[RelayerProxy] feat: implement relayerProxy struct (#82)

* feat: add notifiable observable

Co-authored-by: red-0ne <[email protected]>

* fixup: observable

(cherry picked from commit bcf700405b5e4bd71bf9bb650c988526fa16c728)

* refactor/fix: notifiable observable improvements

* chore: more review improvements

* refactor: renaming

- `notifiable` pkg to `channel`
- `notifiableObservable` struct to `channelObservable`
- `observer` struct to `channelObserver`
- `notifier` vars to `producer`
- `notifee` vars to `observable` (or similar)

* chore: update comments

* refactor: simplify drainCh test helper

* test: fix timeout

* test: rename observable test functions

* test: add test TODOs

* chore: update comments

* refactor: simplify observable & observer

* test: fix & add observable tests

* test: cleanup & comment observable tests

* fixup: observable

(cherry picked from commit 33f3196535b7dae154e01f93aab36f70cda8fc4f)

* fixup: observable test

(cherry picked from commit 9c206da115dc35843d588313c2215a0e649c6df6)

* refactor: simplify & cleanup

* chore: cleanup logs & comments

* chore: improve comments

* refactor: DrainChannel test helper

* shore: cleanup & simplify

* test: comment out flaky test cases

* fixup: drain channel helper

* chore: improve var name

* fixup: drain channel helper

* test: shorten timeout

* chore: cleanup

* chore: cleanup, simplification, review improvements

(cherry picked from commit 92a547da29ec526d415f6967ccfa5988c3f5ca1d)

* chore: improve comments

Co-authored-by: Daniel Olshansky <[email protected]>

* chore: improve comments

Co-authored-by: Daniel Olshansky <[email protected]>

* refactor: rename `Observable#Close()` to `#UnsubscribeAll()`

* chore: improve comments

* chore: misc. review feedback improvements

* chore: improve comment

* chore: review improvements

* chore: last minute improvements

* feat: add RelayerProxy interface

* Fix grammar in comments

Co-authored-by: Daniel Olshansky <[email protected]>

* chore: rename package to relayerproxy

* feat: implement relayerProxy struct and its constructor args

* fix: change directory structure

* fix: change directory structure

* chore: address change requests

* chore: comment unavailable interface and its usage

---------

Co-authored-by: Bryan White <[email protected]>
Co-authored-by: Daniel Olshansky <[email protected]>

pkg/relayer/proxy/proxy.go

@@ -0,0 +1,118 @@
+package proxy
+
+import (
+	"context"
+
+	sdkclient "github.com/cosmos/cosmos-sdk/client"
+	"github.com/cosmos/cosmos-sdk/crypto/keyring"
+	accounttypes "github.com/cosmos/cosmos-sdk/x/auth/types"
+
+	// TODO_INCOMPLETE(@red-0ne): Import the appropriate block client interface once available.
+	// blocktypes "pocket/pkg/client"
+	"pocket/pkg/observable"
+	"pocket/pkg/observable/channel"
+	"pocket/x/service/types"
+	sessiontypes "pocket/x/session/types"
+	suppliertypes "pocket/x/supplier/types"
+)
+
+var _ RelayerProxy = &relayerProxy{}
+
+type relayerProxy struct {
+	// keyName is the supplier's key name in the Cosmos's keybase. It is used along with the keyring to
+	// get the supplier address and sign the relay responses.
+	keyName string
+	keyring keyring.Keyring
+
+	// blocksClient is the client used to get the block at the latest height from the blockchain
+	// and be notified of new incoming blocks. It is used to update the current session data.
+	// TODO_INCOMPLETE(@red-0ne): Uncomment once the BlockClient interface is available.
+	// blockClient blocktypes.BlockClient
+
+	// accountsQuerier is the querier used to get account data (e.g. app publicKey) from the blockchain,
+	// which, in the context of the RelayerProxy, is used to verify the relay request signatures.
+	accountsQuerier accounttypes.QueryClient
+
+	// supplierQuerier is the querier used to get the supplier's advertised information from the blockchain,
+	// which contains the supported services, RPC types, and endpoints, etc...
+	supplierQuerier suppliertypes.QueryClient
+
+	// sessionQuerier is the querier used to get the current session from the blockchain,
+	// which is needed to check if the relay proxy should be serving an incoming relay request.
+	sessionQuerier sessiontypes.QueryClient
+
+	// providedServices is a map of the services provided by the relayer proxy. Each provided service
+	// has the necessary information to start the server that listens for incoming relay requests and
+	// the client that proxies the request to the supported native service.
+	providedServices map[string][]ProvidedService
+
+	// servedRelays is an observable that notifies the miner about the relays that have been served.
+	servedRelays observable.Observable[*types.Relay]
+
+	// servedRelaysProducer is a channel that emits the relays that have been served so that the
+	// servedRelays observable can fan out the notifications to its subscribers.
+	servedRelaysProducer chan<- *types.Relay
+}
+
+func NewRelayerProxy(
+	ctx context.Context,
+	clientCtx sdkclient.Context,
+	keyName string,
+	keyring keyring.Keyring,
+
+	// TODO_INCOMPLETE(@red-0ne): Uncomment once the BlockClient interface is available.
+	// blockClient blocktypes.BlockClient,
+) RelayerProxy {
+	accountQuerier := accounttypes.NewQueryClient(clientCtx)
+	supplierQuerier := suppliertypes.NewQueryClient(clientCtx)
+	sessionQuerier := sessiontypes.NewQueryClient(clientCtx)
+	providedServices := buildProvidedServices(ctx, supplierQuerier)
+	servedRelays, servedRelaysProducer := channel.NewObservable[*types.Relay]()
+
+	return &relayerProxy{
+		// TODO_INCOMPLETE(@red-0ne): Uncomment once the BlockClient interface is available.
+		// blockClient:          blockClient,
+		keyName:              keyName,
+		keyring:              keyring,
+		accountsQuerier:      accountQuerier,
+		supplierQuerier:      supplierQuerier,
+		sessionQuerier:       sessionQuerier,
+		providedServices:     providedServices,
+		servedRelays:         servedRelays,
+		servedRelaysProducer: servedRelaysProducer,
+	}
+}
+
+// Start starts all supported proxies and returns an error if any of them fail to start.
+func (rp *relayerProxy) Start(ctx context.Context) error {
+	panic("TODO: implement relayerProxy.Start")
+}
+
+// Stop stops all supported proxies and returns an error if any of them fail.
+func (rp *relayerProxy) Stop(ctx context.Context) error {
+	panic("TODO: implement relayerProxy.Stop")
+}
+
+// ServedRelays returns an observable that notifies the miner about the relays that have been served.
+// A served relay is one whose RelayRequest's signature and session have been verified,
+// and its RelayResponse has been signed and successfully sent to the client.
+func (rp *relayerProxy) ServedRelays() observable.Observable[*types.Relay] {
+	panic("TODO: implement relayerProxy.ServedRelays")
+}
+
+// buildProvidedServices builds the provided services map from the supplier's advertised information.
+// It loops over the retrieved `SupplierServiceConfig` and, for each `SupplierEndpoint`, it creates the necessary
+// server and client to populate the corresponding `ProvidedService` struct in the map.
+func buildProvidedServices(
+	ctx context.Context,
+	supplierQuerier suppliertypes.QueryClient,
+) map[string]ProvidedService {
+	panic("TODO: implement buildProvidedServices")
+}
+
+// TODO_INCOMPLETE(@red-0ne): Add the appropriate server and client interfaces to be implemented by each RPC type.
+type ProvidedService struct {
+	serviceId string
+	server    struct{}
+	client    struct{}
+}