refactor: do not keep track of membership registration order

* unify terminology for mdetails
* more DRY in LinearPriceCalculator
* improve terminology consistency (#16)
* refactor, minor fixes
* do not reset ongoing grace period on extension (cf. spec change)
* minor renaming, comments
* refactor, group functions by funcitonality
* extract membership expiration calculation to internal function
* save active duration per membership (must carry over after extension)
* optional lazy erasure from membership set
* minor fixes in tests
* fix: off-by-one: end index can't be equal to next free index
* minor refactoring, comments
* define period boundaries: start inclusive, end exclusive
* separate eraseMembership functions to user-focused (lazy) and admin-focused (tree cleanup)
* minor fix to maintain line lengths
* unify membership-related events
* add test for  zero grace period
* fix typo in comment

Co-authored-by: richΛrd <[email protected]>

---------

Co-authored-by: richΛrd <[email protected]>

.gas-snapshot

@@ -1,28 +1,24 @@
-WakuRlnV2Test:test__IdCommitmentToMetadata__DoesntExist() (gas: 27547)
-WakuRlnV2Test:test__InsertionNormalOrder(uint32) (runs: 1005, μ: 1284765, ~: 577056)
-WakuRlnV2Test:test__InvalidPaginationQuery__EndIndexGTnextCommitmentIndex() (gas: 18290)
-WakuRlnV2Test:test__InvalidPaginationQuery__StartIndexGTEndIndex() (gas: 16181)
-WakuRlnV2Test:test__InvalidRegistration__DuplicateIdCommitment() (gas: 322752)
-WakuRlnV2Test:test__InvalidRegistration__FullTree() (gas: 239810)
-WakuRlnV2Test:test__InvalidRegistration__InvalidIdCommitment__LargerThanField() (gas: 36509)
-WakuRlnV2Test:test__InvalidRegistration__InvalidIdCommitment__Zero() (gas: 35220)
-WakuRlnV2Test:test__InvalidRegistration__InvalidUserMessageLimit__MinMax() (gas: 63679)
-WakuRlnV2Test:test__InvalidTokenAmount(uint256,uint32) (runs: 1004, μ: 207863, ~: 207863)
-WakuRlnV2Test:test__LinearPriceCalculation(uint32) (runs: 1015, μ: 26049, ~: 26049)
-WakuRlnV2Test:test__RegistrationWhenMaxRateLimitIsReached() (gas: 638698)
-WakuRlnV2Test:test__RegistrationWhenMaxRateLimitIsReachedAndMultipleExpiredMembersAvailable() (gas: 906196)
-WakuRlnV2Test:test__RegistrationWhenMaxRateLimitIsReachedAndSingleExpiredMemberAvailable() (gas: 461585)
-WakuRlnV2Test:test__RegistrationWhenMaxRateLimitReachedAndMultipleExpiredMembersAvailableWithoutEnoughRateLimit() (gas: 869622)
-WakuRlnV2Test:test__RemoveAllExpiredMemberships(uint32) (runs: 1005, μ: 7359251, ~: 1585880)
-WakuRlnV2Test:test__RemoveExpiredMemberships(uint32) (runs: 1003, μ: 1248285, ~: 1248286)
-WakuRlnV2Test:test__Upgrade() (gas: 7482875)
-WakuRlnV2Test:test__ValidPaginationQuery(uint32) (runs: 1006, μ: 227626, ~: 52991)
-WakuRlnV2Test:test__ValidPaginationQuery__OneElement() (gas: 319333)
-WakuRlnV2Test:test__ValidRegistration(uint32) (runs: 1003, μ: 325571, ~: 325571)
-WakuRlnV2Test:test__ValidRegistrationExpiry(uint32) (runs: 1003, μ: 1456074, ~: 1456074)
-WakuRlnV2Test:test__ValidRegistrationExtend(uint32) (runs: 1003, μ: 1276008, ~: 1276008)
-WakuRlnV2Test:test__ValidRegistrationExtendSingleMembership(uint32) (runs: 1003, μ: 314390, ~: 314390)
-WakuRlnV2Test:test__ValidRegistrationWithEraseList() (gas: 1601871)
-WakuRlnV2Test:test__ValidRegistration__kats() (gas: 295683)
-WakuRlnV2Test:test__WithdrawToken(uint32) (runs: 1003, μ: 301025, ~: 301027)
-WakuRlnV2Test:test__indexReuse_eraseMemberships(uint32) (runs: 1005, μ: 2702739, ~: 1165772)
+WakuRlnV2Test:test__IdCommitmentToMetadata__DoesntExist() (gas: 23299)
+WakuRlnV2Test:test__InvalidPaginationQuery__EndIndexGTnextCommitmentIndex() (gas: 18307)
+WakuRlnV2Test:test__InvalidPaginationQuery__StartIndexGTEndIndex() (gas: 16131)
+WakuRlnV2Test:test__InvalidRegistration__DuplicateIdCommitment() (gas: 272654)
+WakuRlnV2Test:test__InvalidRegistration__FullTree() (gas: 190004)
+WakuRlnV2Test:test__InvalidRegistration__InvalidIdCommitment__LargerThanField() (gas: 36492)
+WakuRlnV2Test:test__InvalidRegistration__InvalidIdCommitment__Zero() (gas: 35192)
+WakuRlnV2Test:test__InvalidRegistration__InvalidUserMessageLimit__MinMax() (gas: 55026)
+WakuRlnV2Test:test__InvalidTokenAmount(uint256,uint32) (runs: 1006, μ: 158053, ~: 158053)
+WakuRlnV2Test:test__LinearPriceCalculation(uint32) (runs: 1015, μ: 26026, ~: 26026)
+WakuRlnV2Test:test__RegistrationWhenMaxRateLimitIsReached() (gas: 527384)
+WakuRlnV2Test:test__RemoveAllExpiredMemberships(uint32) (runs: 1004, μ: 3577547, ~: 653139)
+WakuRlnV2Test:test__RemoveExpiredMemberships(uint32) (runs: 1003, μ: 1044941, ~: 1044943)
+WakuRlnV2Test:test__Upgrade() (gas: 6932864)
+WakuRlnV2Test:test__ValidPaginationQuery(uint32) (runs: 1005, μ: 227459, ~: 52991)
+WakuRlnV2Test:test__ValidPaginationQuery__OneElement() (gas: 269528)
+WakuRlnV2Test:test__ValidRegistration(uint32) (runs: 1003, μ: 275279, ~: 275279)
+WakuRlnV2Test:test__ValidRegistrationExpiry(uint32) (runs: 1003, μ: 256301, ~: 256301)
+WakuRlnV2Test:test__ValidRegistrationExtend(uint32) (runs: 1003, μ: 474309, ~: 474309)
+WakuRlnV2Test:test__ValidRegistrationExtendSingleMembership(uint32) (runs: 1003, μ: 263787, ~: 263787)
+WakuRlnV2Test:test__ValidRegistrationWithEraseList() (gas: 1380002)
+WakuRlnV2Test:test__ValidRegistration__kats() (gas: 245878)
+WakuRlnV2Test:test__WithdrawToken(uint32) (runs: 1003, μ: 260362, ~: 260364)
+WakuRlnV2Test:test__indexReuse_eraseMemberships(uint32) (runs: 1004, μ: 2377343, ~: 975838)

