use core::ops::Bound;
use std::collections::{BTreeMap, HashMap};
use std::marker::PhantomData;
use std::sync::Arc;

use serde::{Deserialize, Serialize};

use garage_db as db;

use garage_rpc::layout::LayoutHelper;
use garage_rpc::system::System;
use garage_util::background::BackgroundRunner;
use garage_util::data::*;
use garage_util::error::*;
use garage_util::migrate::Migrate;
use garage_util::time::*;

use garage_table::crdt::*;
use garage_table::replication::*;
use garage_table::*;

pub trait CountedItem: Clone + PartialEq + Send + Sync + 'static {
	const COUNTER_TABLE_NAME: &'static str;

	type CP: PartitionKey + Clone + PartialEq + Serialize + for<'de> Deserialize<'de> + Send + Sync;
	type CS: SortKey + Clone + PartialEq + Serialize + for<'de> Deserialize<'de> + Send + Sync;

	fn counter_partition_key(&self) -> &Self::CP;
	fn counter_sort_key(&self) -> &Self::CS;
	fn counts(&self) -> Vec<(&'static str, i64)>;
}

mod v08 {
	use super::CountedItem;
	use garage_util::data::Uuid;
	use serde::{Deserialize, Serialize};
	use std::collections::BTreeMap;

	// ---- Global part (the table everyone queries) ----

	/// A counter entry in the global table
	#[derive(Clone, PartialEq, Debug, Serialize, Deserialize)]
	pub struct CounterEntry<T: CountedItem> {
		pub pk: T::CP,
		pub sk: T::CS,
		pub values: BTreeMap<String, CounterValue>,
	}

	/// A counter entry in the global table
	#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
	pub struct CounterValue {
		pub node_values: BTreeMap<Uuid, (u64, i64)>,
	}

	impl<T: CountedItem> garage_util::migrate::InitialFormat for CounterEntry<T> {}

	// ---- Local part (the counter we maintain transactionnaly on each node) ----

	#[derive(PartialEq, Clone, Debug, Serialize, Deserialize)]
	pub(super) struct LocalCounterEntry<T: CountedItem> {
		pub(super) pk: T::CP,
		pub(super) sk: T::CS,
		pub(super) values: BTreeMap<String, (u64, i64)>,
	}

	impl<T: CountedItem> garage_util::migrate::InitialFormat for LocalCounterEntry<T> {}
}

pub use v08::*;

impl<T: CountedItem> Entry<T::CP, T::CS> for CounterEntry<T> {
	fn partition_key(&self) -> &T::CP {
		&self.pk
	}
	fn sort_key(&self) -> &T::CS {
		&self.sk
	}
	fn is_tombstone(&self) -> bool {
		self.values
			.iter()
			.all(|(_, v)| v.node_values.iter().all(|(_, (_, v))| *v == 0))
	}
}

impl<T: CountedItem> CounterEntry<T> {
	pub fn filtered_values(&self, layout: &LayoutHelper) -> HashMap<String, i64> {
		let nodes = layout.all_nongateway_nodes();
		self.filtered_values_with_nodes(&nodes)
	}

	pub fn filtered_values_with_nodes(&self, nodes: &[Uuid]) -> HashMap<String, i64> {
		let mut ret = HashMap::new();
		for (name, vals) in self.values.iter() {
			let new_vals = vals
				.node_values
				.iter()
				.filter(|(n, _)| nodes.contains(n))
				.map(|(_, (_, v))| *v)
				.collect::<Vec<_>>();
			if !new_vals.is_empty() {
				ret.insert(
					name.clone(),
					new_vals.iter().fold(i64::MIN, |a, b| std::cmp::max(a, *b)),
				);
			}
		}

		ret
	}
}

impl<T: CountedItem> Crdt for CounterEntry<T> {
	fn merge(&mut self, other: &Self) {
		for (name, e2) in other.values.iter() {
			if let Some(e) = self.values.get_mut(name) {
				e.merge(e2);
			} else {
				self.values.insert(name.clone(), e2.clone());
			}
		}
	}
}

