package sectorstorage

import (
	"context"

	"golang.org/x/xerrors"

	"github.com/filecoin-project/go-state-types/abi"

	"github.com/filecoin-project/lotus/extern/sector-storage/sealtasks"
	"github.com/filecoin-project/lotus/extern/sector-storage/stores"
	"github.com/filecoin-project/lotus/extern/sector-storage/storiface"
)

type moveSelector struct {
	index       stores.SectorIndex
	sector      abi.SectorID
	alloc       storiface.SectorFileType
	destPtype   storiface.PathType
	allowRemote bool
}

func newMoveSelector(index stores.SectorIndex, sector abi.SectorID, alloc storiface.SectorFileType, destPtype storiface.PathType, allowRemote bool) *moveSelector {
	return &moveSelector{
		index:       index,
		sector:      sector,
		alloc:       alloc,
		destPtype:   destPtype,
		allowRemote: allowRemote,
	}
}

func (s *moveSelector) Ok(ctx context.Context, task sealtasks.TaskType, spt abi.RegisteredSealProof, whnd *WorkerHandle) (bool, bool, error) {
	tasks, err := whnd.TaskTypes(ctx)
	if err != nil {
		return false, false, xerrors.Errorf("getting supported worker task types: %w", err)
	}
	if _, supported := tasks[task]; !supported {
		return false, false, nil
	}

	paths, err := whnd.workerRpc.Paths(ctx)
	if err != nil {
		return false, false, xerrors.Errorf("getting worker paths: %w", err)
	}

	workerPaths := map[storiface.ID]int{}
	for _, path := range paths {
		workerPaths[path.ID] = 0
	}

	ssize, err := spt.SectorSize()
	if err != nil {
		return false, false, xerrors.Errorf("getting sector size: %w", err)
	}

	// note: allowFetch is always false here, because we want to find workers with
	// the sector available locally
	preferred, err := s.index.StorageFindSector(ctx, s.sector, s.alloc, ssize, false)
	if err != nil {
		return false, false, xerrors.Errorf("finding preferred storage: %w", err)
	}

	for _, info := range preferred {
		if _, ok := workerPaths[info.ID]; ok {
			workerPaths[info.ID]++
		}
	}

	best, err := s.index.StorageBestAlloc(ctx, s.alloc, ssize, s.destPtype)
	if err != nil {
		return false, false, xerrors.Errorf("finding best dest storage: %w", err)
	}

	var ok bool

	for _, info := range best {
		if n, has := workerPaths[info.ID]; has {
			ok = true

			// if the worker has a local path with the sector already in it
			// prefer that worker; This usually meant that the move operation is
			// either a no-op because the sector is already in the correct path,
			// or the move a local move.
			if n > 0 {
				return true, true, nil
			}
		}
	}

	return ok && s.allowRemote, false, nil
}

func (s *moveSelector) Cmp(ctx context.Context, task sealtasks.TaskType, a, b *WorkerHandle) (bool, error) {
	return a.Utilization() < b.Utilization(), nil
}

var _ WorkerSelector = &moveSelector{}