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
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
// This file is part of Substrate.

// Copyright (C) 2019-2021 Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: Apache-2.0

// 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.

//! Offchain workers types

use codec::{Encode, Decode};
use sp_std::{prelude::{Vec, Box}, convert::TryFrom};
use crate::{OpaquePeerId, RuntimeDebug};
use sp_runtime_interface::pass_by::{PassByCodec, PassByInner, PassByEnum};

pub use crate::crypto::KeyTypeId;

#[cfg(feature = "std")]
pub mod storage;
#[cfg(feature = "std")]
pub mod testing;

/// Local storage prefix used by the Offchain Worker API to
pub const STORAGE_PREFIX : &'static [u8] = b"storage";

/// Offchain workers local storage.
pub trait OffchainStorage: Clone + Send + Sync {
	/// Persist a value in storage under given key and prefix.
	fn set(&mut self, prefix: &[u8], key: &[u8], value: &[u8]);

	/// Clear a storage entry under given key and prefix.
	fn remove(&mut self, prefix: &[u8], key: &[u8]);

	/// Retrieve a value from storage under given key and prefix.
	fn get(&self, prefix: &[u8], key: &[u8]) -> Option<Vec<u8>>;

	/// Replace the value in storage if given old_value matches the current one.
	///
	/// Returns `true` if the value has been set and false otherwise.
	fn compare_and_set(
		&mut self,
		prefix: &[u8],
		key: &[u8],
		old_value: Option<&[u8]>,
		new_value: &[u8],
	) -> bool;
}

/// A type of supported crypto.
#[derive(Clone, Copy, PartialEq, Eq, Encode, Decode, RuntimeDebug, PassByEnum)]
#[cfg_attr(feature = "std", derive(serde::Serialize, serde::Deserialize))]
#[repr(C)]
pub enum StorageKind {
	/// Persistent storage is non-revertible and not fork-aware. It means that any value
	/// set by the offchain worker triggered at block `N(hash1)` is persisted even
	/// if that block is reverted as non-canonical and is available for the worker
	/// that is re-run at block `N(hash2)`.
	/// This storage can be used by offchain workers to handle forks
	/// and coordinate offchain workers running on different forks.
	PERSISTENT = 1,
	/// Local storage is revertible and fork-aware. It means that any value
	/// set by the offchain worker triggered at block `N(hash1)` is reverted
	/// if that block is reverted as non-canonical and is NOT available for the worker
	/// that is re-run at block `N(hash2)`.
	LOCAL = 2,
}

impl TryFrom<u32> for StorageKind {
	type Error = ();

	fn try_from(kind: u32) -> Result<Self, Self::Error> {
		match kind {
			e if e == u32::from(StorageKind::PERSISTENT as u8) => Ok(StorageKind::PERSISTENT),
			e if e == u32::from(StorageKind::LOCAL as u8) => Ok(StorageKind::LOCAL),
			_ => Err(()),
		}
	}
}

impl From<StorageKind> for u32 {
	fn from(c: StorageKind) -> Self {
		c as u8 as u32
	}
}

/// Opaque type for offchain http requests.
#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, RuntimeDebug, Encode, Decode, PassByInner)]
#[cfg_attr(feature = "std", derive(Hash))]
pub struct HttpRequestId(pub u16);

impl From<HttpRequestId> for u32 {
	fn from(c: HttpRequestId) -> Self {
		c.0 as u32
	}
}

