// Copyright 2017-2019 Parity Technologies (UK) Ltd.
// This file is part of Substrate.

// Substrate 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 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.  If not, see <http://www.gnu.org/licenses/>.

//! Substrate blockchain API.

mod chain_full;
mod chain_light;

#[cfg(test)]
mod tests;

use std::sync::Arc;
use futures::{future, StreamExt, TryStreamExt};
use log::warn;
use rpc::{
	Result as RpcResult,
	futures::{stream, Future, Sink, Stream},
};

use api::Subscriptions;
use client::{
	self, Client, BlockchainEvents,
	light::{fetcher::Fetcher, blockchain::RemoteBlockchain},
};
use jsonrpc_pubsub::{typed::Subscriber, SubscriptionId};
use primitives::{H256, Blake2Hasher};
use rpc_primitives::{number::NumberOrHex, list::ListOrValue};
use sr_primitives::{
	generic::{BlockId, SignedBlock},
	traits::{Block as BlockT, Header, NumberFor},
};

use self::error::{Result, Error, FutureResult};

pub use api::chain::*;

/// Blockchain backend API
trait ChainBackend<B, E, Block: BlockT, RA>: Send + Sync + 'static
	where
		Block: BlockT<Hash=H256> + 'static,
		B: client_api::backend::Backend<Block, Blake2Hasher> + Send + Sync + 'static,
		E: client::CallExecutor<Block, Blake2Hasher> + Send + Sync + 'static,
{
	/// Get client reference.
	fn client(&self) -> &Arc<Client<B, E, Block, RA>>;

	/// Get subscriptions reference.
	fn subscriptions(&self) -> &Subscriptions;

	/// Tries to unwrap passed block hash, or uses best block hash otherwise.
	fn unwrap_or_best(&self, hash: Option<Block::Hash>) -> Block::Hash {
		match hash.into() {
			None => self.client().info().chain.best_hash,
			Some(hash) => hash,
		}
	}

	/// Get header of a relay chain block.
	fn header(&self, hash: Option<Block::Hash>) -> FutureResult<Option<Block::Header>>;

	/// Get header and body of a relay chain block.
	fn block(&self, hash: Option<Block::Hash>) -> FutureResult<Option<SignedBlock<Block>>>;

	/// Get hash of the n-th block in the canon chain.
	///
	/// By default returns latest block hash.
	fn block_hash(
		&self,
		number: Option<NumberOrHex<NumberFor<Block>>>,
	) -> Result<Option<Block::Hash>> {
		Ok(match number {
			None => Some(self.client().info().chain.best_hash),
			Some(num_or_hex) => self.client()
				.header(&BlockId::number(num_or_hex.to_number()?))
				.map_err(client_err)?
				.map(|h| h.hash()),
		})
	}

	/// Get hash of the last finalized block in the canon chain.
	fn finalized_head(&self) -> Result<Block::Hash> {
		Ok(self.client().info().chain.finalized_hash)
	}

	/// New head subscription
	fn subscribe_new_heads(
		&self,
		_metadata: crate::metadata::Metadata,
		subscriber: Subscriber<Block::Header>,
	) {
		subscribe_headers(
			self.client(),
			self.subscriptions(),
			subscriber,
			|| self.client().info().chain.best_hash,
			|| self.client().import_notification_stream()
				.filter(|notification| future::ready(notification.is_new_best))
				.map(|notification| Ok::<_, ()>(notification.header))
				.compat(),
		)
	}

	/// Unsubscribe from new head subscription.
	fn unsubscribe_new_heads(
		&self,
		_metadata: Option<crate::metadata::Metadata>,
		id: SubscriptionId,
	) -> RpcResult<bool> {
		Ok(self.subscriptions().cancel(id))
	}

	/// New head subscription
	fn subscribe_finalized_heads(
		&self,
		_metadata: crate::metadata::Metadata,
		subscriber: Subscriber<Block::Header>,
	) {
		subscribe_headers(
			self.client(),
			self.subscriptions(),
			subscriber,
			|| self.client().info().chain.finalized_hash,
			|| self.client().finality_notification_stream()
				.map(|notification| Ok::<_, ()>(notification.header))
				.compat(),
		)
	}

	/// Unsubscribe from new head subscription.
	fn unsubscribe_finalized_heads(
		&self,
		_metadata: Option<crate::metadata::Metadata>,
		id: SubscriptionId,
	) -> RpcResult<bool> {
		Ok(self.subscriptions().cancel(id))
	}
}

/// Create new state API that works on full node.
pub fn new_full<B, E, Block: BlockT, RA>(
	client: Arc<Client<B, E, Block, RA>>,
	subscriptions: Subscriptions,
) -> Chain<B, E, Block, RA>
	where
		Block: BlockT<Hash=H256> + 'static,
		B: client_api::backend::Backend<Block, Blake2Hasher> + Send + Sync + 'static,
		E: client::CallExecutor<Block, Blake2Hasher> + Send + Sync + 'static + Clone,
		RA: Send + Sync + 'static,
{
	Chain {
		backend: Box::new(self::chain_full::FullChain::new(client, subscriptions)),
	}
}

