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// This file is part of Substrate.

// Copyright (C) 2017-2020 Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0

// This program 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.

// This program 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 this program. If not, see <https://www.gnu.org/licenses/>.

//! Chain utilities.

use crate::error;
use crate::builder::{ServiceBuilderCommand, ServiceBuilder};
use crate::error::Error;
use sc_chain_spec::ChainSpec;
use log::{warn, info};
use futures::{future, prelude::*};
use sp_runtime::traits::{
	Block as BlockT, NumberFor, One, Zero, Header, SaturatedConversion, MaybeSerializeDeserialize,
};
use sp_runtime::generic::{BlockId, SignedBlock};
use codec::{Decode, Encode, IoReader as CodecIoReader};
use crate::client::{Client, LocalCallExecutor};
use sp_consensus::{
	BlockOrigin,
	import_queue::{IncomingBlock, Link, BlockImportError, BlockImportResult, ImportQueue},
};
use sc_executor::{NativeExecutor, NativeExecutionDispatch};
use sp_core::storage::{StorageKey, well_known_keys, ChildInfo, Storage, StorageChild, StorageMap};
use sc_client_api::{StorageProvider, BlockBackend, UsageProvider};

use std::{io::{Read, Write, Seek}, pin::Pin, collections::HashMap};
use std::{thread, time::{Duration, Instant}};
use serde_json::{de::IoRead as JsonIoRead, Deserializer, StreamDeserializer};
use std::convert::{TryFrom, TryInto};
use sp_runtime::traits::{CheckedDiv, Saturating};

/// Number of blocks we will add to the queue before waiting for the queue to catch up.
const MAX_PENDING_BLOCKS: u64 = 1_024;

/// Number of milliseconds to wait until next poll.
const DELAY_TIME: u64 = 2_000;

/// Number of milliseconds that must have passed between two updates.
const TIME_BETWEEN_UPDATES: u64 = 3_000;

/// Build a chain spec json
pub fn build_spec(spec: &dyn ChainSpec, raw: bool) -> error::Result<String> {
	spec.as_json(raw).map_err(Into::into)
}


/// Helper enum that wraps either a binary decoder (from parity-scale-codec), or a JSON decoder (from serde_json).
/// Implements the Iterator Trait, calling `next()` will decode the next SignedBlock and return it.
enum BlockIter<R, B> where
	R: std::io::Read + std::io::Seek,
{
	Binary {
		// Total number of blocks we are expecting to decode.
		num_expected_blocks: u64,
		// Number of blocks we have decoded thus far.
		read_block_count: u64,
		// Reader to the data, used for decoding new blocks.
		reader: CodecIoReader<R>,
	},
	Json {
		// Nubmer of blocks we have decoded thus far.
		read_block_count: u64,
		// Stream to the data, used for decoding new blocks.
		reader: StreamDeserializer<'static, JsonIoRead<R>, SignedBlock<B>>,
	},
}

impl<R, B> BlockIter<R, B> where
	R: Read + Seek + 'static,
	B: BlockT + MaybeSerializeDeserialize,
{
	fn new(input: R, binary: bool) -> Result<Self, String> {
		if binary {
			let mut reader = CodecIoReader(input);
			// If the file is encoded in binary format, it is expected to first specify the number
			// of blocks that are going to be decoded. We read it and add it to our enum struct.
			let num_expected_blocks: u64 = Decode::decode(&mut reader)
				.map_err(|e| format!("Failed to decode the number of blocks: {:?}", e))?;
			Ok(BlockIter::Binary {
				num_expected_blocks,
				read_block_count: 0,
				reader,
			})
		} else {
			let stream_deser = Deserializer::from_reader(input)
				.into_iter::<SignedBlock<B>>();
			Ok(BlockIter::Json {
				reader: stream_deser,
				read_block_count: 0,
			})
		}
	}

	/// Returns the number of blocks read thus far.
	fn read_block_count(&self) -> u64 {
		match self {
			BlockIter::Binary { read_block_count, .. }
			| BlockIter::Json { read_block_count, .. }
			=> *read_block_count,
		}
	}

