Replace service date by numbered forks

src/Chainweb/ForkState.hs

@@ -0,0 +1,113 @@
+{-# LANGUAGE ImportQualifiedPost #-}
+
+-- |
+-- Module: Chainweb.ForkNumber
+-- Copyright: Copyright © 2025 Kadena LLC.
+-- License: MIT
+-- Maintainer: Lars Kuhtz <[email protected]>
+-- Stability: experimental
+--
+module Chainweb.ForkState
+(
+) where
+
+-- | Starting with Chainweb 2.33, forks are identified by a monotonically
+-- increasing fork number. Each block is created according to a specific fork
+-- number.
+--
+-- Each fork number is associated with a specific block height at which it
+-- becomes active. This number is also called the "fork height" for the
+-- respective fork. Forks are either activated on a per chain or a per network
+-- basis. The former are triggered as soon as the specific chain reaches the
+-- block height for the respective fork. The latter are triggered when all
+-- chains in the network have reached the respective block height.
+--
+-- The Fork height of a fork is determined by miners, usually via upgrading to
+-- a new software version that includes the fork activation logic, but it is
+-- also possible that a new software version allows miners to configure whether
+-- they want to support a specific fork or not.
+--
+-- For the purpose of fork activation the feature flags field in the block
+-- header is renamed into the "fork state" field.
+--
+-- The support for a fork by a miner is signaled by increasing the vote count
+-- for the fork in a newly mined block by one. Votes are accumulated over
+-- 120 epochs (5 days), which is called a "fork epoch". I.e. a fork epoch
+-- consists of 12 * 120 block heights.
+--
+-- A fork is activated in an epoch when at least 2/3 of all blocks for the
+-- previous 120 epochs have signaled for the respective fork number. Once a fork
+-- is activated it can not be deactivated again. The fork number is
+-- monontonically increasing.
+--
+-- A block that is signalling a fork number that is larger than the current fork
+-- number plus one is considered invalid. In other words forks can only be
+-- activated successively, one at a time. There will always be at least 120
+-- epochs between the activation of two successive forks.
+--
+-- Starting with chainweb-node version 2.33, a node must accept blocks that have
+-- either the fork number of the block height of the block or the respetive fork
+-- number plus one. It must reject all other blocks. The fork number at the time
+-- that chainweb node version 2.33 is released is zero.
+--
+newtype ForkState = ForkState { _forkState :: Word64 }
+    deriving (Eq, Ord, Generic)
+    deriving anyclass (NFData)
+
+_forkNumber' :: ForkState -> Word32
+_forkNumber' (ForkState w) = int $ w .&. 0xFFFFFFFF
+
+_forkVotes' :: ForkState -> Word32
+_forkVotes' (ForkState w) = int $ (w `shiftR` 32) .&. 0xFFFFFFFF
+
+forkNumber' :: Lens' ForkState Word32
+forkNumber' = lens _forkNumber $ \(ForkState w) v -> ForkState
+    $ (w .&. 0xFFFFFFFF00000000)
+    .|. (fromIntegral v .&. 0xFFFFFFFF)
+
+forkVotes' :: Lens' ForkState Word32
+forkVotes' = lens _forkVotes $ \(ForkState w) v -> ForkState
+    $ (w .&. 0x00000000FFFFFFFF)
+    .|. ((fromIntegral v .&. 0xFFFFFFFF) `shiftL` 32)
+
+-- -------------------------------------------------------------------------- --
+-- Fork State Validation in Block Headers
+
+_forkNumber :: BlockHeader -> Word32
+_forkNumber = view (forkState . forkNumber')
+
+_forkVotes :: BlockHeader -> Word32
+_forkVotes = view (forkState . forkVotes')
+
+forkNumber :: Lens' BlockHeader Word32
+forkNumber = forkState . forkNumber'
+
+forkVotes :: Lens' BlockHeader Word32
+forkVotes = forkState . forkVotes'
+
+forkEpochLength :: Natural
+forkEpochLength = 120 * 120 -- 5 days
+
+isForkEpoch :: BlockHeader -> Bool
+isForkEpoch hdr = mod (view blockHeight hdr) forkEpochLength == 0
+
+getForkNumber :: BlockHeader -> Word32
+getForkNumber = view signaledForkNumber . view forkState
+
+getForkNumberVotes :: BlockHeader -> Word32
+getForkNumberVotes = view signaledNumber . view forkState
+
+validateForkNumber :: Parent BlockHeader -> BlockHeader -> Bool
+validateForkNumber (Parent parent) hdr
+    | isForkEpoch hdr =
+        if view getForkNumberVotes parent >= (forkEpochLength * 2 `div 3)
+          then
+            view getForkNumber hdr == view getForkNumber parent + 1
+            && view getForkNumberVotes hdr <= 1
+          else
+            view getForkNumber hdr == view getForkNumber parent
+            && view getForkNumberVotes hdr <= 1
+    | otherwise =
+        view getForkNumber hdr == view getForkNumber (parent hdr)
+        && view getForkNumberVotes hdr <= view getForkNumberVotes (parent hdr) + 1
+