base.py

import contextlib
import itertools
import logging
from typing import (
    Any,
    ClassVar,
    Iterable,
    Iterator,
    Optional,
    Sequence,
    Set,
    Tuple,
    Type,
    Union,
)

from cached_property import cached_property
from eth_hash.auto import keccak
from eth_typing import (
    Address,
    Hash32,
)
from eth_utils import (
    ValidationError,
)
import rlp

from eth.abc import (
    AtomicDatabaseAPI,
    BlockAPI,
    BlockAndMetaWitness,
    BlockHeaderAPI,
    ChainContextAPI,
    ChainDatabaseAPI,
    ComputationAPI,
    ConsensusAPI,
    ConsensusContextAPI,
    ExecutionContextAPI,
    ReceiptAPI,
    ReceiptBuilderAPI,
    SignedTransactionAPI,
    StateAPI,
    TransactionBuilderAPI,
    UnsignedTransactionAPI,
    VirtualMachineAPI,
)
from eth.consensus.pow import (
    PowConsensus,
)
from eth.constants import (
    GENESIS_PARENT_HASH,
    MAX_PREV_HEADER_DEPTH,
    MAX_UNCLES,
)
from eth.db.trie import make_trie_root_and_nodes
from eth.exceptions import (
    HeaderNotFound,
)
from eth.rlp.headers import (
    BlockHeader,
)
from eth.rlp.sedes import (
    uint32,
)
from eth._utils.datatypes import (
    Configurable,
)
from eth._utils.db import (
    get_parent_header,
    get_block_header_by_hash,
)
from eth.validation import (
    validate_length_lte,
    validate_gas_limit,
)
from eth.vm.execution_context import (
    ExecutionContext,
)
from eth.vm.interrupt import (
    EVMMissingData,
)
from eth.vm.message import (
    Message,
)


class VM(Configurable, VirtualMachineAPI):
    block_class: Type[BlockAPI] = None
    consensus_class: Type[ConsensusAPI] = PowConsensus
    extra_data_max_bytes: ClassVar[int] = 32
    fork: str = None  # noqa: E701  # flake8 bug that's fixed in 3.6.0+
    chaindb: ChainDatabaseAPI = None
    _state_class: Type[StateAPI] = None

    _state = None
    _block = None

    cls_logger = logging.getLogger('eth.vm.base.VM')

    def __init__(self,
                 header: BlockHeaderAPI,
                 chaindb: ChainDatabaseAPI,
                 chain_context: ChainContextAPI,
                 consensus_context: ConsensusContextAPI) -> None:
        self.chaindb = chaindb
        self.chain_context = chain_context
        self.consensus_context = consensus_context
        self._initial_header = header

    def get_header(self) -> BlockHeaderAPI:
        if self._block is None:
            return self._initial_header
        else:
            return self._block.header

    def get_block(self) -> BlockAPI:
        if self._block is None:
            block_class = self.get_block_class()
            self._block = block_class.from_header(header=self._initial_header, chaindb=self.chaindb)
        return self._block

    @property
    def state(self) -> StateAPI:
        if self._state is None:
            self._state = self.build_state(self.chaindb.db,
                                           self.get_header(),
                                           self.chain_context,
                                           self.previous_hashes)
        return self._state

    @classmethod
    def build_state(cls,
                    db: AtomicDatabaseAPI,
                    header: BlockHeaderAPI,
                    chain_context: ChainContextAPI,
                    previous_hashes: Iterable[Hash32] = (),
                    ) -> StateAPI:
        execution_context = cls.create_execution_context(header, previous_hashes, chain_context)
        return cls.get_state_class()(db, execution_context, header.state_root)

    @cached_property
    def _consensus(self) -> ConsensusAPI:
        return self.consensus_class(self.consensus_context)

    #
    # Logging
    #
    @property
    def logger(self) -> logging.Logger:
        return logging.getLogger(f'eth.vm.base.VM.{self.__class__.__name__}')

    #
    # Execution
    #
    def apply_transaction(self,
                          header: BlockHeaderAPI,
                          transaction: SignedTransactionAPI
                          ) -> Tuple[ReceiptAPI, ComputationAPI]:
        self.validate_transaction_against_header(header, transaction)

