Merge pull request #114 from HQ20/new/energy

New/energy

contracts/drafts/examples/energy/EnergyMarket.sol

@@ -0,0 +1,113 @@
+pragma solidity ^0.5.10;
+
+import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
+// import "@hq20/contracts/contracts/access/Whitelist.sol";
+import "./../../../access/Whitelist.sol";
+
+
+/**
+ * @title Energy Market
+ * @notice Implements a simple energy market, using ERC20 and Whitelist.
+ * ERC20 is used to enable payments from the consumers to the distribution
+ * network, represented by this contract, and from the distribution network
+ * to the producers. Whitelist is used to keep a list of compliant smart
+ * meters that communicate the production and consumption of energy.
+ */
+contract EnergyMarket is ERC20, Whitelist {
+
+    event EnergyProduced(address producer, uint256 time);
+    event EnergyConsumed(address consumer, uint256 time);
+
+    // uint128 is used here to facilitate the price formula
+    // Casting between uint128 and int256 never overflows
+    // int256(uint128) - int256(uint128) never overflows
+    mapping(uint256 => uint128) public consumption;
+    mapping(uint256 => uint128) public production;
+    uint128 public basePrice;
+
+    /**
+     * @dev The constructor initializes the underlying currency token and the
+     * smart meter whitelist. The constructor also mints the requested amount
+     * of the underlying currency token to fund the network load. Also sets the
+     * maximum energy price, used for calculating prices.
+     */
+    constructor (uint256 _initialSupply, uint128 _basePrice)
+        public
+        ERC20()
+        Whitelist()
+    {
+        _mint(address(this), _initialSupply);
+        basePrice = _basePrice;
+    }
+
+    /**
+     * @dev The production price for each time slot.
+     */
+    function getProductionPrice(uint256 _time) public view returns(uint256) {
+        return uint256(
+            max(
+                0,
+                int256(basePrice) *
+                    (3 + safeSub(production[_time], consumption[_time]))
+            )
+        );
+    }
+
+    /**
+     * @dev The consumption price for each time slot
+     */
+    function getConsumptionPrice(uint256 _time) public view returns(uint256) {
+        return uint256(
+            max(
+                0,
+                int256(basePrice) *
+                    (3 + safeSub(consumption[_time], production[_time]))
+            )
+        );
+    }
+
+    /**
+     * @dev Add one energy unit to the distribution network at the specified
+     * time and be paid the production price. Only whitelisted smart meters can
+     * call this function.
+     */
+    function produce(uint256 _time) public {
+        require(isMember(msg.sender), "Unknown meter.");
+        this.transfer(
+            msg.sender,
+            getProductionPrice(_time)
+        );
+        production[_time] = production[_time] + 1;
+        emit EnergyProduced(msg.sender, _time);
+    }
+
+    /**
+     * @dev Take one energy unit from the distribution network at the specified
+     * time by paying the consumption price. Only whitelisted smart meters can
+     * call this function.
+     */
+    function consume(uint256 _time) public {
+        require(isMember(msg.sender), "Unknown meter.");
+        this.transferFrom(
+            msg.sender,
+            address(this),
+            getConsumptionPrice(_time)
+        );
+        consumption[_time] = consumption[_time] + 1;
+        emit EnergyConsumed(msg.sender, _time);
+    }
+
+    /**
+     * @dev Returns the largest of two numbers.
+     */
+    function max(int256 a, int256 b) internal pure returns (int256) {
+        return a >= b ? a : b;
+    }
+
+    /**
+     * @dev Substracts b from a using types safely casting from uint128 to int256.
+     */
+    function safeSub(uint128 a, uint128 b) internal pure returns (int256) {
+        return int256(a) - int256(b);
+    }
+}

test/examples/energy/EnergyMarket.test.ts → test/drafts/examples/energy/EnergyMarket.test.ts

@@ -1,9 +1,9 @@
 import { BigNumber } from 'bignumber.js';
 // tslint:disable-next-line:no-var-requires
-import { EnergyMarketInstance } from '../../../types/truffle-contracts';
+import { EnergyMarketInstance } from '../../../../types/truffle-contracts';
 
 const EnergyMarket = artifacts.require(
-    './examples/energy/EnergyMarket.sol',
+    './drafts/examples/energy/EnergyMarket.sol',
     ) as Truffle.Contract<EnergyMarketInstance>;
 
 // tslint:disable:no-var-requires
@@ -23,12 +23,14 @@ contract('EnergyMarket', (accounts) => {
     let energyMarket: EnergyMarketInstance;
 
     const initialSupply = 1000000;
-    const maxPrice = 10;
+    const basePrice = 10;
+
+    const timeSlot = 1;
 
     beforeEach(async () => {
         energyMarket = await EnergyMarket.new(
             initialSupply,
-            maxPrice,
+            basePrice,
         );
         await energyMarket.addMember(authorized);
     });
@@ -37,38 +39,38 @@ contract('EnergyMarket', (accounts) => {
      * @test {EnergyMarket#produce}
      */
     it('Produce energy', async () => {
-        expect(energyMarket.produce({ from: authorized })).to.emit('EnergyProduced').withArgs(authorized);
+        expect(energyMarket.produce(timeSlot, { from: authorized })).to.emit('EnergyProduced').withArgs(authorized);
     });
 
     /**
      * @test {EnergyMarket#produce}
      */
     it('Produce throws with unauthorized producer', async () => {
-        expect(energyMarket.produce({ from: unauthorized })).to.revertWith('Unknown meter.');
+        expect(energyMarket.produce(timeSlot, { from: unauthorized })).to.revertWith('Unknown meter.');
     });
 
     /**
      * @test {EnergyMarket#consume}
      */
     it('Consume energy', async () => {
-        await energyMarket.produce({from: authorized });
+        await energyMarket.produce(timeSlot, {from: authorized });
         await energyMarket.approve(
-            energyMarket.address, await energyMarket.getConsumptionPrice(), { from: authorized },
+            energyMarket.address, await energyMarket.getConsumptionPrice(1), { from: authorized },
         );
-        expect(energyMarket.consume({ from: authorized })).to.emit('EnergyConsumed').withArgs(authorized);
+        expect(energyMarket.consume(timeSlot, { from: authorized })).to.emit('EnergyConsumed').withArgs(authorized);
     });
 
     /**
      * @test {EnergyMarket#consume}
      */
     it('Consume throws with unauthorized consumer', async () => {
-        expect(energyMarket.consume({ from: unauthorized })).to.revertWith('Unknown meter.');
+        expect(energyMarket.consume(timeSlot, { from: unauthorized })).to.revertWith('Unknown meter.');
     });
 
     /**
      * @test {EnergyMarket#consume}
      */
     it('Consume throws if consumer has insufficient balance', async () => {
-        expect(energyMarket.consume({ from: authorized })).to.revert;
+        expect(energyMarket.consume(timeSlot, { from: authorized })).to.revert;
     });
 });