package temporalrepo

import (
	"bytes"
	"encoding/binary"

	"github.com/pkg/errors"

	"github.com/cockroachdb/pebble"
)

type Pebble struct {
	db *pebble.DB
}

func NewPebble(path string) (*Pebble, error) {

	db, err := pebble.Open(path, &pebble.Options{Cache: pebble.NewCache(16 << 20), MaxOpenFiles: 2000})
	repo := &Pebble{db: db}

	return repo, errors.Wrapf(err, "unable to open %s", path)
}

func (repo *Pebble) SetNodesAt(name [][]byte, heights []int32) error {

	// key format: height(4B) + 0(1B) + name(varable length)
	key := bytes.NewBuffer(nil)
	batch := repo.db.NewBatch()
	defer batch.Close()
	for i, name := range name {
		key.Reset()
		binary.Write(key, binary.BigEndian, heights[i])
		binary.Write(key, binary.BigEndian, byte(0))
		key.Write(name)

		err := batch.Set(key.Bytes(), nil, pebble.NoSync)
		if err != nil {
			return errors.Wrap(err, "in set")
		}
	}
	return errors.Wrap(batch.Commit(pebble.NoSync), "in commit")
}

func (repo *Pebble) NodesAt(height int32) ([][]byte, error) {

	prefix := bytes.NewBuffer(nil)
	binary.Write(prefix, binary.BigEndian, height)
	binary.Write(prefix, binary.BigEndian, byte(0))

	end := bytes.NewBuffer(nil)
	binary.Write(end, binary.BigEndian, height)
	binary.Write(end, binary.BigEndian, byte(1))

	prefixIterOptions := &pebble.IterOptions{
		LowerBound: prefix.Bytes(),
		UpperBound: end.Bytes(),
	}

	var names [][]byte

	iter := repo.db.NewIter(prefixIterOptions)
	for iter.First(); iter.Valid(); iter.Next() {
		// Skipping the first 5 bytes (height and a null byte), we get the name.
		name := make([]byte, len(iter.Key())-5)
		copy(name, iter.Key()[5:]) // iter.Key() reuses its buffer
		names = append(names, name)
	}

	return names, errors.Wrap(iter.Close(), "in close")
}

func (repo *Pebble) Close() error {

	err := repo.db.Flush()
	if err != nil {
		// if we fail to close are we going to try again later?
		return errors.Wrap(err, "on flush")
	}

	err = repo.db.Close()
	return errors.Wrap(err, "on close")
}

func (repo *Pebble) Flush() error {
	_, err := repo.db.AsyncFlush()
	return err
}