package coreth

import (
    "math/big"
    "fmt"
    "time"
    "errors"
    "runtime"
    "github.com/ethereum/go-ethereum/core/types"
    "github.com/ethereum/go-ethereum/common"
    //"github.com/ethereum/go-ethereum/eth"
    "github.com/ethereum/go-ethereum/event"
    "github.com/ethereum/go-ethereum/params"
    "github.com/ethereum/go-ethereum/consensus"
    "github.com/ethereum/go-ethereum/core/state"
    "github.com/Determinant/coreth/miner"
    "github.com/Determinant/coreth/eth"
	"github.com/ethereum/go-ethereum/rlp"
	"github.com/ethereum/go-ethereum/rpc"
	"github.com/Determinant/coreth/node"
	"golang.org/x/crypto/sha3"
)

type Tx = types.Transaction
type Block = types.Block
type Hash = common.Hash

type ETHChain struct {
    mux *event.TypeMux
    backend *eth.Ethereum
    worker *miner.Worker
}

type DummyEngine struct {
}

var (
	allowedFutureBlockTime    = 15 * time.Second  // Max time from current time allowed for blocks, before they're considered future blocks
)

var (
	errZeroBlockTime     = errors.New("timestamp equals parent's")
)

// modified from consensus.go
func (self *DummyEngine) verifyHeader(chain consensus.ChainReader, header, parent *types.Header, uncle bool, seal bool) error {
	// Ensure that the header's extra-data section is of a reasonable size
	if uint64(len(header.Extra)) > params.MaximumExtraDataSize {
		return fmt.Errorf("extra-data too long: %d > %d", len(header.Extra), params.MaximumExtraDataSize)
	}
	// Verify the header's timestamp
	if !uncle {
		if header.Time > uint64(time.Now().Add(allowedFutureBlockTime).Unix()) {
			return consensus.ErrFutureBlock
		}
	}
	if header.Time <= parent.Time {
		return errZeroBlockTime
	}
	// Verify that the gas limit is <= 2^63-1
	cap := uint64(0x7fffffffffffffff)
	if header.GasLimit > cap {
		return fmt.Errorf("invalid gasLimit: have %v, max %v", header.GasLimit, cap)
	}
	// Verify that the gasUsed is <= gasLimit
	if header.GasUsed > header.GasLimit {
		return fmt.Errorf("invalid gasUsed: have %d, gasLimit %d", header.GasUsed, header.GasLimit)
	}

	// Verify that the gas limit remains within allowed bounds
	diff := int64(parent.GasLimit) - int64(header.GasLimit)
	if diff < 0 {
		diff *= -1
	}
	limit := parent.GasLimit / params.GasLimitBoundDivisor

	if uint64(diff) >= limit || header.GasLimit < params.MinGasLimit {
		return fmt.Errorf("invalid gas limit: have %d, want %d += %d", header.GasLimit, parent.GasLimit, limit)
	}
	// Verify that the block number is parent's +1
	if diff := new(big.Int).Sub(header.Number, parent.Number); diff.Cmp(big.NewInt(1)) != 0 {
		return consensus.ErrInvalidNumber
	}
	// Verify the engine specific seal securing the block
	if seal {
		if err := self.VerifySeal(chain, header); err != nil {
			return err
		}
	}
	return nil
}

func (self *DummyEngine) verifyHeaderWorker(chain consensus.ChainReader, headers []*types.Header, seals []bool, index int) error {
	var parent *types.Header
	if index == 0 {
		parent = chain.GetHeader(headers[0].ParentHash, headers[0].Number.Uint64()-1)
	} else if headers[index-1].Hash() == headers[index].ParentHash {
		parent = headers[index-1]
	}
	if parent == nil {
		return consensus.ErrUnknownAncestor
	}
	if chain.GetHeader(headers[index].Hash(), headers[index].Number.Uint64()) != nil {
		return nil // known block
	}
	return self.verifyHeader(chain, headers[index], parent, false, seals[index])
}

func (self *DummyEngine) Author(header *types.Header) (common.Address, error) {
    addr := common.Address{}
    return addr, nil
}

func (self *DummyEngine) VerifyHeader(chain consensus.ChainReader, header *types.Header, seal bool) error {
	// Short circuit if the header is known, or it's parent not
	number := header.Number.Uint64()
	if chain.GetHeader(header.Hash(), number) != nil {
		return nil
	}
	parent := chain.GetHeader(header.ParentHash, number-1)
	if parent == nil {
		return consensus.ErrUnknownAncestor
	}
	// Sanity checks passed, do a proper verification
	return self.verifyHeader(chain, header, parent, false, seal)
}

func (self *DummyEngine) VerifyHeaders(chain consensus.ChainReader, headers []*types.Header, seals []bool) (chan<- struct{}, <-chan error) {
	// Spawn as many workers as allowed threads
	workers := runtime.GOMAXPROCS(0)
	if len(headers) < workers {
		workers = len(headers)
	}

