// Copyright 2014 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package core

import (
	"bytes"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"math/big"
	"os"

	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/common/hexutil"
	"github.com/ethereum/go-ethereum/common/math"
	"github.com/ethereum/go-ethereum/ethdb"
	"github.com/ethereum/go-ethereum/rlp"
	blockfactory "github.com/harmony-one/harmony/block/factory"
	"github.com/harmony-one/harmony/internal/params"
	"github.com/harmony-one/harmony/staking/slash"

	"github.com/harmony-one/harmony/core/rawdb"
	"github.com/harmony-one/harmony/core/state"
	"github.com/harmony-one/harmony/core/types"
	"github.com/harmony-one/harmony/internal/utils"
	"github.com/harmony-one/harmony/shard"
)

// no go:generate gencodec -type Genesis -field-override genesisSpecMarshaling -out gen_genesis.go
// no go:generate gencodec -type GenesisAccount -field-override genesisAccountMarshaling -out gen_genesis_account.go

var errGenesisNoConfig = errors.New("genesis has no chain configuration")

const (
	// GenesisEpoch is the number of the genesis epoch.
	GenesisEpoch = 0
)

// Genesis specifies the header fields, state of a genesis block. It also defines hard
// fork switch-over blocks through the chain configuration.
type Genesis struct {
	Config         *params.ChainConfig  `json:"config"`
	Factory        blockfactory.Factory `json:"-"`
	Nonce          uint64               `json:"nonce"`
	ShardID        uint32               `json:"shardID"`
	Timestamp      uint64               `json:"timestamp"`
	ExtraData      []byte               `json:"extraData"`
	GasLimit       uint64               `json:"gasLimit"       gencodec:"required"`
	Mixhash        common.Hash          `json:"mixHash"`
	Coinbase       common.Address       `json:"coinbase"`
	Alloc          GenesisAlloc         `json:"alloc"          gencodec:"required"`
	ShardStateHash common.Hash          `json:"shardStateHash" gencodec:"required"`
	ShardState     shard.State          `json:"shardState"     gencodec:"required"`

	// These fields are used for consensus tests. Please don't use them
	// in actual genesis blocks.
	Number     uint64      `json:"number"`
	GasUsed    uint64      `json:"gasUsed"`
	ParentHash common.Hash `json:"parentHash"`
}

// GenesisAlloc specifies the initial state that is part of the genesis block.
type GenesisAlloc map[common.Address]GenesisAccount

// UnmarshalJSON is to deserialize the data into GenesisAlloc.
func (ga *GenesisAlloc) UnmarshalJSON(data []byte) error {
	m := make(map[common.UnprefixedAddress]GenesisAccount)
	if err := json.Unmarshal(data, &m); err != nil {
		return err
	}
	*ga = make(GenesisAlloc)
	for addr, a := range m {
		(*ga)[common.Address(addr)] = a
	}
	return nil
}

// GenesisAccount is an account in the state of the genesis block.
type GenesisAccount struct {
	Code       []byte                      `json:"code,omitempty"`
	Storage    map[common.Hash]common.Hash `json:"storage,omitempty"`
	Balance    *big.Int                    `json:"balance" gencodec:"required"`
	Nonce      uint64                      `json:"nonce,omitempty"`
	PrivateKey []byte                      `json:"secretKey,omitempty"` // for tests
}

// field type overrides for gencodec
type genesisSpecMarshaling struct {
	Nonce      math.HexOrDecimal64
	Timestamp  math.HexOrDecimal64
	ExtraData  hexutil.Bytes
	GasLimit   math.HexOrDecimal64
	GasUsed    math.HexOrDecimal64
	Number     math.HexOrDecimal64
	Difficulty *math.HexOrDecimal256
	Alloc      map[common.UnprefixedAddress]GenesisAccount
}

type genesisAccountMarshaling struct {
	Code       hexutil.Bytes
	Balance    *math.HexOrDecimal256
	Nonce      math.HexOrDecimal64
	Storage    map[storageJSON]storageJSON
	PrivateKey hexutil.Bytes
}