/// An error enum returned by some http methods.
#[derive(Clone, Copy, PartialEq, Eq, RuntimeDebug, Encode, Decode, PassByEnum)]
#[repr(C)]
pub enum HttpError {
	/// The requested action couldn't been completed within a deadline.
	DeadlineReached = 1,
	/// There was an IO Error while processing the request.
	IoError = 2,
	/// The ID of the request is invalid in this context.
	Invalid = 3,
}

impl TryFrom<u32> for HttpError {
	type Error = ();

	fn try_from(error: u32) -> Result<Self, Self::Error> {
		match error {
			e if e == HttpError::DeadlineReached as u8 as u32 => Ok(HttpError::DeadlineReached),
			e if e == HttpError::IoError as u8 as u32 => Ok(HttpError::IoError),
			e if e == HttpError::Invalid as u8 as u32 => Ok(HttpError::Invalid),
			_ => Err(())
		}
	}
}

impl From<HttpError> for u32 {
	fn from(c: HttpError) -> Self {
		c as u8 as u32
	}
}

/// Status of the HTTP request
#[derive(Clone, Copy, PartialEq, Eq, RuntimeDebug, Encode, Decode, PassByCodec)]
pub enum HttpRequestStatus {
	/// Deadline was reached while we waited for this request to finish.
	///
	/// Note the deadline is controlled by the calling part, it not necessarily
	/// means that the request has timed out.
	DeadlineReached,
	/// An error has occurred during the request, for example a timeout or the
	/// remote has closed our socket.
	///
	/// The request is now considered destroyed. To retry the request you need
	/// to construct it again.
	IoError,
	/// The passed ID is invalid in this context.
	Invalid,
	/// The request has finished with given status code.
	Finished(u16),
}

impl From<HttpRequestStatus> for u32 {
	fn from(status: HttpRequestStatus) -> Self {
		match status {
			HttpRequestStatus::Invalid => 0,
			HttpRequestStatus::DeadlineReached => 10,
			HttpRequestStatus::IoError => 20,
			HttpRequestStatus::Finished(code) => u32::from(code),
		}
	}
}

impl TryFrom<u32> for HttpRequestStatus {
	type Error = ();

	fn try_from(status: u32) -> Result<Self, Self::Error> {
		match status {
			0 => Ok(HttpRequestStatus::Invalid),
			10 => Ok(HttpRequestStatus::DeadlineReached),
			20 => Ok(HttpRequestStatus::IoError),
			100..=999 => u16::try_from(status).map(HttpRequestStatus::Finished).map_err(|_| ()),
			_ => Err(()),
		}
	}
}

/// A blob to hold information about the local node's network state
/// without committing to its format.
#[derive(Clone, Eq, PartialEq, Encode, Decode, RuntimeDebug, PassByCodec)]
#[cfg_attr(feature = "std", derive(Default))]
pub struct OpaqueNetworkState {
	/// PeerId of the local node in SCALE encoded.
	pub peer_id: OpaquePeerId,
	/// List of addresses the node knows it can be reached as.
	pub external_addresses: Vec<OpaqueMultiaddr>,
}

/// Simple blob to hold a `Multiaddr` without committing to its format.
#[derive(Clone, Eq, PartialEq, Encode, Decode, RuntimeDebug, PassByInner)]
pub struct OpaqueMultiaddr(pub Vec<u8>);

impl OpaqueMultiaddr {
	/// Create new `OpaqueMultiaddr`
	pub fn new(vec: Vec<u8>) -> Self {
		OpaqueMultiaddr(vec)
	}
}

/// Opaque timestamp type
#[derive(Clone, Copy, PartialEq, Eq, Ord, PartialOrd, Default, RuntimeDebug, PassByInner, Encode, Decode)]
pub struct Timestamp(u64);

/// Duration type
#[derive(Clone, Copy, PartialEq, Eq, Ord, PartialOrd, Default, RuntimeDebug, PassByInner, Encode, Decode)]
pub struct Duration(u64);

impl Duration {
	/// Create new duration representing given number of milliseconds.
	pub const fn from_millis(millis: u64) -> Self {
		Duration(millis)
	}

	/// Returns number of milliseconds this Duration represents.
	pub fn millis(&self) -> u64 {
		self.0
	}
}

impl Timestamp {
	/// Creates new `Timestamp` given unix timestamp in milliseconds.
	pub fn from_unix_millis(millis: u64) -> Self {
		Timestamp(millis)
	}