        # Mark current state as un-revertable, since new transaction is starting...
        self.state.lock_changes()

        computation = self.state.apply_transaction(transaction)
        receipt = self.make_receipt(header, transaction, computation, self.state)
        self.validate_receipt(receipt)

        return receipt, computation

    @classmethod
    def create_execution_context(cls,
                                 header: BlockHeaderAPI,
                                 prev_hashes: Iterable[Hash32],
                                 chain_context: ChainContextAPI) -> ExecutionContextAPI:
        fee_recipient = cls.consensus_class.get_fee_recipient(header)
        try:
            base_fee = header.base_fee_per_gas
        except AttributeError:
            return ExecutionContext(
                coinbase=fee_recipient,
                timestamp=header.timestamp,
                block_number=header.block_number,
                difficulty=header.difficulty,
                gas_limit=header.gas_limit,
                prev_hashes=prev_hashes,
                chain_id=chain_context.chain_id,
            )
        else:
            return ExecutionContext(
                coinbase=fee_recipient,
                timestamp=header.timestamp,
                block_number=header.block_number,
                difficulty=header.difficulty,
                gas_limit=header.gas_limit,
                prev_hashes=prev_hashes,
                chain_id=chain_context.chain_id,
                base_fee_per_gas=base_fee,
            )

    def execute_bytecode(self,
                         origin: Address,
                         gas_price: int,
                         gas: int,
                         to: Address,
                         sender: Address,
                         value: int,
                         data: bytes,
                         code: bytes,
                         code_address: Address = None,
                         ) -> ComputationAPI:
        if origin is None:
            origin = sender

        # Construct a message
        message = Message(
            gas=gas,
            to=to,
            sender=sender,
            value=value,
            data=data,
            code=code,
            code_address=code_address,
        )

        # Construction a tx context
        transaction_context = self.state.get_transaction_context_class()(
            gas_price=gas_price,
            origin=origin,
        )

        # Execute it in the VM
        return self.state.computation_class.apply_computation(
            self.state,
            message,
            transaction_context,
        )

    def apply_all_transactions(
        self,
        transactions: Sequence[SignedTransactionAPI],
        base_header: BlockHeaderAPI
    ) -> Tuple[BlockHeaderAPI, Tuple[ReceiptAPI, ...], Tuple[ComputationAPI, ...]]:
        vm_header = self.get_header()
        if base_header.block_number != vm_header.block_number:
            raise ValidationError(
                f"This VM instance must only work on block #{self.get_header().block_number}, "
                f"but the target header has block #{base_header.block_number}"
            )

        receipts = []
        computations = []
        previous_header = base_header
        result_header = base_header

        for transaction_index, transaction in enumerate(transactions):
            try:
                snapshot = self.state.snapshot()
                receipt, computation = self.apply_transaction(
                    previous_header,
                    transaction,
                )
            except EVMMissingData:
                self.state.revert(snapshot)
                raise

            result_header = self.add_receipt_to_header(previous_header, receipt)
            previous_header = result_header
            receipts.append(receipt)
            computations.append(computation)

            self.transaction_applied_hook(
                transaction_index,
                transactions,
                vm_header,
                result_header,
                computation,
                receipt,
            )

        receipts_tuple = tuple(receipts)
        computations_tuple = tuple(computations)

        return result_header, receipts_tuple, computations_tuple

    #
    # Mining
    #
    def import_block(self, block: BlockAPI) -> BlockAndMetaWitness:
        if self.get_block().number != block.number:
            raise ValidationError(
                f"This VM can only import blocks at number #{self.get_block().number},"
                f" the attempted block was #{block.number}"
            )

        self._block = self.get_block().copy(
            header=self.configure_header(
                coinbase=block.header.coinbase,
                difficulty=block.header.difficulty,
                gas_limit=block.header.gas_limit,
                timestamp=block.header.timestamp,
                extra_data=block.header.extra_data,
                mix_hash=block.header.mix_hash,
                nonce=block.header.nonce,
                uncles_hash=keccak(rlp.encode(block.uncles)),
            ),
            uncles=block.uncles,
        )

        execution_context = self.create_execution_context(
            block.header, self.previous_hashes, self.chain_context)

        # Zero out the gas_used before applying transactions. Each applied transaction will
        #   increase the gas used in the final new_header.
        header = self.get_header().copy(gas_used=0)
        # we need to re-initialize the `state` to update the execution context.
        self._state = self.get_state_class()(self.chaindb.db, execution_context, header.state_root)