// storageJSON represents a 256 bit byte array, but allows less than 256 bits when
// unmarshaling from hex.
type storageJSON common.Hash

func (h *storageJSON) UnmarshalText(text []byte) error {
	text = bytes.TrimPrefix(text, []byte("0x"))
	if len(text) > 64 {
		return fmt.Errorf("too many hex characters in storage key/value %q", text)
	}
	offset := len(h) - len(text)/2 // pad on the left
	if _, err := hex.Decode(h[offset:], text); err != nil {
		return fmt.Errorf("invalid hex storage key/value %q", text)
	}
	return nil
}

func (h storageJSON) MarshalText() ([]byte, error) {
	return hexutil.Bytes(h[:]).MarshalText()
}

// GenesisMismatchError is raised when trying to overwrite an existing
// genesis block with an incompatible one.
type GenesisMismatchError struct {
	Stored, New common.Hash
}

func (e *GenesisMismatchError) Error() string {
	return fmt.Sprintf("database already contains an incompatible genesis block (have %x, new %x)", e.Stored[:8], e.New[:8])
}

// SetupGenesisBlock writes or updates the genesis block in db.
// The block that will be used is:
//
//                          genesis == nil       genesis != nil
//                       +------------------------------------------
//     db has no genesis |  main-net default  |  genesis
//     db has genesis    |  from DB           |  genesis (if compatible)
//
// The stored chain configuration will be updated if it is compatible (i.e. does not
// specify a fork block below the local head block)
// The returned chain configuration is never nil.
func SetupGenesisBlock(
	db ethdb.Database, genesis *Genesis,
) (*params.ChainConfig, common.Hash, error) {
	if genesis != nil && genesis.Config == nil {
		return params.AllProtocolChanges, common.Hash{}, errGenesisNoConfig
	}

	// Just commit the new block if there is no stored genesis block.
	stored := rawdb.ReadCanonicalHash(db, 0)
	if (stored == common.Hash{}) {
		if genesis == nil {
			utils.Logger().Info().Msg("Writing default main-net genesis block")
			genesis = DefaultGenesisBlock()
		} else {
			utils.Logger().Info().Msg("Writing custom genesis block")
		}
		block, err := genesis.Commit(db)
		return genesis.Config, block.Hash(), err
	}

	// Check whether the genesis block is already written.
	if genesis != nil {
		hash := genesis.ToBlock(nil).Hash()
		if hash != stored {
			return genesis.Config, hash, &GenesisMismatchError{stored, hash}
		}
	}

	// Get the existing chain configuration.
	newcfg := genesis.configOrDefault(stored)
	storedcfg := rawdb.ReadChainConfig(db, stored)
	if storedcfg == nil {
		utils.Logger().Warn().Msg("Found genesis block without chain config")
		rawdb.WriteChainConfig(db, stored, newcfg)
		return newcfg, stored, nil
	}
	// Check config compatibility and write the config. Compatibility errors
	// are returned to the caller unless we're already at block zero.
	height := rawdb.ReadHeaderNumber(db, rawdb.ReadHeadHeaderHash(db))
	if height == nil {
		return newcfg, stored, fmt.Errorf("missing block number for head header hash")
	}
	rawdb.WriteChainConfig(db, stored, newcfg)
	return newcfg, stored, nil
}

func (g *Genesis) configOrDefault(ghash common.Hash) *params.ChainConfig {
	switch {
	case g != nil:
		return g.Config
	default:
		return params.AllProtocolChanges
	}
}