	/// Returns the total number of blocks to be imported, if possible.
	fn num_expected_blocks(&self) -> Option<u64> {
		match self {
			BlockIter::Binary { num_expected_blocks, ..} => Some(*num_expected_blocks),
			BlockIter::Json {..} => None
		}
	}
}

impl<R, B> Iterator for BlockIter<R, B> where
	R: Read + Seek + 'static,
	B: BlockT + MaybeSerializeDeserialize,
{
	type Item = Result<SignedBlock<B>, String>;

	fn next(&mut self) -> Option<Self::Item> {
		match self {
			BlockIter::Binary { num_expected_blocks, read_block_count, reader } => {
				if read_block_count < num_expected_blocks {
					let block_result: Result<SignedBlock::<B>, _> =  SignedBlock::<B>::decode(reader)
						.map_err(|e| e.to_string());
					*read_block_count += 1;
					Some(block_result)
				} else {
					// `read_block_count` == `num_expected_blocks` so we've read enough blocks.
					None
				}
			}
			BlockIter::Json { reader, read_block_count } => {
				let res = Some(reader.next()?.map_err(|e| e.to_string()));
				*read_block_count += 1;
				res
			}
		}
	}
}

/// Imports the SignedBlock to the queue.
fn import_block_to_queue<TBl, TImpQu>(
	signed_block: SignedBlock<TBl>,
	queue: &mut TImpQu,
	force: bool
) where
	TBl: BlockT + MaybeSerializeDeserialize,
	TImpQu: 'static + ImportQueue<TBl>,
{
	let (header, extrinsics) = signed_block.block.deconstruct();
	let hash = header.hash();
	// import queue handles verification and importing it into the client.
	queue.import_blocks(BlockOrigin::File, vec![
		IncomingBlock::<TBl> {
			hash,
			header: Some(header),
			body: Some(extrinsics),
			justification: signed_block.justification,
			origin: None,
			allow_missing_state: false,
			import_existing: force,
		}
	]);
}

/// Returns true if we have imported every block we were supposed to import, else returns false.
fn importing_is_done(
	num_expected_blocks: Option<u64>,
	read_block_count: u64,
	imported_blocks: u64
) -> bool {
	if let Some(num_expected_blocks) = num_expected_blocks {
		imported_blocks >= num_expected_blocks
	} else {
		imported_blocks >= read_block_count
	}
}

/// Structure used to log the block importing speed.
struct Speedometer<B: BlockT> {
	best_number: NumberFor<B>,
	last_number: Option<NumberFor<B>>,
	last_update: Instant,
}

impl<B: BlockT> Speedometer<B> {
	/// Creates a fresh Speedometer.
	fn new() -> Self {
		Self {
			best_number: NumberFor::<B>::from(0),
			last_number: None,
			last_update: Instant::now(),
		}
	}

	/// Calculates `(best_number - last_number) / (now - last_update)` and 
	/// logs the speed of import.
	fn display_speed(&self) {
		// Number of milliseconds elapsed since last time.
		let elapsed_ms = {
			let elapsed = self.last_update.elapsed();
			let since_last_millis = elapsed.as_secs() * 1000;
			let since_last_subsec_millis = elapsed.subsec_millis() as u64;
			since_last_millis + since_last_subsec_millis
		};

		// Number of blocks that have been imported since last time.
		let diff = match self.last_number {
			None => return,
			Some(n) => self.best_number.saturating_sub(n)
		};

		if let Ok(diff) = TryInto::<u128>::try_into(diff) {
			// If the number of blocks can be converted to a regular integer, then it's easy: just
			// do the math and turn it into a `f64`.
			let speed = diff.saturating_mul(10_000).checked_div(u128::from(elapsed_ms))
				.map_or(0.0, |s| s as f64) / 10.0;
			info!("📦 Current best block: {} ({:4.1} bps)", self.best_number, speed);
		} else {
			// If the number of blocks can't be converted to a regular integer, then we need a more
			// algebraic approach and we stay within the realm of integers.
			let one_thousand = NumberFor::<B>::from(1_000);
			let elapsed = NumberFor::<B>::from(
				<u32 as TryFrom<_>>::try_from(elapsed_ms).unwrap_or(u32::max_value())
			);

			let speed = diff.saturating_mul(one_thousand).checked_div(&elapsed)
				.unwrap_or_else(Zero::zero);
			info!("📦 Current best block: {} ({} bps)", self.best_number, speed)
		}
	}

