Intiial commit

exercise1/contracts/Migrations.sol

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+pragma solidity ^0.4.23;
+
+contract Migrations {
+  address public owner;
+  uint public last_completed_migration;
+
+  constructor() public {
+    owner = msg.sender;
+  }
+
+  modifier restricted() {
+    if (msg.sender == owner) _;
+  }
+
+  function setCompleted(uint completed) public restricted {
+    last_completed_migration = completed;
+  }
+
+  function upgrade(address new_address) public restricted {
+    Migrations upgraded = Migrations(new_address);
+    upgraded.setCompleted(last_completed_migration);
+  }
+}

exercise1/contracts/Tokensale.sol

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+pragma solidity ^0.4.21;
+
+contract TokenSale {
+    mapping(address => uint256) public balanceOf;
+    uint256 constant PRICE_PER_TOKEN = 1 ether;
+
+    function TokenSale(address _player) public payable {
+        require(msg.value == 1 ether);
+    }
+
+    function isComplete() public view returns (bool) {
+        return address(this).balance < 1 ether;
+    }
+
+    function buy(uint256 numTokens) public payable {
+        require(msg.value == numTokens * PRICE_PER_TOKEN);
+
+        balanceOf[msg.sender] += numTokens;
+    }
+
+    function sell(uint256 numTokens) public {
+        require(balanceOf[msg.sender] >= numTokens);
+
+        balanceOf[msg.sender] -= numTokens;
+        msg.sender.transfer(numTokens * PRICE_PER_TOKEN);
+    }
+}

exercise1/migrations/1_initial_migration.js

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+var Migrations = artifacts.require("./Migrations.sol");
+
+module.exports = function(deployer) {
+  deployer.deploy(Migrations);
+};

exercise1/truffle-config.js

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+/*
+ * NB: since truffle-hdwallet-provider 0.0.5 you must wrap HDWallet providers in a 
+ * function when declaring them. Failure to do so will cause commands to hang. ex:
+ * ```
+ * mainnet: {
+ *     provider: function() { 
+ *       return new HDWalletProvider(mnemonic, 'https://mainnet.infura.io/<infura-key>') 
+ *     },
+ *     network_id: '1',
+ *     gas: 4500000,
+ *     gasPrice: 10000000000,
+ *   },
+ */
+
+module.exports = {
+  // See <http://truffleframework.com/docs/advanced/configuration>
+  // to customize your Truffle configuration!
+};

exercise1/truffle.js

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+/*
+ * NB: since truffle-hdwallet-provider 0.0.5 you must wrap HDWallet providers in a 
+ * function when declaring them. Failure to do so will cause commands to hang. ex:
+ * ```
+ * mainnet: {
+ *     provider: function() { 
+ *       return new HDWalletProvider(mnemonic, 'https://mainnet.infura.io/<infura-key>') 
+ *     },
+ *     network_id: '1',
+ *     gas: 4500000,
+ *     gasPrice: 10000000000,
+ *   },
+ */
+
+module.exports = {
+  // See <http://truffleframework.com/docs/advanced/configuration>
+  // to customize your Truffle configuration!
+};