package db

import (
	"encoding/json"
	"fmt"

	"github.com/certusone/wormhole/node/pkg/common"
	"github.com/dgraph-io/badger/v3"

	"go.uber.org/zap"
)

type AccountantDB interface {
	AcctStorePendingTransfer(msg *common.MessagePublication) error
	AcctDeletePendingTransfer(msgId string) error
	AcctGetData(logger *zap.Logger) ([]*common.MessagePublication, error)
}

type MockAccountantDB struct {
}

func (d *MockAccountantDB) AcctStorePendingTransfer(msg *common.MessagePublication) error {
	return nil
}

func (d *MockAccountantDB) AcctDeletePendingTransfer(msgId string) error {
	return nil
}

func (d *MockAccountantDB) AcctGetData(logger *zap.Logger) ([]*common.MessagePublication, error) {
	return nil, nil
}

const acctPendingTransfer = "ACCT:PXFER:"
const acctPendingTransferLen = len(acctPendingTransfer)

const acctMinMsgIdLen = len("1/0000000000000000000000000290fb167208af455bb137780163b7b7a9a10c16/0")

func acctPendingTransferMsgID(msgId string) []byte {
	return []byte(fmt.Sprintf("%v%v", acctPendingTransfer, msgId))
}

func acctIsPendingTransfer(keyBytes []byte) bool {
	return (len(keyBytes) >= acctPendingTransferLen+acctMinMsgIdLen) && (string(keyBytes[0:acctPendingTransferLen]) == acctPendingTransfer)
}

// This is called by the accountant on start up to reload pending transfers.
func (d *Database) AcctGetData(logger *zap.Logger) ([]*common.MessagePublication, error) {
	pendingTransfers := []*common.MessagePublication{}
	prefixBytes := []byte(acctPendingTransfer)
	err := d.db.View(func(txn *badger.Txn) error {
		opts := badger.DefaultIteratorOptions
		opts.PrefetchSize = 10
		it := txn.NewIterator(opts)
		defer it.Close()
		for it.Seek(prefixBytes); it.ValidForPrefix(prefixBytes); it.Next() {
			item := it.Item()
			key := item.Key()
			val, err := item.ValueCopy(nil)
			if err != nil {
				return err
			}

			if acctIsPendingTransfer(key) {
				var pt common.MessagePublication
				err := json.Unmarshal(val, &pt)
				if err != nil {
					logger.Error("acct: failed to unmarshal pending transfer for key", zap.String("key", string(key[:])), zap.Error(err))
					continue
				}

				pendingTransfers = append(pendingTransfers, &pt)
			} else {
				return fmt.Errorf("unexpected accountant pending transfer key '%s'", string(key))
			}
		}

		return nil
	})

	return pendingTransfers, err
}

func (d *Database) AcctStorePendingTransfer(msg *common.MessagePublication) error {
	b, _ := json.Marshal(msg)

	err := d.db.Update(func(txn *badger.Txn) error {
		if err := txn.Set(acctPendingTransferMsgID(msg.MessageIDString()), b); err != nil {
			return err
		}
		return nil
	})

	if err != nil {
		return fmt.Errorf("failed to commit accountant pending transfer for tx %s: %w", msg.MessageIDString(), err)
	}

	return nil
}

func (d *Database) AcctDeletePendingTransfer(msgId string) error {
	key := acctPendingTransferMsgID(msgId)
	if err := d.db.Update(func(txn *badger.Txn) error {
		err := txn.Delete(key)
		return err
	}); err != nil {
		return fmt.Errorf("failed to delete accountant pending transfer for tx %s: %w", msgId, err)
	}

	return nil
}