using config hash to map tranche yield

Author: aalavandhan

contracts/BondMinter.sol

@@ -10,6 +10,8 @@ import {IBondMinter} from "./interfaces/IBondMinter.sol";
 // Minor Modification to button wood's version
 // https://github.com/buttonwood-protocol/tranche/blob/main/contracts/bondMinter/
 // in ours configs are immutable and we limit one config per minter
+// and we have a way of checking the config hash of a given bond
+// This can be extened to multi-config
 contract BondMinter is IBondMinter {
     // bond factory
     IBondFactory public immutable bondFactory;
@@ -20,7 +22,7 @@ contract BondMinter is IBondMinter {
 
     // minter bond config
     IBondMinter.BondConfig public config;
-    bytes32 public immutable override configHash;
+    bytes32 private immutable _configHash;
 
     // mapping of minted bonds
     mapping(address => bool) mintedBonds;
@@ -30,7 +32,7 @@ contract BondMinter is IBondMinter {
         bondFactory = bondFactory_;
         waitingPeriod = waitingPeriod_;
         config = config_;
-        configHash = computeHash(config_);
+        _configHash = computeHash(config_);
         lastMintTimestamp = 0;
 
         emit BondConfigAdded(config);
@@ -59,6 +61,10 @@ contract BondMinter is IBondMinter {
         emit BondMinted(bond);
     }
 
+    function getConfigHash(address bond) external view override returns (bytes32) {
+        return mintedBonds[bond] ? _configHash : bytes32(0);
+    }
+
     function computeHash(IBondMinter.BondConfig memory config_) private pure returns (bytes32) {
         return keccak256(abi.encode(config_.collateralToken, config_.trancheRatios, config_.duration));
     }

contracts/YieldStrategy.sol

@@ -11,21 +11,23 @@ contract YieldStrategy is Ownable, IYieldStrategy {
 
 	// todo: add setters
 
-	// tranche yield is specific to a bond minter (which mints a specific class of bonds)
+	// tranche yield is specific a bond class (which is indexed by its config hash)
 	// a bond class is uniquely identified by {collateralToken, trancheRatios, duration}
-	mapping(IBondMinter => uint256[]) private _trancheYields;
+	// the minter returns the config hash for each bond its creates
+	mapping(bytes32 => uint256[]) private _trancheYields;
 
 	function computeTrancheYield(IBondMinter minter, IBondController bond, uint256 seniorityIDX, uint256 trancheAmt) external view override returns (uint256) {
 		return trancheAmt * computeTrancheYieldPerc(minter, bond, seniorityIDX) / (10 ** PCT_DECIMALS);
 	}
 
 	function computeTrancheYieldPerc(IBondMinter minter, IBondController bond, uint256 seniorityIDX) public view returns (uint256) {
-		// assert(minter.isInstance(bond));
 		return trancheYields(minter, bond, seniorityIDX) * computeTranchePrice(bond, seniorityIDX) / (10 ** PRICE_DECIMALS);
 	}
 
 	function trancheYields(IBondMinter minter, IBondController bond, uint256 seniorityIDX) public view returns (uint256) {
-		return _trancheYields[minter][seniorityIDX];
+		// if the bond was not minted by the minter, this will return 0x00..
+		// and thus yeilds will be [0,0...] 
+		return _trancheYields[minter.getConfigHash(address(bond))][seniorityIDX];
 	}
 
 	// Tranche pricing function goes here:

contracts/interfaces/IBondMinter.sol

@@ -13,5 +13,5 @@ interface IBondMinter {
 
     function isInstance(address bond) external view returns (bool);
 
-    function configHash() external view returns (bytes32);
+    function getConfigHash(address bond) external view returns (bytes32);
 }