// Copyright 2017 Parity Technologies (UK) Ltd.
// This file is part of Polkadot.

// Polkadot 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.

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

//! Strongly typed API for Polkadot based around the locally-compiled native
//! runtime.

extern crate polkadot_executor;
extern crate polkadot_runtime as runtime;
extern crate polkadot_primitives as primitives;
extern crate substrate_codec as codec;
extern crate substrate_runtime_io as runtime_io;
extern crate substrate_client as client;
extern crate substrate_executor as substrate_executor;
extern crate substrate_runtime_executive;
extern crate substrate_primitives;
extern crate substrate_state_machine as state_machine;

#[macro_use]
extern crate error_chain;

#[macro_use]
extern crate log;

#[cfg(test)]
extern crate substrate_keyring as keyring;

use client::backend::Backend;
use client::Client;
use polkadot_executor::Executor as LocalDispatch;
use substrate_executor::{NativeExecutionDispatch, NativeExecutor};
use state_machine::OverlayedChanges;
use primitives::{AccountId, BlockId, Index, SessionKey, Timestamp};
use primitives::parachain::DutyRoster;
use runtime::{Block, Header, UncheckedExtrinsic, Extrinsic, Call, TimestampCall};

error_chain! {
	errors {
		/// Unknown runtime code.
		UnknownRuntime {
			description("Unknown runtime code")
			display("Unknown runtime code")
		}
		/// Unknown block ID.
		UnknownBlock(b: BlockId) {
			description("Unknown block")
			display("Unknown block")
		}
		/// Attempted to push an inherent extrinsic manually.
		PushedInherentTransaction(xt: UncheckedExtrinsic) {
			description("Attempted to push an inherent extrinsic to a block."),
			display("Pushed inherent extrinsic to a block: {:?}", xt),
		}
		/// Badly-formed extrinsic.
		BadlyFormedTransaction(xt: UncheckedExtrinsic) {
			description("Attempted to push a badly-formed extrinsic to a block."),
			display("Pushed badly-formed extrinsic to a block: {:?}", xt),
		}
		/// Some other error.
		// TODO: allow to be specified as associated type of PolkadotApi
		Other(e: Box<::std::error::Error + Send>) {
			description("Other error")
			display("Other error: {}", e.description())
		}
	}

	links {
		Executor(substrate_executor::error::Error, substrate_executor::error::ErrorKind);
	}
}

impl From<client::error::Error> for Error {
	fn from(e: client::error::Error) -> Error {
		match e {
			client::error::Error(client::error::ErrorKind::UnknownBlock(b), _) => Error::from_kind(ErrorKind::UnknownBlock(b)),
			other => Error::from_kind(ErrorKind::Other(Box::new(other) as Box<_>)),
		}
	}
}

/// A builder for blocks.
pub trait BlockBuilder: Sized {
	/// Push a non-inherent extrinsic.
	fn push_extrinsic(&mut self, extrinsic: UncheckedExtrinsic) -> Result<()>;

	/// Finalise the block.
	fn bake(self) -> Block;
}

/// A checked block identifier.
pub trait CheckedBlockId: Clone {
	/// Yield the underlying block ID.
	fn block_id(&self) -> &BlockId;
}

/// Trait encapsulating the Polkadot API.
///
/// All calls should fail when the exact runtime is unknown.
pub trait PolkadotApi {
	/// A checked block ID. Used to avoid redundancy of code check.
	type CheckedBlockId: CheckedBlockId;
	/// The type used to build blocks.
	type BlockBuilder: BlockBuilder;

	/// Check whether requests at the given block ID can be served.
	///
	/// It should not be possible to instantiate this type without going
	/// through this function.
	fn check_id(&self, id: BlockId) -> Result<Self::CheckedBlockId>;

	/// Get session keys at a given block.
	fn session_keys(&self, at: &Self::CheckedBlockId) -> Result<Vec<SessionKey>>;

	/// Get validators at a given block.
	fn validators(&self, at: &Self::CheckedBlockId) -> Result<Vec<AccountId>>;

	/// Get the authority duty roster at a block.
	fn duty_roster(&self, at: &Self::CheckedBlockId) -> Result<DutyRoster>;

	/// Get the timestamp registered at a block.
	fn timestamp(&self, at: &Self::CheckedBlockId) -> Result<Timestamp>;

	/// Get the index of an account at a block.
	fn index(&self, at: &Self::CheckedBlockId, account: AccountId) -> Result<Index>;