	/// Increase the timestamp by given `Duration`.
	pub fn add(&self, duration: Duration) -> Timestamp {
		Timestamp(self.0.saturating_add(duration.0))
	}

	/// Decrease the timestamp by given `Duration`
	pub fn sub(&self, duration: Duration) -> Timestamp {
		Timestamp(self.0.saturating_sub(duration.0))
	}

	/// Returns a saturated difference (Duration) between two Timestamps.
	pub fn diff(&self, other: &Self) -> Duration {
		Duration(self.0.saturating_sub(other.0))
	}

	/// Return number of milliseconds since UNIX epoch.
	pub fn unix_millis(&self) -> u64 {
		self.0
	}
}

/// Execution context extra capabilities.
#[derive(Debug, PartialEq, Eq, Clone, Copy)]
#[repr(u8)]
pub enum Capability {
	/// Access to transaction pool.
	TransactionPool = 1,
	/// External http calls.
	Http = 2,
	/// Keystore access.
	Keystore = 4,
	/// Randomness source.
	Randomness = 8,
	/// Access to opaque network state.
	NetworkState = 16,
	/// Access to offchain worker DB (read only).
	OffchainWorkerDbRead = 32,
	/// Access to offchain worker DB (writes).
	OffchainWorkerDbWrite = 64,
	/// Manage the authorized nodes
	NodeAuthorization = 128,
}

/// A set of capabilities
#[derive(Debug, PartialEq, Eq, Clone, Copy)]
pub struct Capabilities(u8);

impl Capabilities {
	/// Return an object representing an empty set of capabilities.
	pub fn none() -> Self {
		Self(0)
	}

	/// Return an object representing all capabilities enabled.
	pub fn all() -> Self {
		Self(u8::max_value())
	}

	/// Return capabilities for rich offchain calls.
	///
	/// Those calls should be allowed to sign and submit transactions
	/// and access offchain workers database (but read only!).
	pub fn rich_offchain_call() -> Self {
		[
			Capability::TransactionPool,
			Capability::Keystore,
			Capability::OffchainWorkerDbRead,
		][..].into()
	}

	/// Check if particular capability is enabled.
	pub fn has(&self, capability: Capability) -> bool {
		self.0 & capability as u8 != 0
	}

	/// Check if this capability object represents all capabilities.
	pub fn has_all(&self) -> bool {
		self == &Capabilities::all()
	}
}

impl<'a> From<&'a [Capability]> for Capabilities {
	fn from(list: &'a [Capability]) -> Self {
		Capabilities(list.iter().fold(0_u8, |a, b| a | *b as u8))
	}
}

/// An extended externalities for offchain workers.
pub trait Externalities: Send {
	/// Returns if the local node is a potential validator.
	///
	/// Even if this function returns `true`, it does not mean that any keys are configured
	/// and that the validator is registered in the chain.
	fn is_validator(&self) -> bool;

	/// Returns information about the local node's network state.
	fn network_state(&self) -> Result<OpaqueNetworkState, ()>;

	/// Returns current UNIX timestamp (in millis)
	fn timestamp(&mut self) -> Timestamp;

	/// Pause the execution until `deadline` is reached.
	fn sleep_until(&mut self, deadline: Timestamp);

	/// Returns a random seed.
	///
	/// This is a truly random non deterministic seed generated by host environment.
	/// Obviously fine in the off-chain worker context.
	fn random_seed(&mut self) -> [u8; 32];

	/// Sets a value in the local storage.
	///
	/// Note this storage is not part of the consensus, it's only accessible by
	/// offchain worker tasks running on the same machine. It _is_ persisted between runs.
	fn local_storage_set(&mut self, kind: StorageKind, key: &[u8], value: &[u8]);

