add Balancer pool and its factory. The 'S' is for slave, as we will e…

…ventually have a master pool and factory too.

contracts/SFactory.sol

@@ -0,0 +1,80 @@
+pragma solidity ^0.5.7;
+// Copyright BigchainDB GmbH and Ocean Protocol contributors
+// SPDX-License-Identifier: (Apache-2.0 AND CC-BY-4.0)
+// Code is Apache-2.0 and docs are CC-BY-4.0
+
+import './Deployer.sol';
+import './Converter.sol';
+import './SPool.sol';
+import './BConst.sol';
+
+/*
+* @title SFactory contract
+* @author Ocean Protocol (with code from Balancer Labs)
+*
+* @dev Ocean implementation of Balancer SPool Factory
+*      SFactory deploys SPool proxy contracts.
+*      New SPool proxy contracts are links to the template contract's bytecode. 
+*      Proxy contract functionality is based on Ocean Protocol custom
+*        implementation of ERC1167 standard.
+*/
+
+contract SFactory is BConst, Deployer, Converter {
+
+    address private _spoolTemplate;
+
+    event SPoolCreated(
+        address indexed newSPoolAddress, 
+        address indexed spoolTemplateAddress
+    );
+
+    event SPoolRegistered(
+        address spoolAddress,
+        address indexed registeredBy,
+        uint256 indexed registeredAt
+    );
+
+    /* @dev Called on contract deployment. Cannot be called with zero address.
+       @param _spoolTemplate -- address of a deployed SPool contract. */
+    constructor(address spoolTemplate) 
+        public 
+    {
+        require(spoolTemplate != address(0), 'ERR_ADDRESS_0');
+        _spoolTemplate = spoolTemplate;
+    }
+
+    /* @dev Deploys new SPool proxy contract.
+       Template contract address could not be a zero address. 
+       @return address of a new proxy SPool contract */
+    function newSPool(address controller) 
+        public
+        returns (address spool)
+    {
+        spool = deploy(_spoolTemplate);
+        require(spool != address(0), 'ERR_ADDRESS_0');
+
+        SPool spoolInstance = SPool(spool);
+
+	address factory = address(this);
+	uint swapFee = MIN_FEE;
+	bool publicSwap = false;
+	bool finalized = false;
+        spoolInstance.initialize(controller, factory, swapFee, publicSwap,
+				 finalized);
+
+        require(spoolInstance.isInitialized(), 'ERR_INITIALIZE_SPOOL');
+        emit SPoolCreated(spool, _spoolTemplate);
+        emit SPoolRegistered(spool, msg.sender, block.number);
+    }
+
+
+    /* @dev get the spool template address
+       @return the template address */
+    function getSPool()
+        external
+        view
+        returns (address)
+    {
+        return _spoolTemplate;
+    }
+}