More currency traits. (#10)

traits/src/lib.rs

 #![cfg_attr(not(feature = "std"), no_std)]
 
 use codec::FullCodec;
-use rstd::{fmt::Debug, result};
+use rstd::{
+	convert::{TryFrom, TryInto},
+	fmt::Debug,
+	result,
+};
 use sr_primitives::traits::{MaybeSerializeDeserialize, SimpleArithmetic};
 
 /// Abstraction over a fungible multi-currency system.
@@ -40,7 +44,7 @@ pub trait MultiCurrency<AccountId> {
 		amount: Self::Balance,
 	) -> result::Result<(), Self::Error>;
 
-	/// Remove `amount` from the balance of `who` under `currency_id` and recude total issuance.
+	/// Remove `amount` from the balance of `who` under `currency_id` and reduce total issuance.
 	fn withdraw(
 		currency_id: Self::CurrencyId,
 		who: &AccountId,
@@ -52,3 +56,58 @@ pub trait MultiCurrency<AccountId> {
 	/// As much funds up to `amount` will be deducted as possible, the actual slashed amount will be returned.
 	fn slash(currency_id: Self::CurrencyId, who: &AccountId, amount: Self::Balance) -> Self::Balance;
 }
+
+/// Extended `MultiCurrency` with additional helper types and methods.
+pub trait MultiCurrencyExtended<AccountId>: MultiCurrency<AccountId> {
+	/// The type for balance related operations, typically signed int.
+	type Amount: TryInto<Self::Balance> + TryFrom<Self::Balance>;
+
+	/// Add or remove abs(`by_amount`) from the balance of `who` under `currency_id`. If positive `by_amount`, do add, else do remove.
+	fn update_balance(
+		currency_id: Self::CurrencyId,
+		who: AccountId,
+		by_amount: Self::Amount,
+	) -> result::Result<(), Self::Error>;
+}
+
+/// Abstraction over a fungible (single) currency system.
+pub trait BasicCurrency<AccountId> {
+	/// The balance of an account.
+	type Balance: SimpleArithmetic + FullCodec + Copy + MaybeSerializeDeserialize + Debug + Default;
+
+	/// The error type.
+	type Error: Into<&'static str>;
+
+	// Public immutables
+
+	/// The total amount of issuance.
+	fn total_inssuance() -> Self::Balance;
+
+	/// The balance of `who`.
+	fn balance(who: &AccountId) -> Self::Balance;
+
+	// Public mutables
+
+	/// Transfer some amount from one account to another.
+	fn transfer(from: &AccountId, to: &AccountId, amount: Self::Balance) -> result::Result<(), Self::Error>;
+
+	/// Add `amount` to the balance of `who` and increase total issuance.
+	fn deposit(who: &AccountId, amount: Self::Balance) -> result::Result<(), Self::Error>;
+
+	/// Remove `amount` from the balance of `who` and reduce total issuance.
+	fn withdraw(who: &AccountId, amount: Self::Balance) -> result::Result<(), Self::Error>;
+
+	/// Deduct the balance of `who` by up to `amount`.
+	///
+	/// As much funds up to `amount` will be deducted as possible, the actual slashed amount will be returned.
+	fn slash(who: &AccountId, amount: Self::Balance) -> Self::Balance;
+}
+
+/// Extended `BasicCurrency` with additional helper types and methods.
+pub trait BasicCurrencyExtended<AccountId>: BasicCurrency<AccountId> {
+	/// The type for balance related operations, typically signed int.
+	type Amount: TryInto<Self::Balance> + TryFrom<Self::Balance>;
+
+	/// Add or remove abs(`by_amount`) from the balance of `who`. If positive `by_amount`, do add, else do remove.
+	fn update_balance(who: AccountId, by_amount: Self::Amount) -> result::Result<(), Self::Error>;
+}