// Copyright 2015, 2016 Ethcore (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/>.

//! Snapshot and restoration commands.

use std::time::Duration;
use std::path::{Path, PathBuf};
use std::sync::Arc;

use ethcore::snapshot::{Progress, RestorationStatus, SnapshotService as SS};
use ethcore::snapshot::io::{SnapshotReader, PackedReader, PackedWriter};
use ethcore::snapshot::service::Service as SnapshotService;
use ethcore::service::ClientService;
use ethcore::client::{Mode, DatabaseCompactionProfile, VMType};
use ethcore::miner::Miner;
use ethcore::ids::BlockId;

use cache::CacheConfig;
use params::{SpecType, Pruning, Switch, tracing_switch_to_bool, fatdb_switch_to_bool};
use helpers::{to_client_config, execute_upgrades};
use dir::Directories;
use user_defaults::UserDefaults;
use fdlimit;

use io::PanicHandler;

/// Kinds of snapshot commands.
#[derive(Debug, PartialEq, Clone, Copy)]
pub enum Kind {
	/// Take a snapshot.
	Take,
	/// Restore a snapshot.
	Restore
}

/// Command for snapshot creation or restoration.
#[derive(Debug, PartialEq)]
pub struct SnapshotCommand {
	pub cache_config: CacheConfig,
	pub dirs: Directories,
	pub spec: SpecType,
	pub pruning: Pruning,
	pub pruning_history: u64,
	pub tracing: Switch,
	pub fat_db: Switch,
	pub compaction: DatabaseCompactionProfile,
	pub file_path: Option<String>,
	pub wal: bool,
	pub kind: Kind,
	pub block_at: BlockId,
}

// helper for reading chunks from arbitrary reader and feeding them into the
// service.
fn restore_using<R: SnapshotReader>(snapshot: Arc<SnapshotService>, reader: &R, recover: bool) -> Result<(), String> {
	use util::sha3::Hashable;

	let manifest = reader.manifest();

	info!("Restoring to block #{} (0x{:?})", manifest.block_number, manifest.block_hash);

	try!(snapshot.init_restore(manifest.clone(), recover).map_err(|e| {
		format!("Failed to begin restoration: {}", e)
	}));

	let (num_state, num_blocks) = (manifest.state_hashes.len(), manifest.block_hashes.len());

	let informant_handle = snapshot.clone();
	::std::thread::spawn(move || {
 		while let RestorationStatus::Ongoing { state_chunks_done, block_chunks_done, .. } = informant_handle.status() {
 			info!("Processed {}/{} state chunks and {}/{} block chunks.",
 				state_chunks_done, num_state, block_chunks_done, num_blocks);
 			::std::thread::sleep(Duration::from_secs(5));
 		}
 	});

 	info!("Restoring state");
 	for &state_hash in &manifest.state_hashes {
 		if snapshot.status() == RestorationStatus::Failed {
 			return Err("Restoration failed".into());
 		}

 		let chunk = try!(reader.chunk(state_hash)
			.map_err(|e| format!("Encountered error while reading chunk {:?}: {}", state_hash, e)));

		let hash = chunk.sha3();
		if hash != state_hash {
			return Err(format!("Mismatched chunk hash. Expected {:?}, got {:?}", state_hash, hash));
		}

 		snapshot.feed_state_chunk(state_hash, &chunk);
 	}

	info!("Restoring blocks");
	for &block_hash in &manifest.block_hashes {
		if snapshot.status() == RestorationStatus::Failed {
			return Err("Restoration failed".into());
		}

 		let chunk = try!(reader.chunk(block_hash)
			.map_err(|e| format!("Encountered error while reading chunk {:?}: {}", block_hash, e)));

		let hash = chunk.sha3();
		if hash != block_hash {
			return Err(format!("Mismatched chunk hash. Expected {:?}, got {:?}", block_hash, hash));
		}
		snapshot.feed_block_chunk(block_hash, &chunk);
	}

	match snapshot.status() {
		RestorationStatus::Ongoing { .. } => Err("Snapshot file is incomplete and missing chunks.".into()),
		RestorationStatus::Failed => Err("Snapshot restoration failed.".into()),
		RestorationStatus::Inactive => {
			info!("Restoration complete.");
			Ok(())
		}
	}
}

impl SnapshotCommand {
	// shared portion of snapshot commands: start the client service
	fn start_service(self) -> Result<(ClientService, Arc<PanicHandler>), String> {
		// Setup panic handler
		let panic_handler = PanicHandler::new_in_arc();

		// load spec file
		let spec = try!(self.spec.spec());

