package client

import (
	"context"
	"errors"
	"time"

	metrics "github.com/armon/go-metrics"
	grpc_retry "github.com/grpc-ecosystem/go-grpc-middleware/retry"
	"github.com/hashicorp/nomad/client/dynamicplugins"
	"github.com/hashicorp/nomad/client/structs"
	"github.com/hashicorp/nomad/plugins/csi"
)

// CSIController endpoint is used for interacting with CSI plugins on a client.
// TODO: Submit metrics with labels to allow debugging per plugin perf problems.
type CSIController struct {
	c *Client
}

const (
	// CSIPluginRequestTimeout is the timeout that should be used when making reqs
	// against CSI Plugins. It is copied from Kubernetes as an initial seed value.
	// https://github.com/kubernetes/kubernetes/blob/e680ad7156f263a6d8129cc0117fda58602e50ad/pkg/volume/csi/csi_plugin.go#L52
	CSIPluginRequestTimeout = 2 * time.Minute
)

var (
	ErrPluginTypeError = errors.New("CSI Plugin loaded incorrectly")
)

// ValidateVolume is used during volume registration to validate
// that a volume exists and that the capabilities it was registered with are
// supported by the CSI Plugin and external volume configuration.
func (c *CSIController) ValidateVolume(req *structs.ClientCSIControllerValidateVolumeRequest, resp *structs.ClientCSIControllerValidateVolumeResponse) error {
	defer metrics.MeasureSince([]string{"client", "csi_controller", "validate_volume"}, time.Now())

	if req.VolumeID == "" {
		return errors.New("VolumeID is required")
	}

	if req.PluginID == "" {
		return errors.New("PluginID is required")
	}

	plugin, err := c.findControllerPlugin(req.PluginID)
	if err != nil {
		return err
	}
	defer plugin.Close()

	caps, err := csi.VolumeCapabilityFromStructs(req.AttachmentMode, req.AccessMode)
	if err != nil {
		return err
	}

	ctx, cancelFn := c.requestContext()
	defer cancelFn()

	// CSI ValidateVolumeCapabilities errors for timeout, codes.Unavailable and
	// codes.ResourceExhausted are retried; all other errors are fatal.
	return plugin.ControllerValidateCapabilities(ctx, req.VolumeID, caps,
		grpc_retry.WithPerRetryTimeout(CSIPluginRequestTimeout),
		grpc_retry.WithMax(3),
		grpc_retry.WithBackoff(grpc_retry.BackoffExponential(100*time.Millisecond)))
}

// AttachVolume is used to attach a volume from a CSI Cluster to
// the storage node provided in the request.
//
// The controller attachment flow currently works as follows:
// 1. Validate the volume request
// 2. Call ControllerPublishVolume on the CSI Plugin to trigger a remote attachment
//
// In the future this may be expanded to request dynamic secrets for attachment.
func (c *CSIController) AttachVolume(req *structs.ClientCSIControllerAttachVolumeRequest, resp *structs.ClientCSIControllerAttachVolumeResponse) error {
	defer metrics.MeasureSince([]string{"client", "csi_controller", "publish_volume"}, time.Now())
	plugin, err := c.findControllerPlugin(req.PluginID)
	if err != nil {
		return err
	}
	defer plugin.Close()

	// The following block of validation checks should not be reached on a
	// real Nomad cluster as all of this data should be validated when registering
	// volumes with the cluster. They serve as a defensive check before forwarding
	// requests to plugins, and to aid with development.

	if req.VolumeID == "" {
		return errors.New("VolumeID is required")
	}

	if req.ClientCSINodeID == "" {
		return errors.New("ClientCSINodeID is required")
	}

	csiReq, err := req.ToCSIRequest()
	if err != nil {
		return err
	}

	// Submit the request for a volume to the CSI Plugin.
	ctx, cancelFn := c.requestContext()
	defer cancelFn()
	// CSI ControllerPublishVolume errors for timeout, codes.Unavailable and
	// codes.ResourceExhausted are retried; all other errors are fatal.
	cresp, err := plugin.ControllerPublishVolume(ctx, csiReq,
		grpc_retry.WithPerRetryTimeout(CSIPluginRequestTimeout),
		grpc_retry.WithMax(3),
		grpc_retry.WithBackoff(grpc_retry.BackoffExponential(100*time.Millisecond)))
	if err != nil {
		return err
	}

	resp.PublishContext = cresp.PublishContext
	return nil
}

// DetachVolume is used to detach a volume from a CSI Cluster from
// the storage node provided in the request.
func (c *CSIController) DetachVolume(req *structs.ClientCSIControllerDetachVolumeRequest, resp *structs.ClientCSIControllerDetachVolumeResponse) error {
	defer metrics.MeasureSince([]string{"client", "csi_controller", "unpublish_volume"}, time.Now())
	plugin, err := c.findControllerPlugin(req.PluginID)
	if err != nil {
		return err
	}
	defer plugin.Close()

	// The following block of validation checks should not be reached on a
	// real Nomad cluster as all of this data should be validated when registering
	// volumes with the cluster. They serve as a defensive check before forwarding
	// requests to plugins, and to aid with development.

	if req.VolumeID == "" {
		return errors.New("VolumeID is required")
	}

	if req.ClientCSINodeID == "" {
		return errors.New("ClientCSINodeID is required")
	}

	csiReq := req.ToCSIRequest()

	// Submit the request for a volume to the CSI Plugin.
	ctx, cancelFn := c.requestContext()
	defer cancelFn()
	// CSI ControllerUnpublishVolume errors for timeout, codes.Unavailable and
	// codes.ResourceExhausted are retried; all other errors are fatal.
	_, err = plugin.ControllerUnpublishVolume(ctx, csiReq,
		grpc_retry.WithPerRetryTimeout(CSIPluginRequestTimeout),
		grpc_retry.WithMax(3),
		grpc_retry.WithBackoff(grpc_retry.BackoffExponential(100*time.Millisecond)))
	if err != nil {
		return err
	}

	return nil
}

func (c *CSIController) findControllerPlugin(name string) (csi.CSIPlugin, error) {
	return c.findPlugin(dynamicplugins.PluginTypeCSIController, name)
}

// TODO: Cache Plugin Clients?
func (c *CSIController) findPlugin(ptype, name string) (csi.CSIPlugin, error) {
	pIface, err := c.c.dynamicRegistry.DispensePlugin(ptype, name)
	if err != nil {
		return nil, err
	}

	plugin, ok := pIface.(csi.CSIPlugin)
	if !ok {
		return nil, ErrPluginTypeError
	}

	return plugin, nil
}

func (c *CSIController) requestContext() (context.Context, context.CancelFunc) {
	return context.WithTimeout(context.Background(), CSIPluginRequestTimeout)
}