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    // Copyright 2015-2017 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/>.

    use std::collections::{VecDeque, HashSet};
    use lru_cache::LruCache;
    use util::cache::MemoryLruCache;
    use util::journaldb::JournalDB;
    use util::hash::{H256};
    use util::hashdb::HashDB;
    use state::Account;
    use header::BlockNumber;
    use util::{Arc, Address, Database, DBTransaction, UtilError, Mutex, Hashable};
    use bloom_journal::{Bloom, BloomJournal};
    use db::COL_ACCOUNT_BLOOM;
    use byteorder::{LittleEndian, ByteOrder};

    pub const ACCOUNT_BLOOM_SPACE: usize = 1048576;
    pub const DEFAULT_ACCOUNT_PRESET: usize = 1000000;

    pub const ACCOUNT_BLOOM_HASHCOUNT_KEY: &'static [u8] = b"account_hash_count";

    const STATE_CACHE_BLOCKS: usize = 12;

    // The percentage of supplied cache size to go to accounts.
    const ACCOUNT_CACHE_RATIO: usize = 90;

    /// Shared canonical state cache.
    struct AccountCache {
    	/// DB Account cache. `None` indicates that account is known to be missing.
    	// When changing the type of the values here, be sure to update `mem_used` and
    	// `new`.
    	accounts: LruCache<Address, Option<Account>>,
    	/// Information on the modifications in recently committed blocks; specifically which addresses
    	/// changed in which block. Ordered by block number.
    	modifications: VecDeque<BlockChanges>,
    }

    /// Buffered account cache item.
    struct CacheQueueItem {
    	/// Account address.
    	address: Address,
    	/// Acccount data or `None` if account does not exist.
    	account: Option<Account>,
    	/// Indicates that the account was modified before being
    	/// added to the cache.
    	modified: bool,
    }

    #[derive(Debug)]
    /// Accumulates a list of accounts changed in a block.
    struct BlockChanges {
    	/// Block number.
    	number: BlockNumber,
    	/// Block hash.
    	hash: H256,
    	/// Parent block hash.
    	parent: H256,
    	/// A set of modified account addresses.
    	accounts: HashSet<Address>,
    	/// Block is part of the canonical chain.
    	is_canon: bool,
    }

    /// State database abstraction.
    /// Manages shared global state cache which reflects the canonical
    /// state as it is on the disk. All the entries in the cache are clean.
    /// A clone of `StateDB` may be created as canonical or not.
    /// For canonical clones local cache is accumulated and applied
    /// in `sync_cache`
    /// For non-canonical clones local cache is dropped.
    ///
    /// Global cache propagation.
    /// After a `State` object has been committed to the trie it
    /// propagates its local cache into the `StateDB` local cache
    /// using `add_to_account_cache` function.
    /// Then, after the block has been added to the chain the local cache in the
    /// `StateDB` is propagated into the global cache.
    pub struct StateDB {
    	/// Backing database.
    	db: Box<JournalDB>,
    	/// Shared canonical state cache.
    	account_cache: Arc<Mutex<AccountCache>>,
    	/// DB Code cache. Maps code hashes to shared bytes.
    	code_cache: Arc<Mutex<MemoryLruCache<H256, Arc<Vec<u8>>>>>,
    	/// Local dirty cache.
    	local_cache: Vec<CacheQueueItem>,
    	/// Shared account bloom. Does not handle chain reorganizations.
    	account_bloom: Arc<Mutex<Bloom>>,
    	cache_size: usize,
    	/// Hash of the block on top of which this instance was created or
    	/// `None` if cache is disabled
    	parent_hash: Option<H256>,
    	/// Hash of the committing block or `None` if not committed yet.
    	commit_hash: Option<H256>,
    	/// Number of the committing block or `None` if not committed yet.
    	commit_number: Option<BlockNumber>,
    }

    impl StateDB {

    	/// Create a new instance wrapping `JournalDB` and the maximum allowed size
    	/// of the LRU cache in bytes. Actual used memory may (read: will) be higher due to bookkeeping.
    	// TODO: make the cache size actually accurate by moving the account storage cache
    	// into the `AccountCache` structure as its own `LruCache<(Address, H256), H256>`.
    	pub fn new(db: Box<JournalDB>, cache_size: usize) -> StateDB {
    		let bloom = Self::load_bloom(db.backing());
    		let acc_cache_size = cache_size * ACCOUNT_CACHE_RATIO / 100;
    		let code_cache_size = cache_size - acc_cache_size;
    		let cache_items = acc_cache_size / ::std::mem::size_of::<Option<Account>>();

