feat: erc20 module (#38)

Co-authored-by: Eric Mastro <github@egonat.me>

.gitignore

@@ -3,3 +3,4 @@
 !*.*
 nimble.develop
 nimble.paths
+.idea

Readme.md

@@ -143,6 +143,25 @@ await subscription.unsubscribe()
 Subscriptions are currently only supported when using a JSON RPC provider that
 is created with a websockets URL such as `ws://localhost:8545`.
 
+Utilities
+---------
+
+This library ships with some optional modules that provides convenience utilities for you such as:
+
+- `ethers/erc20` module provides you with ERC20 token implementation and its events
+
+Contribution
+------------
+
+If you want to run the tests, then before running `nimble test`, you have to
+have installed NodeJS and started a testing node:
+
+```shell
+$ cd testnode
+$ npm ci
+$ npm start
+```
+
 Thanks
 ------
 

ethers/erc20.nim

@@ -0,0 +1,52 @@
+import pkg/stint
+import pkg/ethers
+
+export stint
+export ethers
+
+type
+  Erc20Token* = ref object of Contract
+
+  Transfer* = object of Event
+    sender* {.indexed.}: Address
+    receiver* {.indexed.}: Address
+    value*: UInt256
+
+  Approval* = object of Event
+    owner* {.indexed.}: Address
+    spender* {.indexed.}: Address
+    value*: UInt256
+
+method name*(erc20: Erc20Token): string {.base, contract, view.}
+## Returns the name of the token.
+
+method symbol*(token: Erc20Token): string {.base, contract, view.}
+## Returns the symbol of the token, usually a shorter version of the name.
+
+method decimals*(token: Erc20Token): uint8 {.base, contract, view.}
+## Returns the number of decimals used to get its user representation.
+## For example, if `decimals` equals `2`, a balance of `505` tokens should
+## be displayed to a user as `5.05` (`505 / 10 ** 2`).
+
+method totalSupply*(erc20: Erc20Token): UInt256 {.base, contract, view.}
+## Returns the amount of tokens in existence.
+
+method balanceOf*(erc20: Erc20Token, account: Address): UInt256 {.base, contract, view.}
+## Returns the amount of tokens owned by `account`.
+
+method allowance*(erc20: Erc20Token, owner, spender: Address): UInt256 {.base, contract, view.}
+## Returns the remaining number of tokens that `spender` will be allowed
+## to spend on behalf of `owner` through {transferFrom}. This is zero by default.
+##
+## This value changes when {approve} or {transferFrom} are called.
+
+method transfer*(erc20: Erc20Token, recipient: Address, amount: UInt256) {.base, contract.}
+## Moves `amount` tokens from the caller's account to `recipient`.
+
+method approve*(token: Erc20Token, spender: Address, amount: UInt256) {.base, contract.}
+## Sets `amount` as the allowance of `spender` over the caller's tokens.
+
+method transferFrom*(erc20: Erc20Token, spender: Address, recipient: Address, amount: UInt256) {.base, contract.}
+## Moves `amount` tokens from `from` to `to` using the allowance
+## mechanism. `amount` is then deducted from the caller's allowance.
+

testmodule/test.nim

@@ -6,5 +6,6 @@ import ./testEnums
 import ./testEvents
 import ./testWallet
 import ./testTesting
+import ./testErc20
 
 {.warning[UnusedImport]:off.}

testmodule/testContracts.nim

@@ -3,25 +3,15 @@ import pkg/asynctest
 import pkg/questionable
 import pkg/stint
 import pkg/ethers
+import pkg/ethers/erc20
 import ./hardhat
 import ./miner
 import ./mocks
 
 type
 
-  Erc20* = ref object of Contract
+  TestToken = ref object of Erc20Token
-  TestToken = ref object of Erc20
 
-  Transfer = object of Event
-    sender {.indexed.}: Address
-    receiver {.indexed.}: Address
-    value: UInt256
-
-method name*(erc20: Erc20): string {.base, contract, view.}
-method totalSupply*(erc20: Erc20): UInt256 {.base, contract, view.}
-method balanceOf*(erc20: Erc20, account: Address): UInt256 {.base, contract, view.}
-method allowance*(erc20: Erc20, owner, spender: Address): UInt256 {.base, contract, view.}
-method transfer*(erc20: Erc20, recipient: Address, amount: UInt256) {.base, contract.}
 method mint(token: TestToken, holder: Address, amount: UInt256): ?TransactionResponse {.base, contract.}
 
