Abstract over the chain backend in e2e tests (#2101)

fix #2100 

---

<!-- Consider each and tick it off one way or the other -->
* [x] CHANGELOG updated or not needed
* [x] Documentation updated or not needed
* [x] Haddocks updated or not needed
* [x] No new TODOs introduced or explained herafter

Author: noonio

hydra-cluster/README.md

@@ -31,13 +31,25 @@ The `HYDRA_CONFIG_DIR` environment variable is used to control where the executa
 for its configuration files. By default those files are resolved using the cabal package's
 data structure which is not always convenient.
 
+The `HYDRA_BACKEND` environment variable is used to choose over which backend we will run our
+end-to-end tests. Possible values are _direct_ and _blockfrost_ (eg. export HYDRA_BACKEND="blockfrost").
+If this env variable is not set, the tests will default to _direct_ backend.
+
+To run the e2e tests successfully using blockfrost backend there should be also
+a file named `blocfrost-project.txt` in the root of the repository with the
+appropriate api key for the network you want to run on.
+
 ## Smoke Testing
 
 The `hydra-cluster` executable spins up a `cardano-node` as a network
 participant which synchronizes the block chain and then executes a
 single scenario (single party, full life cycle) using funds available
-to the `config/credentials/faucet.sk` on that network. The Hydra nodes
-can reference pre-existing contracts living at some well-known
+to the `config/credentials/faucet.sk` on that network.
+
+Smoke tests can also run using _Blockfrost_ in which case there is no need to
+start `cardano-node`.
+
+The Hydra nodes can reference pre-existing contracts living at some well-known
 transaction or can post a new transaction to use those contracts.
 
 :warning: do not provide actual funds to this faucet address as the
@@ -153,7 +165,7 @@ P95: 19.81722345ms
 P50: 18.532922ms
 Invalid txs: 0
 Writing report to: out/end-to-end-benchmarks.md
-         line 0: warning: Cannot find or open file "out/system.csv"                
+         line 0: warning: Cannot find or open file "out/system.csv"
 Created plot: out/results.png
 ```
 

hydra-cluster/src/CardanoNode.hs

@@ -24,10 +24,11 @@ import Hydra.Cardano.Api (
 import Hydra.Cardano.Api qualified as Api
 import Hydra.Chain.Backend (ChainBackend)
 import Hydra.Chain.Backend qualified as Backend
+import Hydra.Chain.Blockfrost (BlockfrostBackend (..))
 import Hydra.Chain.Direct (DirectBackend (..))
 import Hydra.Cluster.Fixture (KnownNetwork (..), toNetworkId)
 import Hydra.Cluster.Util (readConfigFile)
-import Hydra.Options (DirectOptions (..))
+import Hydra.Options (BlockfrostOptions (..), DirectOptions (..))
 import Network.HTTP.Simple (getResponseBody, httpBS, parseRequestThrow)
 import System.Directory (createDirectoryIfMissing, doesFileExist, removeFile)
 import System.Exit (ExitCode (..))
@@ -159,6 +160,31 @@ withCardanoNodeDevnet tracer stateDirectory action = do
   args <- setupCardanoDevnet stateDirectory
   withCardanoNode tracer stateDirectory args action
 
+withBlockfrostBackend ::
+  Tracer IO NodeLog ->
+  -- | State directory in which credentials, db & logs are persisted.
+  FilePath ->
+  (NominalDiffTime -> BlockfrostBackend -> IO a) ->
+  IO a
+withBlockfrostBackend _tracer stateDirectory action = do
+  args <- setupCardanoDevnet stateDirectory
+  shelleyGenesis <- readFileBS >=> unsafeDecodeJson $ stateDirectory </> nodeShelleyGenesisFile args
+  let backend = BlockfrostBackend $ BlockfrostOptions{projectPath = ".." </> Backend.blockfrostProjectPath}
+  action (getShelleyGenesisBlockTime shelleyGenesis) backend
+
+withBackend ::
+  forall a.
+  Tracer IO NodeLog ->
+  FilePath ->
+  (forall backend. ChainBackend backend => NominalDiffTime -> backend -> IO a) ->
+  IO a
+withBackend tracer stateDirectory action = do
+  backend <- lookupEnv "HYDRA_BACKEND"
+  case backend of
+    Just "direct" -> withCardanoNodeDevnet tracer stateDirectory action
+    Just "blockfrost" -> withBlockfrostBackend tracer stateDirectory action
+    _ -> withCardanoNodeDevnet tracer stateDirectory action
+
 -- | Run a cardano-node as normal network participant on a known network.
 withCardanoNodeOnKnownNetwork ::
   Tracer IO NodeLog ->
@@ -320,12 +346,13 @@ withCardanoNode tr stateDirectory args action = do
       else do
         let magic = json ^?! key "networkMagic" . _Number
         Api.Testnet (Api.NetworkMagic $ truncate magic)
-  -- Read expected time between blocks from shelley genesis
-  getShelleyGenesisBlockTime :: Value -> NominalDiffTime
-  getShelleyGenesisBlockTime json = do
-    let slotLength = json ^?! key "slotLength" . _Number
-    let activeSlotsCoeff = json ^?! key "activeSlotsCoeff" . _Number
-    computeBlockTime (realToFrac slotLength) (toRational activeSlotsCoeff)
+
+-- Read expected time between blocks from shelley genesis
+getShelleyGenesisBlockTime :: Value -> NominalDiffTime
+getShelleyGenesisBlockTime json = do
+  let slotLength = json ^?! key "slotLength" . _Number
+  let activeSlotsCoeff = json ^?! key "activeSlotsCoeff" . _Number
+  computeBlockTime (realToFrac slotLength) (toRational activeSlotsCoeff)
 
 -- | Compute the block time (expected time between blocks) given a slot length
 -- as diff time and active slot coefficient.