	/// Evaluate a block and see if it gives an error.
	fn evaluate_block(&self, at: &Self::CheckedBlockId, block: Block) -> Result<()>;

	/// Create a block builder on top of the parent block.
	fn build_block(&self, parent: &Self::CheckedBlockId, timestamp: u64) -> Result<Self::BlockBuilder>;
}

/// A checked block ID used for the substrate-client implementation of CheckedBlockId;
#[derive(Debug, Clone, Copy)]
pub struct CheckedId(BlockId);

impl CheckedBlockId for CheckedId {
	fn block_id(&self) -> &BlockId {
		&self.0
	}
}

// set up the necessary scaffolding to execute the runtime.
macro_rules! with_runtime {
	($client: ident, $at: expr, $exec: expr) => {{
		$client.state_at($at.block_id()).map_err(Error::from).and_then(|state| {
			let mut changes = Default::default();
			let mut ext = state_machine::Ext {
				overlay: &mut changes,
				backend: &state,
			};

			::substrate_executor::with_native_environment(&mut ext, $exec).map_err(Into::into)
		})
	}}
}

impl<B: Backend> PolkadotApi for Client<B, NativeExecutor<LocalDispatch>>
	where ::client::error::Error: From<<<B as Backend>::State as state_machine::backend::Backend>::Error>
{
	type CheckedBlockId = CheckedId;
	type BlockBuilder = ClientBlockBuilder<B::State>;

	fn check_id(&self, id: BlockId) -> Result<CheckedId> {
		// bail if the code is not the same as the natively linked.
		if self.code_at(&id)? != LocalDispatch::native_equivalent() {
			bail!("This node is out of date. Block authoring may not work correctly. Bailing.")
		}

		Ok(CheckedId(id))
	}

	fn session_keys(&self, at: &CheckedId) -> Result<Vec<SessionKey>> {
		with_runtime!(self, at, ::runtime::Consensus::authorities)
	}

	fn validators(&self, at: &CheckedId) -> Result<Vec<AccountId>> {
		with_runtime!(self, at, ::runtime::Session::validators)
	}

	fn duty_roster(&self, at: &CheckedId) -> Result<DutyRoster> {
		with_runtime!(self, at, ::runtime::Parachains::calculate_duty_roster)
	}

	fn timestamp(&self, at: &CheckedId) -> Result<Timestamp> {
		with_runtime!(self, at, ::runtime::Timestamp::now)
	}

	fn evaluate_block(&self, at: &CheckedId, block: Block) -> Result<()> {
		with_runtime!(self, at, || ::runtime::Executive::execute_block(block))
	}

	fn index(&self, at: &Self::CheckedBlockId, account: AccountId) -> Result<Index> {
		with_runtime!(self, at, || ::runtime::System::account_index(account))
	}

	fn build_block(&self, parent: &CheckedId, timestamp: Timestamp) -> Result<Self::BlockBuilder> {
		let parent = parent.block_id();
		let header = Header {
			parent_hash: self.block_hash_from_id(parent)?.ok_or(ErrorKind::UnknownBlock(*parent))?,
			number: self.block_number_from_id(parent)?.ok_or(ErrorKind::UnknownBlock(*parent))? + 1,
			state_root: Default::default(),
			extrinsics_root: Default::default(),
			digest: Default::default(),
		};

		let extrinsics = vec![
			UncheckedExtrinsic {
				extrinsic: Extrinsic {
					signed: Default::default(),
					index: Default::default(),
					function: Call::Timestamp(TimestampCall::set(timestamp)),
				},
				signature: Default::default(),
			}
		];

		let mut builder = ClientBlockBuilder {
			parent: *parent,
			changes: OverlayedChanges::default(),
			state: self.state_at(parent)?,
			header,
			timestamp,
			extrinsics: extrinsics.clone(),
		};

		builder.initialise_block()?;

		for inherent in extrinsics {
			builder.apply_extrinsic(inherent)?;
		}

		Ok(builder)
	}
}

/// A polkadot block builder.
#[derive(Debug, Clone)]
pub struct ClientBlockBuilder<S> {
	parent: BlockId,
	changes: OverlayedChanges,
	state: S,
	header: Header,
	timestamp: Timestamp,
	extrinsics: Vec<UncheckedExtrinsic>,
}

impl<S: state_machine::Backend> ClientBlockBuilder<S>
	where S::Error: Into<client::error::Error>
{
	// executes a extrinsic, inherent or otherwise, without appending to the list
	fn initialise_block(&mut self) -> Result<()> {
		let mut ext = state_machine::Ext {
			overlay: &mut self.changes,
			backend: &self.state,
		};

		let h = self.header.clone();

		let result = ::substrate_executor::with_native_environment(
			&mut ext,
			|| runtime::Executive::initialise_block(&h),
		).map_err(Into::into);

		match result {
			Ok(_) => {
				ext.overlay.commit_prospective();
				Ok(())
			}
			Err(e) => {
				ext.overlay.discard_prospective();
				Err(e)
			}
		}
	}

