// Copyright 2015, 2016 Parity Technologies (UK) Ltd.
// This file is part of Parity.

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

//! Account state encoding and decoding

use account_db::{AccountDB, AccountDBMut};
use snapshot::Error;

use util::{U256, FixedHash, H256, Bytes, HashDB, SHA3_EMPTY, SHA3_NULL_RLP};
use util::trie::{TrieDB, Trie};
use rlp::{Rlp, RlpStream, Stream, UntrustedRlp, View};

use std::collections::HashSet;

// An empty account -- these are replaced with RLP null data for a space optimization.
const ACC_EMPTY: Account = Account {
	nonce: U256([0, 0, 0, 0]),
	balance: U256([0, 0, 0, 0]),
	storage_root: SHA3_NULL_RLP,
	code_hash: SHA3_EMPTY,
};

// whether an encoded account has code and how it is referred to.
#[repr(u8)]
enum CodeState {
	// the account has no code.
	Empty = 0,
	// raw code is encoded.
	Inline = 1,
	// the code is referred to by hash.
	Hash = 2,
}

impl CodeState {
	fn from(x: u8) -> Result<Self, Error> {
		match x {
			0 => Ok(CodeState::Empty),
			1 => Ok(CodeState::Inline),
			2 => Ok(CodeState::Hash),
			_ => Err(Error::UnrecognizedCodeState(x))
		}
	}

	fn raw(self) -> u8 {
		self as u8
	}
}

// An alternate account structure from ::account::Account.
#[derive(PartialEq, Clone, Debug)]
pub struct Account {
	nonce: U256,
	balance: U256,
	storage_root: H256,
	code_hash: H256,
}

impl Account {
	// decode the account from rlp.
	pub fn from_thin_rlp(rlp: &[u8]) -> Self {
		let r: Rlp = Rlp::new(rlp);

		Account {
			nonce: r.val_at(0),
			balance: r.val_at(1),
			storage_root: r.val_at(2),
			code_hash: r.val_at(3),
		}
	}

	// encode the account to a standard rlp.
	pub fn to_thin_rlp(&self) -> Bytes {
		let mut stream = RlpStream::new_list(4);
		stream
			.append(&self.nonce)
			.append(&self.balance)
			.append(&self.storage_root)
			.append(&self.code_hash);

		stream.out()
	}

	// walk the account's storage trie, returning an RLP item containing the
	// account properties and the storage.
	pub fn to_fat_rlp(&self, acct_db: &AccountDB, used_code: &mut HashSet<H256>) -> Result<Bytes, Error> {
		if self == &ACC_EMPTY {
			return Ok(::rlp::NULL_RLP.to_vec());
		}

		let db = TrieDB::new(acct_db, &self.storage_root)?;

		let mut pairs = Vec::new();

		for item in db.iter()? {
			let (k, v) = item?;
			pairs.push((k, v));
		}

		let mut stream = RlpStream::new_list(pairs.len());

		for (k, v) in pairs {
			stream.begin_list(2).append(&k).append(&&*v);
		}

		let pairs_rlp = stream.out();

		let mut account_stream = RlpStream::new_list(5);
		account_stream.append(&self.nonce)
					  .append(&self.balance);

		// [has_code, code_hash].
		if self.code_hash == SHA3_EMPTY {
			account_stream.append(&CodeState::Empty.raw()).append_empty_data();
		} else if used_code.contains(&self.code_hash) {
			account_stream.append(&CodeState::Hash.raw()).append(&self.code_hash);
		} else {
			match acct_db.get(&self.code_hash) {
				Some(c) => {
					used_code.insert(self.code_hash.clone());
					account_stream.append(&CodeState::Inline.raw()).append(&&*c);
				}
				None => {
					warn!("code lookup failed during snapshot");
					account_stream.append(&false).append_empty_data();
				}
			}
		}

		account_stream.append_raw(&pairs_rlp, 1);

		Ok(account_stream.out())
	}

	// decode a fat rlp, and rebuild the storage trie as we go.
	// returns the account structure along with its newly recovered code,
	// if it exists.
	pub fn from_fat_rlp(
		acct_db: &mut AccountDBMut,
		rlp: UntrustedRlp,
	) -> Result<(Self, Option<Bytes>), Error> {
		use util::{TrieDBMut, TrieMut};

		// check for special case of empty account.
		if rlp.is_empty() {
			return Ok((ACC_EMPTY, None));
		}

		let nonce = rlp.val_at(0)?;
		let balance = rlp.val_at(1)?;
		let code_state: CodeState = {
			let raw: u8 = rlp.val_at(2)?;
			CodeState::from(raw)?
		};

		// load the code if it exists.
		let (code_hash, new_code) = match code_state {
			CodeState::Empty => (SHA3_EMPTY, None),
			CodeState::Inline => {
				let code: Bytes = rlp.val_at(3)?;
				let code_hash = acct_db.insert(&code);

				(code_hash, Some(code))
			}
			CodeState::Hash => {
				let code_hash = rlp.val_at(3)?;

				(code_hash, None)
			}
		};

		let mut storage_root = H256::zero();

		{
			let mut storage_trie = TrieDBMut::new(acct_db, &mut storage_root);
			let pairs = rlp.at(4)?;
			for pair_rlp in pairs.iter() {
				let k: Bytes  = pair_rlp.val_at(0)?;
				let v: Bytes = pair_rlp.val_at(1)?;

				storage_trie.insert(&k, &v)?;
			}
		}

		let acc = Account {
			nonce: nonce,
			balance: balance,
			storage_root: storage_root,
			code_hash: code_hash,
		};

