Updated the contract interface to avoid sdk encoding functions

contracts/Hyperdrive.sol

@@ -399,31 +399,32 @@ contract Hyperdrive is MultiToken {
     }
 
     /// @notice Closes a short position with a specified maturity time.
-    /// @param _assetId The asset ID of the short.
+    /// @param _openSharePrice The opening share price of the short.
+    /// @param _maturityTime The maturity time of the short.
     /// @param _bondAmount The amount of shorts to close.
-    function closeShort(uint256 _assetId, uint256 _bondAmount) external {
+    function closeShort(
+        uint256 _openSharePrice,
+        uint32 _maturityTime,
+        uint256 _bondAmount
+    ) external {
         if (_bondAmount == 0) {
             revert Errors.ZeroAmount();
         }
 
-        // Ensure that the asset ID refers to a short and get the open share
-        // price and maturity time from the short key.
-        (
-            AssetId.AssetIdPrefix prefix,
-            uint256 openSharePrice,
-            uint256 maturityTime
-        ) = AssetId.decodeAssetId(_assetId);
-        if (prefix != AssetId.AssetIdPrefix.Short) {
-            revert Errors.UnexpectedAssetId();
-        }
-
         // Burn the shorts that are being closed.
-        _burn(_assetId, msg.sender, _bondAmount);
+        uint256 assetId = AssetId.encodeAssetId(
+            AssetId.AssetIdPrefix.Short,
+            _openSharePrice,
+            _maturityTime
+        );
+        _burn(assetId, msg.sender, _bondAmount);
         shortsOutstanding -= _bondAmount;
 
         // Calculate the pool and user deltas using the trading function.
-        uint256 timeRemaining = block.timestamp < maturityTime
-            ? (maturityTime - block.timestamp).divDown(positionDuration) // use divDown to scale to fixed point
+        uint256 timeRemaining = block.timestamp < uint256(_maturityTime)
+            ? (uint256(_maturityTime) - block.timestamp).divDown(
+                positionDuration
+            ) // use divDown to scale to fixed point
             : 0;
         (
             uint256 poolShareDelta,
@@ -453,7 +454,7 @@ contract Hyperdrive is MultiToken {
             sharePrice.mulDown(sharePayment)
         );
         uint256 interestProceeds = sharePrice
-            .divDown(openSharePrice)
+            .divDown(_openSharePrice)
             .sub(FixedPointMath.ONE_18)
             .mulDown(_bondAmount);
         bool success = baseToken.transfer(

contracts/libraries/AssetId.sol

@@ -51,42 +51,4 @@ library AssetId {
         }
         return id;
     }
-
-    /// @dev Decodes an asset ID into an identifier, extra data, and a timestamp.
-    /// @param _id The asset ID.
-    /// TODO: Update this comment when we make the range more restrictive.
-    /// @return prefix A one byte prefix that specifies the asset type.
-    /// @return data Data associated with the asset. This is an efficient way of
-    ///        fingerprinting data as the user can supply this data, and the
-    ///        token balance ensures that the data is associated with the asset.
-    /// @return timestamp_ A timestamp associated with the asset.
-    function decodeAssetId(
-        uint256 _id
-    )
-        internal
-        pure
-        returns (AssetIdPrefix prefix, uint256 data, uint256 timestamp_)
-    {
-        // [identifier: 8 bits][data: 216 bits][timestamp: 32 bits]
-        assembly {
-            prefix := shr(0xf8, _id)
-            data := and(
-                shr(0x20, _id),
-                0xffffffffffffffffffffffffffffffffffffffffffffffffffffff
-            )
-            timestamp_ := and(shr(0x20, _id), 0xffffffff)
-        }
-        // In the case of shorts, extra data is the share price at which the
-        // short was opened. Hyperdrive assumes that the yield source accrues
-        // non-negative interest, so an opening share price less than the fixed
-        // point multiplicative identity indicates corruption. In the case of
-        // longs, the extra data is unused.
-        if (
-            (prefix == AssetIdPrefix.Long && data > 0) ||
-            (prefix == AssetIdPrefix.Short && data < FixedPointMath.ONE_18)
-        ) {
-            revert Errors.AssetIDCorruption();
-        }
-        return (prefix, data, timestamp_);
-    }
 }