// Copyright 2015-2018 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/>.

//! Disk-backed `HashDB` implementation.

use std::collections::HashMap;
use std::collections::hash_map::Entry;
use std::io;
use std::sync::Arc;

use bytes::Bytes;
use ethereum_types::H256;
use hashdb::*;
use keccak_hasher::KeccakHasher;
use kvdb::{KeyValueDB, DBTransaction, DBValue};
use rlp::{encode, decode};
use super::{DB_PREFIX_LEN, LATEST_ERA_KEY, error_key_already_exists, error_negatively_reference_hash};
use super::memorydb::*;
use traits::JournalDB;

/// Implementation of the `HashDB` trait for a disk-backed database with a memory overlay
/// and latent-removal semantics.
///
/// Like `OverlayDB`, there is a memory overlay; `commit()` must be called in order to
/// write operations out to disk. Unlike `OverlayDB`, `remove()` operations do not take effect
/// immediately. As this is an "archive" database, nothing is ever removed. This means
/// that the states of any block the node has ever processed will be accessible.
pub struct ArchiveDB {
	overlay: MemoryDB<KeccakHasher, DBValue>,
	backing: Arc<KeyValueDB>,
	latest_era: Option<u64>,
	column: Option<u32>,
}

impl ArchiveDB {
	/// Create a new instance from a key-value db.
	pub fn new(backing: Arc<KeyValueDB>, column: Option<u32>) -> ArchiveDB {
		let latest_era = backing.get(column, &LATEST_ERA_KEY)
			.expect("Low-level database error.")
			.map(|val| decode::<u64>(&val).expect("decoding db value failed"));
		ArchiveDB {
			overlay: MemoryDB::new(),
			backing,
			latest_era,
			column,
		}
	}

	fn payload(&self, key: &H256) -> Option<DBValue> {
		self.backing.get(self.column, key).expect("Low-level database error. Some issue with your hard disk?")
	}
}

impl HashDB<KeccakHasher, DBValue> for ArchiveDB {
	fn keys(&self) -> HashMap<H256, i32> {
		let mut ret: HashMap<H256, i32> = self.backing.iter(self.column)
			.map(|(key, _)| (H256::from_slice(&*key), 1))
			.collect();

		for (key, refs) in self.overlay.keys() {
			match ret.entry(key) {
				Entry::Occupied(mut entry) => {
					*entry.get_mut() += refs;
				},
				Entry::Vacant(entry) => {
					entry.insert(refs);
				}
			}
		}
		ret
	}

	fn get(&self, key: &H256) -> Option<DBValue> {
		if let Some((d, rc)) = self.overlay.raw(key) {
			if rc > 0 {
				return Some(d);
			}
		}
		self.payload(key)
	}

	fn contains(&self, key: &H256) -> bool {
		self.get(key).is_some()
	}

	fn insert(&mut self, value: &[u8]) -> H256 {
		self.overlay.insert(value)
	}

	fn emplace(&mut self, key: H256, value: DBValue) {
		self.overlay.emplace(key, value);
	}

	fn remove(&mut self, key: &H256) {
		self.overlay.remove(key);
	}
}

impl JournalDB for ArchiveDB {
	fn boxed_clone(&self) -> Box<JournalDB> {
		Box::new(ArchiveDB {
			overlay: self.overlay.clone(),
			backing: self.backing.clone(),
			latest_era: self.latest_era,
			column: self.column.clone(),
		})
	}

	fn mem_used(&self) -> usize {
		self.overlay.mem_used()
 	}

	fn is_empty(&self) -> bool {
		self.latest_era.is_none()
	}

	fn journal_under(&mut self, batch: &mut DBTransaction, now: u64, _id: &H256) -> io::Result<u32> {
		let mut inserts = 0usize;
		let mut deletes = 0usize;

		for i in self.overlay.drain() {
			let (key, (value, rc)) = i;
			if rc > 0 {
				batch.put(self.column, &key, &value);
				inserts += 1;
			}
			if rc < 0 {
				assert!(rc == -1);
				deletes += 1;
			}
		}

		if self.latest_era.map_or(true, |e| now > e) {
			batch.put(self.column, &LATEST_ERA_KEY, &encode(&now));
			self.latest_era = Some(now);
		}
		Ok((inserts + deletes) as u32)
	}

