gateway: eth_subscribe support

cli/util/api.go

@@ -319,11 +319,33 @@ func GetFullNodeAPIV1Single(ctx *cli.Context) (v1api.FullNode, jsonrpc.ClientClo
 	return v1API, closer, nil
 }
 
-func GetFullNodeAPIV1(ctx *cli.Context) (v1api.FullNode, jsonrpc.ClientCloser, error) {
+type GetFullNodeOptions struct {
+	ethSubHandler api.EthSubscriber
+}
+
+type GetFullNodeOption func(*GetFullNodeOptions)
+
+func FullNodeWithEthSubscribtionHandler(sh api.EthSubscriber) GetFullNodeOption {
+	return func(opts *GetFullNodeOptions) {
+		opts.ethSubHandler = sh
+	}
+}
+
+func GetFullNodeAPIV1(ctx *cli.Context, opts ...GetFullNodeOption) (v1api.FullNode, jsonrpc.ClientCloser, error) {
 	if tn, ok := ctx.App.Metadata["testnode-full"]; ok {
 		return tn.(v1api.FullNode), func() {}, nil
 	}
 
+	var options GetFullNodeOptions
+	for _, opt := range opts {
+		opt(&options)
+	}
+
+	var rpcOpts []jsonrpc.Option
+	if options.ethSubHandler != nil {
+		rpcOpts = append(rpcOpts, jsonrpc.WithClientHandler("Filecoin", options.ethSubHandler), jsonrpc.WithClientHandlerAlias("eth_subscription", "Filecoin.EthSubscription"))
+	}
+
 	heads, err := GetRawAPIMulti(ctx, repo.FullNode, "v1")
 	if err != nil {
 		return nil, nil, err