get next proposal id from pnextProposalId

agora/Agora/Governor.hs

@@ -35,6 +35,7 @@ import Agora.Proposal (
   PProposalThresholds,
   ProposalId,
   ProposalThresholds,
+  pnextProposalId 
  )
 import Agora.Utils (
   allInputs,
@@ -208,12 +209,9 @@ governorValidator params =
         -- check that nothing is minted
         passert "Nothing should be minted" $ plength # mint' #== 0
 
-        -- check proposal id +1
+        -- check that proposal is advanced
-        -- TODO: deriving a PNum instance for PProposalId
-        let oldPid = pto $ pfromData $ oldParams.nextProposalId
-            newPid = pto $ pfromData $ newParams.nextProposalId
         passert "Proposal id should be advanced by 1" $
-          oldPid + 1 #== newPid
+          pnextProposalId # oldParams.nextProposalId #== newParams.nextProposalId
 
         -- TODO: waiting for impl of proposal
         ptraceError "Not implemented yet"

agora/Agora/Proposal.hs

@@ -30,6 +30,9 @@ module Agora.Proposal (
 
   -- * Plutarch helpers
   proposalDatumValid,
+
+  -- * Utils
+  pnextProposalId
 ) where
 
 import GHC.Generics qualified as GHC
@@ -434,3 +437,8 @@ proposalDatumValid proposal =
         , ptraceIfFalse "Proposal has fewer cosigners than the limit" $ plength # (pfromData datum.cosigners) #<= pconstant proposal.maximumCosigners
         , ptraceIfFalse "Proposal votes and effects are compatible with each other" $ pkeysEqual # datum.effects # pto (pfromData datum.votes)
         ]
+
+--------------------------------------------------------------------------------
+
+pnextProposalId :: Term s (PProposalId :--> PProposalId)
+pnextProposalId = phoistAcyclic $ plam $ \(pto -> id) -> pcon $ PProposalId $ id + 1