	/// Updates the Speedometer.
	fn update(&mut self, best_number: NumberFor<B>) {
		self.last_number = Some(self.best_number);
		self.best_number = best_number;
		self.last_update = Instant::now();
	}

	// If more than TIME_BETWEEN_UPDATES has elapsed since last update,
	// then print and update the speedometer.
	fn notify_user(&mut self, best_number: NumberFor<B>) {
		let delta = Duration::from_millis(TIME_BETWEEN_UPDATES);
		if Instant::now().duration_since(self.last_update) >= delta {
			self.display_speed();
			self.update(best_number);
		}
	}
}

/// Different State that the `import_blocks` future could be in.
enum ImportState<R, B> where 
	R: Read + Seek + 'static,
	B: BlockT + MaybeSerializeDeserialize,
{
	/// We are reading from the BlockIter structure, adding those blocks to the queue if possible.
	Reading{block_iter: BlockIter<R, B>},
	/// The queue is full (contains at least MAX_PENDING_BLOCKS blocks) and we are waiting for it to catch up.
	WaitingForImportQueueToCatchUp{
		block_iter: BlockIter<R, B>,
		delay: Duration,
		block: SignedBlock<B>
	},
	// We have added all the blocks to the queue but they are still being processed.
	WaitingForImportQueueToFinish{
		num_expected_blocks: Option<u64>, 
		read_block_count: u64,
		delay: Duration,
	},
}

impl<
	TBl, TRtApi, TBackend,
	TExecDisp, TFchr, TSc, TImpQu, TFprb, TFpp,
	TExPool, TRpc, Backend
> ServiceBuilderCommand for ServiceBuilder<
	TBl, TRtApi,
	Client<TBackend, LocalCallExecutor<TBackend, NativeExecutor<TExecDisp>>, TBl, TRtApi>,
	TFchr, TSc, TImpQu, TFprb, TFpp, TExPool, TRpc, Backend
> where
	TBl: BlockT + MaybeSerializeDeserialize,
	TBackend: 'static + sc_client_api::backend::Backend<TBl> + Send,
	TExecDisp: 'static + NativeExecutionDispatch,
	TImpQu: 'static + ImportQueue<TBl>,
	TRtApi: 'static + Send + Sync,
	Self: Send + 'static,
{
	type Block = TBl;
	type NativeDispatch = TExecDisp;

	fn import_blocks(
		mut self,
		input: impl Read + Seek + Send + 'static,
		force: bool,
		binary: bool,
	) -> Pin<Box<dyn Future<Output = Result<(), Error>> + Send>> {
		struct WaitLink {
			imported_blocks: u64,
			has_error: bool,
		}

		impl WaitLink {
			fn new() -> WaitLink {
				WaitLink {
					imported_blocks: 0,
					has_error: false,
				}
			}
		}

		impl<B: BlockT> Link<B> for WaitLink {
			fn blocks_processed(
				&mut self,
				imported: usize,
				_num_expected_blocks: usize,
				results: Vec<(Result<BlockImportResult<NumberFor<B>>, BlockImportError>, B::Hash)>
			) {
				self.imported_blocks += imported as u64;

				for result in results {
					if let (Err(err), hash) = result {
						warn!("There was an error importing block with hash {:?}: {:?}", hash, err);
						self.has_error = true;
						break;
					}
				}
			}
		}

		let mut link = WaitLink::new();
		let block_iter_res: Result<BlockIter<_, Self::Block>, String> = BlockIter::new(input, binary);

		let block_iter = match block_iter_res {
			Ok(block_iter) => block_iter,
			Err(e) => {
				// We've encountered an error while creating the block iterator 
				// so we can just return a future that returns an error.
				return future::ready(Err(Error::Other(e))).boxed()
			}
		};

		let mut state = Some(ImportState::Reading{block_iter});
		let mut speedometer = Speedometer::<TBl>::new();

