1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
// This file is part of Substrate.

// Copyright (C) 2019-2022 Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0

// This program 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.

// This program 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 this program. If not, see <https://www.gnu.org/licenses/>.

//! Transaction pool client facing API.
#![warn(missing_docs)]

pub mod error;

use async_trait::async_trait;
use futures::{Future, Stream};
use serde::{de::DeserializeOwned, Deserialize, Serialize};
use sp_runtime::{
	generic::BlockId,
	traits::{Block as BlockT, Member, NumberFor},
};
use std::{collections::HashMap, hash::Hash, pin::Pin, sync::Arc};

pub use sp_runtime::transaction_validity::{
	TransactionLongevity, TransactionPriority, TransactionSource, TransactionTag,
};

/// Transaction pool status.
#[derive(Debug)]
pub struct PoolStatus {
	/// Number of transactions in the ready queue.
	pub ready: usize,
	/// Sum of bytes of ready transaction encodings.
	pub ready_bytes: usize,
	/// Number of transactions in the future queue.
	pub future: usize,
	/// Sum of bytes of ready transaction encodings.
	pub future_bytes: usize,
}

impl PoolStatus {
	/// Returns true if the are no transactions in the pool.
	pub fn is_empty(&self) -> bool {
		self.ready == 0 && self.future == 0
	}
}

/// Possible transaction status events.
///
/// This events are being emitted by `TransactionPool` watchers,
/// which are also exposed over RPC.
///
/// The status events can be grouped based on their kinds as:
/// 1. Entering/Moving within the pool:
/// 		- `Future`
/// 		- `Ready`
/// 2. Inside `Ready` queue:
/// 		- `Broadcast`
/// 3. Leaving the pool:
/// 		- `InBlock`
/// 		- `Invalid`
/// 		- `Usurped`
/// 		- `Dropped`
/// 	4. Re-entering the pool:
/// 		- `Retracted`
/// 	5. Block finalized:
/// 		- `Finalized`
/// 		- `FinalityTimeout`
///
/// The events will always be received in the order described above, however
/// there might be cases where transactions alternate between `Future` and `Ready`
/// pool, and are `Broadcast` in the meantime.
///
/// There is also only single event causing the transaction to leave the pool.
/// I.e. only one of the listed ones should be triggered.
///
/// Note that there are conditions that may cause transactions to reappear in the pool.
/// 1. Due to possible forks, the transaction that ends up being in included
/// in one block, may later re-enter the pool or be marked as invalid.
/// 2. Transaction `Dropped` at one point, may later re-enter the pool if some other
/// transactions are removed.
/// 3. `Invalid` transaction may become valid at some point in the future.
/// (Note that runtimes are encouraged to use `UnknownValidity` to inform the pool about
/// such case).
/// 4. `Retracted` transactions might be included in some next block.
///
/// The stream is considered finished only when either `Finalized` or `FinalityTimeout`
/// event is triggered. You are however free to unsubscribe from notifications at any point.
/// The first one will be emitted when the block, in which transaction was included gets
/// finalized. The `FinalityTimeout` event will be emitted when the block did not reach finality
/// within 512 blocks. This either indicates that finality is not available for your chain,
/// or that finality gadget is lagging behind. If you choose to wait for finality longer, you can
/// re-subscribe for a particular transaction hash manually again.
#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
#[serde(rename_all = "camelCase")]
pub enum TransactionStatus<Hash, BlockHash> {
	/// Transaction is part of the future queue.
	Future,
	/// Transaction is part of the ready queue.
	Ready,
	/// The transaction has been broadcast to the given peers.
	Broadcast(Vec<String>),
	/// Transaction has been included in block with given hash
	/// at the given position.
	#[serde(with = "v1_compatible")]
	InBlock((BlockHash, TxIndex)),
	/// The block this transaction was included in has been retracted.
	Retracted(BlockHash),
	/// Maximum number of finality watchers has been reached,
	/// old watchers are being removed.
	FinalityTimeout(BlockHash),
	/// Transaction has been finalized by a finality-gadget, e.g GRANDPA.
	#[serde(with = "v1_compatible")]
	Finalized((BlockHash, TxIndex)),
	/// Transaction has been replaced in the pool, by another transaction
	/// that provides the same tags. (e.g. same (sender, nonce)).
	Usurped(Hash),
	/// Transaction has been dropped from the pool because of the limit.
	Dropped,
	/// Transaction is no longer valid in the current state.
	Invalid,
}

/// The stream of transaction events.
pub type TransactionStatusStream<Hash, BlockHash> =
	dyn Stream<Item = TransactionStatus<Hash, BlockHash>> + Send;

/// The import notification event stream.
pub type ImportNotificationStream<H> = futures::channel::mpsc::Receiver<H>;

