package main

import (
	"bytes"
	"encoding/binary"
	"encoding/hex"
	"errors"
	"log"

	"github.com/bsm/go-vlq"
	"github.com/btcsuite/btcutil/base58"

	"github.com/tecbot/gorocksdb"
)

func RepairRocksDB(name string) error {
	log.Printf("rocksdb: repair")
	opts := gorocksdb.NewDefaultOptions()
	return gorocksdb.RepairDb(name, opts)
}

type RocksDB struct {
	db *gorocksdb.DB
	wo *gorocksdb.WriteOptions
	ro *gorocksdb.ReadOptions
}

// NewRocksDB opens an internal handle to RocksDB environment.  Close
// needs to be called to release it.
func NewRocksDB(path string) (d *RocksDB, err error) {
	log.Printf("rocksdb: open %s", path)

	fp := gorocksdb.NewBloomFilter(10)
	bbto := gorocksdb.NewDefaultBlockBasedTableOptions()
	bbto.SetBlockSize(16 << 10)                        // 16kb
	bbto.SetBlockCache(gorocksdb.NewLRUCache(8 << 30)) // 8 gb
	bbto.SetFilterPolicy(fp)

	opts := gorocksdb.NewDefaultOptions()
	opts.SetBlockBasedTableFactory(bbto)
	opts.SetCreateIfMissing(true)
	opts.SetMaxBackgroundCompactions(4)
	opts.SetMaxBackgroundFlushes(2)
	opts.SetBytesPerSync(1 << 20)    // 1mb
	opts.SetWriteBufferSize(2 << 30) // 2 gb
	opts.SetMaxOpenFiles(25000)

	db, err := gorocksdb.OpenDb(opts, path)
	if err != nil {
		return
	}

	wo := gorocksdb.NewDefaultWriteOptions()
	ro := gorocksdb.NewDefaultReadOptions()
	ro.SetFillCache(false)

	return &RocksDB{db, wo, ro}, nil
}

// Close releases the RocksDB environment opened in NewRocksDB.
func (d *RocksDB) Close() error {
	log.Printf("rocksdb: close")
	d.wo.Destroy()
	d.ro.Destroy()
	d.db.Close()
	return nil
}

func (d *RocksDB) GetTransactions(address string, lower uint32, higher uint32, fn func(txid string) error) (err error) {
	log.Printf("rocksdb: address get %d:%d %s", lower, higher, address)

	kstart, err := packOutputKey(address, lower)
	if err != nil {
		return err
	}
	kstop, err := packOutputKey(address, higher)
	if err != nil {
		return err
	}

	it := d.db.NewIterator(d.ro)
	defer it.Close()

	for it.Seek(kstart); it.Valid(); it.Next() {
		key := it.Key()
		val := it.Value()
		if bytes.Compare(key.Data(), kstop) > 0 {
			break
		}
		outpoints, err := unpackOutputValue(val.Data())
		if err != nil {
			return err
		}
		for _, o := range outpoints {
			if err := fn(o.txid); err != nil {
				return err
			}
		}
	}
	return nil
}

const (
	opInsert = 0
	opDelete = 1
)

func (d *RocksDB) ConnectBlock(block *Block) error {
	return d.writeBlock(block, opInsert)
}

func (d *RocksDB) DisconnectBlock(block *Block) error {
	return d.writeBlock(block, opDelete)
}

func (d *RocksDB) writeBlock(block *Block, op int) error {
	wb := gorocksdb.NewWriteBatch()
	defer wb.Destroy()

	switch op {
	case opInsert:
		log.Printf("rocksdb: insert %d %s", block.Height, block.Hash)
	case opDelete:
		log.Printf("rocksdb: delete %d %s", block.Height, block.Hash)
	}

	if err := d.writeHeight(wb, block, op); err != nil {
		return err
	}
	if err := d.writeOutputs(wb, block, op); err != nil {
		return err
	}
	if err := d.writeInputs(wb, block, op); err != nil {
		return err
	}

	return d.db.Write(d.wo, wb)
}

// Output Index

type outpoint struct {
	txid string
	vout uint32
}

func (d *RocksDB) writeOutputs(
	wb *gorocksdb.WriteBatch,
	block *Block,
	op int,
) error {
	records := make(map[string][]outpoint)

	for _, tx := range block.Txs {
		for _, output := range tx.Vout {
			address := output.GetAddress()
			if address != "" {
				records[address] = append(records[address], outpoint{
					txid: tx.Txid,
					vout: output.N,
				})
			}
		}
	}

	for address, outpoints := range records {
		key, err := packOutputKey(address, block.Height)
		if err != nil {
			log.Printf("rocksdb: warning: %v", err)
			continue
		}
		val, err := packOutputValue(outpoints)
		if err != nil {
			log.Printf("rocksdb: warning: %v", err)
			continue
		}