	fn mark_canonical(&mut self, _batch: &mut DBTransaction, _end_era: u64, _canon_id: &H256) -> io::Result<u32> {
		// keep everything! it's an archive, after all.
		Ok(0)
	}

	fn inject(&mut self, batch: &mut DBTransaction) -> io::Result<u32> {
		let mut inserts = 0usize;
		let mut deletes = 0usize;

		for i in self.overlay.drain() {
			let (key, (value, rc)) = i;
			if rc > 0 {
				if self.backing.get(self.column, &key)?.is_some() {
					return Err(error_key_already_exists(&key));
				}
				batch.put(self.column, &key, &value);
				inserts += 1;
			}
			if rc < 0 {
				assert!(rc == -1);
				if self.backing.get(self.column, &key)?.is_none() {
					return Err(error_negatively_reference_hash(&key));
				}
				batch.delete(self.column, &key);
				deletes += 1;
			}
		}

		Ok((inserts + deletes) as u32)
	}

	fn latest_era(&self) -> Option<u64> { self.latest_era }

	fn state(&self, id: &H256) -> Option<Bytes> {
		self.backing.get_by_prefix(self.column, &id[0..DB_PREFIX_LEN]).map(|b| b.into_vec())
	}

	fn is_pruned(&self) -> bool { false }

	fn backing(&self) -> &Arc<KeyValueDB> {
		&self.backing
	}

	fn consolidate(&mut self, with: MemoryDB<KeccakHasher, DBValue>) {
		self.overlay.consolidate(with);
	}
}

#[cfg(test)]
mod tests {

	use keccak::keccak;
	use hashdb::HashDB;
	use super::*;
	use {kvdb_memorydb, JournalDB};

	#[test]
	fn insert_same_in_fork() {
		// history is 1
		let mut jdb = ArchiveDB::new(Arc::new(kvdb_memorydb::create(0)), None);

		let x = jdb.insert(b"X");
		jdb.commit_batch(1, &keccak(b"1"), None).unwrap();
		jdb.commit_batch(2, &keccak(b"2"), None).unwrap();
		jdb.commit_batch(3, &keccak(b"1002a"), Some((1, keccak(b"1")))).unwrap();
		jdb.commit_batch(4, &keccak(b"1003a"), Some((2, keccak(b"2")))).unwrap();

		jdb.remove(&x);
		jdb.commit_batch(3, &keccak(b"1002b"), Some((1, keccak(b"1")))).unwrap();
		let x = jdb.insert(b"X");
		jdb.commit_batch(4, &keccak(b"1003b"), Some((2, keccak(b"2")))).unwrap();

		jdb.commit_batch(5, &keccak(b"1004a"), Some((3, keccak(b"1002a")))).unwrap();
		jdb.commit_batch(6, &keccak(b"1005a"), Some((4, keccak(b"1003a")))).unwrap();

		assert!(jdb.contains(&x));
	}

	#[test]
	fn long_history() {
		// history is 3
		let mut jdb = ArchiveDB::new(Arc::new(kvdb_memorydb::create(0)), None);
		let h = jdb.insert(b"foo");
		jdb.commit_batch(0, &keccak(b"0"), None).unwrap();
		assert!(jdb.contains(&h));
		jdb.remove(&h);
		jdb.commit_batch(1, &keccak(b"1"), None).unwrap();
		assert!(jdb.contains(&h));
		jdb.commit_batch(2, &keccak(b"2"), None).unwrap();
		assert!(jdb.contains(&h));
		jdb.commit_batch(3, &keccak(b"3"), Some((0, keccak(b"0")))).unwrap();
		assert!(jdb.contains(&h));
		jdb.commit_batch(4, &keccak(b"4"), Some((1, keccak(b"1")))).unwrap();
		assert!(jdb.contains(&h));
	}

	#[test]
	#[should_panic]
	fn multiple_owed_removal_not_allowed() {
		let mut jdb = ArchiveDB::new(Arc::new(kvdb_memorydb::create(0)), None);
		let h = jdb.insert(b"foo");
		jdb.commit_batch(0, &keccak(b"0"), None).unwrap();
		assert!(jdb.contains(&h));
		jdb.remove(&h);
		jdb.remove(&h);
		// commit_batch would call journal_under(),
		// and we don't allow multiple owned removals.
		jdb.commit_batch(1, &keccak(b"1"), None).unwrap();
	}

