// Copyright 2016 The Grin Developers
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! Implements storage primitives required by the chain

use secp::pedersen::Commitment;

use types::*;
use codec::ChainCodec;
use core::core::hash::{Hash, Hashed};
use core::core::{Block, BlockHeader, Output};
use grin_store::{self, Error, to_key, u64_to_key, option_to_not_found};
use grin_store::codec::BlockCodec;

const STORE_SUBPATH: &'static str = "chain";

const BLOCK_HEADER_PREFIX: u8 = 'h' as u8;
const BLOCK_PREFIX: u8 = 'b' as u8;
const HEAD_PREFIX: u8 = 'H' as u8;
const HEADER_HEAD_PREFIX: u8 = 'I' as u8;
const HEADER_HEIGHT_PREFIX: u8 = '8' as u8;
const OUTPUT_PREFIX: u8 = 'O' as u8;
const OUTPUT_COMMIT_PREFIX: u8 = 'o' as u8;

/// An implementation of the ChainStore trait backed by a simple key-value
/// store.
pub struct ChainKVStore {
	db: grin_store::Store,
}

impl ChainKVStore {
	pub fn new(root_path: String) -> Result<ChainKVStore, Error> {
		let db = grin_store::Store::open(format!("{}/{}", root_path, STORE_SUBPATH).as_str())?;
		let codec = ChainCodec::default();
		Ok(ChainKVStore { db: db })
	}
}

impl ChainStore for ChainKVStore {
	fn head(&self) -> Result<Tip, Error> {
		option_to_not_found(self.db.get_dec(&mut ChainCodec, &[HEAD_PREFIX]))
	}

	fn head_header(&self) -> Result<BlockHeader, Error> {
		let head: Tip = option_to_not_found(self.db.get_dec(&mut ChainCodec, &[HEAD_PREFIX]))?;
		self.get_block_header(&head.last_block_h)
	}

	fn save_head(&self, t: &Tip) -> Result<(), Error> {
		self.db
			.batch()
			.put_enc(&mut ChainCodec, &[HEAD_PREFIX], t.clone())?
			.put_enc(&mut ChainCodec, &[HEADER_HEAD_PREFIX], t.clone())?
			.write()
	}

	fn save_body_head(&self, t: &Tip) -> Result<(), Error> {
		self.db.put_enc(&mut ChainCodec, &[HEAD_PREFIX], t.clone())
	}

	fn get_header_head(&self) -> Result<Tip, Error> {
		option_to_not_found(self.db.get_dec(&mut ChainCodec, &[HEADER_HEAD_PREFIX]))
	}

	fn save_header_head(&self, t: &Tip) -> Result<(), Error> {
		self.db.put_enc(&mut ChainCodec, &[HEADER_HEAD_PREFIX], t.clone())
	}

	fn get_block(&self, h: &Hash) -> Result<Block, Error> {
		option_to_not_found(self.db.get_dec(&mut BlockCodec::default(),
		                                    &to_key(BLOCK_PREFIX, &mut h.to_vec())))
	}

	fn get_block_header(&self, h: &Hash) -> Result<BlockHeader, Error> {
		option_to_not_found(self.db.get_dec(&mut BlockCodec::default(),
		                                    &to_key(BLOCK_HEADER_PREFIX, &mut h.to_vec())))
	}

	fn check_block_exists(&self, h: &Hash) -> Result<bool, Error> {
		self.db.exists(&to_key(BLOCK_PREFIX, &mut h.to_vec()))
	}

	fn save_block(&self, b: &Block) -> Result<(), Error> {
		// saving the block and its header
		let mut batch = self.db
			.batch()
			.put_enc(&mut BlockCodec::default(),
			         &to_key(BLOCK_PREFIX, &mut b.hash().to_vec())[..],
			         b.clone())?
			.put_enc(&mut BlockCodec::default(),
			         &to_key(BLOCK_HEADER_PREFIX, &mut b.hash().to_vec())[..],
			         b.header.clone())?;

		// saving the full output under its hash, as well as a commitment to hash index
		for out in &b.outputs {
			batch = batch.put_enc(&mut BlockCodec::default(),
				         &to_key(OUTPUT_PREFIX, &mut out.hash().to_vec())[..],
				         out.clone())?
				.put_enc(&mut BlockCodec::default(),
				         &to_key(OUTPUT_COMMIT_PREFIX, &mut out.commit.as_ref().to_vec())[..],
				         out.hash().clone())?;
		}
		batch.write()
	}

	fn save_block_header(&self, bh: &BlockHeader) -> Result<(), Error> {
		self.db.put_enc(&mut BlockCodec::default(),
		                &to_key(BLOCK_HEADER_PREFIX, &mut bh.hash().to_vec())[..],
		                bh.clone())
	}

	fn get_header_by_height(&self, height: u64) -> Result<BlockHeader, Error> {
		option_to_not_found(self.db.get_dec(&mut BlockCodec::default(),
		                                    &u64_to_key(HEADER_HEIGHT_PREFIX, height)))
	}

	fn get_output(&self, h: &Hash) -> Result<Output, Error> {
		option_to_not_found(self.db.get_dec(&mut BlockCodec::default(),
		                                    &to_key(OUTPUT_PREFIX, &mut h.to_vec())))
	}

	fn has_output_commit(&self, commit: &Commitment) -> Result<Hash, Error> {
		option_to_not_found(self.db
			.get_dec(&mut BlockCodec::default(),
			         &to_key(OUTPUT_COMMIT_PREFIX, &mut commit.as_ref().to_vec())))
	}

	fn setup_height(&self, bh: &BlockHeader) -> Result<(), Error> {
		self.db
			.put_enc(&mut BlockCodec::default(),
			         &u64_to_key(HEADER_HEIGHT_PREFIX, bh.height),
			         bh.clone())?;

		let mut prev_h = bh.previous;
		let mut prev_height = bh.height - 1;
		while prev_height > 0 {
			let prev = self.get_header_by_height(prev_height)?;
			if prev.hash() != prev_h {
				let real_prev = self.get_block_header(&prev_h)?;
				self.db
					.put_enc(&mut BlockCodec::default(),
					         &u64_to_key(HEADER_HEIGHT_PREFIX, real_prev.height),
					         real_prev.clone())?;
				prev_h = real_prev.previous;
				prev_height = real_prev.height - 1;
			} else {
				break;
			}
		}
		Ok(())
	}
}