// Copyright 2019-2020 Parity Technologies (UK) Ltd.
// This file is part of Substrate.

// Substrate is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// Substrate is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with Substrate.  If not, see <http://www.gnu.org/licenses/>.

//! # Nicks Module
//!
//! - [`nicks::Trait`](./trait.Trait.html)
//! - [`Call`](./enum.Call.html)
//!
//! ## Overview
//!
//! Nicks is a trivial module for keeping track of account names on-chain. It makes no effort to
//! create a name hierarchy, be a DNS replacement or provide reverse lookups.
//!
//! ## Interface
//!
//! ### Dispatchable Functions
//!
//! * `set_name` - Set the associated name of an account; a small deposit is reserved if not already
//!   taken.
//! * `clear_name` - Remove an account's associated name; the deposit is returned.
//! * `kill_name` - Forcibly remove the associated name; the deposit is lost.
//!
//! [`Call`]: ./enum.Call.html
//! [`Trait`]: ./trait.Trait.html

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

use sp_std::prelude::*;
use sp_runtime::{
	traits::{StaticLookup, EnsureOrigin, Zero}
};
use frame_support::{
	decl_module, decl_event, decl_storage, ensure, decl_error,
	traits::{Currency, ReservableCurrency, OnUnbalanced, Get},
	weights::SimpleDispatchInfo,
};
use frame_system::{self as system, ensure_signed, ensure_root};

type BalanceOf<T> = <<T as Trait>::Currency as Currency<<T as frame_system::Trait>::AccountId>>::Balance;
type NegativeImbalanceOf<T> = <<T as Trait>::Currency as Currency<<T as frame_system::Trait>::AccountId>>::NegativeImbalance;

pub trait Trait: frame_system::Trait {
	/// The overarching event type.
	type Event: From<Event<Self>> + Into<<Self as frame_system::Trait>::Event>;

	/// The currency trait.
	type Currency: ReservableCurrency<Self::AccountId>;

	/// Reservation fee.
	type ReservationFee: Get<BalanceOf<Self>>;

	/// What to do with slashed funds.
	type Slashed: OnUnbalanced<NegativeImbalanceOf<Self>>;

	/// The origin which may forcibly set or remove a name. Root can always do this.
	type ForceOrigin: EnsureOrigin<Self::Origin>;

	/// The minimum length a name may be.
	type MinLength: Get<usize>;

	/// The maximum length a name may be.
	type MaxLength: Get<usize>;
}

decl_storage! {
	trait Store for Module<T: Trait> as Sudo {
		/// The lookup table for names.
		NameOf: map hasher(blake2_256) T::AccountId => Option<(Vec<u8>, BalanceOf<T>)>;
	}
}

decl_event!(
	pub enum Event<T> where AccountId = <T as frame_system::Trait>::AccountId, Balance = BalanceOf<T> {
		/// A name was set.
		NameSet(AccountId),
		/// A name was forcibly set.
		NameForced(AccountId),
		/// A name was changed.
		NameChanged(AccountId),
		/// A name was cleared, and the given balance returned.
		NameCleared(AccountId, Balance),
		/// A name was removed and the given balance slashed.
		NameKilled(AccountId, Balance),
	}
);

decl_error! {
	/// Error for the nicks module.
	pub enum Error for Module<T: Trait> {
		/// A name is too short.
		TooShort,
		/// A name is too long.
		TooLong,
		/// An account in't named.
		Unnamed,
	}
}

decl_module! {
	// Simple declaration of the `Module` type. Lets the macro know what it's working on.
	pub struct Module<T: Trait> for enum Call where origin: T::Origin {
		type Error = Error<T>;

		fn deposit_event() = default;

		/// Reservation fee.
		const ReservationFee: BalanceOf<T> = T::ReservationFee::get();

		/// The minimum length a name may be.
		const MinLength: u32 = T::MinLength::get() as u32;

		/// The maximum length a name may be.
		const MaxLength: u32 = T::MaxLength::get() as u32;

		/// Set an account's name. The name should be a UTF-8-encoded string by convention, though
		/// we don't check it.
		///
		/// The name may not be more than `T::MaxLength` bytes, nor less than `T::MinLength` bytes.
		///
		/// If the account doesn't already have a name, then a fee of `ReservationFee` is reserved
		/// in the account.
		///
		/// The dispatch origin for this call must be _Signed_.
		///
		/// # <weight>
		/// - O(1).
		/// - At most one balance operation.
		/// - One storage read/write.
		/// - One event.
		/// # </weight>
		#[weight = SimpleDispatchInfo::FixedNormal(50_000)]
		fn set_name(origin, name: Vec<u8>) {
			let sender = ensure_signed(origin)?;

			ensure!(name.len() >= T::MinLength::get(), Error::<T>::TooShort);
			ensure!(name.len() <= T::MaxLength::get(), Error::<T>::TooLong);

			let deposit = if let Some((_, deposit)) = <NameOf<T>>::get(&sender) {
				Self::deposit_event(RawEvent::NameSet(sender.clone()));
				deposit
			} else {
				let deposit = T::ReservationFee::get();
				T::Currency::reserve(&sender, deposit.clone())?;
				Self::deposit_event(RawEvent::NameChanged(sender.clone()));
				deposit
			};

