// Copyright (C) Parity Technologies (UK) Ltd. and Dijital Kurdistan Tech Institute
// This file is part of Pezcumulus.
// 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.

//! Pezcumulus timestamp related primitives.
//!
//! Provides a [`InherentDataProvider`] that should be used in the validation phase of the
//! teyrchain. It will be used to create the inherent data and that will be used to check the
//! inherents inside the teyrchain block (in this case the timestamp inherent). As we don't have
//! access to any clock from the runtime the timestamp is always passed as an inherent into the
//! runtime. To check this inherent when validating the block, we will use the relay chain slot. As
//! the relay chain slot is derived from a timestamp, we can easily convert it back to a timestamp
//! by multiplying it with the slot duration. By comparing the relay chain slot derived timestamp
//! with the timestamp we can ensure that the teyrchain timestamp is reasonable.

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

use core::time::Duration;
use pezcumulus_primitives_core::relay_chain::Slot;
use pezsp_inherents::{Error, InherentData};

pub use pezsp_timestamp::{InherentType, INHERENT_IDENTIFIER};

/// The inherent data provider for the timestamp.
///
/// This should be used in the runtime when checking the inherents in the validation phase of the
/// teyrchain.
pub struct InherentDataProvider {
	relay_chain_slot: Slot,
	relay_chain_slot_duration: Duration,
}

impl InherentDataProvider {
	/// Create `Self` from the given relay chain slot and slot duration.
	pub fn from_relay_chain_slot_and_duration(
		relay_chain_slot: Slot,
		relay_chain_slot_duration: Duration,
	) -> Self {
		Self { relay_chain_slot, relay_chain_slot_duration }
	}

	/// Create the inherent data.
	pub fn create_inherent_data(&self) -> Result<InherentData, Error> {
		let mut inherent_data = InherentData::new();
		self.provide_inherent_data(&mut inherent_data).map(|_| inherent_data)
	}

	/// Provide the inherent data into the given `inherent_data`.
	pub fn provide_inherent_data(&self, inherent_data: &mut InherentData) -> Result<(), Error> {
		// As the teyrchain starts building at around `relay_chain_slot + 1` we use that slot to
		// calculate the timestamp.
		let data: InherentType = ((*self.relay_chain_slot + 1)
			* self.relay_chain_slot_duration.as_millis() as u64)
			.into();

		inherent_data.put_data(INHERENT_IDENTIFIER, &data)
	}
}