// Copyright 2020 The Kepler 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.

//! Kepler server implementation, glues the different parts of the system (mostly
//! the peer-to-peer server, the blockchain and the transaction pool) and acts
//! as a facade.

use std::fs;
use std::fs::File;
use std::io::prelude::*;
use std::path::Path;
use std::sync::{mpsc, Arc};
use std::{
	thread::{self, JoinHandle},
	time::{self, Duration},
};

use fs2::FileExt;
use walkdir::WalkDir;

use crate::api;
use crate::api::TLSConfig;
use crate::chain::{self, SyncState, SyncStatus};
use crate::common::adapters::{
	ChainToPoolAndNetAdapter, NetToChainAdapter, PoolToChainAdapter, PoolToNetAdapter,
};
use crate::common::hooks::{init_chain_hooks, init_net_hooks};
use crate::common::stats::{
	ChainStats, DiffBlock, DiffStats, PeerStats, ServerStateInfo, ServerStats, TxStats,
};
use crate::common::types::{Error, ServerConfig, StratumServerConfig};
use crate::core::core::hash::Hashed;
use crate::core::core::verifier_cache::{LruVerifierCache, VerifierCache};
use crate::core::ser::ProtocolVersion;
use crate::core::{consensus, genesis, global, pow};
use crate::kepler::{dandelion_monitor, seed, sync};
use crate::mining::stratumserver;
use crate::mining::test_miner::Miner;
use crate::p2p;
use crate::p2p::types::PeerAddr;
use crate::pool;
use crate::util::file::get_first_line;
use crate::util::{RwLock, StopState};
use kepler_util::logger::LogEntry;

/// Kepler server holding internal structures.
pub struct Server {
	/// server config
	pub config: ServerConfig,
	/// handle to our network server
	pub p2p: Arc<p2p::Server>,
	/// data store access
	pub chain: Arc<chain::Chain>,
	/// in-memory transaction pool
	pub tx_pool: Arc<RwLock<pool::TransactionPool>>,
	/// Shared cache for verification results when
	/// verifying rangeproof and kernel signatures.
	verifier_cache: Arc<RwLock<dyn VerifierCache>>,
	/// Whether we're currently syncing
	pub sync_state: Arc<SyncState>,
	/// To be passed around to collect stats and info
	state_info: ServerStateInfo,
	/// Stop flag
	pub stop_state: Arc<StopState>,
	/// Maintain a lock_file so we do not run multiple Kepler nodes from same dir.
	lock_file: Arc<File>,
	connect_thread: Option<JoinHandle<()>>,
	sync_thread: JoinHandle<()>,
	dandelion_thread: JoinHandle<()>,
}

impl Server {
	/// Instantiates and starts a new server. Optionally takes a callback
	/// for the server to send an ARC copy of itself, to allow another process
	/// to poll info about the server status
	pub fn start<F>(
		config: ServerConfig,
		logs_rx: Option<mpsc::Receiver<LogEntry>>,
		mut info_callback: F,
	) -> Result<(), Error>
	where
		F: FnMut(Server, Option<mpsc::Receiver<LogEntry>>),
	{
		let mining_config = config.stratum_mining_config.clone();
		let enable_test_miner = config.run_test_miner;
		let test_miner_wallet_url = config.test_miner_wallet_url.clone();
		let serv = Server::new(config)?;

		if let Some(c) = mining_config {
			let enable_stratum_server = c.enable_stratum_server;
			if let Some(s) = enable_stratum_server {
				if s {
					{
						let mut stratum_stats = serv.state_info.stratum_stats.write();
						stratum_stats.is_enabled = true;
					}
					serv.start_stratum_server(c.clone());
				}
			}
		}

		if let Some(s) = enable_test_miner {
			if s {
				serv.start_test_miner(test_miner_wallet_url, serv.stop_state.clone());
			}
		}