/// Transaction hash type for a pool.
pub type TxHash<P> = <P as TransactionPool>::Hash;
/// Block hash type for a pool.
pub type BlockHash<P> = <<P as TransactionPool>::Block as BlockT>::Hash;
/// Transaction type for a pool.
pub type TransactionFor<P> = <<P as TransactionPool>::Block as BlockT>::Extrinsic;
/// Type of transactions event stream for a pool.
pub type TransactionStatusStreamFor<P> = TransactionStatusStream<TxHash<P>, BlockHash<P>>;
/// Transaction type for a local pool.
pub type LocalTransactionFor<P> = <<P as LocalTransactionPool>::Block as BlockT>::Extrinsic;
/// Transaction's index within the block in which it was included.
pub type TxIndex = usize;

/// Typical future type used in transaction pool api.
pub type PoolFuture<T, E> = std::pin::Pin<Box<dyn Future<Output = Result<T, E>> + Send>>;

/// In-pool transaction interface.
///
/// The pool is container of transactions that are implementing this trait.
/// See `sp_runtime::ValidTransaction` for details about every field.
pub trait InPoolTransaction {
	/// Transaction type.
	type Transaction;
	/// Transaction hash type.
	type Hash;

	/// Get the reference to the transaction data.
	fn data(&self) -> &Self::Transaction;
	/// Get hash of the transaction.
	fn hash(&self) -> &Self::Hash;
	/// Get priority of the transaction.
	fn priority(&self) -> &TransactionPriority;
	/// Get longevity of the transaction.
	fn longevity(&self) -> &TransactionLongevity;
	/// Get transaction dependencies.
	fn requires(&self) -> &[TransactionTag];
	/// Get tags that transaction provides.
	fn provides(&self) -> &[TransactionTag];
	/// Return a flag indicating if the transaction should be propagated to other peers.
	fn is_propagable(&self) -> bool;
}

/// Transaction pool interface.
pub trait TransactionPool: Send + Sync {
	/// Block type.
	type Block: BlockT;
	/// Transaction hash type.
	type Hash: Hash + Eq + Member + Serialize + DeserializeOwned;
	/// In-pool transaction type.
	type InPoolTransaction: InPoolTransaction<
		Transaction = TransactionFor<Self>,
		Hash = TxHash<Self>,
	>;
	/// Error type.
	type Error: From<crate::error::Error> + crate::error::IntoPoolError;

	// *** RPC

	/// Returns a future that imports a bunch of unverified transactions to the pool.
	fn submit_at(
		&self,
		at: &BlockId<Self::Block>,
		source: TransactionSource,
		xts: Vec<TransactionFor<Self>>,
	) -> PoolFuture<Vec<Result<TxHash<Self>, Self::Error>>, Self::Error>;

	/// Returns a future that imports one unverified transaction to the pool.
	fn submit_one(
		&self,
		at: &BlockId<Self::Block>,
		source: TransactionSource,
		xt: TransactionFor<Self>,
	) -> PoolFuture<TxHash<Self>, Self::Error>;

	/// Returns a future that import a single transaction and starts to watch their progress in the
	/// pool.
	fn submit_and_watch(
		&self,
		at: &BlockId<Self::Block>,
		source: TransactionSource,
		xt: TransactionFor<Self>,
	) -> PoolFuture<Pin<Box<TransactionStatusStreamFor<Self>>>, Self::Error>;

	// *** Block production / Networking
	/// Get an iterator for ready transactions ordered by priority.
	///
	/// Guarantees to return only when transaction pool got updated at `at` block.
	/// Guarantees to return immediately when `None` is passed.
	fn ready_at(
		&self,
		at: NumberFor<Self::Block>,
	) -> Pin<
		Box<
			dyn Future<
					Output = Box<dyn ReadyTransactions<Item = Arc<Self::InPoolTransaction>> + Send>,
				> + Send,
		>,
	>;

	/// Get an iterator for ready transactions ordered by priority.
	fn ready(&self) -> Box<dyn ReadyTransactions<Item = Arc<Self::InPoolTransaction>> + Send>;

	// *** Block production
	/// Remove transactions identified by given hashes (and dependent transactions) from the pool.
	fn remove_invalid(&self, hashes: &[TxHash<Self>]) -> Vec<Arc<Self::InPoolTransaction>>;

	// *** logging
	/// Returns pool status.
	fn status(&self) -> PoolStatus;

	// *** logging / RPC / networking
	/// Return an event stream of transactions imported to the pool.
	fn import_notification_stream(&self) -> ImportNotificationStream<TxHash<Self>>;

	// *** networking
	/// Notify the pool about transactions broadcast.
	fn on_broadcasted(&self, propagations: HashMap<TxHash<Self>, Vec<String>>);

	/// Returns transaction hash
	fn hash_of(&self, xt: &TransactionFor<Self>) -> TxHash<Self>;

	/// Return specific ready transaction by hash, if there is one.
	fn ready_transaction(&self, hash: &TxHash<Self>) -> Option<Arc<Self::InPoolTransaction>>;
}

/// An iterator of ready transactions.
///
/// The trait extends regular [`std::iter::Iterator`] trait and allows reporting
/// last-returned element as invalid.
///
/// The implementation is then allowed, for performance reasons, to change the elements
/// returned next, by e.g.  skipping elements that are known to depend on the reported
/// transaction, which yields them invalid as well.
pub trait ReadyTransactions: Iterator {
	/// Report given transaction as invalid.
	///
	/// This might affect subsequent elements returned by the iterator, so dependent transactions
	/// are skipped for performance reasons.
	fn report_invalid(&mut self, _tx: &Self::Item);
}

