feat: add random extraction helper-methods to UsingWitRandomness

Author: guidiaz

contracts/UsingWitRandomness.sol

@@ -19,7 +19,7 @@ abstract contract UsingWitRandomness {
         WIT_RANDOMNESS = WitRandomness(randomizer);    
     }
 
-    /// Retrieves the result of keccak256-hashing the specified block number with the randomness value 
+    /// @notice Retrieves the result of keccak256-hashing the specified block number with the randomness value 
     /// generated by the Witnet blockchain in response to the first non-failing randomize request solved 
     /// after such block number.
     ///
@@ -36,14 +36,62 @@ abstract contract UsingWitRandomness {
         );
     }
 
-    /// Generates a pseudo-random number uniformly distributed within the range [0 .. _faces), 
+    /// @notice Generates a pseudo-random number uniformly distributed within the range [0 .. _faces), 
     /// by using the specified `_nonce` and `_seed`.
     /// @dev Fails under same conditions as `_fetchRandomnessAfter(uint256)` does.
-    function _rollTheDice(uint64 _faces, uint256 _nonce, bytes32 _seed) internal pure returns (uint64) {
+    function _randomDice(uint64 _faces, uint256 _nonce, bytes32 _seed) internal pure returns (uint64) {
         return Witnet.randomUniformUint64(
             _faces,
             _nonce,
             _seed
         );
     }
+
+    /// @notice Generates a pseudo-random uniformly distributed extraction, with repetitions. 
+    function _randomExtractionWithReps(
+            uint64  _range, 
+            uint16  _extractions, 
+            bytes32 _seed
+        )
+        internal pure
+        returns (uint64[] memory _balls)
+    {
+        unchecked {
+            _balls = new uint64[](_extractions);
+            for (uint16 _ix; _ix < _extractions; _ix ++) {
+                _balls[_ix] = Witnet.randomUniformUint64(
+                    _range, 
+                    _ix, 
+                    _seed
+                );
+            }
+        }
+    }
+
+    /// @notice Generates a pseudo-random uniformly distributed extraction, with no repetitions. 
+    function _randomExtractionNoReps(
+            uint64  _range, 
+            uint16  _extractions, 
+            bytes32 _seed
+        )
+        internal pure
+        returns (uint64[] memory _balls)
+    {
+        unchecked {
+            uint64[] memory _numbers = new uint64[](_range);
+            for (uint64 _ix; _ix < _range; _ix ++) {
+                _numbers[_ix] = _ix;
+            }
+            _balls = new uint64[](_extractions);
+            for (uint16 _jx; _jx < _extractions; _jx ++) {
+                uint64 _pos = Witnet.randomUniformUint64(
+                    _range - _jx, 
+                    _jx, 
+                    _seed
+                );
+                _balls[_jx] = _numbers[_pos];
+                _numbers[_pos] = _numbers[_range - 1 - _jx];
+            }
+        }
+    }
 }

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@witnet/solidity",
-  "version": "3.0.1",
+  "version": "3.0.2",
   "description": "Wit/Oracle Solidity Framework for EVM-compatible chains",
   "author": "Witnet Foundation <[email protected]>",
   "license": "MIT",
@@ -16,7 +16,7 @@
   ],
   "exports": {
     ".": "./src/index.js",
-    "./contracts/": "./contracts/",
+    "./contracts/*": "./contracts/",
     "./utils": "./src/utils.js"
   },
   "files": [