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
// This file is part of Substrate.

// Copyright (C) 2017-2022 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.

//! # Timestamp Pallet
//!
//! The Timestamp pallet provides functionality to get and set the on-chain time.
//!
//! - [`Config`]
//! - [`Call`]
//! - [`Pallet`]
//!
//! ## Overview
//!
//! The Timestamp pallet allows the validators to set and validate a timestamp with each block.
//!
//! It uses inherents for timestamp data, which is provided by the block author and
//! validated/verified by other validators. The timestamp can be set only once per block and must be
//! set each block. There could be a constraint on how much time must pass before setting the new
//! timestamp.
//!
//! **NOTE:** The Timestamp pallet is the recommended way to query the on-chain time instead of
//! using an approach based on block numbers. The block number based time measurement can cause
//! issues because of cumulative calculation errors and hence should be avoided.
//!
//! ## Interface
//!
//! ### Dispatchable Functions
//!
//! * `set` - Sets the current time.
//!
//! ### Public functions
//!
//! * `get` - Gets the current time for the current block. If this function is called prior to
//! setting the timestamp, it will return the timestamp of the previous block.
//!
//! ### Config Getters
//!
//! * `MinimumPeriod` - Gets the minimum (and advised) period between blocks for the chain.
//!
//! ## Usage
//!
//! The following example shows how to use the Timestamp pallet in your custom pallet to query the
//! current timestamp.
//!
//! ### Prerequisites
//!
//! Import the Timestamp pallet into your custom pallet and derive the pallet configuration
//! trait from the timestamp trait.
//!
//! ### Get current timestamp
//!
//! ```
//! use pallet_timestamp::{self as timestamp};
//!
//! #[frame_support::pallet]
//! pub mod pallet {
//! 	use super::*;
//! 	use frame_support::pallet_prelude::*;
//! 	use frame_system::pallet_prelude::*;
//!
//! 	#[pallet::pallet]
//! 	pub struct Pallet<T>(_);
//!
//! 	#[pallet::config]
//! 	pub trait Config: frame_system::Config + timestamp::Config {}
//!
//! 	#[pallet::call]
//! 	impl<T: Config> Pallet<T> {
//! 		#[pallet::weight(0)]
//! 		pub fn get_time(origin: OriginFor<T>) -> DispatchResult {
//! 			let _sender = ensure_signed(origin)?;
//! 			let _now = <timestamp::Pallet<T>>::get();
//! 			Ok(())
//! 		}
//! 	}
//! }
//! # fn main() {}
//! ```
//!
//! ### Example from the FRAME
//!
//! The [Session pallet](https://github.com/paritytech/substrate/blob/master/frame/session/src/lib.rs) uses
//! the Timestamp pallet for session management.
//!
//! ## Related Pallets
//!
//! * [Session](../pallet_session/index.html)

#![cfg_attr(not(feature = "std"), no_std)]

mod benchmarking;
#[cfg(test)]
mod mock;
#[cfg(test)]
mod tests;
pub mod weights;

use frame_support::traits::{OnTimestampSet, Time, UnixTime};
use sp_runtime::traits::{AtLeast32Bit, SaturatedConversion, Scale, Zero};
use sp_std::{cmp, result};
use sp_timestamp::{InherentError, InherentType, INHERENT_IDENTIFIER};
pub use weights::WeightInfo;

pub use pallet::*;

#[frame_support::pallet]
pub mod pallet {
	use super::*;
	use frame_support::pallet_prelude::*;
	use frame_system::pallet_prelude::*;

	/// The pallet configuration trait
	#[pallet::config]
	pub trait Config: frame_system::Config {
		/// Type used for expressing timestamp.
		type Moment: Parameter
			+ Default
			+ AtLeast32Bit
			+ Scale<Self::BlockNumber, Output = Self::Moment>
			+ Copy
			+ MaxEncodedLen
			+ scale_info::StaticTypeInfo;

		/// Something which can be notified when the timestamp is set. Set this to `()` if not
		/// needed.
		type OnTimestampSet: OnTimestampSet<Self::Moment>;

		/// The minimum period between blocks. Beware that this is different to the *expected*
		/// period that the block production apparatus provides. Your chosen consensus system will
		/// generally work with this to determine a sensible block time. e.g. For Aura, it will be
		/// double this period on default settings.
		#[pallet::constant]
		type MinimumPeriod: Get<Self::Moment>;

		/// Weight information for extrinsics in this pallet.
		type WeightInfo: WeightInfo;
	}

	#[pallet::pallet]
	#[pallet::generate_store(pub(super) trait Store)]
	pub struct Pallet<T>(PhantomData<T>);

	/// Current time for the current block.
	#[pallet::storage]
	#[pallet::getter(fn now)]
	pub type Now<T: Config> = StorageValue<_, T::Moment, ValueQuery>;

	/// Did the timestamp get updated in this block?
	#[pallet::storage]
	pub(super) type DidUpdate<T: Config> = StorageValue<_, bool, ValueQuery>;

	#[pallet::hooks]
	impl<T: Config> Hooks<BlockNumberFor<T>> for Pallet<T> {
		/// dummy `on_initialize` to return the weight used in `on_finalize`.
		fn on_initialize(_n: BlockNumberFor<T>) -> Weight {
			// weight of `on_finalize`
			T::WeightInfo::on_finalize()
		}