        # run all of the transactions.
        new_header, receipts, _ = self.apply_all_transactions(block.transactions, header)

        block_with_transactions = self.set_block_transactions(
            self.get_block(),
            new_header,
            block.transactions,
            receipts,
        )

        return self.mine_block(block_with_transactions)

    def mine_block(self, block: BlockAPI, *args: Any, **kwargs: Any) -> BlockAndMetaWitness:
        packed_block = self.pack_block(block, *args, **kwargs)

        block_result = self.finalize_block(packed_block)

        # Perform validation
        self.validate_block(block_result.block)

        return block_result

    def set_block_transactions(self,
                               base_block: BlockAPI,
                               new_header: BlockHeaderAPI,
                               transactions: Sequence[SignedTransactionAPI],
                               receipts: Sequence[ReceiptAPI]) -> BlockAPI:

        tx_root_hash, tx_kv_nodes = make_trie_root_and_nodes(transactions)
        self.chaindb.persist_trie_data_dict(tx_kv_nodes)

        receipt_root_hash, receipt_kv_nodes = make_trie_root_and_nodes(receipts)
        self.chaindb.persist_trie_data_dict(receipt_kv_nodes)

        return base_block.copy(
            transactions=transactions,
            header=new_header.copy(
                transaction_root=tx_root_hash,
                receipt_root=receipt_root_hash,
            ),
        )

    #
    # Finalization
    #
    def _assign_block_rewards(self, block: BlockAPI) -> None:
        block_reward = self.get_block_reward() + (
            len(block.uncles) * self.get_nephew_reward()
        )

        if block_reward != 0:
            self.state.delta_balance(block.header.coinbase, block_reward)
            self.logger.debug(
                "BLOCK REWARD: %s -> %s",
                block_reward,
                block.header.coinbase,
            )
        else:
            self.logger.debug("No block reward given to %s", block.header.coinbase)

        for uncle in block.uncles:
            uncle_reward = self.get_uncle_reward(block.number, uncle)

            if uncle_reward != 0:
                self.state.delta_balance(uncle.coinbase, uncle_reward)
                self.logger.debug(
                    "UNCLE REWARD REWARD: %s -> %s",
                    uncle_reward,
                    uncle.coinbase,
                )
            else:
                self.logger.debug("No uncle reward given to %s", uncle.coinbase)

    def finalize_block(self, block: BlockAPI) -> BlockAndMetaWitness:
        if block.number > 0:
            snapshot = self.state.snapshot()
            try:
                self._assign_block_rewards(block)
            except EVMMissingData:
                self.state.revert(snapshot)
                raise
            else:
                self.state.commit(snapshot)

        # We need to call `persist` here since the state db batches
        # all writes until we tell it to write to the underlying db
        meta_witness = self.state.persist()

        final_block = block.copy(header=block.header.copy(state_root=self.state.state_root))

        self.logger.debug(
            "%s reads %d unique node hashes, %d addresses, %d bytecodes, and %d storage slots",
            final_block,
            len(meta_witness.hashes),
            len(meta_witness.accounts_queried),
            len(meta_witness.account_bytecodes_queried),
            meta_witness.total_slots_queried,
        )

        return BlockAndMetaWitness(final_block, meta_witness)

    def pack_block(self, block: BlockAPI, *args: Any, **kwargs: Any) -> BlockAPI:
        if 'uncles' in kwargs:
            uncles = kwargs.pop('uncles')
            kwargs.setdefault('uncles_hash', keccak(rlp.encode(uncles)))
        else:
            uncles = block.uncles

        provided_fields = set(kwargs.keys())
        known_fields = set(BlockHeader._meta.field_names)
        unknown_fields = provided_fields.difference(known_fields)

        if unknown_fields:
            raise AttributeError(
                f"Unable to set the field(s) {', '.join(known_fields)} "
                "on the `BlockHeader` class. "
                f"Received the following unexpected fields: {', '.join(unknown_fields)}."
            )

        header: BlockHeaderAPI = block.header.copy(**kwargs)
        packed_block = block.copy(uncles=uncles, header=header)

        return packed_block

    #
    # Blocks
    #
    @classmethod
    def generate_block_from_parent_header_and_coinbase(cls,
                                                       parent_header: BlockHeaderAPI,
                                                       coinbase: Address) -> BlockAPI:
        block_header = cls.create_header_from_parent(parent_header, coinbase=coinbase)
        block = cls.get_block_class()(
            block_header,
            transactions=[],
            uncles=[],
        )
        return block

