Merge pull request #1219 from opentensor/feat/slippage-safe-stake-moving

Feat/slippage safe stake moving

Author: sam0x17

pallets/subtensor/src/lib.rs

@@ -1887,6 +1887,8 @@ where
                     *origin_netuid,
                     *destination_netuid,
                     *alpha_amount,
+                    *alpha_amount,
+                    None,
                 ))
             }
             Some(Call::transfer_stake {
@@ -1905,6 +1907,8 @@ where
                     *origin_netuid,
                     *destination_netuid,
                     *alpha_amount,
+                    *alpha_amount,
+                    None,
                 ))
             }
             Some(Call::swap_stake {
@@ -1922,6 +1926,36 @@ where
                     *origin_netuid,
                     *destination_netuid,
                     *alpha_amount,
+                    *alpha_amount,
+                    None,
+                ))
+            }
+            Some(Call::swap_stake_limit {
+                hotkey,
+                origin_netuid,
+                destination_netuid,
+                alpha_amount,
+                limit_price,
+                allow_partial,
+            }) => {
+                // Get the max amount possible to exchange
+                let max_amount = Pallet::<T>::get_max_amount_move(
+                    *origin_netuid,
+                    *destination_netuid,
+                    *limit_price,
+                );
+
+                // Fully validate the user input
+                Self::result_to_validity(Pallet::<T>::validate_stake_transition(
+                    who,
+                    who,
+                    hotkey,
+                    hotkey,
+                    *origin_netuid,
+                    *destination_netuid,
+                    *alpha_amount,
+                    max_amount,
+                    Some(*allow_partial),
                 ))
             }
             Some(Call::register { netuid, .. } | Call::burned_register { netuid, .. }) => {

pallets/subtensor/src/macros/dispatches.rs

@@ -1769,10 +1769,10 @@ mod dispatches {
         /// 	- The amount of stake to be added to the hotkey staking account.
         ///
         ///  * 'limit_price' (u64):
-        /// 	- The limit price expressed in units of RAO per one Alpha.
+        ///     - The limit price expressed in units of RAO per one Alpha.
         ///
         ///  * 'allow_partial' (bool):
-        /// 	- Allows partial execution of the amount. If set to false, this becomes
+        ///     - Allows partial execution of the amount. If set to false, this becomes
         ///       fill or kill type or order.
         ///
         /// # Event:
@@ -1811,5 +1811,52 @@ mod dispatches {
                 allow_partial,
             )
         }
+
+        /// Swaps a specified amount of stake from one subnet to another, while keeping the same coldkey and hotkey.
+        ///
+        /// # Arguments
+        /// * `origin` - The origin of the transaction, which must be signed by the coldkey that owns the `hotkey`.
+        /// * `hotkey` - The hotkey whose stake is being swapped.
+        /// * `origin_netuid` - The network/subnet ID from which stake is removed.
+        /// * `destination_netuid` - The network/subnet ID to which stake is added.
+        /// * `alpha_amount` - The amount of stake to swap.
+        /// * `limit_price` - The limit price expressed in units of RAO per one Alpha.
+        /// * `allow_partial` - Allows partial execution of the amount. If set to false, this becomes fill or kill type or order.
+        ///
+        /// # Errors
+        /// Returns an error if:
+        /// * The transaction is not signed by the correct coldkey (i.e., `coldkey_owns_hotkey` fails).
+        /// * Either `origin_netuid` or `destination_netuid` does not exist.
+        /// * The hotkey does not exist.
+        /// * There is insufficient stake on `(coldkey, hotkey, origin_netuid)`.
+        /// * The swap amount is below the minimum stake requirement.
+        ///
+        /// # Events
+        /// May emit a `StakeSwapped` event on success.
+        #[pallet::call_index(90)]
+        #[pallet::weight((
+            Weight::from_parts(3_000_000, 0).saturating_add(T::DbWeight::get().writes(1)),
+            DispatchClass::Operational,
+            Pays::No
+        ))]
+        pub fn swap_stake_limit(
+            origin: T::RuntimeOrigin,
+            hotkey: T::AccountId,
+            origin_netuid: u16,
+            destination_netuid: u16,
+            alpha_amount: u64,
+            limit_price: u64,
+            allow_partial: bool,
+        ) -> DispatchResult {
+            Self::do_swap_stake_limit(
+                origin,
+                hotkey,
+                origin_netuid,
+                destination_netuid,
+                alpha_amount,
+                limit_price,
+                allow_partial,
+            )
+        }
     }
 }

pallets/subtensor/src/staking/add_stake.rs

@@ -1,7 +1,5 @@
 use super::*;
-use safe_math::*;
 use sp_core::Get;
-use substrate_fixed::types::U96F32;
 
 impl<T: Config> Pallet<T> {
     /// ---- The implementation for the extrinsic add_stake: Adds stake to a hotkey account.
@@ -174,34 +172,39 @@ impl<T: Config> Pallet<T> {
         if alpha_in == 0 {
             return 0;
         }
-        let alpha_in_float: U96F32 = U96F32::saturating_from_num(alpha_in);
+        let alpha_in_u128 = alpha_in as u128;
 
         // Corner case: SubnetTAO is zero. Staking can't happen, so max amount is zero.
         let tao_reserve = SubnetTAO::<T>::get(netuid);
         if tao_reserve == 0 {
             return 0;
         }
-        let tao_reserve_float: U96F32 = U96F32::saturating_from_num(tao_reserve);
+        let tao_reserve_u128 = tao_reserve as u128;
 
         // Corner case: limit_price < current_price (price cannot decrease with staking)
-        let limit_price_float: U96F32 = U96F32::saturating_from_num(limit_price)
-            .checked_div(U96F32::saturating_from_num(1_000_000_000))
-            .unwrap_or(U96F32::saturating_from_num(0));
-        if limit_price_float < Self::get_alpha_price(netuid) {
+        let tao = 1_000_000_000_u128;
+        let limit_price_u128 = limit_price as u128;
+        if (limit_price_u128
+            < Self::get_alpha_price(netuid)
+                .saturating_to_num::<u128>()
+                .saturating_mul(tao))
+            || (limit_price == 0u64)
+        {
             return 0;
         }
 
-        // Main case: return SQRT(limit_price * SubnetTAO * SubnetAlphaIn) - SubnetTAO
-        // This is the positive solution of quare equation for finding additional TAO from
-        // limit_price.
-        let zero: U96F32 = U96F32::saturating_from_num(0.0);
-        let epsilon: U96F32 = U96F32::saturating_from_num(0.1);
-        let sqrt: U96F32 =
-            checked_sqrt(limit_price_float.saturating_mul(tao_reserve_float), epsilon)
-                .unwrap_or(zero)
-                .saturating_mul(checked_sqrt(alpha_in_float, epsilon).unwrap_or(zero));
-
-        sqrt.saturating_sub(U96F32::saturating_from_num(tao_reserve_float))
-            .saturating_to_num::<u64>()
+        // Main case: return limit_price * SubnetAlphaIn - SubnetTAO
+        // Non overflowing calculation: limit_price * alpha_in <= u64::MAX * u64::MAX <= u128::MAX
+        // May overflow result, then it will be capped at u64::MAX, which is OK because that matches balance u64 size.
+        let result = limit_price_u128
+            .saturating_mul(alpha_in_u128)
+            .checked_div(tao)
+            .unwrap_or(0)
+            .saturating_sub(tao_reserve_u128);
+        if result < u64::MAX as u128 {
+            result as u64
+        } else {
+            u64::MAX
+        }
     }
 }