// ToBlock creates the genesis block and writes state of a genesis specification
// to the given database (or discards it if nil).
func (g *Genesis) ToBlock(db ethdb.Database) *types.Block {
	if db == nil {
		utils.Logger().Error().Msg("db should be initialized")
		os.Exit(1)
	}
	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
	for addr, account := range g.Alloc {
		statedb.AddBalance(addr, account.Balance)
		statedb.SetCode(addr, account.Code)
		statedb.SetNonce(addr, account.Nonce)
		for key, value := range account.Storage {
			statedb.SetState(addr, key, value)
		}
	}
	root := statedb.IntermediateRoot(false)
	shardStateBytes, err := shard.EncodeWrapper(g.ShardState, false)
	if err != nil {
		utils.Logger().Error().Msg("failed to rlp-serialize genesis shard state")
		os.Exit(1)
	}
	head := g.Factory.NewHeader(common.Big0).With().
		Number(new(big.Int).SetUint64(g.Number)).
		ShardID(g.ShardID).
		Time(new(big.Int).SetUint64(g.Timestamp)).
		ParentHash(g.ParentHash).
		Extra(g.ExtraData).
		GasLimit(g.GasLimit).
		GasUsed(g.GasUsed).
		MixDigest(g.Mixhash).
		Coinbase(g.Coinbase).
		Root(root).
		ShardStateHash(g.ShardStateHash).
		ShardState(shardStateBytes).
		Header()
	statedb.Commit(false)
	statedb.Database().TrieDB().Commit(root, true)

	return types.NewBlock(head, nil, nil, nil, nil, nil)
}

// Commit writes the block and state of a genesis specification to the database.
// The block is committed as the canonical head block.
func (g *Genesis) Commit(db ethdb.Database) (*types.Block, error) {
	block := g.ToBlock(db)
	if block.Number().Sign() != 0 {
		return nil, fmt.Errorf("can't commit genesis block with number > 0")
	}

	rawdb.WriteBlock(db, block)
	rawdb.WriteReceipts(db, block.Hash(), block.NumberU64(), nil)
	rawdb.WriteCanonicalHash(db, block.Hash(), block.NumberU64())
	rawdb.WriteHeadBlockHash(db, block.Hash())
	rawdb.WriteHeadHeaderHash(db, block.Hash())

	err := rawdb.WriteShardStateBytes(db, block.Header().Epoch(), block.Header().ShardState())

	if err != nil {
		utils.Logger().Error().Err(err).Msg("Failed to store genesis shard state")
	}

	config := g.Config
	if config == nil {
		config = params.AllProtocolChanges
	}
	rawdb.WriteChainConfig(db, block.Hash(), config)
	return block, nil
}

// MustCommit writes the genesis block and state to db, panicking on error.
// The block is committed as the canonical head block.
func (g *Genesis) MustCommit(db ethdb.Database) *types.Block {
	block, err := g.Commit(db)
	if err != nil {
		panic(err)
	}
	rawdb.WriteBlockRewardAccumulator(db, big.NewInt(0), 0)
	data, err := rlp.EncodeToBytes(slash.Records{})
	if err != nil {
		panic(err)
	}
	if err := rawdb.WritePendingSlashingCandidates(db, data); err != nil {
		panic(err)
	}
	return block
}

// GenesisBlockForTesting creates and writes a block in which addr has the given Nano balance.
func GenesisBlockForTesting(db ethdb.Database, addr common.Address, balance *big.Int) *types.Block {
	g := Genesis{Alloc: GenesisAlloc{addr: {Balance: balance}}}
	return g.MustCommit(db)
}

// DefaultGenesisBlock returns the Ethereum main net genesis block.
func DefaultGenesisBlock() *Genesis {
	return &Genesis{
		Config:    params.MainnetChainConfig,
		Factory:   blockfactory.ForMainnet,
		Nonce:     66,
		ExtraData: hexutil.MustDecode("0x11bbe8db4e347b4e8c937c1c8370e4b5ed33adb3db69cbdb7a38e1e50b1b82fa"),
		GasLimit:  5000,
		Alloc:     decodePrealloc("empty"),
	}
}

func decodePrealloc(data string) GenesisAlloc {
	var p []struct{ Addr, Balance *big.Int }

	// Create empty allocation for now
	// TODO: create genesis block with actual content
	//if err := rlp.NewStream(strings.NewReader(data), 0).Decode(&p); err != nil {
	//	panic(err)
	//}
	_ = data
	ga := make(GenesisAlloc, len(p))
	for _, account := range p {
		ga[common.BigToAddress(account.Addr)] = GenesisAccount{Balance: account.Balance}
	}
	return ga
}