    @classmethod
    def create_genesis_header(cls, **genesis_params: Any) -> BlockHeaderAPI:
        # Create genesis header by setting the parent to None
        return cls.create_header_from_parent(None, **genesis_params)

    @classmethod
    def get_block_class(cls) -> Type[BlockAPI]:
        if cls.block_class is None:
            raise AttributeError("No `block_class` has been set for this VM")
        else:
            return cls.block_class

    @classmethod
    def get_prev_hashes(cls,
                        last_block_hash: Hash32,
                        chaindb: ChainDatabaseAPI) -> Optional[Iterable[Hash32]]:
        if last_block_hash == GENESIS_PARENT_HASH:
            return

        block_header = get_block_header_by_hash(last_block_hash, chaindb)

        for _ in range(MAX_PREV_HEADER_DEPTH):
            yield block_header.hash
            try:
                block_header = get_parent_header(block_header, chaindb)
            except (IndexError, HeaderNotFound):
                break

    @property
    def previous_hashes(self) -> Optional[Iterable[Hash32]]:
        return self.get_prev_hashes(self.get_header().parent_hash, self.chaindb)

    #
    # Transactions
    #
    def create_transaction(self, *args: Any, **kwargs: Any) -> SignedTransactionAPI:
        return self.get_transaction_builder().new_transaction(*args, **kwargs)

    @classmethod
    def create_unsigned_transaction(cls,
                                    *,
                                    nonce: int,
                                    gas_price: int,
                                    gas: int,
                                    to: Address,
                                    value: int,
                                    data: bytes) -> UnsignedTransactionAPI:
        return cls.get_transaction_builder().create_unsigned_transaction(
            nonce=nonce,
            gas_price=gas_price,
            gas=gas,
            to=to,
            value=value,
            data=data
        )

    @classmethod
    def get_transaction_builder(cls) -> Type[TransactionBuilderAPI]:
        return cls.get_block_class().get_transaction_builder()

    @classmethod
    def get_receipt_builder(cls) -> Type[ReceiptBuilderAPI]:
        return cls.get_block_class().get_receipt_builder()

    #
    # Validate
    #
    @classmethod
    def validate_receipt(cls, receipt: ReceiptAPI) -> None:
        already_checked: Set[Union[Address, int]] = set()

        for log_idx, log in enumerate(receipt.logs):
            if log.address in already_checked:
                continue
            elif log.address not in receipt.bloom_filter:
                raise ValidationError(
                    f"The address from the log entry at position {log_idx} is not "
                    "present in the provided bloom filter."
                )
            already_checked.add(log.address)

        for log_idx, log in enumerate(receipt.logs):
            for topic_idx, topic in enumerate(log.topics):
                if topic in already_checked:
                    continue
                elif uint32.serialize(topic) not in receipt.bloom_filter:
                    raise ValidationError(
                        f"The topic at position {topic_idx} from the log entry at "
                        f"position {log_idx} is not present in the provided bloom filter."
                    )
                already_checked.add(topic)

    def validate_block(self, block: BlockAPI) -> None:
        if not isinstance(block, self.get_block_class()):
            raise ValidationError(
                f"This vm ({self!r}) is not equipped to validate a block of type {block!r}"
            )

        if block.is_genesis:
            validate_length_lte(
                block.header.extra_data,
                self.extra_data_max_bytes,
                title="BlockHeader.extra_data"
            )
        else:
            parent_header = get_parent_header(block.header, self.chaindb)
            self.validate_header(block.header, parent_header)

        tx_root_hash, _ = make_trie_root_and_nodes(block.transactions)
        if tx_root_hash != block.header.transaction_root:
            raise ValidationError(
                f"Block's transaction_root ({block.header.transaction_root!r}) "
                f"does not match expected value: {tx_root_hash!r}"
            )

        if len(block.uncles) > MAX_UNCLES:
            raise ValidationError(
                f"Blocks may have a maximum of {MAX_UNCLES} uncles.  "
                f"Found {len(block.uncles)}."
            )

        if not self.chaindb.exists(block.header.state_root):
            raise ValidationError(
                "`state_root` was not found in the db.\n"
                f"- state_root: {block.header.state_root!r}"
            )
        local_uncle_hash = keccak(rlp.encode(block.uncles))
        if local_uncle_hash != block.header.uncles_hash:
            raise ValidationError(
                "`uncles_hash` and block `uncles` do not match.\n"
                f" - num_uncles       : {len(block.uncles)}\n"
                f" - block uncle_hash : {local_uncle_hash!r}\n"
                f" - header uncle_hash: {block.header.uncles_hash!r}"
            )