    		StateDB {
    			db: db,
    			account_cache: Arc::new(Mutex::new(AccountCache {
    				accounts: LruCache::new(cache_items),
    				modifications: VecDeque::new(),
    			})),
    			code_cache: Arc::new(Mutex::new(MemoryLruCache::new(code_cache_size))),
    			local_cache: Vec::new(),
    			account_bloom: Arc::new(Mutex::new(bloom)),
    			cache_size: cache_size,
    			parent_hash: None,
    			commit_hash: None,
    			commit_number: None,
    		}
    	}

    	/// Loads accounts bloom from the database
    	/// This bloom is used to handle request for the non-existant account fast
    	pub fn load_bloom(db: &Database) -> Bloom {
    		let hash_count_entry = db.get(COL_ACCOUNT_BLOOM, ACCOUNT_BLOOM_HASHCOUNT_KEY)
    			.expect("Low-level database error");

    		let hash_count_bytes = match hash_count_entry {
    			Some(bytes) => bytes,
    			None => return Bloom::new(ACCOUNT_BLOOM_SPACE, DEFAULT_ACCOUNT_PRESET),
    		};

    		assert_eq!(hash_count_bytes.len(), 1);
    		let hash_count = hash_count_bytes[0];

    		let mut bloom_parts = vec![0u64; ACCOUNT_BLOOM_SPACE / 8];
    		let mut key = [0u8; 8];
    		for i in 0..ACCOUNT_BLOOM_SPACE / 8 {
    			LittleEndian::write_u64(&mut key, i as u64);
    			bloom_parts[i] = db.get(COL_ACCOUNT_BLOOM, &key).expect("low-level database error")
    				.and_then(|val| Some(LittleEndian::read_u64(&val[..])))
    				.unwrap_or(0u64);
    		}

    		let bloom = Bloom::from_parts(&bloom_parts, hash_count as u32);
    		trace!(target: "account_bloom", "Bloom is {:?} full, hash functions count = {:?}", bloom.saturation(), hash_count);
    		bloom
    	}

    	pub fn check_non_null_bloom(&self, address: &Address) -> bool {
    		trace!(target: "account_bloom", "Check account bloom: {:?}", address);
    		let bloom = self.account_bloom.lock();
    		bloom.check(&*address.sha3())
    	}

    	pub fn note_non_null_account(&self, address: &Address) {
    		trace!(target: "account_bloom", "Note account bloom: {:?}", address);
    		let mut bloom = self.account_bloom.lock();
    		bloom.set(&*address.sha3());
    	}

    	pub fn commit_bloom(batch: &mut DBTransaction, journal: BloomJournal) -> Result<(), UtilError> {
    		assert!(journal.hash_functions <= 255);
    		batch.put(COL_ACCOUNT_BLOOM, ACCOUNT_BLOOM_HASHCOUNT_KEY, &[journal.hash_functions as u8]);
    		let mut key = [0u8; 8];
    		let mut val = [0u8; 8];

    		for (bloom_part_index, bloom_part_value) in journal.entries {
    			LittleEndian::write_u64(&mut key, bloom_part_index as u64);
    			LittleEndian::write_u64(&mut val, bloom_part_value);
    			batch.put(COL_ACCOUNT_BLOOM, &key, &val);
    		}
    		Ok(())
    	}

    	/// Journal all recent operations under the given era and ID.
    	pub fn journal_under(&mut self, batch: &mut DBTransaction, now: u64, id: &H256) -> Result<u32, UtilError> {
    		{
     			let mut bloom_lock = self.account_bloom.lock();
     			Self::commit_bloom(batch, bloom_lock.drain_journal())?;
     		}
    		let records = self.db.journal_under(batch, now, id)?;
    		self.commit_hash = Some(id.clone());
    		self.commit_number = Some(now);
    		Ok(records)
    	}