		// Importing blocks is implemented as a future, because we want the operation to be
		// interruptible.
		//
		// Every time we read a block from the input or import a bunch of blocks from the import
		// queue, the `Future` re-schedules itself and returns `Poll::Pending`.
		// This makes it possible either to interleave other operations in-between the block imports,
		// or to stop the operation completely.
		let import = future::poll_fn(move |cx| {
			let client = &self.client;
			let queue = &mut self.import_queue;
			match state.take().expect("state should never be None; qed") {
				ImportState::Reading{mut block_iter} => {
					match block_iter.next() {
						None => {
							// The iterator is over: we now need to wait for the import queue to finish.
							let num_expected_blocks = block_iter.num_expected_blocks();
							let read_block_count = block_iter.read_block_count();
							let delay = Duration::from_millis(DELAY_TIME);
							state = Some(ImportState::WaitingForImportQueueToFinish{num_expected_blocks, read_block_count, delay});
						},
						Some(block_result) => {
							let read_block_count = block_iter.read_block_count();
							match block_result {
								Ok(block) => {
									if read_block_count - link.imported_blocks >= MAX_PENDING_BLOCKS {
										// The queue is full, so do not add this block and simply wait until
										// the queue has made some progress.
										let delay = Duration::from_millis(DELAY_TIME);
										state = Some(ImportState::WaitingForImportQueueToCatchUp{block_iter, delay, block});
									} else {
										// Queue is not full, we can keep on adding blocks to the queue.
										import_block_to_queue(block, queue, force);
										state = Some(ImportState::Reading{block_iter});
									}
								}
								Err(e) => {
									return std::task::Poll::Ready(
										Err(Error::Other(format!("Error reading block #{}: {}", read_block_count, e))))
								}
							}
						}
					}
				},
				ImportState::WaitingForImportQueueToCatchUp{block_iter, delay, block} => {
					let read_block_count = block_iter.read_block_count();
					if read_block_count - link.imported_blocks >= MAX_PENDING_BLOCKS {
						thread::sleep(delay);
						// Queue is still full, so wait until there is room to insert our block.
						state = Some(ImportState::WaitingForImportQueueToCatchUp{block_iter, delay, block});
					} else {
						// Queue is no longer full, so we can add our block to the queue.
						import_block_to_queue(block, queue, force);
						// Switch back to Reading state.
						state = Some(ImportState::Reading{block_iter});
					}
				},
				ImportState::WaitingForImportQueueToFinish{num_expected_blocks, read_block_count, delay} => {
					// All the blocks have been added to the queue, which doesn't mean they 
					// have all been properly imported.
					if importing_is_done(num_expected_blocks, read_block_count, link.imported_blocks) {
						// Importing is done, we can log the result and return.
						info!(
							"🎉 Imported {} blocks. Best: #{}",
							read_block_count, client.chain_info().best_number
						);
						return std::task::Poll::Ready(Ok(()))
					} else {
						thread::sleep(delay);
						// Importing is not done, we still have to wait for the queue to finish.
						state = Some(ImportState::WaitingForImportQueueToFinish{num_expected_blocks, read_block_count, delay});
					}
				}
			}

			queue.poll_actions(cx, &mut link);

			let best_number = client.chain_info().best_number;
			speedometer.notify_user(best_number);

			if link.has_error {
				return std::task::Poll::Ready(Err(
					Error::Other(
						format!("Stopping after #{} blocks because of an error", link.imported_blocks)
					)
				))
			}

			cx.waker().wake_by_ref();
			std::task::Poll::Pending
		});
		Box::pin(import)
	}

	fn export_blocks(
		self,
		mut output: impl Write + 'static,
		from: NumberFor<TBl>,
		to: Option<NumberFor<TBl>>,
		binary: bool
	) -> Pin<Box<dyn Future<Output = Result<(), Error>>>> {
		let mut block = from;

		let last = match to {
			Some(v) if v.is_zero() => One::one(),
			Some(v) => v,
			None => self.client.chain_info().best_number,
		};

		let mut wrote_header = false;

