use std::{convert::AsRef, fmt::Debug, sync::Arc};

use conduwuit::Result;
use futures::{FutureExt, Stream, StreamExt, TryFutureExt, TryStreamExt};
use rocksdb::Direction;
use serde::{Deserialize, Serialize};

use super::stream_from::is_cached;
use crate::{
	keyval::{Key, result_deserialize_key, serialize_key},
	stream,
};

impl super::Map {
	pub fn keys_from<'a, K, P>(
		self: &'a Arc<Self>,
		from: &P,
	) -> impl Stream<Item = Result<Key<'a, K>>> + Send + use<'a, K, P>
	where
		P: Serialize + ?Sized + Debug,
		K: Deserialize<'a> + Send,
	{
		self.keys_from_raw(from).map(result_deserialize_key::<K>)
	}

	#[tracing::instrument(skip(self), level = "trace")]
	pub fn keys_from_raw<P>(
		self: &Arc<Self>,
		from: &P,
	) -> impl Stream<Item = Result<Key<'_>>> + Send + use<'_, P>
	where
		P: Serialize + ?Sized + Debug,
	{
		let key = serialize_key(from).expect("failed to serialize query key");
		self.raw_keys_from(&key)
	}

	pub fn keys_raw_from<'a, K, P>(
		self: &'a Arc<Self>,
		from: &P,
	) -> impl Stream<Item = Result<Key<'a, K>>> + Send + use<'a, K, P>
	where
		P: AsRef<[u8]> + ?Sized + Debug + Sync,
		K: Deserialize<'a> + Send,
	{
		self.raw_keys_from(from).map(result_deserialize_key::<K>)
	}

	#[tracing::instrument(skip(self, from), fields(%self), level = "trace")]
	pub fn raw_keys_from<P>(
		self: &Arc<Self>,
		from: &P,
	) -> impl Stream<Item = Result<Key<'_>>> + Send + use<'_, P>
	where
		P: AsRef<[u8]> + ?Sized + Debug,
	{
		use crate::pool::Seek;

		let opts = super::iter_options_default(&self.db);
		let state = stream::State::new(self, opts);
		if is_cached(self, from) {
			return stream::Keys::<'_>::from(state.init_fwd(from.as_ref().into())).boxed();
		}

		let seek = Seek {
			map: self.clone(),
			dir: Direction::Forward,
			key: Some(from.as_ref().into()),
			state: crate::pool::into_send_seek(state),
			res: None,
		};

		self.db
			.pool
			.execute_iter(seek)
			.ok_into::<stream::Keys<'_>>()
			.into_stream()
			.try_flatten()
			.boxed()
	}
}
