(0)
	for {
		select {
		case <-ctx.Done():
			return
		case <-d.ctx.Done():
			return
		case <-ticker.C:
			ticker.Reset(fingerprintPeriod)
			ch <- d.buildFingerprint()
		}
	}
}

func (d *Driver) buildFingerprint() *drivers.Fingerprint {
	fp := &drivers.Fingerprint{
		Attributes:        map[string]string{},
		Health:            drivers.HealthStateHealthy,
		HealthDescription: "healthy",
	}

	if runtime.GOOS == "linux" {
		// Only enable if w are root and cgroups are mounted when running on linux system
		if syscall.Geteuid() != 0 {
			fp.Health = drivers.HealthStateUnhealthy
			fp.HealthDescription = "run as root"
			return fp
		}

		mount, err := fingerprint.FindCgroupMountpointDir()
		if err != nil {
			fp.Health = drivers.HealthStateUnhealthy
			fp.HealthDescription = "failed to discover cgroup mount point"
			d.logger.Warn(fp.HealthDescription, "error", err)
			return fp
		}

		if mount == "" {
			fp.Health = drivers.HealthStateUnhealthy
			fp.HealthDescription = "cgroups are unavailable"
			return fp
		}
	}

	version, runtime, vm, err := javaVersionInfo()
	if err != nil {
		// return no error, as it isn't an error to not find java, it just means we
		// can't use it.
		fp.Health = drivers.HealthStateUndetected
		fp.HealthDescription = ""
		return fp
	}

	fp.Attributes[driverAttr] = "1"
	fp.Attributes[driverVersionAttr] = version
	fp.Attributes["driver.java.runtime"] = runtime
	fp.Attributes["driver.java.vm"] = vm

	return fp
}

func (d *Driver) RecoverTask(handle *drivers.TaskHandle) error {
	if handle == nil {
		return fmt.Errorf("handle cannot be nil")
	}

	// If already attached to handle there's nothing to recover.
	if _, ok := d.tasks.Get(handle.Config.ID); ok {
		d.logger.Debug("nothing to recover; task already exists",
			"task_id", handle.Config.ID,
			"task_name", handle.Config.Name,
		)
		return nil
	}

	var taskState TaskState
	if err := handle.GetDriverState(&taskState); err != nil {
		d.logger.Error("failed to decode taskConfig state from handle", "error", err, "task_id", handle.Config.ID)
		return fmt.Errorf("failed to decode taskConfig state from handle: %v", err)
	}

	plugRC, err := shared.ReattachConfigToGoPlugin(taskState.ReattachConfig)
	if err != nil {
		d.logger.Error("failed to build ReattachConfig from taskConfig state", "error", err, "task_id", handle.Config.ID)
		return fmt.Errorf("failed to build ReattachConfig from taskConfig state: %v", err)
	}

	pluginConfig := &plugin.ClientConfig{
		Reattach: plugRC,
	}

	execImpl, pluginClient, err := utils.CreateExecutorWithConfig(pluginConfig, os.Stderr)
	if err != nil {
		d.logger.Error("failed to reattach to executor", "error", err, "task_id", handle.Config.ID)
		return fmt.Errorf("failed to reattach to executor: %v", err)
	}

	h := &taskHandle{
		exec:         execImpl,
		pid:          taskState.Pid,
		pluginClient: pluginClient,
		taskConfig:   taskState.TaskConfig,
		procState:    drivers.TaskStateRunning,
		startedAt:    taskState.StartedAt,
		exitResult:   &drivers.ExitResult{},
	}

	d.tasks.Set(taskState.TaskConfig.ID, h)

	go h.run()
	return nil
}

func (d *Driver) StartTask(cfg *drivers.TaskConfig) (*drivers.TaskHandle, *cstructs.DriverNetwork, error) {
	if _, ok := d.tasks.Get(cfg.ID); ok {
		return nil, nil, fmt.Errorf("task with ID %q already started", cfg.ID)
	}

