// 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.

//! Smaller traits used in FRAME which don't need their own file.

use sp_runtime::traits::{StoredMapError, Block as BlockT};
use sp_arithmetic::traits::AtLeast32Bit;
use crate::dispatch::Parameter;

/// Anything that can have a `::len()` method.
pub trait Len {
	/// Return the length of data type.
	fn len(&self) -> usize;
}

impl<T: IntoIterator + Clone,> Len for T where <T as IntoIterator>::IntoIter: ExactSizeIterator {
	fn len(&self) -> usize {
		self.clone().into_iter().len()
	}
}

/// A trait for querying a single value from a type.
///
/// It is not required that the value is constant.
pub trait Get<T> {
	/// Return the current value.
	fn get() -> T;
}

impl<T: Default> Get<T> for () {
	fn get() -> T { T::default() }
}

/// Implement Get by returning Default for any type that implements Default.
pub struct GetDefault;
impl<T: Default> Get<T> for GetDefault {
	fn get() -> T {
		T::default()
	}
}

/// A type for which some values make sense to be able to drop without further consideration.
pub trait TryDrop: Sized {
	/// Drop an instance cleanly. Only works if its value represents "no-operation".
	fn try_drop(self) -> Result<(), Self>;
}

/// Return type used when we need to return one of two items, each of the opposite direction or
/// sign, with one (`Same`) being of the same type as the `self` or primary argument of the function
/// that returned it.
pub enum SameOrOther<A, B> {
	/// No item.
	None,
	/// An item of the same type as the `Self` on which the return function was called.
	Same(A),
	/// An item of the opposite type to the `Self` on which the return function was called.
	Other(B),
}

impl<A, B> TryDrop for SameOrOther<A, B> {
	fn try_drop(self) -> Result<(), Self> {
		if let SameOrOther::None = self {
			Ok(())
		} else {
			Err(self)
		}
	}
}

impl<A, B> SameOrOther<A, B> {
	/// Returns `Ok` with the inner value of `Same` if `self` is that, otherwise returns `Err` with
	/// `self`.
	pub fn try_same(self) -> Result<A, Self> {
		match self {
			SameOrOther::Same(a) => Ok(a),
			x => Err(x),
		}
	}

	/// Returns `Ok` with the inner value of `Other` if `self` is that, otherwise returns `Err` with
	/// `self`.
	pub fn try_other(self) -> Result<B, Self> {
		match self {
			SameOrOther::Other(b) => Ok(b),
			x => Err(x),
		}
	}

	/// Returns `Ok` if `self` is `None`, otherwise returns `Err` with `self`.
	pub fn try_none(self) -> Result<(), Self> {
		match self {
			SameOrOther::None => Ok(()),
			x => Err(x),
		}
	}

	pub fn same(self) -> Result<A, B> where A: Default {
		match self {
			SameOrOther::Same(a) => Ok(a),
			SameOrOther::None => Ok(A::default()),
			SameOrOther::Other(b) => Err(b),
		}
	}

	pub fn other(self) -> Result<B, A> where B: Default {
		match self {
			SameOrOther::Same(a) => Err(a),
			SameOrOther::None => Ok(B::default()),
			SameOrOther::Other(b) => Ok(b),
		}
	}
}

/// Handler for when a new account has been created.
#[impl_trait_for_tuples::impl_for_tuples(30)]
pub trait OnNewAccount<AccountId> {
	/// A new account `who` has been registered.
	fn on_new_account(who: &AccountId);
}

/// The account with the given id was reaped.
#[impl_trait_for_tuples::impl_for_tuples(30)]
pub trait OnKilledAccount<AccountId> {
	/// The account with the given id was reaped.
	fn on_killed_account(who: &AccountId);
}

/// A simple, generic one-parameter event notifier/handler.
pub trait HandleLifetime<T> {
	/// An account was created.
	fn created(_t: &T) -> Result<(), StoredMapError> { Ok(()) }

