use std::collections::HashSet;
use time::precise_time_s;
use orphan_blocks_pool::OrphanBlocksPool;
use orphan_transactions_pool::OrphanTransactionsPool;
use synchronization_peers::Peers;
use primitives::hash::H256;

/// Management interval (in ms)
pub const MANAGEMENT_INTERVAL_MS: u64 = 10 * 1000;
/// Response time before getting block to decrease peer score
const DEFAULT_PEER_BLOCK_FAILURE_INTERVAL_MS: u32 = 60 * 1000;
/// Response time before getting inventory to decrease peer score
const DEFAULT_PEER_INVENTORY_FAILURE_INTERVAL_MS: u32 = 60 * 1000;
/// Unknown orphan block removal time
const DEFAULT_UNKNOWN_BLOCK_REMOVAL_TIME_MS: u32 = 20 * 60 * 1000;
/// Maximal number of orphaned blocks
const DEFAULT_UNKNOWN_BLOCKS_MAX_LEN: usize = 16;
/// Unknown orphan transaction removal time
const DEFAULT_ORPHAN_TRANSACTION_REMOVAL_TIME_MS: u32 = 10 * 60 * 1000;
/// Maximal number of orphaned transactions
const DEFAULT_ORPHAN_TRANSACTIONS_MAX_LEN: usize = 10000;

/// Peers management configuration
pub struct ManagePeersConfig {
	/// Time interval (in milliseconds) to wait block from the peer before penalizing && reexecuting tasks
	pub block_failure_interval_ms: u32,
	/// Time interval (in milliseconds) to wait inventory from the peer before penalizing && reexecuting tasks
	pub inventory_failure_interval_ms: u32,
}

impl Default for ManagePeersConfig {
	fn default() -> Self {
		ManagePeersConfig {
			block_failure_interval_ms: DEFAULT_PEER_BLOCK_FAILURE_INTERVAL_MS,
			inventory_failure_interval_ms: DEFAULT_PEER_INVENTORY_FAILURE_INTERVAL_MS,
		}
	}
}

/// Unknown blocks management configuration
pub struct ManageUnknownBlocksConfig {
	/// Time interval (in milliseconds) to wait before removing unknown blocks from in-memory pool
	pub removal_time_ms: u32,
	/// Maximal # of unknown blocks in the in-memory pool
	pub max_number: usize,
}

impl Default for ManageUnknownBlocksConfig {
	fn default() -> Self {
		ManageUnknownBlocksConfig {
			removal_time_ms: DEFAULT_UNKNOWN_BLOCK_REMOVAL_TIME_MS,
			max_number: DEFAULT_UNKNOWN_BLOCKS_MAX_LEN,
		}
	}
}

/// Orphan transactions management configuration
pub struct ManageOrphanTransactionsConfig {
	/// Time interval (in milliseconds) to wait before removing orphan transactions from orphan pool
	pub removal_time_ms: u32,
	/// Maximal # of unknown transactions in the orphan pool
	pub max_number: usize,
}

impl Default for ManageOrphanTransactionsConfig {
	fn default() -> Self {
		ManageOrphanTransactionsConfig {
			removal_time_ms: DEFAULT_ORPHAN_TRANSACTION_REMOVAL_TIME_MS,
			max_number: DEFAULT_ORPHAN_TRANSACTIONS_MAX_LEN,
		}
	}
}

/// Manage stalled synchronization peers blocks tasks
pub fn manage_synchronization_peers_blocks(config: &ManagePeersConfig, peers: &mut Peers) -> Option<Vec<H256>> {
	let mut blocks_to_request: Vec<H256> = Vec::new();
	let now = precise_time_s();

	// reset tasks for peers, which has not responded during given period
	for (worst_peer_index, worst_peer_time) in peers.ordered_blocks_requests() {
		// check if peer has not responded within given time
		let time_diff = now - worst_peer_time;
		if time_diff <= config.block_failure_interval_ms as f64 / 1000f64 {
			break;
		}

		// decrease score && move to the idle queue
		warn!(target: "sync", "Failed to get requested block from peer#{} in {} seconds", worst_peer_index, time_diff);
		let peer_tasks = peers.reset_blocks_tasks(worst_peer_index);
		blocks_to_request.extend(peer_tasks);