src/LinearPriceCalculator.sol

@@ -5,7 +5,7 @@ import { Ownable2Step } from "openzeppelin-contracts/contracts/access/Ownable2St
 import { IPriceCalculator } from "./IPriceCalculator.sol";
 
 /// Address 0x0000...0000 was used instead of an ERC20 token address
-error OnlyERC20TokensAllowed();
+error OnlyTokensAllowed();
 
 /// @title Linear Price Calculator to determine the price to acquire a membership
 contract LinearPriceCalculator is IPriceCalculator, Ownable2Step {
@@ -16,18 +16,23 @@ contract LinearPriceCalculator is IPriceCalculator, Ownable2Step {
     uint256 public pricePerMessagePerEpoch;
 
     constructor(address _token, uint256 _pricePerMessagePerEpoch) Ownable2Step() {
-        if (_token == address(0)) revert OnlyERC20TokensAllowed();
-        token = _token;
-        pricePerMessagePerEpoch = _pricePerMessagePerEpoch;
+        _setTokenAndPrice(_token, _pricePerMessagePerEpoch);
+    }
+
+    /// Set accepted token and price per message per epoch per period
+    /// @param _token The token accepted by RLN membership management
+    /// @param _pricePerMessagePerEpoch Price per message per epoch
+    function setTokenAndPrice(address _token, uint256 _pricePerMessagePerEpoch) external onlyOwner {
+        _setTokenAndPrice(_token, _pricePerMessagePerEpoch);
     }
 
     /// Set accepted token and price per message per epoch per period
-    /// @param _token The token accepted by the membership management for RLN
-    /// @param _pricePerPeriod Price per message per epoch
-    function setTokenAndPrice(address _token, uint256 _pricePerPeriod) external onlyOwner {
-        require(_token != address(0), "only tokens can be used");
+    /// @param _token The token accepted by RLN membership management
+    /// @param _pricePerMessagePerEpoch Price per message per epoch
+    function _setTokenAndPrice(address _token, uint256 _pricePerMessagePerEpoch) internal {
+        if (_token == address(0)) revert OnlyTokensAllowed();
         token = _token;
-        pricePerMessagePerEpoch = _pricePerPeriod;
+        pricePerMessagePerEpoch = _pricePerMessagePerEpoch;
     }
 
     /// Returns the token and price to pay in `token` for some `_rateLimit`