// This file is part of Substrate.

// Copyright (C) 2021-2022 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.

//! Migrate the reference counting state.

use codec::{Decode, Encode, FullCodec};
use frame_support::{
	pallet_prelude::ValueQuery, traits::PalletInfoAccess, weights::Weight, Blake2_128Concat,
	RuntimeDebug,
};
use sp_std::prelude::*;

/// Type used to encode the number of references an account has.
type RefCount = u32;

/// Information of an account.
#[derive(Clone, Eq, PartialEq, Default, RuntimeDebug, Encode, Decode)]
struct AccountInfo<Index, AccountData> {
	nonce: Index,
	consumers: RefCount,
	providers: RefCount,
	sufficients: RefCount,
	data: AccountData,
}

/// Trait to implement to give information about types used for migration
pub trait V2ToV3 {
	/// The system pallet.
	type Pallet: 'static + PalletInfoAccess;

	/// System config account id
	type AccountId: 'static + FullCodec;

	/// System config index
	type Index: 'static + FullCodec + Copy;

	/// System config account data
	type AccountData: 'static + FullCodec;
}

// ### Warning
//
// The call below is only valid because the name System is enforced
// at runtime construction level for the system pallet.
frame_support::generate_storage_alias!(
	System, UpgradedToU32RefCount => Value<
		bool,
		ValueQuery
	>
);

// ### Warning
//
// The call below is only valid because the name System is enforced
// at runtime construction level for the system pallet.
frame_support::generate_storage_alias!(
	System, UpgradedToTripleRefCount => Value<
		bool,
		ValueQuery
	>
);

// ### Warning
//
// The call below is only valid because the name System is enforced
// at runtime construction level for the system pallet.
frame_support::generate_storage_alias!(
	System, Account<T: V2ToV3> => Map<
		(Blake2_128Concat, T::AccountId),
		AccountInfo<T::Index, T::AccountData>
	>
);

/// Migrate from unique `u8` reference counting to triple `u32` reference counting.
pub fn migrate_from_single_u8_to_triple_ref_count<T: V2ToV3>() -> Weight {
	let mut translated: usize = 0;
	<Account<T>>::translate::<(T::Index, u8, T::AccountData), _>(|_key, (nonce, rc, data)| {
		translated = translated + 1;
		Some(AccountInfo { nonce, consumers: rc as RefCount, providers: 1, sufficients: 0, data })
	});
	log::info!(
		target: "runtime::system",
		"Applied migration from single u8 to triple reference counting to {:?} elements.",
		translated
	);
	<UpgradedToU32RefCount>::put(true);
	<UpgradedToTripleRefCount>::put(true);
	Weight::max_value()
}

/// Migrate from unique `u32` reference counting to triple `u32` reference counting.
pub fn migrate_from_single_to_triple_ref_count<T: V2ToV3>() -> Weight {
	let mut translated: usize = 0;
	<Account<T>>::translate::<(T::Index, RefCount, T::AccountData), _>(
		|_key, (nonce, consumers, data)| {
			translated = translated + 1;
			Some(AccountInfo { nonce, consumers, providers: 1, sufficients: 0, data })
		},
	);
	log::info!(
		target: "runtime::system",
		"Applied migration from single to triple reference counting to {:?} elements.",
		translated
	);
	<UpgradedToTripleRefCount>::put(true);
	Weight::max_value()
}

/// Migrate from dual `u32` reference counting to triple `u32` reference counting.
pub fn migrate_from_dual_to_triple_ref_count<T: V2ToV3>() -> Weight {
	let mut translated: usize = 0;
	<Account<T>>::translate::<(T::Index, RefCount, RefCount, T::AccountData), _>(
		|_key, (nonce, consumers, providers, data)| {
			translated = translated + 1;
			Some(AccountInfo { nonce, consumers, providers, sufficients: 0, data })
		},
	);
	log::info!(
		target: "runtime::system",
		"Applied migration from dual to triple reference counting to {:?} elements.",
		translated
	);
	<UpgradedToTripleRefCount>::put(true);
	Weight::max_value()
}