		info_callback(serv, logs_rx);
		Ok(())
	}

	// Exclusive (advisory) lock_file to ensure we do not run multiple
	// instance of kepler server from the same dir.
	// This uses fs2 and should be safe cross-platform unless somebody abuses the file itself.
	fn one_kepler_at_a_time(config: &ServerConfig) -> Result<Arc<File>, Error> {
		let path = Path::new(&config.db_root);
		fs::create_dir_all(path.clone())?;
		let path = path.join("kepler.lock");
		let lock_file = fs::OpenOptions::new()
			.read(true)
			.write(true)
			.create(true)
			.open(&path)?;
		lock_file.try_lock_exclusive().map_err(|e| {
			let mut stderr = std::io::stderr();
			writeln!(
				&mut stderr,
				"Failed to lock {:?} (kepler server already running?)",
				path
			)
			.expect("Could not write to stderr");
			e
		})?;
		Ok(Arc::new(lock_file))
	}

	/// Instantiates a new server associated with the provided future reactor.
	pub fn new(config: ServerConfig) -> Result<Server, Error> {
		// Obtain our lock_file or fail immediately with an error.
		let lock_file = Server::one_kepler_at_a_time(&config)?;

		// Defaults to None (optional) in config file.
		// This translates to false here.
		let archive_mode = match config.archive_mode {
			None => false,
			Some(b) => b,
		};

		let stop_state = Arc::new(StopState::new());

		// Shared cache for verification results.
		// We cache rangeproof verification and kernel signature verification.
		let verifier_cache = Arc::new(RwLock::new(LruVerifierCache::new()));

		let pool_adapter = Arc::new(PoolToChainAdapter::new());
		let pool_net_adapter = Arc::new(PoolToNetAdapter::new(config.dandelion_config.clone()));
		let tx_pool = Arc::new(RwLock::new(pool::TransactionPool::new(
			config.pool_config.clone(),
			pool_adapter.clone(),
			verifier_cache.clone(),
			pool_net_adapter.clone(),
		)));

		let sync_state = Arc::new(SyncState::new());

		let chain_adapter = Arc::new(ChainToPoolAndNetAdapter::new(
			tx_pool.clone(),
			init_chain_hooks(&config),
		));

		let genesis = match config.chain_type {
			global::ChainTypes::AutomatedTesting => pow::mine_genesis_block().unwrap(),
			global::ChainTypes::UserTesting => pow::mine_genesis_block().unwrap(),
			global::ChainTypes::Floonet => genesis::genesis_floo(),
			global::ChainTypes::Mainnet => genesis::genesis_main(),
		};

		info!("Starting server, genesis block: {}", genesis.hash());

		let shared_chain = Arc::new(chain::Chain::init(
			config.db_root.clone(),
			chain_adapter.clone(),
			genesis.clone(),
			pow::verify_size,
			verifier_cache.clone(),
			archive_mode,
		)?);

		pool_adapter.set_chain(shared_chain.clone());

		let net_adapter = Arc::new(NetToChainAdapter::new(
			sync_state.clone(),
			shared_chain.clone(),
			tx_pool.clone(),
			verifier_cache.clone(),
			config.clone(),
			init_net_hooks(&config),
		));

		let p2p_server = Arc::new(p2p::Server::new(
			&config.db_root,
			config.p2p_config.capabilities,
			config.p2p_config.clone(),
			net_adapter.clone(),
			genesis.hash(),
			stop_state.clone(),
		)?);

