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// Copyright 2018-2020 Parity Technologies (UK) Ltd.
// This file is part of Substrate Consensus Common.

// Substrate Demo is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// Substrate Consensus Common 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 General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with Substrate Consensus Common.  If not, see <http://www.gnu.org/licenses/>.

//! Common utilities for building and using consensus engines in substrate.
//!
//! Much of this crate is _unstable_ and thus the API is likely to undergo
//! change. Implementors of traits should not rely on the interfaces to remain
//! the same.

// This provides "unused" building blocks to other crates
#![allow(dead_code)]

// our error-chain could potentially blow up otherwise
#![recursion_limit="128"]

#[macro_use] extern crate log;

use std::sync::Arc;
use std::time::Duration;

use sp_runtime::{
	generic::BlockId, traits::{Block as BlockT, DigestFor, NumberFor, HashFor},
};
use futures::prelude::*;
pub use sp_inherents::InherentData;

pub mod block_validation;
pub mod offline_tracker;
pub mod error;
pub mod block_import;
mod select_chain;
pub mod import_queue;
pub mod evaluation;
mod metrics;

pub use self::error::Error;
pub use block_import::{
	BlockImport, BlockOrigin, ForkChoiceStrategy, ImportedAux, BlockImportParams, BlockCheckParams,
	ImportResult, JustificationImport,
};
pub use select_chain::SelectChain;
pub use sp_state_machine::Backend as StateBackend;
pub use import_queue::DefaultImportQueue;

/// Block status.
#[derive(Debug, PartialEq, Eq)]
pub enum BlockStatus {
	/// Added to the import queue.
	Queued,
	/// Already in the blockchain and the state is available.
	InChainWithState,
	/// In the blockchain, but the state is not available.
	InChainPruned,
	/// Block or parent is known to be bad.
	KnownBad,
	/// Not in the queue or the blockchain.
	Unknown,
}

/// Environment for a Consensus instance.
///
/// Creates proposer instance.
pub trait Environment<B: BlockT> {
	/// The proposer type this creates.
	type Proposer: Proposer<B> + Send + 'static;
	/// A future that resolves to the proposer.
	type CreateProposer: Future<Output = Result<Self::Proposer, Self::Error>>
		+ Send + Unpin + 'static;
	/// Error which can occur upon creation.
	type Error: From<Error> + std::fmt::Debug + 'static;

	/// Initialize the proposal logic on top of a specific header. Provide
	/// the authorities at that header.
	fn init(&mut self, parent_header: &B::Header) -> Self::CreateProposer;
}

/// A proposal that is created by a [`Proposer`].
pub struct Proposal<Block: BlockT, Transaction> {
	/// The block that was build.
	pub block: Block,
	/// Optional proof that was recorded while building the block.
	pub proof: Option<sp_state_machine::StorageProof>,
	/// The storage changes while building this block.
	pub storage_changes: sp_state_machine::StorageChanges<Transaction, HashFor<Block>, NumberFor<Block>>,
}

/// Used as parameter to [`Proposer`] to tell the requirement on recording a proof.
///
/// When `RecordProof::Yes` is given, all accessed trie nodes should be saved. These recorded
/// trie nodes can be used by a third party to proof this proposal without having access to the
/// full storage.
#[derive(Copy, Clone, PartialEq)]
pub enum RecordProof {
	/// `Yes`, record a proof.
	Yes,
	/// `No`, don't record any proof.
	No,
}

impl RecordProof {
	/// Returns if `Self` == `Yes`.
	pub fn yes(&self) -> bool {
		match self {
			Self::Yes => true,
			Self::No => false,
		}
	}
}

/// Will return [`RecordProof::No`] as default value.
impl Default for RecordProof {
	fn default() -> Self {
		Self::No
	}
}

impl From<bool> for RecordProof {
	fn from(val: bool) -> Self {
		if val {
			Self::Yes
		} else {
			Self::No
		}
	}
}

/// Logic for a proposer.
///
/// This will encapsulate creation and evaluation of proposals at a specific
/// block.
///
/// Proposers are generic over bits of "consensus data" which are engine-specific.
pub trait Proposer<B: BlockT> {
	/// Error type which can occur when proposing or evaluating.
	type Error: From<Error> + std::fmt::Debug + 'static;
	/// The transaction type used by the backend.
	type Transaction: Default + Send + 'static;
	/// Future that resolves to a committed proposal with an optional proof.
	type Proposal: Future<Output = Result<Proposal<B, Self::Transaction>, Self::Error>> +
		Send + Unpin + 'static;