			<NameOf<T>>::insert(&sender, (name, deposit));
		}

		/// Clear an account's name and return the deposit. Fails if the account was not named.
		///
		/// The dispatch origin for this call must be _Signed_.
		///
		/// # <weight>
		/// - O(1).
		/// - One balance operation.
		/// - One storage read/write.
		/// - One event.
		/// # </weight>
		fn clear_name(origin) {
			let sender = ensure_signed(origin)?;

			let deposit = <NameOf<T>>::take(&sender).ok_or(Error::<T>::Unnamed)?.1;

			let _ = T::Currency::unreserve(&sender, deposit.clone());

			Self::deposit_event(RawEvent::NameCleared(sender, deposit));
		}

		/// Remove an account's name and take charge of the deposit.
		///
		/// Fails if `who` has not been named. The deposit is dealt with through `T::Slashed`
		/// imbalance handler.
		///
		/// The dispatch origin for this call must be _Root_ or match `T::ForceOrigin`.
		///
		/// # <weight>
		/// - O(1).
		/// - One unbalanced handler (probably a balance transfer)
		/// - One storage read/write.
		/// - One event.
		/// # </weight>
		#[weight = SimpleDispatchInfo::FixedNormal(70_000)]
		fn kill_name(origin, target: <T::Lookup as StaticLookup>::Source) {
			T::ForceOrigin::try_origin(origin)
				.map(|_| ())
				.or_else(ensure_root)?;

			// Figure out who we're meant to be clearing.
			let target = T::Lookup::lookup(target)?;
			// Grab their deposit (and check that they have one).
			let deposit = <NameOf<T>>::take(&target).ok_or(Error::<T>::Unnamed)?.1;
			// Slash their deposit from them.
			T::Slashed::on_unbalanced(T::Currency::slash_reserved(&target, deposit.clone()).0);

			Self::deposit_event(RawEvent::NameKilled(target, deposit));
		}

		/// Set a third-party account's name with no deposit.
		///
		/// No length checking is done on the name.
		///
		/// The dispatch origin for this call must be _Root_ or match `T::ForceOrigin`.
		///
		/// # <weight>
		/// - O(1).
		/// - At most one balance operation.
		/// - One storage read/write.
		/// - One event.
		/// # </weight>
		#[weight = SimpleDispatchInfo::FixedNormal(70_000)]
		fn force_name(origin, target: <T::Lookup as StaticLookup>::Source, name: Vec<u8>) {
			T::ForceOrigin::try_origin(origin)
				.map(|_| ())
				.or_else(ensure_root)?;

			let target = T::Lookup::lookup(target)?;
			let deposit = <NameOf<T>>::get(&target).map(|x| x.1).unwrap_or_else(Zero::zero);
			<NameOf<T>>::insert(&target, (name, deposit));

			Self::deposit_event(RawEvent::NameForced(target));
		}
	}
}

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

	use frame_support::{
		assert_ok, assert_noop, impl_outer_origin, parameter_types, weights::Weight,
		ord_parameter_types
	};
	use sp_core::H256;
	use frame_system::EnsureSignedBy;
	// The testing primitives are very useful for avoiding having to work with signatures
	// or public keys. `u64` is used as the `AccountId` and no `Signature`s are required.
	use sp_runtime::{
		Perbill, testing::Header, traits::{BlakeTwo256, IdentityLookup, BadOrigin},
	};

	impl_outer_origin! {
		pub enum Origin for Test  where system = frame_system {}
	}