	/// Removes a value in the local storage.
	///
	/// Note this storage is not part of the consensus, it's only accessible by
	/// offchain worker tasks running on the same machine. It _is_ persisted between runs.
	fn local_storage_clear(&mut self, kind: StorageKind, key: &[u8]);

	/// Sets a value in the local storage if it matches current value.
	///
	/// Since multiple offchain workers may be running concurrently, to prevent
	/// data races use CAS to coordinate between them.
	///
	/// Returns `true` if the value has been set, `false` otherwise.
	///
	/// Note this storage is not part of the consensus, it's only accessible by
	/// offchain worker tasks running on the same machine. It _is_ persisted between runs.
	fn local_storage_compare_and_set(
		&mut self,
		kind: StorageKind,
		key: &[u8],
		old_value: Option<&[u8]>,
		new_value: &[u8],
	) -> bool;

	/// Gets a value from the local storage.
	///
	/// If the value does not exist in the storage `None` will be returned.
	/// Note this storage is not part of the consensus, it's only accessible by
	/// offchain worker tasks running on the same machine. It _is_ persisted between runs.
	fn local_storage_get(&mut self, kind: StorageKind, key: &[u8]) -> Option<Vec<u8>>;

	/// Initiates a http request given HTTP verb and the URL.
	///
	/// Meta is a future-reserved field containing additional, parity-scale-codec encoded parameters.
	/// Returns the id of newly started request.
	///
	/// Returns an error if:
	/// - No new request identifier could be allocated.
	/// - The method or URI contain invalid characters.
	///
	fn http_request_start(
		&mut self,
		method: &str,
		uri: &str,
		meta: &[u8]
	) -> Result<HttpRequestId, ()>;

	/// Append header to the request.
	///
	/// Calling this function multiple times with the same header name continues appending new
	/// headers. In other words, headers are never replaced.
	///
	/// Returns an error if:
	/// - The request identifier is invalid.
	/// - You have called `http_request_write_body` on that request.
	/// - The name or value contain invalid characters.
	///
	/// An error doesn't poison the request, and you can continue as if the call had never been
	/// made.
	///
	fn http_request_add_header(
		&mut self,
		request_id: HttpRequestId,
		name: &str,
		value: &str
	) -> Result<(), ()>;

	/// Write a chunk of request body.
	///
	/// Calling this function with a non-empty slice may or may not start the
	/// HTTP request. Calling this function with an empty chunks finalizes the
	/// request and always starts it. It is no longer valid to write more data
	/// afterwards.
	/// Passing `None` as deadline blocks forever.
	///
	/// Returns an error if:
	/// - The request identifier is invalid.
	/// - `http_response_wait` has already been called on this request.
	/// - The deadline is reached.
	/// - An I/O error has happened, for example the remote has closed our
	///   request. The request is then considered invalid.
	///
	fn http_request_write_body(
		&mut self,
		request_id: HttpRequestId,
		chunk: &[u8],
		deadline: Option<Timestamp>
	) -> Result<(), HttpError>;

	/// Block and wait for the responses for given requests.
	///
	/// Returns a vector of request statuses (the len is the same as ids).
	/// Note that if deadline is not provided the method will block indefinitely,
	/// otherwise unready responses will produce `DeadlineReached` status.
	///
	/// If a response returns an `IoError`, it is then considered destroyed.
	/// Its id is then invalid.
	///
	/// Passing `None` as deadline blocks forever.
	fn http_response_wait(
		&mut self,
		ids: &[HttpRequestId],
		deadline: Option<Timestamp>
	) -> Vec<HttpRequestStatus>;

	/// Read all response headers.
	///
	/// Returns a vector of pairs `(HeaderKey, HeaderValue)`.
	///
	/// Dispatches the request if it hasn't been done yet. It is no longer
	/// valid to modify the headers or write data to the request.
	///
	/// Returns an empty list if the identifier is unknown/invalid, hasn't
	/// received a response, or has finished.
	fn http_response_headers(
		&mut self,
		request_id: HttpRequestId
	) -> Vec<(Vec<u8>, Vec<u8>)>;

