package sealing

import (
	"math/bits"

	sectorbuilder "github.com/filecoin-project/go-sectorbuilder"
)

func fillersFromRem(toFill uint64) ([]uint64, error) {
	// Convert to in-sector bytes for easier math:
	//
	// Sector size to user bytes ratio is constant, e.g. for 1024B we have 1016B
	// of user-usable data.
	//
	// (1024/1016 = 128/127)
	//
	// Given that we can get sector size by simply adding 1/127 of the user
	// bytes
	//
	// (we convert to sector bytes as they are nice round binary numbers)

	toFill += toFill / 127

	// We need to fill the sector with pieces that are powers of 2. Conveniently
	// computers store numbers in binary, which means we can look at 1s to get
	// all the piece sizes we need to fill the sector. It also means that number
	// of pieces is the number of 1s in the number of remaining bytes to fill
	out := make([]uint64, bits.OnesCount64(toFill))
	for i := range out {
		// Extract the next lowest non-zero bit
		next := bits.TrailingZeros64(toFill)
		psize := uint64(1) << next
		// e.g: if the number is 0b010100, psize will be 0b000100

		// set that bit to 0 by XORing it, so the next iteration looks at the
		// next bit
		toFill ^= psize

		// Add the piece size to the list of pieces we need to create
		out[i] = sectorbuilder.UserBytesForSectorSize(psize)
	}
	return out, nil
}

func (m *Sealing) ListSectors() ([]SectorInfo, error) {
	var sectors []SectorInfo
	if err := m.sectors.List(&sectors); err != nil {
		return nil, err
	}
	return sectors, nil
}

func (m *Sealing) GetSectorInfo(sid uint64) (SectorInfo, error) {
	var out SectorInfo
	err := m.sectors.Get(sid).Get(&out)
	return out, err
}