		// if peer failed many times => forget it
		if peers.on_peer_block_failure(worst_peer_index) {
			warn!(target: "sync", "Too many failures for peer#{}. Excluding from synchronization", worst_peer_index);
		}
	}

	if blocks_to_request.is_empty() { None } else { Some(blocks_to_request) }
}

/// Manage stalled synchronization peers inventory tasks
pub fn manage_synchronization_peers_inventory(config: &ManagePeersConfig, peers: &mut Peers) {
	let now = precise_time_s();
	// reset tasks for peers, which has not responded during given period
	for (worst_peer_index, worst_peer_time) in peers.ordered_inventory_requests() {
		// check if peer has not responded within given time
		let time_diff = now - worst_peer_time;
		if time_diff <= config.inventory_failure_interval_ms as f64 / 1000f64 {
			break;
		}

		peers.on_peer_inventory_failure(worst_peer_index);
	}
}

/// Manage unknown orphaned blocks
pub fn manage_unknown_orphaned_blocks(config: &ManageUnknownBlocksConfig, orphaned_blocks_pool: &mut OrphanBlocksPool) -> Option<Vec<H256>> {
	let unknown_to_remove = {
		let unknown_blocks = orphaned_blocks_pool.unknown_blocks();
		let mut unknown_to_remove: HashSet<H256> = HashSet::new();
		let mut remove_num = if unknown_blocks.len() > config.max_number { unknown_blocks.len() - config.max_number } else { 0 };
		let now = precise_time_s();
		for (hash, time) in unknown_blocks {
			// remove oldest blocks if there are more unknown blocks that we can hold in memory
			if remove_num > 0 {
				unknown_to_remove.insert(hash.clone());
				remove_num -= 1;
				continue;
			}

			// check if block is unknown for too long
			let time_diff = now - time;
			if time_diff <= config.removal_time_ms as f64 / 1000f64 {
				break;
			}
			unknown_to_remove.insert(hash.clone());
		}

		unknown_to_remove
	};

	// remove unknown blocks
	let unknown_to_remove: Vec<H256> = orphaned_blocks_pool.remove_blocks(&unknown_to_remove).into_iter()
		.map(|t| t.0)
		.collect();

	if unknown_to_remove.is_empty() { None } else { Some(unknown_to_remove) }
}

/// Manage orphaned transactions
pub fn manage_orphaned_transactions(config: &ManageOrphanTransactionsConfig, orphaned_transactions_pool: &mut OrphanTransactionsPool) -> Option<Vec<H256>> {
	let orphans_to_remove = {
		let unknown_transactions = orphaned_transactions_pool.transactions();
		let mut orphans_to_remove: Vec<H256> = Vec::new();
		let mut remove_num = if unknown_transactions.len() > config.max_number { unknown_transactions.len() - config.max_number } else { 0 };
		let now = precise_time_s();
		for (hash, orphan_tx) in unknown_transactions {
			// remove oldest blocks if there are more unknown blocks that we can hold in memory
			if remove_num > 0 {
				orphans_to_remove.push(hash.clone());
				remove_num -= 1;
				continue;
			}

			// check if block is unknown for too long
			let time_diff = now - orphan_tx.insertion_time;
			if time_diff <= config.removal_time_ms as f64 / 1000f64 {
				break;
			}
			orphans_to_remove.push(hash.clone());
		}

		orphans_to_remove
	};

	// remove unknown blocks
	let orphans_to_remove: Vec<H256> = orphaned_transactions_pool.remove_transactions(&orphans_to_remove).into_iter()
		.map(|t| t.0)
		.collect();

	if orphans_to_remove.is_empty() { None } else { Some(orphans_to_remove) }
}

#[cfg(test)]
mod tests {
	use std::collections::HashSet;
	use super::{ManagePeersConfig, ManageUnknownBlocksConfig, ManageOrphanTransactionsConfig, manage_synchronization_peers_blocks,
		manage_unknown_orphaned_blocks, manage_orphaned_transactions};
	use synchronization_peers::Peers;
	use primitives::hash::H256;
	use test_data;
	use orphan_blocks_pool::OrphanBlocksPool;
	use orphan_transactions_pool::OrphanTransactionsPool;

	#[test]
	fn manage_good_peer() {
		let config = ManagePeersConfig { block_failure_interval_ms: 1000, ..Default::default() };
		let mut peers = Peers::new();
		peers.on_blocks_requested(1, &vec![H256::from(0), H256::from(1)]);
		peers.on_block_received(1, &H256::from(0));
		assert_eq!(manage_synchronization_peers_blocks(&config, &mut peers), None);
		assert_eq!(peers.idle_peers_for_blocks(), vec![]);
	}

	#[test]
	fn manage_bad_peers() {
		use std::thread::sleep;
		use std::time::Duration;
		let config = ManagePeersConfig { block_failure_interval_ms: 0, ..Default::default() };
		let mut peers = Peers::new();
		peers.on_blocks_requested(1, &vec![H256::from(0)]);
		peers.on_blocks_requested(2, &vec![H256::from(1)]);
		sleep(Duration::from_millis(1));

		let managed_tasks = manage_synchronization_peers_blocks(&config, &mut peers).expect("managed tasks");
		assert!(managed_tasks.contains(&H256::from(0)));
		assert!(managed_tasks.contains(&H256::from(1)));
		let idle_peers = peers.idle_peers_for_blocks();
		assert_eq!(2, idle_peers.len());
		assert!(idle_peers.contains(&1));
		assert!(idle_peers.contains(&2));
	}

