package allocrunner

import (
	"context"
	"fmt"

	hclog "github.com/hashicorp/go-hclog"
	"github.com/hashicorp/nomad/client/pluginmanager/csimanager"
	"github.com/hashicorp/nomad/nomad/structs"
)

// csiHook will wait for remote csi volumes to be attached to the host before
// continuing.
//
// It is a noop for allocs that do not depend on CSI Volumes.
type csiHook struct {
	alloc      *structs.Allocation
	logger     hclog.Logger
	csimanager csimanager.Manager
	rpcClient  RPCer
}

func (c *csiHook) Name() string {
	return "csi_hook"
}

func (c *csiHook) Prerun() error {
	if !c.shouldRun() {
		return nil
	}

	ctx := context.TODO()
	volumes, err := c.csiVolumesFromAlloc()
	if err != nil {
		return err
	}

	mounts := make(map[string]*csimanager.MountInfo, len(volumes))
	for alias, volume := range volumes {
		mounter, err := c.csimanager.MounterForVolume(ctx, volume)
		if err != nil {
			return err
		}

		mountInfo, err := mounter.MountVolume(ctx, volume, c.alloc)
		if err != nil {
			return err
		}

		mounts[alias] = mountInfo
	}

	// TODO: Propagate mounts back to the tasks.

	return nil
}

// csiVolumesFromAlloc finds all the CSI Volume requests from the allocation's
// task group and then fetches them from the Nomad Server, before returning
// them in the form of map[RequestedAlias]*structs.CSIVolume.
//
// If any volume fails to validate then we return an error.
func (c *csiHook) csiVolumesFromAlloc() (map[string]*structs.CSIVolume, error) {
	vols := make(map[string]*structs.VolumeRequest)
	tg := c.alloc.Job.LookupTaskGroup(c.alloc.TaskGroup)
	for alias, vol := range tg.Volumes {
		if vol.Type == structs.VolumeTypeCSI {
			vols[alias] = vol
		}
	}

	csiVols := make(map[string]*structs.CSIVolume, len(vols))
	for alias, request := range vols {
		req := &structs.CSIVolumeGetRequest{
			ID: request.Source,
		}
		req.Region = c.alloc.Job.Region

		var resp structs.CSIVolumeGetResponse
		if err := c.rpcClient.RPC("CSIVolume.Get", req, &resp); err != nil {
			return nil, err
		}

		if resp.Volume == nil {
			return nil, fmt.Errorf("Unexpected nil volume returned for ID: %v", request.Source)
		}

		csiVols[alias] = resp.Volume
	}

	return csiVols, nil
}

func newCSIHook(logger hclog.Logger, alloc *structs.Allocation, rpcClient RPCer, csi csimanager.Manager) *csiHook {
	return &csiHook{
		alloc:      alloc,
		logger:     logger.Named("csi_hook"),
		rpcClient:  rpcClient,
		csimanager: csi,
	}
}

func (h *csiHook) shouldRun() bool {
	tg := h.alloc.Job.LookupTaskGroup(h.alloc.TaskGroup)
	for _, vol := range tg.Volumes {
		if vol.Type == structs.VolumeTypeCSI {
			return true
		}
	}

	return false
}