		switch op {
		case opInsert:
			wb.Put(key, val)
		case opDelete:
			wb.Delete(key)
		}
	}

	return nil
}

func packOutputKey(address string, height uint32) ([]byte, error) {
	baddress, err := packAddress(address)
	if err != nil {
		return nil, err
	}
	bheight := packUint(height)
	buf := make([]byte, 0, len(baddress)+len(bheight))
	buf = append(buf, baddress...)
	buf = append(buf, bheight...)
	return buf, nil
}

func packOutputValue(outpoints []outpoint) ([]byte, error) {
	buf := make([]byte, 0)
	for _, o := range outpoints {
		btxid, err := packTxid(o.txid)
		if err != nil {
			return nil, err
		}
		bvout := packVaruint(o.vout)
		buf = append(buf, btxid...)
		buf = append(buf, bvout...)
	}
	return buf, nil
}

func unpackOutputValue(buf []byte) ([]outpoint, error) {
	outpoints := make([]outpoint, 0)
	for i := 0; i < len(buf); {
		txid, err := unpackTxid(buf[i : i+txIdUnpackedLen])
		if err != nil {
			return nil, err
		}
		i += txIdUnpackedLen
		vout, voutLen := unpackVaruint(buf[i:])
		i += voutLen
		outpoints = append(outpoints, outpoint{
			txid: txid,
			vout: vout,
		})
	}
	return outpoints, nil
}

// Input index

func (d *RocksDB) writeInputs(
	wb *gorocksdb.WriteBatch,
	block *Block,
	op int,
) error {
	for _, tx := range block.Txs {
		for i, input := range tx.Vin {
			if input.Coinbase != "" {
				continue
			}
			key, err := packOutpoint(input.Txid, input.Vout)
			if err != nil {
				return err
			}
			val, err := packOutpoint(tx.Txid, uint32(i))
			if err != nil {
				return err
			}
			switch op {
			case opInsert:
				wb.Put(key, val)
			case opDelete:
				wb.Delete(key)
			}
		}
	}
	return nil
}

func packOutpoint(txid string, vout uint32) ([]byte, error) {
	btxid, err := packTxid(txid)
	if err != nil {
		return nil, err
	}
	bvout := packVaruint(vout)
	buf := make([]byte, 0, len(btxid)+len(bvout))
	buf = append(buf, btxid...)
	buf = append(buf, bvout...)
	return buf, nil
}

// Block index

func (d *RocksDB) GetBestBlockHash() (string, error) {
	return "", nil // TODO
}

func (d *RocksDB) GetBlockHash(height uint32) (string, error) {
	key := packUint(height)
	val, err := d.db.Get(d.ro, key)
	if err != nil {
		return "", err
	}
	defer val.Free()
	return unpackBlockValue(val.Data())
}

func (d *RocksDB) writeHeight(
	wb *gorocksdb.WriteBatch,
	block *Block,
	op int,
) error {
	key := packUint(block.Height)

	switch op {
	case opInsert:
		val, err := packBlockValue(block.Hash)
		if err != nil {
			return err
		}
		wb.Put(key, val)
	case opDelete:
		wb.Delete(key)
	}

	return nil
}

// Helpers

const txIdUnpackedLen = 32

var ErrInvalidAddress = errors.New("invalid address")

func packUint(i uint32) []byte {
	buf := make([]byte, 4)
	binary.BigEndian.PutUint32(buf, i)
	return buf
}

func packVaruint(i uint32) []byte {
	buf := make([]byte, vlq.MaxLen32)
	ofs := vlq.PutUint(buf, uint64(i))
	return buf[:ofs]
}

func unpackVaruint(buf []byte) (uint32, int) {
	i, ofs := vlq.Uint(buf)
	return uint32(i), ofs
}

func packAddress(address string) ([]byte, error) {
	buf := base58.Decode(address)
	if len(buf) <= 4 {
		return nil, ErrInvalidAddress
	}
	return buf[:len(buf)-4], nil // Slice off the checksum
}

func unpackAddress(buf []byte) (string, error) {
	if len(buf) < 2 {
		return "", ErrInvalidAddress
	}
	return base58.CheckEncode(buf[1:], buf[0]), nil
}

func packTxid(txid string) ([]byte, error) {
	return hex.DecodeString(txid)
}

func unpackTxid(buf []byte) (string, error) {
	return hex.EncodeToString(buf), nil
}

func packBlockValue(hash string) ([]byte, error) {
	return hex.DecodeString(hash)
}

func unpackBlockValue(buf []byte) (string, error) {
	return hex.EncodeToString(buf), nil
}