	#[test]
	fn manage_unknown_blocks_good() {
		let config = ManageUnknownBlocksConfig { removal_time_ms: 1000, max_number: 100 };
		let mut pool = OrphanBlocksPool::new();
		let block = test_data::genesis();
		pool.insert_unknown_block(block.hash(), block.into());
		assert_eq!(manage_unknown_orphaned_blocks(&config, &mut pool), None);
		assert_eq!(pool.len(), 1);
	}

	#[test]
	fn manage_unknown_blocks_by_time() {
		use std::thread::sleep;
		use std::time::Duration;
		let config = ManageUnknownBlocksConfig { removal_time_ms: 0, max_number: 100 };
		let mut pool = OrphanBlocksPool::new();
		let block = test_data::genesis();
		let block_hash = block.hash();
		pool.insert_unknown_block(block_hash.clone(), block.into());
		sleep(Duration::from_millis(1));

		assert_eq!(manage_unknown_orphaned_blocks(&config, &mut pool), Some(vec![block_hash]));
		assert_eq!(pool.len(), 0);
	}

	#[test]
	fn manage_unknown_blocks_by_max_number() {
		let config = ManageUnknownBlocksConfig { removal_time_ms: 100, max_number: 1 };
		let mut pool = OrphanBlocksPool::new();
		let block1 = test_data::genesis();
		let block1_hash = block1.hash();
		let block2 = test_data::block_h2();
		let block2_hash = block2.hash();
		pool.insert_unknown_block(block1_hash.clone(), block1.into());
		pool.insert_unknown_block(block2_hash.clone(), block2.into());
		assert_eq!(manage_unknown_orphaned_blocks(&config, &mut pool), Some(vec![block1_hash]));
		assert_eq!(pool.len(), 1);
	}

	#[test]
	fn manage_orphan_transactions_good() {
		let config = ManageOrphanTransactionsConfig { removal_time_ms: 1000, max_number: 100 };
		let mut pool = OrphanTransactionsPool::new();
		let transaction = test_data::block_h170().transactions[1].clone();
		let unknown_inputs: HashSet<H256> = transaction.inputs.iter().map(|i| i.previous_output.hash.clone()).collect();
		pool.insert(transaction.hash(), transaction, unknown_inputs);
		assert_eq!(manage_orphaned_transactions(&config, &mut pool), None);
		assert_eq!(pool.len(), 1);
	}

	#[test]
	fn manage_orphan_transactions_by_time() {
		use std::thread::sleep;
		use std::time::Duration;
		let config = ManageOrphanTransactionsConfig { removal_time_ms: 0, max_number: 100 };
		let mut pool = OrphanTransactionsPool::new();
		let transaction = test_data::block_h170().transactions[1].clone();
		let unknown_inputs: HashSet<H256> = transaction.inputs.iter().map(|i| i.previous_output.hash.clone()).collect();
		let transaction_hash = transaction.hash();
		pool.insert(transaction_hash.clone(), transaction, unknown_inputs);
		sleep(Duration::from_millis(1));

		assert_eq!(manage_orphaned_transactions(&config, &mut pool), Some(vec![transaction_hash]));
		assert_eq!(pool.len(), 0);
	}

	#[test]
	fn manage_orphan_transactions_by_max_number() {
		let config = ManageOrphanTransactionsConfig { removal_time_ms: 100, max_number: 1 };
		let mut pool = OrphanTransactionsPool::new();
		let transaction1 = test_data::block_h170().transactions[1].clone();
		let unknown_inputs1: HashSet<H256> = transaction1.inputs.iter().map(|i| i.previous_output.hash.clone()).collect();
		let transaction1_hash = transaction1.hash();
		let transaction2 = test_data::block_h182().transactions[1].clone();
		let unknown_inputs2: HashSet<H256> = transaction2.inputs.iter().map(|i| i.previous_output.hash.clone()).collect();
		let transaction2_hash = transaction2.hash();
		pool.insert(transaction1_hash.clone(), transaction1, unknown_inputs1);
		pool.insert(transaction2_hash.clone(), transaction2, unknown_inputs2);
		assert_eq!(manage_orphaned_transactions(&config, &mut pool), Some(vec![transaction1_hash]));
		assert_eq!(pool.len(), 1);
	}
}