/// Create new state API that works on light node.
pub fn new_light<B, E, Block: BlockT, RA, F: Fetcher<Block>>(
	client: Arc<Client<B, E, Block, RA>>,
	subscriptions: Subscriptions,
	remote_blockchain: Arc<dyn RemoteBlockchain<Block>>,
	fetcher: Arc<F>,
) -> Chain<B, E, Block, RA>
	where
		Block: BlockT<Hash=H256> + 'static,
		B: client_api::backend::Backend<Block, Blake2Hasher> + Send + Sync + 'static,
		E: client::CallExecutor<Block, Blake2Hasher> + Send + Sync + 'static + Clone,
		RA: Send + Sync + 'static,
		F: Send + Sync + 'static,
{
	Chain {
		backend: Box::new(self::chain_light::LightChain::new(
			client,
			subscriptions,
			remote_blockchain,
			fetcher,
		)),
	}
}

/// Chain API with subscriptions support.
pub struct Chain<B, E, Block: BlockT, RA> {
	backend: Box<dyn ChainBackend<B, E, Block, RA>>,
}

impl<B, E, Block, RA> ChainApi<NumberFor<Block>, Block::Hash, Block::Header, SignedBlock<Block>> for Chain<B, E, Block, RA> where
	Block: BlockT<Hash=H256> + 'static,
	B: client_api::backend::Backend<Block, Blake2Hasher> + Send + Sync + 'static,
	E: client::CallExecutor<Block, Blake2Hasher> + Send + Sync + 'static,
	RA: Send + Sync + 'static
{
	type Metadata = crate::metadata::Metadata;

	fn header(&self, hash: Option<Block::Hash>) -> FutureResult<Option<Block::Header>> {
		self.backend.header(hash)
	}

	fn block(&self, hash: Option<Block::Hash>) -> FutureResult<Option<SignedBlock<Block>>>
	{
		self.backend.block(hash)
	}

	fn block_hash(
		&self,
		number: Option<ListOrValue<NumberOrHex<NumberFor<Block>>>>
	) -> Result<ListOrValue<Option<Block::Hash>>> {
		match number {
			None => self.backend.block_hash(None).map(ListOrValue::Value),
			Some(ListOrValue::Value(number)) => self.backend.block_hash(Some(number)).map(ListOrValue::Value),
			Some(ListOrValue::List(list)) => Ok(ListOrValue::List(list
				.into_iter()
				.map(|number| self.backend.block_hash(Some(number)))
				.collect::<Result<_>>()?
			))
		}
	}

	fn finalized_head(&self) -> Result<Block::Hash> {
		self.backend.finalized_head()
	}

	fn subscribe_new_heads(&self, metadata: Self::Metadata, subscriber: Subscriber<Block::Header>) {
		self.backend.subscribe_new_heads(metadata, subscriber)
	}

	fn unsubscribe_new_heads(&self, metadata: Option<Self::Metadata>, id: SubscriptionId) -> RpcResult<bool> {
		self.backend.unsubscribe_new_heads(metadata, id)
	}

	fn subscribe_finalized_heads(&self, metadata: Self::Metadata, subscriber: Subscriber<Block::Header>) {
		self.backend.subscribe_finalized_heads(metadata, subscriber)
	}

	fn unsubscribe_finalized_heads(&self, metadata: Option<Self::Metadata>, id: SubscriptionId) -> RpcResult<bool> {
		self.backend.unsubscribe_finalized_heads(metadata, id)
	}
}

/// Subscribe to new headers.
fn subscribe_headers<B, E, Block, RA, F, G, S, ERR>(
	client: &Arc<Client<B, E, Block, RA>>,
	subscriptions: &Subscriptions,
	subscriber: Subscriber<Block::Header>,
	best_block_hash: G,
	stream: F,
) where
	Block: BlockT<Hash=H256> + 'static,
	B: client_api::backend::Backend<Block, Blake2Hasher> + Send + Sync + 'static,
	E: client::CallExecutor<Block, Blake2Hasher> + Send + Sync + 'static,
	F: FnOnce() -> S,
	G: FnOnce() -> Block::Hash,
	ERR: ::std::fmt::Debug,
	S: Stream<Item=Block::Header, Error=ERR> + Send + 'static,
{
	subscriptions.add(subscriber, |sink| {
		// send current head right at the start.
		let header = client.header(&BlockId::Hash(best_block_hash()))
			.map_err(client_err)
			.and_then(|header| {
				header.ok_or_else(|| "Best header missing.".to_owned().into())
			})
			.map_err(Into::into);

		// send further subscriptions
		let stream = stream()
			.map(|res| Ok(res))
			.map_err(|e| warn!("Block notification stream error: {:?}", e));

		sink
			.sink_map_err(|e| warn!("Error sending notifications: {:?}", e))
			.send_all(
				stream::iter_result(vec![Ok(header)])
					.chain(stream)
			)
			// we ignore the resulting Stream (if the first stream is over we are unsubscribed)
			.map(|_| ())
	});
}

fn client_err(err: client::error::Error) -> Error {
	Error::Client(Box::new(err))
}