impl Crdt for CounterValue {
	fn merge(&mut self, other: &Self) {
		for (node, (t2, e2)) in other.node_values.iter() {
			if let Some((t, e)) = self.node_values.get_mut(node) {
				if t2 > t {
					*e = *e2;
				}
			} else {
				self.node_values.insert(*node, (*t2, *e2));
			}
		}
	}
}

pub struct CounterTable<T: CountedItem> {
	_phantom_t: PhantomData<T>,
}

impl<T: CountedItem> TableSchema for CounterTable<T> {
	const TABLE_NAME: &'static str = T::COUNTER_TABLE_NAME;

	type P = T::CP;
	type S = T::CS;
	type E = CounterEntry<T>;
	type Filter = (DeletedFilter, Vec<Uuid>);

	fn matches_filter(entry: &Self::E, filter: &Self::Filter) -> bool {
		if filter.0 == DeletedFilter::Any {
			return true;
		}

		let is_tombstone = entry
			.filtered_values_with_nodes(&filter.1[..])
			.iter()
			.all(|(_, v)| *v == 0);
		filter.0.apply(is_tombstone)
	}
}

// ----

pub struct IndexCounter<T: CountedItem> {
	this_node: Uuid,
	local_counter: db::Tree,
	pub table: Arc<Table<CounterTable<T>, TableShardedReplication>>,
}

impl<T: CountedItem> IndexCounter<T> {
	pub fn new(
		system: Arc<System>,
		replication: TableShardedReplication,
		db: &db::Db,
	) -> Arc<Self> {
		Arc::new(Self {
			this_node: system.id,
			local_counter: db
				.open_tree(format!("local_counter_v2:{}", T::COUNTER_TABLE_NAME))
				.expect("Unable to open local counter tree"),
			table: Table::new(
				CounterTable {
					_phantom_t: Default::default(),
				},
				replication,
				system,
				db,
			),
		})
	}

	pub fn spawn_workers(&self, bg: &BackgroundRunner) {
		self.table.spawn_workers(bg);
	}

	pub fn count(
		&self,
		tx: &mut db::Transaction,
		old: Option<&T>,
		new: Option<&T>,
	) -> db::TxResult<(), Error> {
		let pk = old
			.map(|e| e.counter_partition_key())
			.unwrap_or_else(|| new.unwrap().counter_partition_key());
		let sk = old
			.map(|e| e.counter_sort_key())
			.unwrap_or_else(|| new.unwrap().counter_sort_key());

		// calculate counter differences
		let mut counts = HashMap::new();
		for (k, v) in old.map(|x| x.counts()).unwrap_or_default() {
			*counts.entry(k).or_insert(0) -= v;
		}
		for (k, v) in new.map(|x| x.counts()).unwrap_or_default() {
			*counts.entry(k).or_insert(0) += v;
		}

		// update local counter table
		let tree_key = self.table.data.tree_key(pk, sk);

		let mut entry = match tx.get(&self.local_counter, &tree_key[..])? {
			Some(old_bytes) => LocalCounterEntry::<T>::decode(&old_bytes)
				.ok_or_message("Cannot decode local counter entry")
				.map_err(db::TxError::Abort)?,
			None => LocalCounterEntry {
				pk: pk.clone(),
				sk: sk.clone(),
				values: BTreeMap::new(),
			},
		};

		let now = now_msec();
		for (s, inc) in counts.iter() {
			let ent = entry.values.entry(s.to_string()).or_insert((0, 0));
			ent.0 = std::cmp::max(ent.0 + 1, now);
			ent.1 += *inc;
		}

		let new_entry_bytes = entry
			.encode()
			.map_err(Error::RmpEncode)
			.map_err(db::TxError::Abort)?;
		tx.insert(&self.local_counter, &tree_key[..], new_entry_bytes)?;

		let dist_entry = entry.into_counter_entry(self.this_node);
		self.table.queue_insert(tx, &dist_entry)?;

