feature/accounts (#70)

* add accounts module

modules/accounts/Cargo.toml

@@ -0,0 +1,41 @@
+[package]
+name = "module-accounts"
+version = "0.0.1"
+authors = ["Acala Developers"]
+edition = "2018"
+
+[dependencies]
+serde = { version = "1.0", optional = true }
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false }
+sp-runtime = { git = "https://github.com/paritytech/substrate.git", default-features = false }
+frame-support = { package = "frame-support", git = "https://github.com/paritytech/substrate.git", default-features = false }
+system = { package = "frame-system", git = "https://github.com/paritytech/substrate.git", default-features = false }
+rstd = { package = "sp-std", git = "https://github.com/paritytech/substrate.git", default-features = false }
+orml-traits = { package = "orml-traits", path = "../../orml/traits", default-features = false }
+orml-tokens = { package = "orml-tokens", path = "../../orml/tokens", default-features = false }
+orml-currencies = { package = "orml-currencies", path = "../../orml/currencies", default-features = false }
+support = { package = "module-support", path = "../support", default-features = false }
+pallet-transaction-payment = { git = "https://github.com/paritytech/substrate.git", default-features = false }
+
+[dev-dependencies]
+primitives = { package = "sp-core",  git = "https://github.com/paritytech/substrate.git", default-features = false }
+runtime-io = { package = "sp-io", git = "https://github.com/paritytech/substrate.git", default-features = false }
+pallet-balances= { package = "pallet-balances", git = "https://github.com/paritytech/substrate.git", default-features = false }
+pallet-timestamp= { package = "pallet-timestamp", git = "https://github.com/paritytech/substrate.git", default-features = false }
+
+
+[features]
+default = ["std"]
+std = [
+	"serde",
+	"codec/std",
+	"sp-runtime/std",
+	"frame-support/std",
+	"system/std",
+	"rstd/std",
+	"orml-traits/std",
+	"orml-tokens/std",
+	"orml-currencies/std",
+	"support/std",
+	"pallet-transaction-payment/std",
+]