	#[test]
	fn complex() {
		// history is 1
		let mut jdb = ArchiveDB::new(Arc::new(kvdb_memorydb::create(0)), None);

		let foo = jdb.insert(b"foo");
		let bar = jdb.insert(b"bar");
		jdb.commit_batch(0, &keccak(b"0"), None).unwrap();
		assert!(jdb.contains(&foo));
		assert!(jdb.contains(&bar));

		jdb.remove(&foo);
		jdb.remove(&bar);
		let baz = jdb.insert(b"baz");
		jdb.commit_batch(1, &keccak(b"1"), Some((0, keccak(b"0")))).unwrap();
		assert!(jdb.contains(&foo));
		assert!(jdb.contains(&bar));
		assert!(jdb.contains(&baz));

		let foo = jdb.insert(b"foo");
		jdb.remove(&baz);
		jdb.commit_batch(2, &keccak(b"2"), Some((1, keccak(b"1")))).unwrap();
		assert!(jdb.contains(&foo));
		assert!(jdb.contains(&baz));

		jdb.remove(&foo);
		jdb.commit_batch(3, &keccak(b"3"), Some((2, keccak(b"2")))).unwrap();
		assert!(jdb.contains(&foo));

		jdb.commit_batch(4, &keccak(b"4"), Some((3, keccak(b"3")))).unwrap();
	}

	#[test]
	fn fork() {
		// history is 1
		let mut jdb = ArchiveDB::new(Arc::new(kvdb_memorydb::create(0)), None);

		let foo = jdb.insert(b"foo");
		let bar = jdb.insert(b"bar");
		jdb.commit_batch(0, &keccak(b"0"), None).unwrap();
		assert!(jdb.contains(&foo));
		assert!(jdb.contains(&bar));

		jdb.remove(&foo);
		let baz = jdb.insert(b"baz");
		jdb.commit_batch(1, &keccak(b"1a"), Some((0, keccak(b"0")))).unwrap();

		jdb.remove(&bar);
		jdb.commit_batch(1, &keccak(b"1b"), Some((0, keccak(b"0")))).unwrap();

		assert!(jdb.contains(&foo));
		assert!(jdb.contains(&bar));
		assert!(jdb.contains(&baz));

		jdb.commit_batch(2, &keccak(b"2b"), Some((1, keccak(b"1b")))).unwrap();
		assert!(jdb.contains(&foo));
	}

	#[test]
	fn overwrite() {
		// history is 1
		let mut jdb = ArchiveDB::new(Arc::new(kvdb_memorydb::create(0)), None);

		let foo = jdb.insert(b"foo");
		jdb.commit_batch(0, &keccak(b"0"), None).unwrap();
		assert!(jdb.contains(&foo));

		jdb.remove(&foo);
		jdb.commit_batch(1, &keccak(b"1"), Some((0, keccak(b"0")))).unwrap();
		jdb.insert(b"foo");
		assert!(jdb.contains(&foo));
		jdb.commit_batch(2, &keccak(b"2"), Some((1, keccak(b"1")))).unwrap();
		assert!(jdb.contains(&foo));
		jdb.commit_batch(3, &keccak(b"2"), Some((0, keccak(b"2")))).unwrap();
		assert!(jdb.contains(&foo));
	}

	#[test]
	fn fork_same_key() {
		// history is 1
		let mut jdb = ArchiveDB::new(Arc::new(kvdb_memorydb::create(0)), None);
		jdb.commit_batch(0, &keccak(b"0"), None).unwrap();

		let foo = jdb.insert(b"foo");
		jdb.commit_batch(1, &keccak(b"1a"), Some((0, keccak(b"0")))).unwrap();

		jdb.insert(b"foo");
		jdb.commit_batch(1, &keccak(b"1b"), Some((0, keccak(b"0")))).unwrap();
		assert!(jdb.contains(&foo));

		jdb.commit_batch(2, &keccak(b"2a"), Some((1, keccak(b"1a")))).unwrap();
		assert!(jdb.contains(&foo));
	}

