runtime: Add staking-handler crate

- add new crate
- copy StakingHandler trait

Cargo.lock

@@ -7362,6 +7362,22 @@ version = "1.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a8f112729512f8e442d81f95a8a7ddf2b7c6b8a1a6f509a95864142b30cab2d3"
 
+[[package]]
+name = "staking-handler"
+version = "1.0.0"
+dependencies = [
+ "frame-support",
+ "frame-system",
+ "pallet-balances",
+ "pallet-membership",
+ "pallet-timestamp",
+ "parity-scale-codec",
+ "serde",
+ "sp-arithmetic",
+ "sp-runtime",
+ "sp-std",
+]
+
 [[package]]
 name = "static_assertions"
 version = "1.1.0"

Cargo.toml

@@ -21,6 +21,7 @@ members = [
 	"runtime-modules/working-group",
 	"runtime-modules/content-directory",
 	"runtime-modules/constitution",
+	"runtime-modules/staking-handler",
 	"node",
 	"utils/chain-spec-builder/"
 ]

runtime-modules/staking-handler/Cargo.toml

@@ -0,0 +1,18 @@
+[package]
+name = 'staking-handler'
+version = '1.0.0'
+authors = ['Joystream contributors']
+edition = '2018'
+
+[dependencies]
+serde = { version = "1.0.101", optional = true, features = ["derive"] }
+codec = { package = 'parity-scale-codec', version = '1.3.4', default-features = false, features = ['derive'] }
+sp-std = { package = 'sp-std', default-features = false, git = 'https://github.com/paritytech/substrate.git', rev = 'a200cdb93c6af5763b9c7bf313fa708764ac88ca'}
+frame-support = { package = 'frame-support', default-features = false, git = 'https://github.com/paritytech/substrate.git', rev = 'a200cdb93c6af5763b9c7bf313fa708764ac88ca'}
+frame-system = { package = 'frame-system', default-features = false, git = 'https://github.com/paritytech/substrate.git', rev = 'a200cdb93c6af5763b9c7bf313fa708764ac88ca'}
+sp-arithmetic = { package = 'sp-arithmetic', default-features = false, git = 'https://github.com/paritytech/substrate.git', rev = 'a200cdb93c6af5763b9c7bf313fa708764ac88ca'}
+sp-runtime = { package = 'sp-runtime', default-features = false, git = 'https://github.com/paritytech/substrate.git', rev = 'a200cdb93c6af5763b9c7bf313fa708764ac88ca'}
+pallet-timestamp = { package = 'pallet-timestamp', default-features = false, git = 'https://github.com/paritytech/substrate.git', rev = 'a200cdb93c6af5763b9c7bf313fa708764ac88ca'}
+balances = { package = 'pallet-balances', default-features = false, git = 'https://github.com/paritytech/substrate.git', rev = 'a200cdb93c6af5763b9c7bf313fa708764ac88ca'}
+membership = { package = 'pallet-membership', default-features = false, path = '../membership'}
+

runtime-modules/staking-handler/src/lib.rs

@@ -0,0 +1,41 @@
+use frame_support::dispatch::DispatchResult;
+
+// Type alias for member id.
+pub type MemberId<T> = <T as membership::Trait>::MemberId;
+
+/// Balance alias for `balances` module.
+pub type BalanceOf<T> = <T as balances::Trait>::Balance;
+
+/// Defines abstract staking handler to manage user stakes for different activities
+/// like adding a proposal. Implementation should use built-in LockableCurrency
+/// and LockIdentifier to lock balance consistently with pallet_staking.
+pub trait StakingHandler<T: frame_system::Trait + membership::Trait + balances::Trait> {
+    /// Locks the specified balance on the account using specific lock identifier.
+    fn lock(account_id: &T::AccountId, amount: BalanceOf<T>);
+
+    /// Removes the specified lock on the account.
+    fn unlock(account_id: &T::AccountId);
+
+    /// Slash the specified balance on the account using specific lock identifier.
+    /// No limits, no actions on zero stake.
+    /// If slashing balance greater than the existing stake - stake is slashed to zero.
+    /// Returns actually slashed balance.
+    fn slash(account_id: &T::AccountId, amount: Option<BalanceOf<T>>) -> BalanceOf<T>;
+
+    /// Sets the new stake to a given amount.
+    fn set_stake(account_id: &T::AccountId, new_stake: BalanceOf<T>) -> DispatchResult;
+
+    /// Verifies that staking account bound to the member.
+    fn is_member_staking_account(member_id: &MemberId<T>, account_id: &T::AccountId) -> bool;
+
+    /// Verifies that there no conflicting stakes on the staking account.
+    fn is_account_free_of_conflicting_stakes(account_id: &T::AccountId) -> bool;
+
+    /// Verifies that staking account balance is sufficient for staking.
+    /// During the balance check we should consider already locked stake. Effective balance to check
+    /// is 'already locked funds' + 'usable funds'.
+    fn is_enough_balance_for_stake(account_id: &T::AccountId, amount: BalanceOf<T>) -> bool;
+
+    /// Returns the current stake on the account.
+    fn current_stake(account_id: &T::AccountId) -> BalanceOf<T>;
+}