		// Initialize various adapters with our dynamic set of connected peers.
		chain_adapter.init(p2p_server.peers.clone());
		pool_net_adapter.init(p2p_server.peers.clone());
		net_adapter.init(p2p_server.peers.clone());

		let mut connect_thread = None;

		if config.p2p_config.seeding_type != p2p::Seeding::Programmatic {
			let seeder = match config.p2p_config.seeding_type {
				p2p::Seeding::None => {
					warn!("No seed configured, will stay solo until connected to");
					seed::predefined_seeds(vec![])
				}
				p2p::Seeding::List => match &config.p2p_config.seeds {
					Some(seeds) => seed::predefined_seeds(seeds.peers.clone()),
					None => {
						return Err(Error::Configuration(
							"Seeds must be configured for seeding type List".to_owned(),
						));
					}
				},
				p2p::Seeding::DNSSeed => seed::default_dns_seeds(),
				_ => unreachable!(),
			};

			let preferred_peers = config.p2p_config.peers_preferred.clone().map(|p| p.peers);

			connect_thread = Some(seed::connect_and_monitor(
				p2p_server.clone(),
				config.p2p_config.capabilities,
				seeder,
				preferred_peers,
				stop_state.clone(),
			)?);
		}

		// Defaults to None (optional) in config file.
		// This translates to false here so we do not skip by default.
		let skip_sync_wait = config.skip_sync_wait.unwrap_or(false);
		sync_state.update(SyncStatus::AwaitingPeers(!skip_sync_wait));

		let sync_thread = sync::run_sync(
			sync_state.clone(),
			p2p_server.peers.clone(),
			shared_chain.clone(),
			stop_state.clone(),
		)?;

		let p2p_inner = p2p_server.clone();
		let _ = thread::Builder::new()
			.name("p2p-server".to_string())
			.spawn(move || {
				if let Err(e) = p2p_inner.listen() {
					error!("P2P server failed with erorr: {:?}", e);
				}
			})?;

		info!("Starting rest apis at: {}", &config.api_http_addr);
		let api_secret = get_first_line(config.api_secret_path.clone());
		let foreign_api_secret = get_first_line(config.foreign_api_secret_path.clone());
		let tls_conf = match config.tls_certificate_file.clone() {
			None => None,
			Some(file) => {
				let key = match config.tls_certificate_key.clone() {
					Some(k) => k,
					None => {
						let msg = format!("Private key for certificate is not set");
						return Err(Error::ArgumentError(msg));
					}
				};
				Some(TLSConfig::new(file, key))
			}
		};

		// TODO fix API shutdown and join this thread
		api::node_apis(
			&config.api_http_addr,
			shared_chain.clone(),
			tx_pool.clone(),
			p2p_server.peers.clone(),
			sync_state.clone(),
			api_secret.clone(),
			foreign_api_secret.clone(),
			tls_conf.clone(),
		)?;

		info!("Starting dandelion monitor: {}", &config.api_http_addr);
		let dandelion_thread = dandelion_monitor::monitor_transactions(
			config.dandelion_config.clone(),
			tx_pool.clone(),
			pool_net_adapter.clone(),
			verifier_cache.clone(),
			stop_state.clone(),
		)?;

		warn!("Kepler server started.");
		Ok(Server {
			config,
			p2p: p2p_server,
			chain: shared_chain,
			tx_pool,
			verifier_cache,
			sync_state,
			state_info: ServerStateInfo {
				..Default::default()
			},
			stop_state,
			lock_file,
			connect_thread,
			sync_thread,
			dandelion_thread,
		})
	}

	/// Asks the server to connect to a peer at the provided network address.
	pub fn connect_peer(&self, addr: PeerAddr) -> Result<(), Error> {
		self.p2p.connect(addr)?;
		Ok(())
	}

	/// Ping all peers, mostly useful for tests to have connected peers share
	/// their heights
	pub fn ping_peers(&self) -> Result<(), Error> {
		let head = self.chain.head()?;
		self.p2p.peers.check_all(head.total_difficulty, head.height);
		Ok(())
	}

	/// Number of peers
	pub fn peer_count(&self) -> u32 {
		self.p2p.peers.peer_count()
	}

