package skeleton

import (
	"context"
	"fmt"
	"time"

	hclog "github.com/hashicorp/go-hclog"
	"github.com/hashicorp/nomad/drivers/shared/eventer"
	"github.com/hashicorp/nomad/plugins/base"
	"github.com/hashicorp/nomad/plugins/drivers"
	"github.com/hashicorp/nomad/plugins/shared/hclspec"
	structs "github.com/hashicorp/nomad/plugins/shared/structs"
)

const (
	// pluginName is the name of the plugin
	pluginName = "test-plugin"

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

	// taskHandleVersion is the version of task handle which this driver sets
	// and understands how to decode driver state
	taskHandleVersion = 1
)

var (
	// pluginInfo is the response returned for the PluginInfo RPC
	pluginInfo = &base.PluginInfoResponse{
		Type:              base.PluginTypeDriver,
		PluginApiVersions: []string{"0.1.0"},
		PluginVersion:     "0.0.1",
		Name:              pluginName,
	}

	// configSpec is the hcl specification returned by the ConfigSchema RPC
	configSpec = hclspec.NewObject(map[string]*hclspec.Spec{
		"enabled": hclspec.NewDefault(
			hclspec.NewAttr("enabled", "bool", false),
			hclspec.NewLiteral("true"),
		),
	})

	// 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{
		"strconfig":   hclspec.NewAttr("strconfig", "string", true),
		"boolcfg": hclspec.NewAttr("boolcfg", "bool", false),
	})

	// capabilities is returned by the Capabilities RPC and indicates what
	// optional features this driver supports. This should be set according
	// to the target run time
	capabilities = &drivers.Capabilities{
		SendSignals: true,
		Exec:        false,
	}
)

// Driver is a skeleton driver implementation. The fields in this struct
// are to help plugin authors get started writing their runtime plugins.
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

	// config is the driver configuration set by the SetConfig RPC
	config *Config

	// nomadConfig is the client config from nomad
	nomadConfig *base.ClientDriverConfig

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

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

	// 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
}

// Config is the driver configuration set by the SetConfig RPC call
type Config struct {
	// Enabled is set to true to enable this driver
	Enabled bool `codec:"enabled"`
}

// TaskConfig is the driver configuration of a task within a job
type TaskConfig struct {
	StrConfig string   `codec:"strconfig"`
	BoolConfig  bool `codec:"boolconfig"`
}

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

// NewSkeletonDriver returns a new DriverPlugin implementation
func NewSkeletonDriver(logger hclog.Logger) drivers.DriverPlugin {
	ctx, cancel := context.WithCancel(context.Background())
	logger = logger.Named(pluginName)

	return &Driver{
		eventer:        eventer.NewEventer(ctx, logger),
		config:         &Config{},
		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(cfg *base.Config) error {
	var config Config
	if len(cfg.PluginConfig) != 0 {
		if err := base.MsgPackDecode(cfg.PluginConfig, &config); err != nil {
			return err
		}
	}

	d.config = &config
	if cfg.AgentConfig != nil {
		d.nomadConfig = cfg.AgentConfig.Driver
	}

	return nil
}

func (d *Driver) Shutdown(ctx context.Context) error {
	d.signalShutdown()
	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) {
	defer close(ch)
	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 {
	var health drivers.HealthState
	var desc string
	attrs := map[string]*structs.Attribute{}

	// Implement finger printing logic here to populate health and driver attributes

	return &drivers.Fingerprint{
		Attributes:        attrs,
		Health:            health,
		HealthDescription: desc,
	}
}

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

	if _, ok := d.tasks.Get(handle.Config.ID); ok {
		return nil
	}

	var taskState TaskState
	if err := handle.GetDriverState(&taskState); err != nil {
		return fmt.Errorf("failed to decode task state from handle: %v", err)
	}

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

	// Implement driver specific way to reattach to a running task or restart
	return nil
}

// StartTask setup the task exec and calls the container excecutor
func (d *Driver) StartTask(cfg *drivers.TaskConfig) (*drivers.TaskHandle, *drivers.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)
	}

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

	// Implement driver specific mechanism to start the task here

	return nil, nil, nil

}

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)

	ticker := time.NewTicker(1 * time.Second)
	defer ticker.Stop()

	for {
		select {
		case <-ctx.Done():
			return
		case <-d.ctx.Done():
			return
		case <-ticker.C:
			s := handle.TaskStatus()
			if s.State == drivers.TaskStateExited {
				ch <- handle.exitResult
			}
		}
	}
}

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.shutdown(timeout); err != 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")
	}

	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(ctx context.Context, taskID string, interval time.Duration) (<-chan *drivers.TaskResourceUsage, error) {
	handle, ok := d.tasks.Get(taskID)
	if !ok {
		return nil, drivers.ErrTaskNotFound
	}

	return handle.stats(ctx, interval)
}

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 {
	return fmt.Errorf("This driver does not support signals")
}

func (d *Driver) ExecTask(taskID string, cmd []string, timeout time.Duration) (*drivers.ExecTaskResult, error) {
	return nil, fmt.Errorf("This driver does not support exec") //TODO
}