		Ok(())
	}

	pub fn offline_recount_all<TS, TR>(
		&self,
		counted_table: &Arc<Table<TS, TR>>,
	) -> Result<(), Error>
	where
		TS: TableSchema<E = T>,
		TR: TableReplication,
	{
		// 1. Set all old local counters to zero
		let now = now_msec();
		let mut next_start: Option<Vec<u8>> = None;
		loop {
			let low_bound = match next_start.take() {
				Some(v) => Bound::Excluded(v),
				None => Bound::Unbounded,
			};
			let mut batch = vec![];
			for item in self.local_counter.range((low_bound, Bound::Unbounded))? {
				batch.push(item?);
				if batch.len() > 1000 {
					break;
				}
			}

			if batch.is_empty() {
				break;
			}

			info!("zeroing old counters... ({})", hex::encode(&batch[0].0));
			for (local_counter_k, local_counter) in batch {
				let mut local_counter = LocalCounterEntry::<T>::decode(&local_counter)
					.ok_or_message("Cannot decode local counter entry")?;

				for (_, tv) in local_counter.values.iter_mut() {
					tv.0 = std::cmp::max(tv.0 + 1, now);
					tv.1 = 0;
				}

				let local_counter_bytes = local_counter.encode()?;
				self.local_counter
					.insert(&local_counter_k, &local_counter_bytes)?;

				let counter_entry = local_counter.into_counter_entry(self.this_node);
				self.local_counter
					.db()
					.transaction(|tx| self.table.queue_insert(tx, &counter_entry))?;

				next_start = Some(local_counter_k);
			}
		}

		// 2. Recount all table entries
		let now = now_msec();
		let mut next_start: Option<Vec<u8>> = None;
		loop {
			let low_bound = match next_start.take() {
				Some(v) => Bound::Excluded(v),
				None => Bound::Unbounded,
			};
			let mut batch = vec![];
			for item in counted_table
				.data
				.store
				.range((low_bound, Bound::Unbounded))?
			{
				batch.push(item?);
				if batch.len() > 1000 {
					break;
				}
			}

			if batch.is_empty() {
				break;
			}

			info!("counting entries... ({})", hex::encode(&batch[0].0));
			for (counted_entry_k, counted_entry) in batch {
				let counted_entry = counted_table.data.decode_entry(&counted_entry)?;

				let pk = counted_entry.counter_partition_key();
				let sk = counted_entry.counter_sort_key();
				let counts = counted_entry.counts();

				let local_counter_key = self.table.data.tree_key(pk, sk);
				let mut local_counter = match self.local_counter.get(&local_counter_key)? {
					Some(old_bytes) => {
						let ent = LocalCounterEntry::<T>::decode(&old_bytes)
							.ok_or_message("Cannot decode local counter entry")?;
						assert!(ent.pk == *pk);
						assert!(ent.sk == *sk);
						ent
					}
					None => LocalCounterEntry {
						pk: pk.clone(),
						sk: sk.clone(),
						values: BTreeMap::new(),
					},
				};
				for (s, v) in counts.iter() {
					let tv = local_counter.values.entry(s.to_string()).or_insert((0, 0));
					tv.0 = std::cmp::max(tv.0 + 1, now);
					tv.1 += v;
				}

				let local_counter_bytes = local_counter.encode()?;
				self.local_counter
					.insert(&local_counter_key, local_counter_bytes)?;

				let counter_entry = local_counter.into_counter_entry(self.this_node);
				self.local_counter
					.db()
					.transaction(|tx| self.table.queue_insert(tx, &counter_entry))?;

				next_start = Some(counted_entry_k);
			}
		}

		// Done
		Ok(())
	}
}

// ----

impl<T: CountedItem> LocalCounterEntry<T> {
	fn into_counter_entry(self, this_node: Uuid) -> CounterEntry<T> {
		CounterEntry {
			pk: self.pk,
			sk: self.sk,
			values: self
				.values
				.into_iter()
				.map(|(name, (ts, v))| {
					let mut node_values = BTreeMap::new();
					node_values.insert(this_node, (ts, v));
					(name, CounterValue { node_values })
				})
				.collect(),
		}
	}
}