		// Exporting blocks is implemented as a future, because we want the operation to be
		// interruptible.
		//
		// Every time we write a block to the output, the `Future` re-schedules itself and returns
		// `Poll::Pending`.
		// This makes it possible either to interleave other operations in-between the block exports,
		// or to stop the operation completely.
		let export = future::poll_fn(move |cx| {
			let client = &self.client;

			if last < block {
				return std::task::Poll::Ready(Err("Invalid block range specified".into()));
			}

			if !wrote_header {
				info!("Exporting blocks from #{} to #{}", block, last);
				if binary {
					let last_: u64 = last.saturated_into::<u64>();
					let block_: u64 = block.saturated_into::<u64>();
					let len: u64 = last_ - block_ + 1;
					output.write_all(&len.encode())?;
				}
				wrote_header = true;
			}

			match client.block(&BlockId::number(block))? {
				Some(block) => {
					if binary {
						output.write_all(&block.encode())?;
					} else {
						serde_json::to_writer(&mut output, &block)
							.map_err(|e| format!("Error writing JSON: {}", e))?;
					}
			},
				// Reached end of the chain.
				None => return std::task::Poll::Ready(Ok(())),
			}
			if (block % 10000.into()).is_zero() {
				info!("#{}", block);
			}
			if block == last {
				return std::task::Poll::Ready(Ok(()));
			}
			block += One::one();

			// Re-schedule the task in order to continue the operation.
			cx.waker().wake_by_ref();
			std::task::Poll::Pending
		});

		Box::pin(export)
	}

	fn revert_chain(
		&self,
		blocks: NumberFor<TBl>
	) -> Result<(), Error> {
		let reverted = self.client.revert(blocks)?;
		let info = self.client.chain_info();

		if reverted.is_zero() {
			info!("There aren't any non-finalized blocks to revert.");
		} else {
			info!("Reverted {} blocks. Best: #{} ({})", reverted, info.best_number, info.best_hash);
		}
		Ok(())
	}

	fn check_block(
		self,
		block_id: BlockId<TBl>
	) -> Pin<Box<dyn Future<Output = Result<(), Error>> + Send>> {
		match self.client.block(&block_id) {
			Ok(Some(block)) => {
				let mut buf = Vec::new();
				1u64.encode_to(&mut buf);
				block.encode_to(&mut buf);
				let reader = std::io::Cursor::new(buf);
				self.import_blocks(reader, true, true)
			}
			Ok(None) => Box::pin(future::err("Unknown block".into())),
			Err(e) => Box::pin(future::err(format!("Error reading block: {:?}", e).into())),
		}
	}

	fn export_raw_state(
		&self,
		block: Option<BlockId<Self::Block>>,
	) -> Result<Storage, Error> {
		let block = block.unwrap_or_else(
			|| BlockId::Hash(self.client.usage_info().chain.best_hash)
		);

		let empty_key = StorageKey(Vec::new());
		let mut top_storage = self.client.storage_pairs(&block, &empty_key)?;
		let mut children_default = HashMap::new();

		// Remove all default child storage roots from the top storage and collect the child storage
		// pairs.
		while let Some(pos) = top_storage
			.iter()
			.position(|(k, _)| k.0.starts_with(well_known_keys::DEFAULT_CHILD_STORAGE_KEY_PREFIX)) {
			let (key, _) = top_storage.swap_remove(pos);

			let key = StorageKey(
				key.0[well_known_keys::DEFAULT_CHILD_STORAGE_KEY_PREFIX.len()..].to_vec(),
			);
			let child_info = ChildInfo::new_default(&key.0);

			let keys = self.client.child_storage_keys(&block, &child_info, &empty_key)?;
			let mut pairs = StorageMap::new();
			keys.into_iter().try_for_each(|k| {
				if let Some(value) = self.client.child_storage(&block, &child_info, &k)? {
					pairs.insert(k.0, value.0);
				}

				Ok::<_, Error>(())
			})?;

			children_default.insert(key.0, StorageChild { child_info, data: pairs });
		}

		let top = top_storage.into_iter().map(|(k, v)| (k.0, v.0)).collect();
		Ok(Storage { top, children_default })
	}
}