PLT-1311 Add JSON-RPC querying of the stake pool delegation (SPD) by …

…epoch in `marconi-sidechain`.

* Add indexing and JSON-RPC querying of the SPD by epoch in `marconi-sidechain`.

* Added golden test for JSON response of stake pool delegation by
  epoch

* Fixed resuming of Utxo indexer to include *all* possible chain points,
  not only the latest ones.

* Updated README of `marconi-sidechain` to include an example of request
  and response for the JSON-RPC server on that specific endpoint.

marconi-chain-index/marconi-chain-index.cabal

@@ -61,6 +61,7 @@ library
     Marconi.ChainIndex.Node.Client.GenesisConfig
     Marconi.ChainIndex.Orphans
     Marconi.ChainIndex.Types
+    Marconi.ChainIndex.Utils
 
   --------------------
   -- Local components

marconi-chain-index/src/Marconi/ChainIndex/Indexers.hs

@@ -28,7 +28,7 @@ import Control.Concurrent.STM.TChan (TChan, dupTChan, newBroadcastTChanIO, readT
 import Control.Exception (catch)
 import Control.Lens (view)
 import Control.Lens.Operators ((^.))
-import Control.Monad (forever, unless, void)
+import Control.Monad (forever, void)
 import Control.Monad.Trans.Except (runExceptT)
 import Data.List (findIndex, foldl1', intersect)
 import Data.Map (Map)
@@ -265,7 +265,7 @@ scriptTxWorker onInsert coordinator path = do
 
 epochStakepoolSizeWorker_
   :: FilePath
-  -> (Storable.StorableEvent EpochSPDHandle -> IO ())
+  -> ((Storable.State EpochSPDHandle, Storable.StorableEvent EpochSPDHandle) -> IO ())
   -> Word64 -- Security param
   -> Coordinator
   -> TChan (ChainSyncEvent (BlockInMode CardanoMode))
@@ -295,7 +295,7 @@ epochStakepoolSizeWorker_
             chainSyncEvent <- atomically $ readTChan ch
 
             newLedgerState <- case chainSyncEvent of
-              RollForward blockInMode@(C.BlockInMode (C.Block (C.BlockHeader slotNo bh bn) _) _) _ct -> do
+              RollForward blockInMode@(C.BlockInMode (C.Block (C.BlockHeader slotNo bh bn) _) _) chainTip -> do
                   -- Compute new LedgerState given block and old LedgerState
                   let newLedgerState =
                           O.lrResult
@@ -305,12 +305,21 @@ epochStakepoolSizeWorker_
                                   currentLedgerState
                   let newEpochNo = EpochSPD.getEpochNo newLedgerState
 
-                  -- If the currentLedgerState has a different epochNo than the newLedgerState, this
-                  -- means that we need to index currentLedgerState
-                  unless (maybeEpochNo == newEpochNo) $ do
-                      let storableEvent = EpochSPD.toStorableEvent currentLedgerState slotNo bh bn
-                      modifyMVar_ indexerMVar $ Storable.insert storableEvent
-                      onInsert storableEvent
+                  -- If the block is rollbackable, we always store the LedgerState. If the block is
+                  -- immutable, we only store it right before a new epoch.
+                  -- let isLastEventOfEpoch = maybeEpochNo /= newEpochNo
+                  let isLastEventOfEpoch = maybeEpochNo /= newEpochNo
+                  let storableEvent =
+                          EpochSPD.toStorableEvent
+                            currentLedgerState
+                            slotNo
+                            bh
+                            bn
+                            chainTip
+                            securityParam
+                            isLastEventOfEpoch
+                  newIndexer <- modifyMVar indexerMVar $ \idx -> fmap (\newIdx -> (newIdx, newIdx)) $ Storable.insert storableEvent idx
+                  onInsert (newIndexer, storableEvent) -- refresh the query STM/CPS with new storage pointers/counters state
 
                   pure newLedgerState
 
@@ -341,7 +350,7 @@ epochStakepoolSizeWorker_
 
 epochStakepoolSizeWorker
     :: FilePath
-    -> (Storable.StorableEvent EpochSPDHandle -> IO ())
+    -> ((Storable.State EpochSPDHandle, Storable.StorableEvent EpochSPDHandle) -> IO ())
     -> Worker
 epochStakepoolSizeWorker nodeConfigPath onInsert coordinator path = do
   workerChannel <- atomically . dupTChan $ _channel coordinator