// Copyright 2015-2019 Parity Technologies (UK) Ltd.
// This file is part of Parity Ethereum.

// Parity Ethereum 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.

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

//! Snapshot test helpers. These are used to build blockchains and state tries
//! which can be queried before and after a full snapshot/restore cycle.

use std::sync::Arc;
use std::sync::atomic::AtomicBool;

use account_db::AccountDBMut;
use account_state;
use blockchain::{BlockChain, BlockChainDB};
use client_traits::ChainInfo;
use common_types::{
	ids::BlockId,
	basic_account::BasicAccount,
	errors::EthcoreError,
	snapshot::Progress,
};
use engine::Engine;
use ethcore::client::Client;
use ethereum_types::H256;
use ethtrie::{SecTrieDBMut, TrieDB, TrieDBMut};
use hash_db::HashDB;
use journaldb;
use keccak_hash::{KECCAK_NULL_RLP};
use keccak_hasher::KeccakHasher;
use kvdb::DBValue;
use log::trace;
use parking_lot::RwLock;
use rand::Rng;
use rlp;
use snapshot::{
	SnapshotClient,
	StateRebuilder,
	io::{SnapshotReader, PackedWriter, PackedReader},
	chunker,
};
use tempdir::TempDir;
use trie_db::{TrieMut, Trie};
use trie_standardmap::{Alphabet, StandardMap, ValueMode};

// the proportion of accounts we will alter each tick.
const ACCOUNT_CHURN: f32 = 0.01;

/// This structure will incrementally alter a state given an rng.
pub struct StateProducer {
	state_root: H256,
	storage_seed: H256,
}

impl StateProducer {
	/// Create a new `StateProducer`.
	pub fn new() -> Self {
		StateProducer {
			state_root: KECCAK_NULL_RLP,
			storage_seed: H256::zero(),
		}
	}

	/// Tick the state producer. This alters the state, writing new data into
	/// the database.
	pub fn tick<R: Rng>(&mut self, rng: &mut R, db: &mut dyn HashDB<KeccakHasher, DBValue>) {
		// modify existing accounts.
		let mut accounts_to_modify: Vec<_> = {
			let trie = TrieDB::new(&db, &self.state_root).unwrap();
			let temp = trie.iter().unwrap() // binding required due to complicated lifetime stuff
				.filter(|_| rng.gen::<f32>() < ACCOUNT_CHURN)
				.map(Result::unwrap)
				.map(|(k, v)| (H256::from_slice(&k), v.to_owned()))
				.collect();

			temp
		};

		// sweep once to alter storage tries.
		for &mut (ref mut address_hash, ref mut account_data) in &mut accounts_to_modify {
			let mut account: BasicAccount = rlp::decode(&*account_data).expect("error decoding basic account");
			let acct_db = AccountDBMut::from_hash(db, *address_hash);
			fill_storage(acct_db, &mut account.storage_root, &mut self.storage_seed);
			*account_data = rlp::encode(&account);
		}

		// sweep again to alter account trie.
		let mut trie = TrieDBMut::from_existing(db, &mut self.state_root).unwrap();

		for (address_hash, account_data) in accounts_to_modify {
			trie.insert(&address_hash[..], &account_data).unwrap();
		}

		// add between 0 and 5 new accounts each tick.
		let new_accs = rng.gen::<u32>() % 5;

		for _ in 0..new_accs {
			let address_hash = H256(rng.gen());
			let balance: usize = rng.gen();
			let nonce: usize = rng.gen();
			let acc = account_state::Account::new_basic(balance.into(), nonce.into()).rlp();
			trie.insert(&address_hash[..], &acc).unwrap();
		}
	}

	/// Get the current state root.
	pub fn state_root(&self) -> H256 {
		self.state_root
	}
}

/// Fill the storage of an account.
pub fn fill_storage(mut db: AccountDBMut, root: &mut H256, seed: &mut H256) {
	let map = StandardMap {
		alphabet: Alphabet::All,
		min_key: 6,
		journal_key: 6,
		value_mode: ValueMode::Random,
		count: 100,
	};
	{
		let mut trie = if *root == KECCAK_NULL_RLP {
			SecTrieDBMut::new(&mut db, root)
		} else {
			SecTrieDBMut::from_existing(&mut db, root).unwrap()
		};

		for (k, v) in map.make_with(&mut seed.to_fixed_bytes()) {
			trie.insert(&k, &v).unwrap();
		}
	}
}

/// Take a snapshot from the given client into a temporary file.
/// Return a snapshot reader for it.
pub fn snap(client: &Client) -> (Box<dyn SnapshotReader>, TempDir) {
	let tempdir = TempDir::new("").unwrap();
	let path = tempdir.path().join("file");
	let writer = PackedWriter::new(&path).unwrap();
	let progress = RwLock::new(Progress::new());

	let hash = client.chain_info().best_block_hash;
	client.take_snapshot(writer, BlockId::Hash(hash), &progress).unwrap();

	let reader = PackedReader::new(&path).unwrap().unwrap();

	(Box::new(reader), tempdir)
}

/// Restore a snapshot into a given database. This will read chunks from the given reader
/// write into the given database.
pub fn restore(
	db: Arc<dyn BlockChainDB>,
	engine: &dyn Engine,
	reader: &dyn SnapshotReader,
	genesis: &[u8],
) -> Result<(), EthcoreError> {
	let flag = AtomicBool::new(true);
	let chunker = chunker(engine.snapshot_mode()).expect("the engine used here supports snapshots");
	let manifest = reader.manifest();

	let mut state = StateRebuilder::new(db.key_value().clone(), journaldb::Algorithm::Archive);
	let mut secondary = {
		let chain = BlockChain::new(Default::default(), genesis, db.clone());
		chunker.rebuilder(chain, db, manifest).unwrap()
	};

	let mut snappy_buffer = Vec::new();

	trace!(target: "snapshot", "restoring state");
	for state_chunk_hash in manifest.state_hashes.iter() {
		trace!(target: "snapshot", "state chunk hash: {}", state_chunk_hash);
		let chunk = reader.chunk(*state_chunk_hash).unwrap();
		let len = snappy::decompress_into(&chunk, &mut snappy_buffer).unwrap();
		state.feed(&snappy_buffer[..len], &flag)?;
	}

	trace!(target: "snapshot", "restoring secondary");
	for chunk_hash in manifest.block_hashes.iter() {
		let chunk = reader.chunk(*chunk_hash).unwrap();
		let len = snappy::decompress_into(&chunk, &mut snappy_buffer).unwrap();
		secondary.feed(&snappy_buffer[..len], engine, &flag)?;
	}

	trace!(target: "snapshot", "finalizing");
	state.finalize(manifest.block_number, manifest.block_hash)?;
	secondary.finalize()
}