 suite "Contracts":

testmodule/testErc20.nim

@@ -0,0 +1,96 @@
+import std/json
+import pkg/asynctest
+import pkg/questionable
+import pkg/stint
+import pkg/ethers
+import pkg/ethers/erc20
+import ./hardhat
+import ./miner
+import ./mocks
+
+type
+  TestToken = ref object of Erc20Token
+
+method mint(token: TestToken, holder: Address, amount: UInt256): ?TransactionResponse {.base, contract.}
+
+suite "ERC20":
+
+  var token, token1: Erc20Token
+  var testToken: TestToken
+  var provider: JsonRpcProvider
+  var snapshot: JsonNode
+  var accounts: seq[Address]
+
+  setup:
+    provider = JsonRpcProvider.new("ws://localhost:8545")
+    snapshot = await provider.send("evm_snapshot")
+    accounts = await provider.listAccounts()
+    let deployment = readDeployment()
+    testToken = TestToken.new(!deployment.address(TestToken), provider.getSigner())
+    token = Erc20Token.new(!deployment.address(TestToken), provider.getSigner())
+
+  teardown:
+    discard await provider.send("evm_revert", @[snapshot])
+
+  test "retrieves basic information":
+    check (await token.name()) == "TestToken"
+    check (await token.symbol()) == "TST"
+    check (await token.decimals()) == 12
+    check (await token.totalSupply()) == 0.u256
+    check (await token.balanceOf(accounts[0])) == 0.u256
+    check (await token.allowance(accounts[0], accounts[1])) == 0.u256
+
+  test "transfer tokens":
+    check (await token.balanceOf(accounts[0])) == 0.u256
+    check (await token.allowance(accounts[0], accounts[1])) == 0.u256
+
+    discard await testToken.mint(accounts[0], 100.u256)
+
+    check (await token.totalSupply()) == 100.u256
+    check (await token.balanceOf(accounts[0])) == 100.u256
+    check (await token.balanceOf(accounts[1])) == 0.u256
+
+    await token.transfer(accounts[1], 50.u256)
+
+    check (await token.balanceOf(accounts[0])) == 50.u256
+    check (await token.balanceOf(accounts[1])) == 50.u256
+
+  test "approve tokens":
+    discard await testToken.mint(accounts[0], 100.u256)
+
+    check (await token.allowance(accounts[0], accounts[1])) == 0.u256
+    check (await token.balanceOf(accounts[0])) == 100.u256
+    check (await token.balanceOf(accounts[1])) == 0.u256
+
+    await token.approve(accounts[1], 50.u256)
+
+    check (await token.allowance(accounts[0], accounts[1])) == 50.u256
+    check (await token.balanceOf(accounts[0])) == 100.u256
+    check (await token.balanceOf(accounts[1])) == 0.u256
+
+  test "transferFrom tokens":
+    let senderAccount = accounts[0]
+    let receiverAccount = accounts[1]
+    let receiverAccountSigner = provider.getSigner(receiverAccount)
+
+    check (await token.balanceOf(senderAccount)) == 0.u256
+    check (await token.allowance(senderAccount, receiverAccount)) == 0.u256
+
+    discard await testToken.mint(senderAccount, 100.u256)
+
+    check (await token.totalSupply()) == 100.u256
+    check (await token.balanceOf(senderAccount)) == 100.u256
+    check (await token.balanceOf(receiverAccount)) == 0.u256
+
+    await token.approve(receiverAccount, 50.u256)
+
+    check (await token.allowance(senderAccount, receiverAccount)) == 50.u256
+    check (await token.balanceOf(senderAccount)) == 100.u256
+    check (await token.balanceOf(receiverAccount)) == 0.u256
+
+    await token.connect(receiverAccountSigner).transferFrom(senderAccount, receiverAccount, 50.u256)
+
+    check (await token.balanceOf(senderAccount)) == 50.u256
+    check (await token.balanceOf(receiverAccount)) == 50.u256
+    check (await token.allowance(senderAccount, receiverAccount)) == 0.u256
+

testnode/contracts/TestToken.sol

@@ -6,7 +6,15 @@ import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
 contract TestToken is ERC20 {
   constructor() ERC20("TestToken", "TST") {}
 
+  function decimals() public view virtual override returns (uint8) {
+    return 12;
+  }
+
   function mint(address holder, uint amount) public {
     _mint(holder, amount);
   }
+
+  function burn(address holder, uint amount) public {
+    _burn(holder, amount);
+  }
 }