modules/accounts/src/lib.rs

@@ -0,0 +1,167 @@
+#![cfg_attr(not(feature = "std"), no_std)]
+
+use codec::{Decode, Encode};
+use frame_support::{
+	decl_module, decl_storage,
+	dispatch::Dispatchable,
+	traits::{Currency, ExistenceRequirement, Get, OnReapAccount, OnUnbalanced, Time, WithdrawReason},
+	weights::DispatchInfo,
+	IsSubType, Parameter,
+};
+use orml_traits::MultiCurrency;
+use rstd::prelude::*;
+use sp_runtime::{
+	traits::{SaturatedConversion, Saturating, SignedExtension, Zero},
+	transaction_validity::{
+		InvalidTransaction, TransactionPriority, TransactionValidity, TransactionValidityError, ValidTransaction,
+	},
+};
+
+mod mock;
+mod tests;
+
+//type BalanceOf<T> = <<T as Trait>::Currency as MultiCurrency<<T as system::Trait>::AccountId>>::Balance;
+type MomentOf<T> = <<T as Trait>::Time as Time>::Moment;
+type PalletBalanceOf<T> =
+	<<T as pallet_transaction_payment::Trait>::Currency as Currency<<T as system::Trait>::AccountId>>::Balance;
+
+pub trait Trait: system::Trait + pallet_transaction_payment::Trait + orml_currencies::Trait {
+	type FreeTransferCount: Get<u8>;
+	type FreeTransferPeriod: Get<MomentOf<Self>>;
+	type Time: Time;
+	type Currency: MultiCurrency<Self::AccountId> + Send + Sync;
+	type Call: Parameter
+		+ Dispatchable<Origin = <Self as system::Trait>::Origin>
+		+ IsSubType<orml_currencies::Module<Self>, Self>;
+}
+
+decl_storage! {
+	trait Store for Module<T: Trait> as Accounts {
+		LastFreeTransfers get(fn last_free_transfers): map T::AccountId => Vec<MomentOf<T>>;
+	}
+}
+
+decl_module! {
+	pub struct Module<T: Trait> for enum Call where origin: T::Origin {
+		const FreeTransferCount: u8 = T::FreeTransferCount::get();
+		const FreeTransferPeriod: MomentOf<T> = T::FreeTransferPeriod::get();
+	}
+}
+
+impl<T: Trait> Module<T> {
+	pub fn try_free_transfer(who: &T::AccountId) -> bool {
+		let mut last_free_transfer = Self::last_free_transfers(who);
+		let now = T::Time::now();
+		let free_transfer_period = T::FreeTransferPeriod::get();
+
+		// remove all the expired entries
+		last_free_transfer.retain(|&x| x.saturating_add(free_transfer_period) > now);
+
+		// check if can transfer for free
+		if last_free_transfer.len() < T::FreeTransferCount::get() as usize {
+			// add entry to last_free_transfer
+			last_free_transfer.push(now);
+			<LastFreeTransfers<T>>::insert(who, last_free_transfer);
+			true
+		} else {
+			false
+		}
+	}
+}
+
+impl<T: Trait> OnReapAccount<T::AccountId> for Module<T> {
+	fn on_reap_account(who: &T::AccountId) {
+		<LastFreeTransfers<T>>::remove(who);
+	}
+}
+
+/// Require the transactor pay for themselves and maybe include a tip to gain additional priority
+/// in the queue.
+#[derive(Encode, Decode, Clone, Eq, PartialEq)]
+pub struct ChargeTransactionPayment<T: Trait + Send + Sync>(#[codec(compact)] PalletBalanceOf<T>);
+
+impl<T: Trait + Send + Sync> ChargeTransactionPayment<T> {
+	/// utility constructor. Used only in client/factory code.
+	pub fn from(fee: PalletBalanceOf<T>) -> Self {
+		Self(fee)
+	}
+}
+
+impl<T: Trait + Send + Sync> rstd::fmt::Debug for ChargeTransactionPayment<T> {
+	#[cfg(feature = "std")]
+	fn fmt(&self, f: &mut rstd::fmt::Formatter) -> rstd::fmt::Result {
+		write!(f, "ChargeTransactionPayment<{:?}>", self.0)
+	}
+	#[cfg(not(feature = "std"))]
+	fn fmt(&self, _: &mut rstd::fmt::Formatter) -> rstd::fmt::Result {
+		Ok(())
+	}
+}
+
+impl<T: Trait + Send + Sync> SignedExtension for ChargeTransactionPayment<T>
+where
+	PalletBalanceOf<T>: Send + Sync,
+{
+	type AccountId = T::AccountId;
+	type Call = <T as Trait>::Call;
+	type AdditionalSigned = ();
+	type DispatchInfo = DispatchInfo;
+	type Pre = ();
+	fn additional_signed(&self) -> rstd::result::Result<(), TransactionValidityError> {
+		Ok(())
+	}
+
+	fn validate(
+		&self,
+		who: &Self::AccountId,
+		call: &Self::Call,
+		info: Self::DispatchInfo,
+		len: usize,
+	) -> TransactionValidity {
+		// pay any fees.
+		let tip = self.0;
+		let fee: PalletBalanceOf<T> =
+			pallet_transaction_payment::ChargeTransactionPayment::<T>::compute_fee(len as u32, info, tip);
+
+		// check call type
+		let call = match call.is_sub_type() {
+			Some(call) => call,
+			None => return Ok(ValidTransaction::default()),
+		};
+		let skip_pay_fee = match call {
+			orml_currencies::Call::transfer(..) => {
+				// call try_free_transfer
+				if <Module<T>>::try_free_transfer(who) {
+					true
+				} else {
+					false
+				}
+			}
+			_ => false,
+		};
+
+		// skip payment withdraw if match conditions
+		if !skip_pay_fee {
+			let imbalance = match <T as pallet_transaction_payment::Trait>::Currency::withdraw(
+				who,
+				fee,
+				if tip.is_zero() {
+					WithdrawReason::TransactionPayment.into()
+				} else {
+					WithdrawReason::TransactionPayment | WithdrawReason::Tip
+				},
+				ExistenceRequirement::KeepAlive,
+			) {
+				Ok(imbalance) => imbalance,
+				Err(_) => return InvalidTransaction::Payment.into(),
+			};
+			<T as pallet_transaction_payment::Trait>::OnTransactionPayment::on_unbalanced(imbalance);
+		}
+
+		let mut r = ValidTransaction::default();
+		// NOTE: we probably want to maximize the _fee (of any type) per weight unit_ here, which
+		// will be a bit more than setting the priority to tip. For now, this is enough.
+		r.priority = fee.saturated_into::<TransactionPriority>();
+		Ok(r)
+	}
+}