package rawdbv3

import (
	"encoding/binary"
	"fmt"
	"sort"

	"github.com/ledgerwatch/erigon-lib/kv"
)

type txNums struct{}

var TxNums txNums

// Min - returns maxTxNum in given block. If block not found - return last available value (`latest`/`pending` state)
func (txNums) Max(tx kv.Tx, blockNum uint64) (maxTxNum uint64, err error) {
	var k [8]byte
	binary.BigEndian.PutUint64(k[:], blockNum)
	c, err := tx.Cursor(kv.MaxTxNum)
	if err != nil {
		return 0, err
	}
	defer c.Close()
	_, v, err := c.SeekExact(k[:])
	if err != nil {
		return 0, err
	}
	if len(v) == 0 {
		_, v, err = c.Last()
		if err != nil {
			return 0, err
		}
		if len(v) == 0 {
			return 0, nil
		}
	}
	return binary.BigEndian.Uint64(v), nil
}

// Min = `max(blockNum-1)+1` returns minTxNum in given block. If block not found - return last available value (`latest`/`pending` state)
func (txNums) Min(tx kv.Tx, blockNum uint64) (maxTxNum uint64, err error) {
	if blockNum == 0 {
		return 0, nil
	}
	var k [8]byte
	binary.BigEndian.PutUint64(k[:], blockNum-1)
	c, err := tx.Cursor(kv.MaxTxNum)
	if err != nil {
		return 0, err
	}
	defer c.Close()

	_, v, err := c.SeekExact(k[:])
	if err != nil {
		return 0, err
	}
	if len(v) == 0 {
		_, v, err = c.Last()
		if err != nil {
			return 0, err
		}
		if len(v) == 0 {
			return 0, nil
		}
	}
	return binary.BigEndian.Uint64(v) + 1, nil
}

func (txNums) Append(tx kv.RwTx, blockNum, maxTxNum uint64) (err error) {
	lastK, err := LastKey(tx, kv.MaxTxNum)
	if err != nil {
		return err
	}
	if len(lastK) != 0 {
		lastBlockNum := binary.BigEndian.Uint64(lastK)
		if lastBlockNum > 1 && lastBlockNum+1 != blockNum { //allow genesis
			return fmt.Errorf("append with gap blockNum=%d, but current heigh=%d", blockNum, lastBlockNum)
		}
	}

	var k, v [8]byte
	binary.BigEndian.PutUint64(k[:], blockNum)
	binary.BigEndian.PutUint64(v[:], maxTxNum)
	if err := tx.Append(kv.MaxTxNum, k[:], v[:]); err != nil {
		return err
	}
	return nil
}
func (txNums) WriteForGenesis(tx kv.RwTx, maxTxNum uint64) (err error) {
	var k, v [8]byte
	binary.BigEndian.PutUint64(k[:], 0)
	binary.BigEndian.PutUint64(v[:], maxTxNum)
	return tx.Put(kv.MaxTxNum, k[:], v[:])
}
func (txNums) Truncate(tx kv.RwTx, blockNum uint64) (err error) {
	var seek [8]byte
	binary.BigEndian.PutUint64(seek[:], blockNum)
	c, err := tx.RwCursor(kv.MaxTxNum)
	if err != nil {
		return err
	}
	defer c.Close()
	for k, _, err := c.Seek(seek[:]); k != nil; k, _, err = c.Next() {
		if err != nil {
			return err
		}
		if err = c.DeleteCurrent(); err != nil {
			return err
		}

	}
	return nil
}
func (txNums) FindBlockNum(tx kv.Tx, endTxNumMinimax uint64) (ok bool, blockNum uint64, err error) {
	var seek [8]byte
	c, err := tx.Cursor(kv.MaxTxNum)
	if err != nil {
		return false, 0, err
	}
	defer c.Close()

	cnt, err := c.Count()
	if err != nil {
		return false, 0, err
	}

	blockNum = uint64(sort.Search(int(cnt), func(i int) bool {
		binary.BigEndian.PutUint64(seek[:], uint64(i))
		var v []byte
		_, v, err = c.SeekExact(seek[:])
		return binary.BigEndian.Uint64(v) >= endTxNumMinimax
	}))
	if err != nil {
		return false, 0, err
	}
	if blockNum == cnt {
		return false, 0, nil
	}
	return true, blockNum, nil
}

// LastKey
func LastKey(tx kv.Tx, table string) ([]byte, error) {
	c, err := tx.Cursor(table)
	if err != nil {
		return nil, err
	}
	defer c.Close()
	k, _, err := c.Last()
	if err != nil {
		return nil, err
	}
	return k, nil
}

// Last - candidate on move to kv.Tx interface
func Last(tx kv.Tx, table string) ([]byte, []byte, error) {
	c, err := tx.Cursor(table)
	if err != nil {
		return nil, nil, err
	}
	defer c.Close()
	k, v, err := c.Last()
	if err != nil {
		return nil, nil, err
	}
	return k, v, nil
}

// SecondKey - useful if table always has zero-key (for example genesis block)
func SecondKey(tx kv.Tx, table string) ([]byte, error) {
	c, err := tx.Cursor(table)
	if err != nil {
		return nil, err
	}
	defer c.Close()
	_, _, err = c.First()
	if err != nil {
		return nil, err
	}
	k, _, err := c.Next()
	if err != nil {
		return nil, err
	}
	return k, nil
}