	/// Create a proposal.
	///
	/// Gets the `inherent_data` and `inherent_digests` as input for the proposal. Additionally
	/// a maximum duration for building this proposal is given. If building the proposal takes
	/// longer than this maximum, the proposal will be very likely discarded.
	///
	/// # Return
	///
	/// Returns a future that resolves to a [`Proposal`] or to [`Error`].
	fn propose(
		self,
		inherent_data: InherentData,
		inherent_digests: DigestFor<B>,
		max_duration: Duration,
		record_proof: RecordProof,
	) -> Self::Proposal;
}

/// An oracle for when major synchronization work is being undertaken.
///
/// Generally, consensus authoring work isn't undertaken while well behind
/// the head of the chain.
pub trait SyncOracle {
	/// Whether the synchronization service is undergoing major sync.
	/// Returns true if so.
	fn is_major_syncing(&mut self) -> bool;
	/// Whether the synchronization service is offline.
	/// Returns true if so.
	fn is_offline(&mut self) -> bool;
}

/// A synchronization oracle for when there is no network.
#[derive(Clone, Copy, Debug)]
pub struct NoNetwork;

impl SyncOracle for NoNetwork {
	fn is_major_syncing(&mut self) -> bool { false }
	fn is_offline(&mut self) -> bool { false }
}

impl<T> SyncOracle for Arc<T> where T: ?Sized, for<'r> &'r T: SyncOracle {
	fn is_major_syncing(&mut self) -> bool {
		<&T>::is_major_syncing(&mut &**self)
	}

	fn is_offline(&mut self) -> bool {
		<&T>::is_offline(&mut &**self)
	}
}

/// Checks if the current active native block authoring implementation can author with the runtime
/// at the given block.
pub trait CanAuthorWith<Block: BlockT> {
	/// See trait docs for more information.
	///
	/// # Return
	///
	/// - Returns `Ok(())` when authoring is supported.
	/// - Returns `Err(_)` when authoring is not supported.
	fn can_author_with(&self, at: &BlockId<Block>) -> Result<(), String>;
}

/// Checks if the node can author blocks by using
/// [`NativeVersion::can_author_with`](sp_version::NativeVersion::can_author_with).
#[derive(Clone)]
pub struct CanAuthorWithNativeVersion<T>(T);

impl<T> CanAuthorWithNativeVersion<T> {
	/// Creates a new instance of `Self`.
	pub fn new(inner: T) -> Self {
		Self(inner)
	}
}

impl<T: sp_version::GetRuntimeVersion<Block>, Block: BlockT> CanAuthorWith<Block>
	for CanAuthorWithNativeVersion<T>
{
	fn can_author_with(&self, at: &BlockId<Block>) -> Result<(), String> {
		match self.0.runtime_version(at) {
			Ok(version) => self.0.native_version().can_author_with(&version),
			Err(e) => {
				Err(format!(
					"Failed to get runtime version at `{}` and will disable authoring. Error: {}",
					at,
					e,
				))
			}
		}
	}
}

/// Returns always `true` for `can_author_with`. This is useful for tests.
#[derive(Clone)]
pub struct AlwaysCanAuthor;

impl<Block: BlockT> CanAuthorWith<Block> for AlwaysCanAuthor {
	fn can_author_with(&self, _: &BlockId<Block>) -> Result<(), String> {
		Ok(())
	}
}

/// Never can author.
#[derive(Clone)]
pub struct NeverCanAuthor;

impl<Block: BlockT> CanAuthorWith<Block> for NeverCanAuthor {
	fn can_author_with(&self, _: &BlockId<Block>) -> Result<(), String> {
		Err("Authoring is always disabled.".to_string())
	}
}

/// A type from which a slot duration can be obtained.
pub trait SlotData {
	/// Gets the slot duration.
	fn slot_duration(&self) -> u64;

	/// The static slot key
	const SLOT_KEY: &'static [u8];
}

impl SlotData for u64 {
	fn slot_duration(&self) -> u64 {
		*self
	}

	const SLOT_KEY: &'static [u8] = b"aura_slot_duration";
}