	var driverConfig TaskConfig
	if err := cfg.DecodeDriverConfig(&driverConfig); err != nil {
		return nil, nil, fmt.Errorf("failed to decode driver config: %v", err)
	}

	if driverConfig.Class == "" && driverConfig.JarPath == "" {
		return nil, nil, fmt.Errorf("jar_path or class must be specified")
	}

	absPath, err := GetAbsolutePath("java")
	if err != nil {
		return nil, nil, fmt.Errorf("failed to find java binary: %s", err)
	}

	args := javaCmdArgs(driverConfig)

	d.logger.Info("starting java task", "driver_cfg", hclog.Fmt("%+v", driverConfig), "args", args)

	handle := drivers.NewTaskHandle(pluginName)
	handle.Config = cfg

	pluginLogFile := filepath.Join(cfg.TaskDir().Dir, "executor.out")
	executorConfig := &dstructs.ExecutorConfig{
		LogFile:  pluginLogFile,
		LogLevel: "debug",
	}

	exec, pluginClient, err := utils.CreateExecutor(os.Stderr, hclog.Debug, d.nomadConfig, executorConfig)
	if err != nil {
		return nil, nil, fmt.Errorf("failed to create executor: %v", err)
	}

	execCmd := &executor.ExecCommand{
		Cmd:            absPath,
		Args:           args,
		Env:            cfg.EnvList(),
		User:           cfg.User,
		ResourceLimits: true,
		Resources: &executor.Resources{
			CPU:      cfg.Resources.NomadResources.CPU,
			MemoryMB: cfg.Resources.NomadResources.MemoryMB,
			DiskMB:   cfg.Resources.NomadResources.DiskMB,
		},
		TaskDir:    cfg.TaskDir().Dir,
		StdoutPath: cfg.StdoutPath,
		StderrPath: cfg.StderrPath,
	}

	ps, err := exec.Launch(execCmd)
	if err != nil {
		pluginClient.Kill()
		return nil, nil, fmt.Errorf("failed to launch command with executor: %v", err)
	}

	h := &taskHandle{
		exec:         exec,
		pid:          ps.Pid,
		pluginClient: pluginClient,
		taskConfig:   cfg,
		procState:    drivers.TaskStateRunning,
		startedAt:    time.Now().Round(time.Millisecond),
		logger:       d.logger,
	}

	driverState := TaskState{
		ReattachConfig: shared.ReattachConfigFromGoPlugin(pluginClient.ReattachConfig()),
		Pid:            ps.Pid,
		TaskConfig:     cfg,
		StartedAt:      h.startedAt,
	}

	if err := handle.SetDriverState(&driverState); err != nil {
		d.logger.Error("failed to start task, error setting driver state", "error", err)
		exec.Shutdown("", 0)
		pluginClient.Kill()
		return nil, nil, fmt.Errorf("failed to set driver state: %v", err)
	}

	d.tasks.Set(cfg.ID, h)
	go h.run()
	return handle, nil, nil
}

func javaCmdArgs(driverConfig TaskConfig) []string {
	args := []string{}
	// Look for jvm options
	if len(driverConfig.JvmOpts) != 0 {
		args = append(args, driverConfig.JvmOpts...)
	}

	// Add the classpath
	if driverConfig.ClassPath != "" {
		args = append(args, "-cp", driverConfig.ClassPath)
	}

	// Add the jar
	if driverConfig.JarPath != "" {
		args = append(args, "-jar", driverConfig.JarPath)
	}

	// Add the class
	if driverConfig.Class != "" {
		args = append(args, driverConfig.Class)
	}