		/// # <weight>
		/// - `O(1)`
		/// - 1 storage deletion (codec `O(1)`).
		/// # </weight>
		fn on_finalize(_n: BlockNumberFor<T>) {
			assert!(DidUpdate::<T>::take(), "Timestamp must be updated once in the block");
		}
	}

	#[pallet::call]
	impl<T: Config> Pallet<T> {
		/// Set the current time.
		///
		/// This call should be invoked exactly once per block. It will panic at the finalization
		/// phase, if this call hasn't been invoked by that time.
		///
		/// The timestamp should be greater than the previous one by the amount specified by
		/// `MinimumPeriod`.
		///
		/// The dispatch origin for this call must be `Inherent`.
		///
		/// # <weight>
		/// - `O(1)` (Note that implementations of `OnTimestampSet` must also be `O(1)`)
		/// - 1 storage read and 1 storage mutation (codec `O(1)`). (because of `DidUpdate::take` in
		///   `on_finalize`)
		/// - 1 event handler `on_timestamp_set`. Must be `O(1)`.
		/// # </weight>
		#[pallet::call_index(0)]
		#[pallet::weight((
			T::WeightInfo::set(),
			DispatchClass::Mandatory
		))]
		pub fn set(origin: OriginFor<T>, #[pallet::compact] now: T::Moment) -> DispatchResult {
			ensure_none(origin)?;
			assert!(!DidUpdate::<T>::exists(), "Timestamp must be updated only once in the block");
			let prev = Self::now();
			assert!(
				prev.is_zero() || now >= prev + T::MinimumPeriod::get(),
				"Timestamp must increment by at least <MinimumPeriod> between sequential blocks"
			);
			Now::<T>::put(now);
			DidUpdate::<T>::put(true);

			<T::OnTimestampSet as OnTimestampSet<_>>::on_timestamp_set(now);

			Ok(())
		}
	}

	#[pallet::inherent]
	impl<T: Config> ProvideInherent for Pallet<T> {
		type Call = Call<T>;
		type Error = InherentError;
		const INHERENT_IDENTIFIER: InherentIdentifier = INHERENT_IDENTIFIER;

		fn create_inherent(data: &InherentData) -> Option<Self::Call> {
			let inherent_data = data
				.get_data::<InherentType>(&INHERENT_IDENTIFIER)
				.expect("Timestamp inherent data not correctly encoded")
				.expect("Timestamp inherent data must be provided");
			let data = (*inherent_data).saturated_into::<T::Moment>();

			let next_time = cmp::max(data, Self::now() + T::MinimumPeriod::get());
			Some(Call::set { now: next_time })
		}

		fn check_inherent(
			call: &Self::Call,
			data: &InherentData,
		) -> result::Result<(), Self::Error> {
			const MAX_TIMESTAMP_DRIFT_MILLIS: sp_timestamp::Timestamp =
				sp_timestamp::Timestamp::new(30 * 1000);

			let t: u64 = match call {
				Call::set { ref now } => (*now).saturated_into::<u64>(),
				_ => return Ok(()),
			};

			let data = data
				.get_data::<InherentType>(&INHERENT_IDENTIFIER)
				.expect("Timestamp inherent data not correctly encoded")
				.expect("Timestamp inherent data must be provided");

			let minimum = (Self::now() + T::MinimumPeriod::get()).saturated_into::<u64>();
			if t > *(data + MAX_TIMESTAMP_DRIFT_MILLIS) {
				Err(InherentError::TooFarInFuture)
			} else if t < minimum {
				Err(InherentError::ValidAtTimestamp(minimum.into()))
			} else {
				Ok(())
			}
		}

		fn is_inherent(call: &Self::Call) -> bool {
			matches!(call, Call::set { .. })
		}
	}
}

impl<T: Config> Pallet<T> {
	/// Get the current time for the current block.
	///
	/// NOTE: if this function is called prior to setting the timestamp,
	/// it will return the timestamp of the previous block.
	pub fn get() -> T::Moment {
		Self::now()
	}

	/// Set the timestamp to something in particular. Only used for tests.
	#[cfg(any(feature = "runtime-benchmarks", feature = "std"))]
	pub fn set_timestamp(now: T::Moment) {
		Now::<T>::put(now);
		DidUpdate::<T>::put(true);
		<T::OnTimestampSet as OnTimestampSet<_>>::on_timestamp_set(now);
	}
}

impl<T: Config> Time for Pallet<T> {
	type Moment = T::Moment;

	/// Before the first set of now with inherent the value returned is zero.
	fn now() -> Self::Moment {
		Self::now()
	}
}

/// Before the timestamp inherent is applied, it returns the time of previous block.
///
/// On genesis the time returned is not valid.
impl<T: Config> UnixTime for Pallet<T> {
	fn now() -> core::time::Duration {
		// now is duration since unix epoch in millisecond as documented in
		// `sp_timestamp::InherentDataProvider`.
		let now = Self::now();
		sp_std::if_std! {
			if now == T::Moment::zero() {
				log::error!(
					target: "runtime::timestamp",
					"`pallet_timestamp::UnixTime::now` is called at genesis, invalid value returned: 0",
				);
			}
		}
		core::time::Duration::from_millis(now.saturated_into::<u64>())
	}
}