	/// Start a minimal "stratum" mining service on a separate thread
	pub fn start_stratum_server(&self, config: StratumServerConfig) {
		let edge_bits = global::min_edge_bits();
		let proof_size = global::proofsize();
		let sync_state = self.sync_state.clone();

		let mut stratum_server = stratumserver::StratumServer::new(
			config.clone(),
			self.chain.clone(),
			self.tx_pool.clone(),
			self.verifier_cache.clone(),
			self.state_info.stratum_stats.clone(),
		);
		let _ = thread::Builder::new()
			.name("stratum_server".to_string())
			.spawn(move || {
				stratum_server.run_loop(edge_bits as u32, proof_size, sync_state);
			});
	}

	/// Start mining for blocks internally on a separate thread. Relies on
	/// internal miner, and should only be used for automated testing. Burns
	/// reward if wallet_listener_url is 'None'
	pub fn start_test_miner(
		&self,
		wallet_listener_url: Option<String>,
		stop_state: Arc<StopState>,
	) {
		info!("start_test_miner - start",);
		let sync_state = self.sync_state.clone();
		let config_wallet_url = match wallet_listener_url.clone() {
			Some(u) => u,
			None => String::from("http://127.0.0.1:17415"),
		};

		let config = StratumServerConfig {
			attempt_time_per_block: 60,
			burn_reward: false,
			enable_stratum_server: None,
			stratum_server_addr: None,
			wallet_listener_url: config_wallet_url,
			minimum_share_difficulty: 1,
		};

		let mut miner = Miner::new(
			config.clone(),
			self.chain.clone(),
			self.tx_pool.clone(),
			self.verifier_cache.clone(),
			stop_state,
			sync_state,
		);
		miner.set_debug_output_id(format!("Port {}", self.config.p2p_config.port));
		let _ = thread::Builder::new()
			.name("test_miner".to_string())
			.spawn(move || miner.run_loop(wallet_listener_url));
	}

	/// The chain head
	pub fn head(&self) -> Result<chain::Tip, Error> {
		self.chain.head().map_err(|e| e.into())
	}

	/// The head of the block header chain
	pub fn header_head(&self) -> Result<chain::Tip, Error> {
		self.chain.header_head().map_err(|e| e.into())
	}

	/// The p2p layer protocol version for this node.
	pub fn protocol_version() -> ProtocolVersion {
		ProtocolVersion::local()
	}

	/// Returns a set of stats about this server. This and the ServerStats
	/// structure
	/// can be updated over time to include any information needed by tests or
	/// other consumers
	pub fn get_server_stats(&self) -> Result<ServerStats, Error> {
		let stratum_stats = self.state_info.stratum_stats.read().clone();

		// Fill out stats on our current difficulty calculation
		// TODO: check the overhead of calculating this again isn't too much
		// could return it from next_difficulty, but would rather keep consensus
		// code clean. This may be handy for testing but not really needed
		// for release
		let diff_stats = {
			let last_blocks: Vec<consensus::HeaderInfo> =
				global::difficulty_data_to_vector(self.chain.difficulty_iter()?)
					.into_iter()
					.collect();

			let tip_height = self.head()?.height as i64;
			let mut height = tip_height as i64 - last_blocks.len() as i64 + 1;

			let diff_entries: Vec<DiffBlock> = last_blocks
				.windows(2)
				.map(|pair| {
					let prev = &pair[0];
					let next = &pair[1];

					height += 1;

					DiffBlock {
						block_height: height,
						block_hash: next.block_hash,
						difficulty: next.difficulty.to_num(),
						time: next.timestamp,
						duration: next.timestamp - prev.timestamp,
						secondary_scaling: next.secondary_scaling,
						is_secondary: next.is_secondary,
					}
				})
				.collect();

			let block_time_sum = diff_entries.iter().fold(0, |sum, t| sum + t.duration);
			let block_diff_sum = diff_entries.iter().fold(0, |sum, d| sum + d.difficulty);
			DiffStats {
				height: height as u64,
				last_blocks: diff_entries,
				average_block_time: block_time_sum / (consensus::DIFFICULTY_ADJUST_WINDOW - 1),
				average_difficulty: block_diff_sum / (consensus::DIFFICULTY_ADJUST_WINDOW - 1),
				window_size: consensus::DIFFICULTY_ADJUST_WINDOW,
			}
		};

		let peer_stats = self
			.p2p
			.peers
			.connected_peers()
			.into_iter()
			.map(|p| PeerStats::from_peer(&p))
			.collect();