	// executes a extrinsic, inherent or otherwise, without appending to the list
	fn apply_extrinsic(&mut self, extrinsic: UncheckedExtrinsic) -> Result<()> {
		let mut ext = state_machine::Ext {
			overlay: &mut self.changes,
			backend: &self.state,
		};

		let result = ::substrate_executor::with_native_environment(
			&mut ext,
			move || runtime::Executive::apply_extrinsic(extrinsic),
		).map_err(Into::into);

		match result {
			Ok(_) => {
				ext.overlay.commit_prospective();
				Ok(())
			}
			Err(e) => {
				ext.overlay.discard_prospective();
				Err(e)
			}
		}
	}
}

impl<S: state_machine::Backend> BlockBuilder for ClientBlockBuilder<S>
	where S::Error: Into<client::error::Error>
{
	fn push_extrinsic(&mut self, extrinsic: UncheckedExtrinsic) -> Result<()> {
		// Check that this is not an "inherent" extrinsic.
		if extrinsic.signature == Default::default() {
			bail!(ErrorKind::PushedInherentTransaction(extrinsic));
		} else {
			self.apply_extrinsic(extrinsic.clone())?;
			self.extrinsics.push(extrinsic);
			Ok(())
		}
	}

	fn bake(mut self) -> Block {
		let mut ext = state_machine::Ext {
			overlay: &mut self.changes,
			backend: &self.state,
		};

		let final_header = ::substrate_executor::with_native_environment(
			&mut ext,
			move || runtime::Executive::finalise_block()
		).expect("all inherent extrinsics pushed; all other extrinsics executed correctly; qed");
		Block {
			header: final_header,
			extrinsics: self.extrinsics,
		}
	}
}

#[cfg(test)]
mod tests {
	use super::*;
	use runtime_io::with_externalities;
	use keyring::Keyring;
	use codec::Slicable;
	use client::in_mem::Backend as InMemory;
	use substrate_executor::NativeExecutionDispatch;
	use runtime::{GenesisConfig, ConsensusConfig, SessionConfig, BuildExternalities};

	fn validators() -> Vec<AccountId> {
		vec![
			Keyring::One.to_raw_public(),
			Keyring::Two.to_raw_public(),
		]
	}

	fn client() -> Client<InMemory, NativeExecutor<LocalDispatch>> {
		let genesis_config = GenesisConfig {
			consensus: Some(ConsensusConfig {
				code: LocalDispatch::native_equivalent().to_vec(),
				authorities: validators(),
			}),
			system: None,
			session: Some(SessionConfig {
				validators: validators(),
				session_length: 100,
			}),
			council: Some(Default::default()),
			democracy: Some(Default::default()),
			parachains: Some(Default::default()),
			staking: Some(Default::default()),
		};
		::client::new_in_mem(
			LocalDispatch::new(),
			|| {
				let mut storage = genesis_config.build_externalities();
				let block = ::client::genesis::construct_genesis_block(&storage);
				with_externalities(&mut storage, ||
					// TODO: use api.rs to dispatch instead
					runtime::System::initialise_genesis_state(&block.header)
				);
				(substrate_primitives::block::Header::decode(&mut block.header.encode().as_ref()).expect("to_vec() always gives a valid serialisation; qed"), storage.into_iter().collect())
			}
		).unwrap()
	}

	#[test]
	fn gets_session_and_validator_keys() {
		let client = client();
		let id = client.check_id(BlockId::Number(0)).unwrap();
		assert_eq!(client.session_keys(&id).unwrap(), validators());
		assert_eq!(client.validators(&id).unwrap(), validators());
	}

	#[test]
	fn build_block() {
		let client = client();

		let id = client.check_id(BlockId::Number(0)).unwrap();
		let block_builder = client.build_block(&id, 1_000_000).unwrap();
		let block = block_builder.bake();

		assert_eq!(block.header.number, 1);
		assert!(block.header.extrinsics_root != Default::default());
	}

	#[test]
	fn fails_to_check_id_for_unknown_block() {
		assert!(client().check_id(BlockId::Number(100)).is_err());
	}
}