	// For testing the module, we construct most of a mock runtime. This means
	// first constructing a configuration type (`Test`) which `impl`s each of the
	// configuration traits of modules we want to use.
	#[derive(Clone, Eq, PartialEq)]
	pub struct Test;
	parameter_types! {
		pub const BlockHashCount: u64 = 250;
		pub const MaximumBlockWeight: Weight = 1024;
		pub const MaximumBlockLength: u32 = 2 * 1024;
		pub const AvailableBlockRatio: Perbill = Perbill::one();
	}
	impl frame_system::Trait for Test {
		type Origin = Origin;
		type Index = u64;
		type BlockNumber = u64;
		type Hash = H256;
		type Call = ();
		type Hashing = BlakeTwo256;
		type AccountId = u64;
		type Lookup = IdentityLookup<Self::AccountId>;
		type Header = Header;
		type Event = ();
		type BlockHashCount = BlockHashCount;
		type MaximumBlockWeight = MaximumBlockWeight;
		type MaximumBlockLength = MaximumBlockLength;
		type AvailableBlockRatio = AvailableBlockRatio;
		type Version = ();
		type ModuleToIndex = ();
		type AccountData = pallet_balances::AccountData<u64>;
		type OnNewAccount = ();
		type OnReapAccount = Balances;
	}
	parameter_types! {
		pub const ExistentialDeposit: u64 = 1;
	}
	impl pallet_balances::Trait for Test {
		type Balance = u64;
		type Event = ();
		type DustRemoval = ();
		type ExistentialDeposit = ExistentialDeposit;
		type AccountStore = System;
	}
	parameter_types! {
		pub const ReservationFee: u64 = 2;
		pub const MinLength: usize = 3;
		pub const MaxLength: usize = 16;
	}
	ord_parameter_types! {
		pub const One: u64 = 1;
	}
	impl Trait for Test {
		type Event = ();
		type Currency = Balances;
		type ReservationFee = ReservationFee;
		type Slashed = ();
		type ForceOrigin = EnsureSignedBy<One, u64>;
		type MinLength = MinLength;
		type MaxLength = MaxLength;
	}
	type System = frame_system::Module<Test>;
	type Balances = pallet_balances::Module<Test>;
	type Nicks = Module<Test>;

	// This function basically just builds a genesis storage key/value store according to
	// our desired mockup.
	fn new_test_ext() -> sp_io::TestExternalities {
		let mut t = frame_system::GenesisConfig::default().build_storage::<Test>().unwrap();
		// We use default for brevity, but you can configure as desired if needed.
		pallet_balances::GenesisConfig::<Test> {
			balances: vec![
				(1, 10),
				(2, 10),
			],
		}.assimilate_storage(&mut t).unwrap();
		t.into()
	}

	#[test]
	fn kill_name_should_work() {
		new_test_ext().execute_with(|| {
			assert_ok!(Nicks::set_name(Origin::signed(2), b"Dave".to_vec()));
			assert_eq!(Balances::total_balance(&2), 10);
			assert_ok!(Nicks::kill_name(Origin::signed(1), 2));
			assert_eq!(Balances::total_balance(&2), 8);
			assert_eq!(<NameOf<Test>>::get(2), None);
		});
	}

	#[test]
	fn force_name_should_work() {
		new_test_ext().execute_with(|| {
			assert_noop!(
				Nicks::set_name(Origin::signed(2), b"Dr. David Brubeck, III".to_vec()),
				Error::<Test>::TooLong,
			);

			assert_ok!(Nicks::set_name(Origin::signed(2), b"Dave".to_vec()));
			assert_eq!(Balances::reserved_balance(2), 2);
			assert_ok!(Nicks::force_name(Origin::signed(1), 2, b"Dr. David Brubeck, III".to_vec()));
			assert_eq!(Balances::reserved_balance(2), 2);
			assert_eq!(<NameOf<Test>>::get(2).unwrap(), (b"Dr. David Brubeck, III".to_vec(), 2));
		});
	}

	#[test]
	fn normal_operation_should_work() {
		new_test_ext().execute_with(|| {
			assert_ok!(Nicks::set_name(Origin::signed(1), b"Gav".to_vec()));
			assert_eq!(Balances::reserved_balance(1), 2);
			assert_eq!(Balances::free_balance(1), 8);
			assert_eq!(<NameOf<Test>>::get(1).unwrap().0, b"Gav".to_vec());

			assert_ok!(Nicks::set_name(Origin::signed(1), b"Gavin".to_vec()));
			assert_eq!(Balances::reserved_balance(1), 2);
			assert_eq!(Balances::free_balance(1), 8);
			assert_eq!(<NameOf<Test>>::get(1).unwrap().0, b"Gavin".to_vec());

			assert_ok!(Nicks::clear_name(Origin::signed(1)));
			assert_eq!(Balances::reserved_balance(1), 0);
			assert_eq!(Balances::free_balance(1), 10);
		});
	}

	#[test]
	fn error_catching_should_work() {
		new_test_ext().execute_with(|| {
			assert_noop!(Nicks::clear_name(Origin::signed(1)), Error::<Test>::Unnamed);

			assert_noop!(
				Nicks::set_name(Origin::signed(3), b"Dave".to_vec()),
				pallet_balances::Error::<Test, _>::InsufficientBalance
			);

			assert_noop!(Nicks::set_name(Origin::signed(1), b"Ga".to_vec()), Error::<Test>::TooShort);
			assert_noop!(
				Nicks::set_name(Origin::signed(1), b"Gavin James Wood, Esquire".to_vec()),
				Error::<Test>::TooLong
			);
			assert_ok!(Nicks::set_name(Origin::signed(1), b"Dave".to_vec()));
			assert_noop!(Nicks::kill_name(Origin::signed(2), 1), BadOrigin);
			assert_noop!(Nicks::force_name(Origin::signed(2), 1, b"Whatever".to_vec()), BadOrigin);
		});
	}
}