    	/// Mark a given candidate from an ancient era as canonical, enacting its removals from the
    	/// backing database and reverting any non-canonical historical commit's insertions.
    	pub fn mark_canonical(&mut self, batch: &mut DBTransaction, end_era: u64, canon_id: &H256) -> Result<u32, UtilError> {
    		self.db.mark_canonical(batch, end_era, canon_id)
    	}

    	/// Propagate local cache into the global cache and synchonize
    	/// the global cache with the best block state.
    	/// This function updates the global cache by removing entries
    	/// that are invalidated by chain reorganization. `sync_cache`
    	/// should be called after the block has been committed and the
    	/// blockchain route has ben calculated.
    	pub fn sync_cache(&mut self, enacted: &[H256], retracted: &[H256], is_best: bool) {
    		trace!("sync_cache id = (#{:?}, {:?}), parent={:?}, best={}", self.commit_number, self.commit_hash, self.parent_hash, is_best);
    		let mut cache = self.account_cache.lock();
    		let mut cache = &mut *cache;

    		// Purge changes from re-enacted and retracted blocks.
    		// Filter out commiting block if any.
    		let mut clear = false;
    		for block in enacted.iter().filter(|h| self.commit_hash.as_ref().map_or(true, |p| *h != p)) {
    			clear = clear || {
    				if let Some(ref mut m) = cache.modifications.iter_mut().find(|m| &m.hash == block) {
    					trace!("Reverting enacted block {:?}", block);
    					m.is_canon = true;
    					for a in &m.accounts {
    						trace!("Reverting enacted address {:?}", a);
    						cache.accounts.remove(a);
    					}
    					false
    				} else {
    					true
    				}
    			};
    		}

    		for block in retracted {
    			clear = clear || {
    				if let Some(ref mut m) = cache.modifications.iter_mut().find(|m| &m.hash == block) {
    					trace!("Retracting block {:?}", block);
    					m.is_canon = false;
    					for a in &m.accounts {
    						trace!("Retracted address {:?}", a);
    						cache.accounts.remove(a);
    					}
    					false
    				} else {
    					true
    				}
    			};
    		}
    		if clear {
    			// We don't know anything about the block; clear everything
    			trace!("Wiping cache");
    			cache.accounts.clear();
    			cache.modifications.clear();
    		}

    		// Propagate cache only if committing on top of the latest canonical state
    		// blocks are ordered by number and only one block with a given number is marked as canonical
    		// (contributed to canonical state cache)
    		if let (Some(ref number), Some(ref hash), Some(ref parent)) = (self.commit_number, self.commit_hash, self.parent_hash) {
    			if cache.modifications.len() == STATE_CACHE_BLOCKS {
    				cache.modifications.pop_back();
    			}
    			let mut modifications = HashSet::new();
    			trace!("committing {} cache entries", self.local_cache.len());
    			for account in self.local_cache.drain(..) {
    				if account.modified {
    					modifications.insert(account.address.clone());
    				}
    				if is_best {
    					if let Some(&mut Some(ref mut existing)) = cache.accounts.get_mut(&account.address) {
    						if let Some(new) = account.account {
    							if account.modified {
    								existing.overwrite_with(new);
    							}
    							continue;
    						}
    					}
    					cache.accounts.insert(account.address, account.account);
    				}
    			}

    			// Save modified accounts. These are ordered by the block number.
    			let block_changes = BlockChanges {
    				accounts: modifications,
    				number: *number,
    				hash: hash.clone(),
    				is_canon: is_best,
    				parent: parent.clone(),
    			};
    			let insert_at = cache.modifications.iter().enumerate().find(|&(_, m)| m.number < *number).map(|(i, _)| i);
    			trace!("inserting modifications at {:?}", insert_at);
    			if let Some(insert_at) = insert_at {
    				cache.modifications.insert(insert_at, block_changes);
    			} else {
    				cache.modifications.push_back(block_changes);
    			}
    		}
    	}

    	/// Returns an interface to HashDB.
    	pub fn as_hashdb(&self) -> &HashDB {
    		self.db.as_hashdb()
    	}

    	/// Returns an interface to mutable HashDB.
    	pub fn as_hashdb_mut(&mut self) -> &mut HashDB {
    		self.db.as_hashdb_mut()
    	}