    @classmethod
    def validate_header(cls,
                        header: BlockHeaderAPI,
                        parent_header: BlockHeaderAPI) -> None:

        if parent_header is None:
            # to validate genesis header, check if it equals canonical header at block number 0
            raise ValidationError("Must have access to parent header to validate current header")
        else:
            validate_length_lte(
                header.extra_data, cls.extra_data_max_bytes, title="BlockHeader.extra_data")

            cls.validate_gas(header, parent_header)

            if header.block_number != parent_header.block_number + 1:
                raise ValidationError(
                    "Blocks must be numbered consecutively. "
                    f"Block number #{header.block_number} "
                    f"has parent #{parent_header.block_number}"
                )

            # timestamp
            if header.timestamp <= parent_header.timestamp:
                raise ValidationError(
                    "timestamp must be strictly later than parent, "
                    f"but is {parent_header.timestamp - header.timestamp} seconds before.\n"
                    f"- child  : {header.timestamp}\n"
                    f"- parent : {parent_header.timestamp}. "
                )

    @classmethod
    def validate_gas(
            cls,
            header: BlockHeaderAPI,
            parent_header: BlockHeaderAPI) -> None:
        validate_gas_limit(header.gas_limit, parent_header.gas_limit)

    def validate_seal(self, header: BlockHeaderAPI) -> None:
        try:
            self._consensus.validate_seal(header)
        except ValidationError as exc:
            self.cls_logger.debug(
                "Failed to validate seal on header: %r. Error: %s",
                header.as_dict(),
                exc,
            )
            raise

    def validate_seal_extension(self,
                                header: BlockHeaderAPI,
                                parents: Iterable[BlockHeaderAPI]) -> None:
        self._consensus.validate_seal_extension(header, parents)

    @classmethod
    def validate_uncle(cls,
                       block: BlockAPI,
                       uncle: BlockHeaderAPI,
                       uncle_parent: BlockHeaderAPI) -> None:

        if uncle.block_number >= block.number:
            raise ValidationError(
                f"Uncle number ({uncle.block_number}) is higher than "
                f"block number ({block.number})"
            )
        if uncle.block_number != uncle_parent.block_number + 1:
            raise ValidationError(
                f"Uncle number ({uncle.block_number}) is not one above "
                f"ancestor's number ({uncle_parent.block_number})"
            )
        if uncle.timestamp <= uncle_parent.timestamp:
            raise ValidationError(
                f"Uncle timestamp ({uncle.timestamp}) is not newer than its "
                f"parent's timestamp ({uncle_parent.timestamp})"
            )
        if uncle.gas_used > uncle.gas_limit:
            raise ValidationError(
                f"Uncle's gas usage ({uncle.gas_used}) is above "
                f"the limit ({uncle.gas_limit})"
            )

        uncle_parent_gas_limit = uncle_parent.gas_limit
        if not hasattr(uncle_parent, 'base_fee_per_gas') and hasattr(uncle, 'base_fee_per_gas'):
            # if Berlin -> London transition, double the parent limit for validation
            uncle_parent_gas_limit *= 2

        validate_gas_limit(uncle.gas_limit, uncle_parent_gas_limit)

    #
    # State
    #
    @classmethod
    def get_state_class(cls) -> Type[StateAPI]:
        if cls._state_class is None:
            raise AttributeError("No `_state_class` has been set for this VM")

        return cls._state_class

    @contextlib.contextmanager
    def in_costless_state(self) -> Iterator[StateAPI]:
        header = self.get_header()

        temp_block = self.generate_block_from_parent_header_and_coinbase(header, header.coinbase)
        prev_hashes = itertools.chain((header.hash,), self.previous_hashes)

        if hasattr(temp_block.header, 'base_fee_per_gas'):
            free_header = temp_block.header.copy(base_fee_per_gas=0)
        else:
            free_header = temp_block.header

        state = self.build_state(self.chaindb.db,
                                 free_header,
                                 self.chain_context,
                                 prev_hashes)

        snapshot = state.snapshot()
        yield state
        state.revert(snapshot)