	// Add any args
	if len(driverConfig.Args) != 0 {
		args = append(args, driverConfig.Args...)
	}

	return args
}

func (d *Driver) WaitTask(ctx context.Context, taskID string) (<-chan *drivers.ExitResult, error) {
	handle, ok := d.tasks.Get(taskID)
	if !ok {
		return nil, drivers.ErrTaskNotFound
	}

	ch := make(chan *drivers.ExitResult)
	go d.handleWait(ctx, handle, ch)

	return ch, nil
}

func (d *Driver) handleWait(ctx context.Context, handle *taskHandle, ch chan *drivers.ExitResult) {
	defer close(ch)
	var result *drivers.ExitResult
	ps, err := handle.exec.Wait()
	if err != nil {
		result = &drivers.ExitResult{
			Err: fmt.Errorf("executor: error waiting on process: %v", err),
		}
	} else {
		result = &drivers.ExitResult{
			ExitCode: ps.ExitCode,
			Signal:   ps.Signal,
		}
	}

	select {
	case <-ctx.Done():
		return
	case <-d.ctx.Done():
		return
	case ch <- result:
	}
}

func (d *Driver) StopTask(taskID string, timeout time.Duration, signal string) error {
	handle, ok := d.tasks.Get(taskID)
	if !ok {
		return drivers.ErrTaskNotFound
	}

	if err := handle.exec.Shutdown(signal, timeout); err != nil {
		if handle.pluginClient.Exited() {
			return nil
		}
		return fmt.Errorf("executor Shutdown failed: %v", err)
	}

	return nil
}

func (d *Driver) DestroyTask(taskID string, force bool) error {
	handle, ok := d.tasks.Get(taskID)
	if !ok {
		return drivers.ErrTaskNotFound
	}

	if handle.IsRunning() && !force {
		return fmt.Errorf("cannot destroy running task")
	}

	if !handle.pluginClient.Exited() {
		if handle.IsRunning() {
			if err := handle.exec.Shutdown("", 0); err != nil {
				handle.logger.Error("destroying executor failed", "err", err)
			}
		}

		handle.pluginClient.Kill()
	}

	d.tasks.Delete(taskID)
	return nil
}

func (d *Driver) InspectTask(taskID string) (*drivers.TaskStatus, error) {
	handle, ok := d.tasks.Get(taskID)
	if !ok {
		return nil, drivers.ErrTaskNotFound
	}

	return handle.TaskStatus(), nil
}

func (d *Driver) TaskStats(taskID string) (*cstructs.TaskResourceUsage, error) {
	handle, ok := d.tasks.Get(taskID)
	if !ok {
		return nil, drivers.ErrTaskNotFound
	}

	return handle.exec.Stats()
}

func (d *Driver) TaskEvents(ctx context.Context) (<-chan *drivers.TaskEvent, error) {
	return d.eventer.TaskEvents(ctx)
}

func (d *Driver) SignalTask(taskID string, signal string) error {
	handle, ok := d.tasks.Get(taskID)
	if !ok {
		return drivers.ErrTaskNotFound
	}

	sig := os.Interrupt
	if s, ok := signals.SignalLookup[signal]; ok {
		d.logger.Warn("signal to send to task unknown, using SIGINT", "signal", signal, "task_id", handle.taskConfig.ID)
		sig = s
	}
	return handle.exec.Signal(sig)
}

func (d *Driver) ExecTask(taskID string, cmd []string, timeout time.Duration) (*drivers.ExecTaskResult, error) {
	if len(cmd) == 0 {
		return nil, fmt.Errorf("error cmd must have at least one value")
	}
	handle, ok := d.tasks.Get(taskID)
	if !ok {
		return nil, drivers.ErrTaskNotFound
	}

	out, exitCode, err := handle.exec.Exec(time.Now().Add(timeout), cmd[0], cmd[1:])
	if err != nil {
		return nil, err
	}

	return &drivers.ExecTaskResult{
		Stdout: out,
		ExitResult: &drivers.ExitResult{
			ExitCode: exitCode,
		},
	}, nil
}

// GetAbsolutePath returns the absolute path of the passed binary by resolving
// it in the path and following symlinks.
func GetAbsolutePath(bin string) (string, error) {
	lp, err := exec.LookPath(bin)
	if err != nil {
		return "", fmt.Errorf("failed to resolve path to %q executable: %v", bin, err)
	}

	return filepath.EvalSymlinks(lp)
}