    	/// Clone the database.
    	pub fn boxed_clone(&self) -> StateDB {
    		StateDB {
    			db: self.db.boxed_clone(),
    			account_cache: self.account_cache.clone(),
    			code_cache: self.code_cache.clone(),
    			local_cache: Vec::new(),
    			account_bloom: self.account_bloom.clone(),
    			cache_size: self.cache_size,
    			parent_hash: None,
    			commit_hash: None,
    			commit_number: None,
    		}
    	}

    	/// Clone the database for a canonical state.
    	pub fn boxed_clone_canon(&self, parent: &H256) -> StateDB {
    		StateDB {
    			db: self.db.boxed_clone(),
    			account_cache: self.account_cache.clone(),
    			code_cache: self.code_cache.clone(),
    			local_cache: Vec::new(),
    			account_bloom: self.account_bloom.clone(),
    			cache_size: self.cache_size,
    			parent_hash: Some(parent.clone()),
    			commit_hash: None,
    			commit_number: None,
    		}
    	}

    	/// Check if pruning is enabled on the database.
    	pub fn is_pruned(&self) -> bool {
    		self.db.is_pruned()
    	}

    	/// Heap size used.
    	pub fn mem_used(&self) -> usize {
    		// TODO: account for LRU-cache overhead; this is a close approximation.
    		self.db.mem_used() + {
    			let accounts = self.account_cache.lock().accounts.len();
    			let code_size = self.code_cache.lock().current_size();
    			code_size + accounts * ::std::mem::size_of::<Option<Account>>()
    		}
    	}

    	/// Returns underlying `JournalDB`.
    	pub fn journal_db(&self) -> &JournalDB {
    		&*self.db
    	}

    	/// Add a local cache entry.
    	/// The entry will be propagated to the global cache in `sync_cache`.
    	/// `modified` indicates that the entry was changed since being read from disk or global cache.
    	/// `data` can be set to an existing (`Some`), or non-existing account (`None`).
    	pub fn add_to_account_cache(&mut self, addr: Address, data: Option<Account>, modified: bool) {
    		self.local_cache.push(CacheQueueItem {
    			address: addr,
    			account: data,
    			modified: modified,
    		})
    	}

    	/// Add a global code cache entry. This doesn't need to worry about canonicality because
    	/// it simply maps hashes to raw code and will always be correct in the absence of
    	/// hash collisions.
    	pub fn cache_code(&self, hash: H256, code: Arc<Vec<u8>>) {
    		let mut cache = self.code_cache.lock();

    		cache.insert(hash, code);
    	}

    	/// Get basic copy of the cached account. Does not include storage.
    	/// Returns 'None' if cache is disabled or if the account is not cached.
    	pub fn get_cached_account(&self, addr: &Address) -> Option<Option<Account>> {
    		let mut cache = self.account_cache.lock();
    		if !Self::is_allowed(addr, &self.parent_hash, &cache.modifications) {
    			return None;
    		}
    		cache.accounts.get_mut(addr).map(|a| a.as_ref().map(|a| a.clone_basic()))
    	}

    	/// Get cached code based on hash.
    	#[cfg_attr(feature="dev", allow(map_clone))]
    	pub fn get_cached_code(&self, hash: &H256) -> Option<Arc<Vec<u8>>> {
    		let mut cache = self.code_cache.lock();

    		cache.get_mut(hash).map(|code| code.clone())
    	}

    	/// Get value from a cached account.
    	/// Returns 'None' if cache is disabled or if the account is not cached.
    	pub fn get_cached<F, U>(&self, a: &Address, f: F) -> Option<U>
    		where F: FnOnce(Option<&mut Account>) -> U {
    		let mut cache = self.account_cache.lock();
    		if !Self::is_allowed(a, &self.parent_hash, &cache.modifications) {
    			return None;
    		}
    		cache.accounts.get_mut(a).map(|c| f(c.as_mut()))
    	}

    	/// Query how much memory is set aside for the accounts cache (in bytes).
    	pub fn cache_size(&self) -> usize {
    		self.cache_size
    	}