	// Create a task channel and spawn the verifiers
	var (
		inputs = make(chan int)
		done   = make(chan int, workers)
		errors = make([]error, len(headers))
		abort  = make(chan struct{})
	)
	for i := 0; i < workers; i++ {
		go func() {
			for index := range inputs {
				errors[index] = self.verifyHeaderWorker(chain, headers, seals, index)
				done <- index
			}
		}()
	}

	errorsOut := make(chan error, len(headers))
	go func() {
		defer close(inputs)
		var (
			in, out = 0, 0
			checked = make([]bool, len(headers))
			inputs  = inputs
		)
		for {
			select {
			case inputs <- in:
				if in++; in == len(headers) {
					// Reached end of headers. Stop sending to workers.
					inputs = nil
				}
			case index := <-done:
				for checked[index] = true; checked[out]; out++ {
					errorsOut <- errors[out]
					if out == len(headers)-1 {
						return
					}
				}
			case <-abort:
				return
			}
		}
	}()
	return abort, errorsOut
}

func (self *DummyEngine) VerifyUncles(chain consensus.ChainReader, block *types.Block) error {
    return nil
}

func (self *DummyEngine) VerifySeal(chain consensus.ChainReader, header *types.Header) error {
    return nil
}

func (self *DummyEngine) Prepare(chain consensus.ChainReader, header *types.Header) error {
	header.Difficulty = new(big.Int).SetUint64(0)
	return nil
}

func (self *DummyEngine) Finalize(chain consensus.ChainReader, header *types.Header, state *state.StateDB, txs []*types.Transaction,
    uncles []*types.Header) {
	// commit the final state root
	header.Root = state.IntermediateRoot(chain.Config().IsEIP158(header.Number))
}

func (self *DummyEngine) FinalizeAndAssemble(chain consensus.ChainReader, header *types.Header, state *state.StateDB, txs []*types.Transaction,
	uncles []*types.Header, receipts []*types.Receipt) (*types.Block, error) {
	// commit the final state root
	header.Root = state.IntermediateRoot(chain.Config().IsEIP158(header.Number))

	// Header seems complete, assemble into a block and return
	return types.NewBlock(header, txs, uncles, receipts), nil
}

func (self *DummyEngine) Seal(chain consensus.ChainReader, block *types.Block, results chan<- *types.Block, stop <-chan struct{}) error {
    return nil
}

func (self *DummyEngine) SealHash(header *types.Header) (hash common.Hash) {
	hasher := sha3.NewLegacyKeccak256()

	rlp.Encode(hasher, []interface{}{
		header.ParentHash,
		header.UncleHash,
		header.Coinbase,
		header.Root,
		header.TxHash,
		header.ReceiptHash,
		header.Bloom,
		header.Difficulty,
		header.Number,
		header.GasLimit,
		header.GasUsed,
		header.Time,
		header.Extra,
	})
	hasher.Sum(hash[:0])
	return hash
}

func (self *DummyEngine) CalcDifficulty(chain consensus.ChainReader, time uint64, parent *types.Header) *big.Int {
    return new(big.Int).SetUint64(0)
}

func (self *DummyEngine) APIs(chain consensus.ChainReader) []rpc.API {
    return nil
}

func (self *DummyEngine) Close() error {
    return nil
}

func isLocalBlock(block *types.Block) bool {
	return false
}

func NewETHChain(config *eth.Config, chainConfig *params.ChainConfig, etherBase *common.Address) *ETHChain {
    if config == nil {
        config = &eth.DefaultConfig
    }
    if chainConfig == nil {
        chainConfig = params.MainnetChainConfig
    }
    mux := new(event.TypeMux)
    ctx := node.NewServiceContext(mux)
    backend, _ := eth.New(&ctx, config)
    chain := &ETHChain {
        mux: mux,
        backend: backend,
        worker: miner.NewWorker(&config.Miner, chainConfig, &DummyEngine{}, backend, mux, isLocalBlock),
    }
    if etherBase == nil {
        etherBase = &common.Address{
            1, 0, 0, 0, 0, 0, 0, 0, 0, 0,
            0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        }
    }
    chain.worker.SetEtherbase(*etherBase)
    return chain
}

func (self *ETHChain) Start() {
    self.worker.Start()
}

func (self *ETHChain) Stop() {
    self.worker.Stop()
}

func (self *ETHChain) AddRemoteTxs(txs []*types.Transaction) []error {
    return self.backend.TxPool().AddRemotes(txs)
}

func (self *ETHChain) AddLocalTxs(txs []*types.Transaction) []error {
    return self.backend.TxPool().AddLocals(txs)
}