		Ok((acc, new_code))
	}

	/// Get the account's code hash.
	pub fn code_hash(&self) -> &H256 {
		&self.code_hash
	}

	#[cfg(test)]
	pub fn storage_root_mut(&mut self) -> &mut H256 {
		&mut self.storage_root
	}
}

#[cfg(test)]
mod tests {
	use account_db::{AccountDB, AccountDBMut};
	use tests::helpers::get_temp_state_db;
	use snapshot::tests::helpers::fill_storage;

	use util::sha3::{SHA3_EMPTY, SHA3_NULL_RLP};
	use util::{Address, FixedHash, H256, HashDB, DBValue};
	use rlp::{UntrustedRlp, View};

	use std::collections::HashSet;

	use super::{ACC_EMPTY, Account};

	#[test]
	fn encoding_basic() {
		let mut db = get_temp_state_db();
		let addr = Address::random();

		let account = Account {
			nonce: 50.into(),
			balance: 123456789.into(),
			storage_root: SHA3_NULL_RLP,
			code_hash: SHA3_EMPTY,
		};

		let thin_rlp = account.to_thin_rlp();
		assert_eq!(Account::from_thin_rlp(&thin_rlp), account);

		let fat_rlp = account.to_fat_rlp(&AccountDB::new(db.as_hashdb(), &addr), &mut Default::default()).unwrap();
		let fat_rlp = UntrustedRlp::new(&fat_rlp);
		assert_eq!(Account::from_fat_rlp(&mut AccountDBMut::new(db.as_hashdb_mut(), &addr), fat_rlp).unwrap().0, account);
	}

	#[test]
	fn encoding_storage() {
		let mut db = get_temp_state_db();
		let addr = Address::random();

		let account = {
			let acct_db = AccountDBMut::new(db.as_hashdb_mut(), &addr);
			let mut root = SHA3_NULL_RLP;
			fill_storage(acct_db, &mut root, &mut H256::zero());
			Account {
				nonce: 25.into(),
				balance: 987654321.into(),
				storage_root: root,
				code_hash: SHA3_EMPTY,
			}
		};

		let thin_rlp = account.to_thin_rlp();
		assert_eq!(Account::from_thin_rlp(&thin_rlp), account);

		let fat_rlp = account.to_fat_rlp(&AccountDB::new(db.as_hashdb(), &addr), &mut Default::default()).unwrap();
		let fat_rlp = UntrustedRlp::new(&fat_rlp);
		assert_eq!(Account::from_fat_rlp(&mut AccountDBMut::new(db.as_hashdb_mut(), &addr), fat_rlp).unwrap().0, account);
	}

	#[test]
	fn encoding_code() {
		let mut db = get_temp_state_db();

		let addr1 = Address::random();
		let addr2 = Address::random();

		let code_hash = {
			let mut acct_db = AccountDBMut::new(db.as_hashdb_mut(), &addr1);
			acct_db.insert(b"this is definitely code")
		};

		{
			let mut acct_db = AccountDBMut::new(db.as_hashdb_mut(), &addr2);
			acct_db.emplace(code_hash.clone(), DBValue::from_slice(b"this is definitely code"));
		}

		let account1 = Account {
			nonce: 50.into(),
			balance: 123456789.into(),
			storage_root: SHA3_NULL_RLP,
			code_hash: code_hash,
		};

		let account2 = Account {
			nonce: 400.into(),
			balance: 98765432123456789usize.into(),
			storage_root: SHA3_NULL_RLP,
			code_hash: code_hash,
		};

		let mut used_code = HashSet::new();

		let fat_rlp1 = account1.to_fat_rlp(&AccountDB::new(db.as_hashdb(), &addr1), &mut used_code).unwrap();
		let fat_rlp2 = account2.to_fat_rlp(&AccountDB::new(db.as_hashdb(), &addr2), &mut used_code).unwrap();
		assert_eq!(used_code.len(), 1);

		let fat_rlp1 = UntrustedRlp::new(&fat_rlp1);
		let fat_rlp2 = UntrustedRlp::new(&fat_rlp2);

		let (acc, maybe_code) = Account::from_fat_rlp(&mut AccountDBMut::new(db.as_hashdb_mut(), &addr2), fat_rlp2).unwrap();
		assert!(maybe_code.is_none());
		assert_eq!(acc, account2);

		let (acc, maybe_code) = Account::from_fat_rlp(&mut AccountDBMut::new(db.as_hashdb_mut(), &addr1), fat_rlp1).unwrap();
		assert_eq!(maybe_code, Some(b"this is definitely code".to_vec()));
		assert_eq!(acc, account1);
	}

	#[test]
	fn encoding_empty_acc() {
		let mut db = get_temp_state_db();
		let mut used_code = HashSet::new();

		assert_eq!(ACC_EMPTY.to_fat_rlp(&AccountDB::new(db.as_hashdb(), &Address::default()), &mut used_code).unwrap(), ::rlp::NULL_RLP.to_vec());
		assert_eq!(Account::from_fat_rlp(&mut AccountDBMut::new(db.as_hashdb_mut(), &Address::default()), UntrustedRlp::new(&::rlp::NULL_RLP)).unwrap(), (ACC_EMPTY, None));
	}
}