    	/// Check if the account can be returned from cache by matching current block parent hash against canonical
    	/// state and filtering out account modified in later blocks.
    	fn is_allowed(addr: &Address, parent_hash: &Option<H256>, modifications: &VecDeque<BlockChanges>) -> bool {
    		let mut parent = match *parent_hash {
    			None => {
    				trace!("Cache lookup skipped for {:?}: no parent hash", addr);
    				return false;
    			}
    			Some(ref parent) => parent,
    		};
    		if modifications.is_empty() {
    			return true;
    		}
    		// Ignore all accounts modified in later blocks
    		// Modifications contains block ordered by the number
    		// We search for our parent in that list first and then for
    		// all its parent until we hit the canonical block,
    		// checking against all the intermediate modifications.
    		for m in modifications {
    			if &m.hash == parent {
    				if m.is_canon {
    					return true;
    				}
    				parent = &m.parent;
    			}
    			if m.accounts.contains(addr) {
    				trace!("Cache lookup skipped for {:?}: modified in a later block", addr);
    				return false;
    			}
    		}
    		trace!("Cache lookup skipped for {:?}: parent hash is unknown", addr);
    		false
    	}
    }

    #[cfg(test)]
    mod tests {
    	use util::{U256, H256, FixedHash, Address, DBTransaction};
    	use tests::helpers::*;
    	use state::Account;
    	use util::log::init_log;

    	#[test]
    	fn state_db_smoke() {
    		init_log();

    		let mut state_db_result = get_temp_state_db();
    		let state_db = state_db_result.take();
    		let root_parent = H256::random();
    		let address = Address::random();
    		let h0 = H256::random();
    		let h1a = H256::random();
    		let h1b = H256::random();
    		let h2a = H256::random();
    		let h2b = H256::random();
    		let h3a = H256::random();
    		let h3b = H256::random();
    		let mut batch = DBTransaction::new(state_db.journal_db().backing());

    		// blocks  [ 3a(c) 2a(c) 2b 1b 1a(c) 0 ]
    	    // balance [ 5     5     4  3  2     2 ]
    		let mut s = state_db.boxed_clone_canon(&root_parent);
    		s.add_to_account_cache(address, Some(Account::new_basic(2.into(), 0.into())), false);
    		s.journal_under(&mut batch, 0, &h0).unwrap();
    		s.sync_cache(&[], &[], true);

    		let mut s = state_db.boxed_clone_canon(&h0);
    		s.journal_under(&mut batch, 1, &h1a).unwrap();
    		s.sync_cache(&[], &[], true);

    		let mut s = state_db.boxed_clone_canon(&h0);
    		s.add_to_account_cache(address, Some(Account::new_basic(3.into(), 0.into())), true);
    		s.journal_under(&mut batch, 1, &h1b).unwrap();
    		s.sync_cache(&[], &[], false);

    		let mut s = state_db.boxed_clone_canon(&h1b);
    		s.add_to_account_cache(address, Some(Account::new_basic(4.into(), 0.into())), true);
    		s.journal_under(&mut batch, 2, &h2b).unwrap();
    		s.sync_cache(&[], &[], false);

    		let mut s = state_db.boxed_clone_canon(&h1a);
    		s.add_to_account_cache(address, Some(Account::new_basic(5.into(), 0.into())), true);
    		s.journal_under(&mut batch, 2, &h2a).unwrap();
    		s.sync_cache(&[], &[], true);

    		let mut s = state_db.boxed_clone_canon(&h2a);
    		s.journal_under(&mut batch, 3, &h3a).unwrap();
    		s.sync_cache(&[], &[], true);

    		let s = state_db.boxed_clone_canon(&h3a);
    		assert_eq!(s.get_cached_account(&address).unwrap().unwrap().balance(), &U256::from(5));

    		let s = state_db.boxed_clone_canon(&h1a);
    		assert!(s.get_cached_account(&address).is_none());

    		let s = state_db.boxed_clone_canon(&h2b);
    		assert!(s.get_cached_account(&address).is_none());

    		let s = state_db.boxed_clone_canon(&h1b);
    		assert!(s.get_cached_account(&address).is_none());

    		// reorg to 3b
    		// blocks  [ 3b(c) 3a 2a 2b(c) 1b 1a 0 ]
    		let mut s = state_db.boxed_clone_canon(&h2b);
    		s.journal_under(&mut batch, 3, &h3b).unwrap();
    		s.sync_cache(&[h1b.clone(), h2b.clone(), h3b.clone()], &[h1a.clone(), h2a.clone(), h3a.clone()], true);
    		let s = state_db.boxed_clone_canon(&h3a);
    		assert!(s.get_cached_account(&address).is_none());
    	}
    }

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