	/// An account was killed.
	fn killed(_t: &T) -> Result<(), StoredMapError> { Ok(()) }
}

impl<T> HandleLifetime<T> for () {}

pub trait Time {
	type Moment: AtLeast32Bit + Parameter + Default + Copy;

	fn now() -> Self::Moment;
}

/// Trait to deal with unix time.
pub trait UnixTime {
	/// Return duration since `SystemTime::UNIX_EPOCH`.
	fn now() -> core::time::Duration;
}

/// Trait to be used when types are exactly same.
///
/// This allow to convert back and forth from type, a reference and a mutable reference.
pub trait IsType<T>: Into<T> + From<T> {
	/// Cast reference.
	fn from_ref(t: &T) -> &Self;

	/// Cast reference.
	fn into_ref(&self) -> &T;

	/// Cast mutable reference.
	fn from_mut(t: &mut T) -> &mut Self;

	/// Cast mutable reference.
	fn into_mut(&mut self) -> &mut T;
}

impl<T> IsType<T> for T {
	fn from_ref(t: &T) -> &Self { t }
	fn into_ref(&self) -> &T { self }
	fn from_mut(t: &mut T) -> &mut Self { t }
	fn into_mut(&mut self) -> &mut T { self }
}

/// Something that can be checked to be a of sub type `T`.
///
/// This is useful for enums where each variant encapsulates a different sub type, and
/// you need access to these sub types.
///
/// For example, in FRAME, this trait is implemented for the runtime `Call` enum. Pallets use this
/// to check if a certain call is an instance of the local pallet's `Call` enum.
///
/// # Example
///
/// ```
/// # use frame_support::traits::IsSubType;
///
/// enum Test {
///     String(String),
///     U32(u32),
/// }
///
/// impl IsSubType<String> for Test {
///     fn is_sub_type(&self) -> Option<&String> {
///         match self {
///             Self::String(ref r) => Some(r),
///             _ => None,
///         }
///     }
/// }
///
/// impl IsSubType<u32> for Test {
///     fn is_sub_type(&self) -> Option<&u32> {
///         match self {
///             Self::U32(ref r) => Some(r),
///             _ => None,
///         }
///     }
/// }
///
/// fn main() {
///     let data = Test::String("test".into());
///
///     assert_eq!("test", IsSubType::<String>::is_sub_type(&data).unwrap().as_str());
/// }
/// ```
pub trait IsSubType<T> {
	/// Returns `Some(_)` if `self` is an instance of sub type `T`.
	fn is_sub_type(&self) -> Option<&T>;
}

/// Something that can execute a given block.
///
/// Executing a block means that all extrinsics in a given block will be executed and the resulting
/// header will be checked against the header of the given block.
pub trait ExecuteBlock<Block: BlockT> {
	/// Execute the given `block`.
	///
	/// This will execute all extrinsics in the block and check that the resulting header is correct.
	///
	/// # Panic
	///
	/// Panics when an extrinsics panics or the resulting header doesn't match the expected header.
	fn execute_block(block: Block);
}

/// Off-chain computation trait.
///
/// Implementing this trait on a module allows you to perform long-running tasks
/// that make (by default) validators generate transactions that feed results
/// of those long-running computations back on chain.
///
/// NOTE: This function runs off-chain, so it can access the block state,
/// but cannot preform any alterations. More specifically alterations are
/// not forbidden, but they are not persisted in any way after the worker
/// has finished.
#[impl_trait_for_tuples::impl_for_tuples(30)]
pub trait OffchainWorker<BlockNumber> {
	/// This function is being called after every block import (when fully synced).
	///
	/// Implement this and use any of the `Offchain` `sp_io` set of APIs
	/// to perform off-chain computations, calls and submit transactions
	/// with results to trigger any on-chain changes.
	/// Any state alterations are lost and are not persisted.
	fn offchain_worker(_n: BlockNumber) {}
}