		// Updating TUI stats should not block any other processing so only attempt to
		// acquire various read locks with a timeout.
		let read_timeout = Duration::from_millis(500);

		let tx_stats = self.tx_pool.try_read_for(read_timeout).map(|pool| TxStats {
			tx_pool_size: pool.txpool.size(),
			tx_pool_kernels: pool.txpool.kernel_count(),
			stem_pool_size: pool.stempool.size(),
			stem_pool_kernels: pool.stempool.kernel_count(),
		});

		let head = self.chain.head_header()?;
		let head_stats = ChainStats {
			latest_timestamp: head.timestamp,
			height: head.height,
			last_block_h: head.prev_hash,
			total_difficulty: head.total_difficulty(),
		};

		let header_stats = match self.chain.try_header_head(read_timeout)? {
			Some(head) => self.chain.get_block_header(&head.hash()).map(|header| {
				Some(ChainStats {
					latest_timestamp: header.timestamp,
					height: header.height,
					last_block_h: header.prev_hash,
					total_difficulty: header.total_difficulty(),
				})
			})?,
			_ => None,
		};

		let disk_usage_bytes = WalkDir::new(&self.config.db_root)
			.min_depth(1)
			.max_depth(3)
			.into_iter()
			.filter_map(|entry| entry.ok())
			.filter_map(|entry| entry.metadata().ok())
			.filter(|metadata| metadata.is_file())
			.fold(0, |acc, m| acc + m.len());

		let disk_usage_gb = format!("{:.*}", 3, (disk_usage_bytes as f64 / 1_000_000_000 as f64));

		Ok(ServerStats {
			peer_count: self.peer_count(),
			chain_stats: head_stats,
			header_stats: header_stats,
			sync_status: self.sync_state.status(),
			disk_usage_gb: disk_usage_gb,
			stratum_stats: stratum_stats,
			peer_stats: peer_stats,
			diff_stats: diff_stats,
			tx_stats: tx_stats,
		})
	}

	/// Stop the server.
	pub fn stop(self) {
		{
			self.sync_state.update(SyncStatus::Shutdown);
			self.stop_state.stop();

			if let Some(connect_thread) = self.connect_thread {
				match connect_thread.join() {
					Err(e) => error!("failed to join to connect_and_monitor thread: {:?}", e),
					Ok(_) => info!("connect_and_monitor thread stopped"),
				}
			} else {
				info!("No active connect_and_monitor thread")
			}

			match self.sync_thread.join() {
				Err(e) => error!("failed to join to sync thread: {:?}", e),
				Ok(_) => info!("sync thread stopped"),
			}

			match self.dandelion_thread.join() {
				Err(e) => error!("failed to join to dandelion_monitor thread: {:?}", e),
				Ok(_) => info!("dandelion_monitor thread stopped"),
			}
		}
		// this call is blocking and makes sure all peers stop, however
		// we can't be sure that we stopped a listener blocked on accept, so we don't join the p2p thread
		self.p2p.stop();
		let _ = self.lock_file.unlock();
		warn!("Shutdown complete");
	}

	/// Pause the p2p server.
	pub fn pause(&self) {
		self.stop_state.pause();
		thread::sleep(time::Duration::from_secs(1));
		self.p2p.pause();
	}

	/// Resume p2p server.
	/// TODO - We appear not to resume the p2p server (peer connections) here?
	pub fn resume(&self) {
		self.stop_state.resume();
	}

	/// Stops the test miner without stopping the p2p layer
	pub fn stop_test_miner(&self, stop: Arc<StopState>) {
		stop.stop();
		info!("stop_test_miner - stop",);
	}
}