		// load genesis hash
		let genesis_hash = spec.genesis_header().hash();

		// database paths
		let db_dirs = self.dirs.database(genesis_hash, None, spec.data_dir.clone());

		// user defaults path
		let user_defaults_path = db_dirs.user_defaults_path();

		// load user defaults
		let user_defaults = try!(UserDefaults::load(&user_defaults_path));

		fdlimit::raise_fd_limit();

		// select pruning algorithm
		let algorithm = self.pruning.to_algorithm(&user_defaults);

		// check if tracing is on
		let tracing = try!(tracing_switch_to_bool(self.tracing, &user_defaults));

		// check if fatdb is on
		let fat_db = try!(fatdb_switch_to_bool(self.fat_db, &user_defaults, algorithm));

		// prepare client and snapshot paths.
		let client_path = db_dirs.client_path(algorithm);
		let snapshot_path = db_dirs.snapshot_path();

		// execute upgrades
		try!(execute_upgrades(&db_dirs, algorithm, self.compaction.compaction_profile(db_dirs.db_root_path().as_path())));

		// prepare client config
		let client_config = to_client_config(&self.cache_config, Mode::Active, tracing, fat_db, self.compaction, self.wal, VMType::default(), "".into(), algorithm, self.pruning_history, true);

		let service = try!(ClientService::start(
			client_config,
			&spec,
			&client_path,
			&snapshot_path,
			&self.dirs.ipc_path(),
			Arc::new(Miner::with_spec(&spec))
		).map_err(|e| format!("Client service error: {:?}", e)));

		Ok((service, panic_handler))
	}
	/// restore from a snapshot
	pub fn restore(self) -> Result<(), String> {
		let file = self.file_path.clone();
		let (service, _panic_handler) = try!(self.start_service());

		warn!("Snapshot restoration is experimental and the format may be subject to change.");
		warn!("On encountering an unexpected error, please ensure that you have a recent snapshot.");

		let snapshot = service.snapshot_service();

		if let Some(file) = file {
			info!("Attempting to restore from snapshot at '{}'", file);

			let reader = PackedReader::new(Path::new(&file))
				.map_err(|e| format!("Couldn't open snapshot file: {}", e))
				.and_then(|x| x.ok_or("Snapshot file has invalid format.".into()));

			let reader = try!(reader);
			try!(restore_using(snapshot, &reader, true));
		} else {
			info!("Attempting to restore from local snapshot.");

			// attempting restoration with recovery will lead to deadlock
			// as we currently hold a read lock on the service's reader.
			match *snapshot.reader() {
				Some(ref reader) => try!(restore_using(snapshot.clone(), reader, false)),
				None => return Err("No local snapshot found.".into()),
			}
		}

		Ok(())
	}

	/// Take a snapshot from the head of the chain.
	pub fn take_snapshot(self) -> Result<(), String> {
		let file_path = try!(self.file_path.clone().ok_or("No file path provided.".to_owned()));
		let file_path: PathBuf = file_path.into();
		let block_at = self.block_at;
		let (service, _panic_handler) = try!(self.start_service());

		warn!("Snapshots are currently experimental. File formats may be subject to change.");

		let writer = try!(PackedWriter::new(&file_path)
			.map_err(|e| format!("Failed to open snapshot writer: {}", e)));

		let progress = Arc::new(Progress::default());
		let p = progress.clone();
		let informant_handle = ::std::thread::spawn(move || {
			::std::thread::sleep(Duration::from_secs(5));

			let mut last_size = 0;
			while !p.done() {
				let cur_size = p.size();
				if cur_size != last_size {
					last_size = cur_size;
					let bytes = ::informant::format_bytes(p.size());
					info!("Snapshot: {} accounts {} blocks {}", p.accounts(), p.blocks(), bytes);
				}

				::std::thread::sleep(Duration::from_secs(5));
			}
 		});

		if let Err(e) = service.client().take_snapshot(writer, block_at, &*progress) {
			let _ = ::std::fs::remove_file(&file_path);
			return Err(format!("Encountered fatal error while creating snapshot: {}", e));
		}

		info!("snapshot creation complete");

		assert!(progress.done());
		try!(informant_handle.join().map_err(|_| "failed to join logger thread"));

		Ok(())
	}
}

/// Execute this snapshot command.
pub fn execute(cmd: SnapshotCommand) -> Result<String, String> {
	match cmd.kind {
		Kind::Take => try!(cmd.take_snapshot()),
		Kind::Restore => try!(cmd.restore()),
	}

	Ok(String::new())
}