	#[test]
	fn reopen() {
		let shared_db = Arc::new(kvdb_memorydb::create(0));
		let bar = H256::random();

		let foo = {
			let mut jdb = ArchiveDB::new(shared_db.clone(), None);
			// history is 1
			let foo = jdb.insert(b"foo");
			jdb.emplace(bar.clone(), DBValue::from_slice(b"bar"));
			jdb.commit_batch(0, &keccak(b"0"), None).unwrap();
			foo
		};

		{
			let mut jdb = ArchiveDB::new(shared_db.clone(), None);
			jdb.remove(&foo);
			jdb.commit_batch(1, &keccak(b"1"), Some((0, keccak(b"0")))).unwrap();
		}

		{
			let mut jdb = ArchiveDB::new(shared_db, None);
			assert!(jdb.contains(&foo));
			assert!(jdb.contains(&bar));
			jdb.commit_batch(2, &keccak(b"2"), Some((1, keccak(b"1")))).unwrap();
		}
	}

	#[test]
	fn reopen_remove() {
		let shared_db = Arc::new(kvdb_memorydb::create(0));

		let foo = {
			let mut jdb = ArchiveDB::new(shared_db.clone(), None);
			// history is 1
			let foo = jdb.insert(b"foo");
			jdb.commit_batch(0, &keccak(b"0"), None).unwrap();
			jdb.commit_batch(1, &keccak(b"1"), Some((0, keccak(b"0")))).unwrap();

			// foo is ancient history.

			jdb.insert(b"foo");
			jdb.commit_batch(2, &keccak(b"2"), Some((1, keccak(b"1")))).unwrap();
			foo
		};

		{
			let mut jdb = ArchiveDB::new(shared_db, None);
			jdb.remove(&foo);
			jdb.commit_batch(3, &keccak(b"3"), Some((2, keccak(b"2")))).unwrap();
			assert!(jdb.contains(&foo));
			jdb.remove(&foo);
			jdb.commit_batch(4, &keccak(b"4"), Some((3, keccak(b"3")))).unwrap();
			jdb.commit_batch(5, &keccak(b"5"), Some((4, keccak(b"4")))).unwrap();
		}
	}

	#[test]
	fn reopen_fork() {
		let shared_db = Arc::new(kvdb_memorydb::create(0));
		let (foo, _, _) = {
			let mut jdb = ArchiveDB::new(shared_db.clone(), None);
			// history is 1
			let foo = jdb.insert(b"foo");
			let bar = jdb.insert(b"bar");
			jdb.commit_batch(0, &keccak(b"0"), None).unwrap();
			jdb.remove(&foo);
			let baz = jdb.insert(b"baz");
			jdb.commit_batch(1, &keccak(b"1a"), Some((0, keccak(b"0")))).unwrap();

			jdb.remove(&bar);
			jdb.commit_batch(1, &keccak(b"1b"), Some((0, keccak(b"0")))).unwrap();
			(foo, bar, baz)
		};

		{
			let mut jdb = ArchiveDB::new(shared_db, None);
			jdb.commit_batch(2, &keccak(b"2b"), Some((1, keccak(b"1b")))).unwrap();
			assert!(jdb.contains(&foo));
		}
	}

	#[test]
	fn returns_state() {
		let shared_db = Arc::new(kvdb_memorydb::create(0));

		let key = {
			let mut jdb = ArchiveDB::new(shared_db.clone(), None);
			let key = jdb.insert(b"foo");
			jdb.commit_batch(0, &keccak(b"0"), None).unwrap();
			key
		};

		{
			let jdb = ArchiveDB::new(shared_db, None);
			let state = jdb.state(&key);
			assert!(state.is_some());
		}
	}

	#[test]
	fn inject() {
		let mut jdb = ArchiveDB::new(Arc::new(kvdb_memorydb::create(0)), None);
		let key = jdb.insert(b"dog");
		jdb.inject_batch().unwrap();

		assert_eq!(jdb.get(&key).unwrap(), DBValue::from_slice(b"dog"));
		jdb.remove(&key);
		jdb.inject_batch().unwrap();

		assert!(jdb.get(&key).is_none());
	}
}