	/// Read a chunk of body response to given buffer.
	///
	/// Dispatches the request if it hasn't been done yet. It is no longer
	/// valid to modify the headers or write data to the request.
	///
	/// Returns the number of bytes written or an error in case a deadline
	/// is reached or server closed the connection.
	/// Passing `None` as a deadline blocks forever.
	///
	/// If `Ok(0)` or `Err(IoError)` is returned, the request is considered
	/// destroyed. Doing another read or getting the response's headers, for
	/// example, is then invalid.
	///
	/// Returns an error if:
	/// - The request identifier is invalid.
	/// - The deadline is reached.
	/// - An I/O error has happened, for example the remote has closed our
	///   request. The request is then considered invalid.
	///
	fn http_response_read_body(
		&mut self,
		request_id: HttpRequestId,
		buffer: &mut [u8],
		deadline: Option<Timestamp>
	) -> Result<usize, HttpError>;

	/// Set the authorized nodes from runtime.
	///
	/// In a permissioned network, the connections between nodes need to reach a
	/// consensus between participants.
	///
	/// - `nodes`: a set of nodes which are allowed to connect for the local node.
	/// each one is identified with an `OpaquePeerId`, here it just use plain bytes
	/// without any encoding. Invalid `OpaquePeerId`s are silently ignored.
	/// - `authorized_only`: if true, only the authorized nodes are allowed to connect,
	/// otherwise unauthorized nodes can also be connected through other mechanism.
	fn set_authorized_nodes(&mut self, nodes: Vec<OpaquePeerId>, authorized_only: bool);
}

impl<T: Externalities + ?Sized> Externalities for Box<T> {
	fn is_validator(&self) -> bool {
		(& **self).is_validator()
	}

	fn network_state(&self) -> Result<OpaqueNetworkState, ()> {
		(& **self).network_state()
	}

	fn timestamp(&mut self) -> Timestamp {
		(&mut **self).timestamp()
	}

	fn sleep_until(&mut self, deadline: Timestamp) {
		(&mut **self).sleep_until(deadline)
	}

	fn random_seed(&mut self) -> [u8; 32] {
		(&mut **self).random_seed()
	}

	fn local_storage_set(&mut self, kind: StorageKind, key: &[u8], value: &[u8]) {
		(&mut **self).local_storage_set(kind, key, value)
	}

	fn local_storage_clear(&mut self, kind: StorageKind, key: &[u8]) {
		(&mut **self).local_storage_clear(kind, key)
	}

	fn local_storage_compare_and_set(
		&mut self,
		kind: StorageKind,
		key: &[u8],
		old_value: Option<&[u8]>,
		new_value: &[u8],
	) -> bool {
		(&mut **self).local_storage_compare_and_set(kind, key, old_value, new_value)
	}

	fn local_storage_get(&mut self, kind: StorageKind, key: &[u8]) -> Option<Vec<u8>> {
		(&mut **self).local_storage_get(kind, key)
	}

	fn http_request_start(&mut self, method: &str, uri: &str, meta: &[u8]) -> Result<HttpRequestId, ()> {
		(&mut **self).http_request_start(method, uri, meta)
	}

	fn http_request_add_header(&mut self, request_id: HttpRequestId, name: &str, value: &str) -> Result<(), ()> {
		(&mut **self).http_request_add_header(request_id, name, value)
	}

	fn http_request_write_body(
		&mut self,
		request_id: HttpRequestId,
		chunk: &[u8],
		deadline: Option<Timestamp>
	) -> Result<(), HttpError> {
		(&mut **self).http_request_write_body(request_id, chunk, deadline)
	}

	fn http_response_wait(&mut self, ids: &[HttpRequestId], deadline: Option<Timestamp>) -> Vec<HttpRequestStatus> {
		(&mut **self).http_response_wait(ids, deadline)
	}

