Implement NetworkLayer getNext for Jörmungandr

[Anviking]

Issue Number

#219

Overview

WIP!

Comments

Fetching blocks with nextBlocks: stack ghci cardano-wallet-jormungandr

import Cardano.Wallet.Jormungandr.Network
import Cardano.Wallet.Primitive.Types
import Cardano.Wallet.Network
import Cardano.Wallet
import Data.Generics.Internal.VL.Lens ( view, (^.) )
:m -Cardano.Wallet.Jormungandr.Binary
:set -XOverloadedLabels

let nul = Hash "\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL"
let t0 = BlockHeader (SlotId 0 0) nul
nw <- newNetworkLayer (BaseUrl Http "localhost" 8081 "/api")
unsafeRunExceptT $ nextBlocks nw t0

(mapM_ (\b -> print $ b ^. #header ^. #slotId)) =<< (unsafeRunExceptT $ nextBlocks nw t0)

How to do required setup:

:set -XTypeApplications
:set -XDataKinds
import qualified Cardano.Wallet.DB.MVar as MVar
let tl = undefined
db <- MVar.newDBLayer

-- Setup a network layer, but we also need to talk to the underlying client ('j') directly here
mgr <- newManager defaultManagerSettings
let j = mkJormungandrLayer mgr (BaseUrl Http "localhost" 8081 "/api")
let nw = mkNetworkLayer j
waitForConnection nw defaultRetryPolicy

-- since the 'NetworkLayer' is connected, the underlying 'JormungandrLayer' is too
let absentParent = Hash "\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL"
[block0Id] <- unsafeRunExceptT $ getDescendantIds j absentParent 1
block0 <- unsafeRunExceptT $ getBlock j block0Id

-- TODO: setup initial state in a custom way

wallet <- newWalletLayer @_ @(Jormungandr 'Mainnet) block0 db nw tl

[KtorZ]

Hmm... not fond of this raw Text here. We use Haskell! Let's use type 😶 ..especially when we have a nice Hash "BlockHeader" we can pass around. Even more context would be nice:

• What's the starting point?
• How many descendant are we trying to fetch?
• What's the parent hash?

[Anviking]

Hm… good point. I suppose we manage with Hash "BlockHeader". ErrGetBlock is defined in Cardano.Wallet.Network, and thus shared, but in practice it will work out since it is not used in http-bridge.

Do we want to go make ErrGetBlock completely tailored to Jormungandr?

[KtorZ]

Hmmm. No. These were just a few suggestions. We can at least have the Hash "BlockHeader" of block. Any other detail that isn't jormungandr-specific is welcome.

[KtorZ]

Hmmm... what?
We should change initWallet to not take a block header but the actual first block. This will make the akward call to applyBlocks superfluous; initializing a wallet does the genesis block application (for what it's worth) and return an initial checkpoint.

[Anviking]

@KtorZ I reworked this commit be7931d to use prefilterBlock inside initWallet block0

[KtorZ]

Hmmmm. What about applyBlock block (Wallet mempty mempty (header block) s ?
Feels a bit weird to copy paste partial stuff from applyBlock, especially because, there could be some transactions that are ours in the genesis block (and there will be actually).

[Anviking]

We will then transition from
(Wallet mempty mempty (header block) s
to
(Wallet x y (header block) s'

i.e, the header inside the first applyBlock will be incorrect. I was deliberately trying to avoid this.

I'd be fine with this anyway, if it indeed compiles though.

[KtorZ]

Hmmm. It's probably not important for now since there will be no transactions yet. And maybe it's best to leave it for later actually until we have confirmation of how the current mainnet is going to be included in the genesis block. So, leave it be 👍

[Anviking]

could be some transactions that are ours in the genesis block

I thought (Set.fromList txs) would add them though 🤔 ?

[KtorZ]

👍

[KtorZ]

👌