/// A no-op implementation for an empty iterator.
impl<T> ReadyTransactions for std::iter::Empty<T> {
	fn report_invalid(&mut self, _tx: &T) {}
}

/// Events that the transaction pool listens for.
pub enum ChainEvent<B: BlockT> {
	/// New best block have been added to the chain.
	NewBestBlock {
		/// Hash of the block.
		hash: B::Hash,
		/// Tree route from old best to new best parent that was calculated on import.
		///
		/// If `None`, no re-org happened on import.
		tree_route: Option<Arc<sp_blockchain::TreeRoute<B>>>,
	},
	/// An existing block has been finalized.
	Finalized {
		/// Hash of just finalized block.
		hash: B::Hash,
		/// Path from old finalized to new finalized parent.
		tree_route: Arc<[B::Hash]>,
	},
}

/// Trait for transaction pool maintenance.
#[async_trait]
pub trait MaintainedTransactionPool: TransactionPool {
	/// Perform maintenance
	async fn maintain(&self, event: ChainEvent<Self::Block>);
}

/// Transaction pool interface for submitting local transactions that exposes a
/// blocking interface for submission.
pub trait LocalTransactionPool: Send + Sync {
	/// Block type.
	type Block: BlockT;
	/// Transaction hash type.
	type Hash: Hash + Eq + Member + Serialize;
	/// Error type.
	type Error: From<crate::error::Error> + crate::error::IntoPoolError;

	/// Submits the given local unverified transaction to the pool blocking the
	/// current thread for any necessary pre-verification.
	/// NOTE: It MUST NOT be used for transactions that originate from the
	/// network or RPC, since the validation is performed with
	/// `TransactionSource::Local`.
	fn submit_local(
		&self,
		at: &BlockId<Self::Block>,
		xt: LocalTransactionFor<Self>,
	) -> Result<Self::Hash, Self::Error>;
}

/// An abstraction for transaction pool.
///
/// This trait is used by offchain calls to be able to submit transactions.
/// The main use case is for offchain workers, to feed back the results of computations,
/// but since the transaction pool access is a separate `ExternalitiesExtension` it can
/// be also used in context of other offchain calls. For one may generate and submit
/// a transaction for some misbehavior reports (say equivocation).
pub trait OffchainSubmitTransaction<Block: BlockT>: Send + Sync {
	/// Submit transaction.
	///
	/// The transaction will end up in the pool and be propagated to others.
	fn submit_at(&self, at: &BlockId<Block>, extrinsic: Block::Extrinsic) -> Result<(), ()>;
}

impl<TPool: LocalTransactionPool> OffchainSubmitTransaction<TPool::Block> for TPool {
	fn submit_at(
		&self,
		at: &BlockId<TPool::Block>,
		extrinsic: <TPool::Block as BlockT>::Extrinsic,
	) -> Result<(), ()> {
		log::debug!(
			target: "txpool",
			"(offchain call) Submitting a transaction to the pool: {:?}",
			extrinsic
		);

		let result = self.submit_local(at, extrinsic);

		result.map(|_| ()).map_err(|e| {
			log::warn!(
				target: "txpool",
				"(offchain call) Error submitting a transaction to the pool: {}",
				e
			)
		})
	}
}

/// Wrapper functions to keep the API backwards compatible over the wire for the old RPC spec.
mod v1_compatible {
	use serde::{Deserialize, Deserializer, Serialize, Serializer};

	pub fn serialize<S, H>(data: &(H, usize), serializer: S) -> Result<S::Ok, S::Error>
	where
		S: Serializer,
		H: Serialize,
	{
		let (hash, _) = data;
		serde::Serialize::serialize(&hash, serializer)
	}

	pub fn deserialize<'de, D, H>(deserializer: D) -> Result<(H, usize), D::Error>
	where
		D: Deserializer<'de>,
		H: Deserialize<'de>,
	{
		let hash: H = serde::Deserialize::deserialize(deserializer)?;
		Ok((hash, 0))
	}
}

#[cfg(test)]
mod tests {
	use super::*;

	#[test]
	fn tx_status_compatibility() {
		let event: TransactionStatus<u8, u8> = TransactionStatus::InBlock((1, 2));
		let ser = serde_json::to_string(&event).unwrap();

		let exp = r#"{"inBlock":1}"#;
		assert_eq!(ser, exp);

		let event_dec: TransactionStatus<u8, u8> = serde_json::from_str(exp).unwrap();
		assert_eq!(event_dec, TransactionStatus::InBlock((1, 0)));

		let event: TransactionStatus<u8, u8> = TransactionStatus::Finalized((1, 2));
		let ser = serde_json::to_string(&event).unwrap();

		let exp = r#"{"finalized":1}"#;
		assert_eq!(ser, exp);

		let event_dec: TransactionStatus<u8, u8> = serde_json::from_str(exp).unwrap();
		assert_eq!(event_dec, TransactionStatus::Finalized((1, 0)));
	}
}