	fn http_response_headers(&mut self, request_id: HttpRequestId) -> Vec<(Vec<u8>, Vec<u8>)> {
		(&mut **self).http_response_headers(request_id)
	}

	fn http_response_read_body(
		&mut self,
		request_id: HttpRequestId,
		buffer: &mut [u8],
		deadline: Option<Timestamp>
	) -> Result<usize, HttpError> {
		(&mut **self).http_response_read_body(request_id, buffer, deadline)
	}

	fn set_authorized_nodes(&mut self, nodes: Vec<OpaquePeerId>, authorized_only: bool) {
		(&mut **self).set_authorized_nodes(nodes, authorized_only)
	}
}

/// An `OffchainExternalities` implementation with limited capabilities.
pub struct LimitedExternalities<T> {
	capabilities: Capabilities,
	externalities: T,
}

impl<T> LimitedExternalities<T> {
	/// Create new externalities limited to given `capabilities`.
	pub fn new(capabilities: Capabilities, externalities: T) -> Self {
		Self {
			capabilities,
			externalities,
		}
	}

	/// Check if given capability is allowed.
	///
	/// Panics in case it is not.
	fn check(&self, capability: Capability, name: &'static str) {
		if !self.capabilities.has(capability) {
			panic!("Accessing a forbidden API: {}. No: {:?} capability.", name, capability);
		}
	}
}

impl<T: Externalities> Externalities for LimitedExternalities<T> {
	fn is_validator(&self) -> bool {
		self.check(Capability::Keystore, "is_validator");
		self.externalities.is_validator()
	}

	fn network_state(&self) -> Result<OpaqueNetworkState, ()> {
		self.check(Capability::NetworkState, "network_state");
		self.externalities.network_state()
	}

	fn timestamp(&mut self) -> Timestamp {
		self.check(Capability::Http, "timestamp");
		self.externalities.timestamp()
	}

	fn sleep_until(&mut self, deadline: Timestamp) {
		self.check(Capability::Http, "sleep_until");
		self.externalities.sleep_until(deadline)
	}

	fn random_seed(&mut self) -> [u8; 32] {
		self.check(Capability::Randomness, "random_seed");
		self.externalities.random_seed()
	}

	fn local_storage_set(&mut self, kind: StorageKind, key: &[u8], value: &[u8]) {
		self.check(Capability::OffchainWorkerDbWrite, "local_storage_set");
		self.externalities.local_storage_set(kind, key, value)
	}

	fn local_storage_clear(&mut self, kind: StorageKind, key: &[u8]) {
		self.check(Capability::OffchainWorkerDbWrite, "local_storage_clear");
		self.externalities.local_storage_clear(kind, key)
	}

	fn local_storage_compare_and_set(
		&mut self,
		kind: StorageKind,
		key: &[u8],
		old_value: Option<&[u8]>,
		new_value: &[u8],
	) -> bool {
		self.check(Capability::OffchainWorkerDbWrite, "local_storage_compare_and_set");
		self.externalities.local_storage_compare_and_set(kind, key, old_value, new_value)
	}

	fn local_storage_get(&mut self, kind: StorageKind, key: &[u8]) -> Option<Vec<u8>> {
		self.check(Capability::OffchainWorkerDbRead, "local_storage_get");
		self.externalities.local_storage_get(kind, key)
	}

	fn http_request_start(&mut self, method: &str, uri: &str, meta: &[u8]) -> Result<HttpRequestId, ()> {
		self.check(Capability::Http, "http_request_start");
		self.externalities.http_request_start(method, uri, meta)
	}

	fn http_request_add_header(&mut self, request_id: HttpRequestId, name: &str, value: &str) -> Result<(), ()> {
		self.check(Capability::Http, "http_request_add_header");
		self.externalities.http_request_add_header(request_id, name, value)
	}

