More ergonomic contracts interfaces (RxJs only initial) (#1015)

* More ergnomic contracts interfaces

* extend SubmittableResult

* Allow creation of contract from blueprint

* "decorate" Contract (just playing with interfaces)

* Make actual messages calls

* Rename to Rx{Blueprint, Cond, Contract}

* Add exports

* Support contract & contracts endpoints

* Remove unneeded ApiType generics (may return)

* Comment 2.x/1.x detection

packages/api-contract/src/RxBase.ts

@@ -0,0 +1,29 @@
+// Copyright 2017-2019 @polkadot/api-contract authors & contributors
+// This software may be modified and distributed under the terms
+// of the Apache-2.0 license. See the LICENSE file for details.
+
+import { SubmittableModuleExtrinsics } from '@polkadot/api/types';
+import { ApiObject, ContractABI, IContractBase } from './types';
+
+import { assert } from '@polkadot/util';
+
+import Abi from './Abi';
+
+// NOTE Experimental, POC, bound to change
+export default abstract class RxBase implements IContractBase<'rxjs'> {
+  readonly abi: Abi;
+  readonly api: ApiObject<'rxjs'>;
+  readonly apiContracts: SubmittableModuleExtrinsics<'rxjs'>;
+
+  constructor (api: ApiObject<'rxjs'>, abi: ContractABI | Abi) {
+    this.abi = abi instanceof Abi
+      ? abi
+      : new Abi(abi);
+    this.api = api;
+
+    // cater for substrate 2.x & 1.x (in order)
+    this.apiContracts = api.tx.contracts || api.tx.contract;
+
+    assert(this.apiContracts && this.apiContracts.putCode, `You need to connect to a node with the contracts module, the metadata does not enable api.tx.contracts on this instance`);
+  }
+}