add additional IRToken functions (#47)

* add additional IRToken functions

- token
- name/symbol/decimals
- ias
- savingAssetConversionRate

contracts/IRToken.sol

@@ -7,6 +7,7 @@ pragma solidity >=0.5.10 <0.6.0;
 pragma experimental ABIEncoderV2;
 
 import {RTokenStructs} from "./RTokenStructs.sol";
+import {IAllocationStrategy} from "./IAllocationStrategy.sol";
 import {IERC20} from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
 
 /**
@@ -15,6 +16,39 @@ import {IERC20} from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
  *      addresses and pay earned interest in new _rTokens_.
  */
 contract IRToken is RTokenStructs, IERC20 {
+
+    ////////////////////////////////////////////////////////////////////////////
+    // Token details
+    ////////////////////////////////////////////////////////////////////////////
+
+    /// @notice Returning the underlying token
+    function token() external returns (IERC20);
+
+    /**
+     * @notice Returns the name of the token.
+     */
+    function name() external view returns (string memory);
+
+    /**
+     * @notice Returns the symbol of the token, usually a shorter version of the
+     * name.
+     */
+    function symbol() external view returns (string memory);
+
+    /**
+     * @notice Returns the number of decimals used to get its user representation.
+     * For example, if `decimals` equals `2`, a balance of `505` tokens should
+     * be displayed to a user as `5,05` (`505 / 10 ** 2`).
+     *
+     * Tokens usually opt for a value of 18, imitating the relationship between
+     * Ether and Wei.
+     *
+     * NOTE: This information is only used for _display_ purposes: it in
+     * no way affects any of the arithmetic of the contract, including
+     * {IERC20-balanceOf} and {IERC20-transfer}.
+     */
+    function decimals() external view returns (uint256);
+
     ////////////////////////////////////////////////////////////////////////////
     // For external transactions
     ////////////////////////////////////////////////////////////////////////////
@@ -194,6 +228,27 @@ contract IRToken is RTokenStructs, IERC20 {
         view
         returns (uint256 amount);
 
+    /// @notice Get current saving strategy
+    function ias() external returns (IAllocationStrategy);
+
+    /// @notice Saving asset original to internal amount conversion rate.
+    ///
+    /// @dev About the saving asset original to internal conversaioon rate:
+    ///
+    ///      - It has 18 decimals
+    ///      - It starts with value 1
+    ///      - Each strategy switching results a new conversion rate
+    ///
+    /// NOTE:
+    ///
+    /// 1. The reason there is an exchange rate is that, each time the
+    ///    allocation strategy is switched, the unit of the original amount gets
+    ///    changed, it is impossible to change all the internal savings
+    ///    accounting entries for all accounts, hence instead a conversaion rate
+    ///    is used to simplify the process.
+    /// 2. internalSavings == originalSavings * savingAssetConversionRate
+    function savingAssetConversionRate() external returns (uint256);
+
     ////////////////////////////////////////////////////////////////////////////
     // statistics views
     ////////////////////////////////////////////////////////////////////////////

contracts/RToken.sol

@@ -21,9 +21,9 @@ import {IAllocationStrategy} from "./IAllocationStrategy.sol";
  * @notice RToken an ERC20 token that is 1:1 redeemable to its underlying ERC20 token.
  */
 contract RToken is
-    RTokenStorage,
     IRToken,
     IRTokenAdmin,
+    RTokenStorage,
     Ownable,
     Proxiable,
     LibraryLock,

contracts/RTokenStorage.sol

@@ -39,19 +39,7 @@ contract RTokenStorage is RTokenStructs, IERC20 {
     /// @dev Saving assets original amount
     /// This amount is in the same unit used in allocation strategy
     uint256 public savingAssetOrignalAmount;
-    /// @dev Saving asset original to internal amount conversion rate.
-    ///      - It has 18 decimals
-    ///      - It starts with value 1.
-    ///      - Each strategy switching results a new conversion rate
-    ///
-    /// NOTE:
-    ///
-    /// 1. The reason there is an exchange rate is that, each time the
-    ///    allocation strategy is switched, the unit of the original amount gets
-    ///    changed, it is impossible to change all the internal savings
-    ///    accounting entries for all accounts, hence instead a conversaion rate
-    ///    is used to simplify the process.
-    /// 2. internalSavings == originalSavings * savingAssetConversionRate
+    /// @dev Saving asset original to internal amount conversion rate
     uint256 public savingAssetConversionRate;
     /// @dev Approved token transfer amounts on behalf of others
     mapping(address => mapping(address => uint256)) public transferAllowances;