	fn http_request_write_body(
		&mut self,
		request_id: HttpRequestId,
		chunk: &[u8],
		deadline: Option<Timestamp>
	) -> Result<(), HttpError> {
		self.check(Capability::Http, "http_request_write_body");
		self.externalities.http_request_write_body(request_id, chunk, deadline)
	}

	fn http_response_wait(&mut self, ids: &[HttpRequestId], deadline: Option<Timestamp>) -> Vec<HttpRequestStatus> {
		self.check(Capability::Http, "http_response_wait");
		self.externalities.http_response_wait(ids, deadline)
	}

	fn http_response_headers(&mut self, request_id: HttpRequestId) -> Vec<(Vec<u8>, Vec<u8>)> {
		self.check(Capability::Http, "http_response_headers");
		self.externalities.http_response_headers(request_id)
	}

	fn http_response_read_body(
		&mut self,
		request_id: HttpRequestId,
		buffer: &mut [u8],
		deadline: Option<Timestamp>
	) -> Result<usize, HttpError> {
		self.check(Capability::Http, "http_response_read_body");
		self.externalities.http_response_read_body(request_id, buffer, deadline)
	}

	fn set_authorized_nodes(&mut self, nodes: Vec<OpaquePeerId>, authorized_only: bool) {
		self.check(Capability::NodeAuthorization, "set_authorized_nodes");
		self.externalities.set_authorized_nodes(nodes, authorized_only)
	}
}

#[cfg(feature = "std")]
sp_externalities::decl_extension! {
	/// The offchain extension that will be registered at the Substrate externalities.
	pub struct OffchainExt(Box<dyn Externalities>);
}

#[cfg(feature = "std")]
impl OffchainExt {
	/// Create a new instance of `Self`.
	pub fn new<O: Externalities + 'static>(offchain: O) -> Self {
		Self(Box::new(offchain))
	}
}

/// Abstraction over transaction pool.
///
/// This trait is currently used within the `ExternalitiesExtension`
/// to provide offchain calls with access to the transaction pool without
/// tight coupling with any pool implementation.
#[cfg(feature = "std")]
pub trait TransactionPool {
	/// Submit transaction.
	///
	/// The transaction will end up in the pool and be propagated to others.
	fn submit_transaction(&mut self, extrinsic: Vec<u8>) -> Result<(), ()>;
}

#[cfg(feature = "std")]
sp_externalities::decl_extension! {
	/// An externalities extension to submit transactions to the pool.
	pub struct TransactionPoolExt(Box<dyn TransactionPool + Send>);
}

#[cfg(feature = "std")]
impl TransactionPoolExt {
	/// Create a new instance of `TransactionPoolExt`.
	pub fn new<O: TransactionPool + Send + 'static>(pool: O) -> Self {
		Self(Box::new(pool))
	}
}

/// Change to be applied to the offchain worker db in regards to a key.
#[derive(Debug, Clone, Hash, Eq, PartialEq)]
pub enum OffchainOverlayedChange {
	/// Remove the data associated with the key
	Remove,
	/// Overwrite the value of an associated key
	SetValue(Vec<u8>),
}

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

	#[test]
	fn timestamp_ops() {
		let t = Timestamp(5);
		assert_eq!(t.add(Duration::from_millis(10)), Timestamp(15));
		assert_eq!(t.sub(Duration::from_millis(10)), Timestamp(0));
		assert_eq!(t.diff(&Timestamp(3)), Duration(2));
	}

	#[test]
	fn capabilities() {
		let none = Capabilities::none();
		let all = Capabilities::all();
		let some = Capabilities::from(&[Capability::Keystore, Capability::Randomness][..]);

		assert!(!none.has(Capability::Keystore));
		assert!(all.has(Capability::Keystore));
		assert!(some.has(Capability::Keystore));
		assert!(!none.has(Capability::TransactionPool));
		assert!(all.has(Capability::TransactionPool));
		assert!(!some.has(Capability::TransactionPool));
	}
}