feature: expose last token id function in the contract (#124)

* feat: add function to get the last token id

* test: add getLastTokenId tests

contracts/contracts/FleekERC721.sol

@@ -9,6 +9,8 @@ import "@openzeppelin/contracts/utils/Strings.sol";
 import "./FleekAccessControl.sol";
 import "./util/FleekStrings.sol";
 
+error ThereIsNoTokenMinted();
+
 contract FleekERC721 is Initializable, ERC721Upgradeable, FleekAccessControl {
     using Strings for uint256;
     using Counters for Counters.Counter;
@@ -173,6 +175,15 @@ contract FleekERC721 is Initializable, ERC721Upgradeable, FleekAccessControl {
         return (app.name, app.description, app.externalURL, app.ENS, app.currentBuild, app.logo, app.color);
     }
 
+    /**
+     * @dev Returns the last minted tokenId.
+     */
+    function getLastTokenId() public view virtual returns (uint256) {
+        uint256 current = _appIds.current();
+        if (current == 0) revert ThereIsNoTokenMinted();
+        return current - 1;
+    }
+
     /**
      * @dev See {IERC165-supportsInterface}.
      */

contracts/test/foundry/FleekERC721/GetLastTokenId.t.sol

@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.17;
+
+import "./TestBase.sol";
+import "contracts/FleekERC721.sol";
+
+contract Test_FleekERC721_GetLastTokenId is Test_FleekERC721_Base {
+    function setUp() public {
+        baseSetUp();
+    }
+
+    function test_cannotGetLastTokenIdWhenThereIsNoTokenMinted() public {
+        vm.expectRevert(ThereIsNoTokenMinted.selector);
+        CuT.getLastTokenId();
+    }
+
+    function test_getLastTokenIdForOneToken() public {
+        uint256 mint = mintDefault(deployer);
+
+        assertEq(mint, CuT.getLastTokenId());
+    }
+
+    function test_getLastTokenIdAfterThreeMints() public {
+        mintDefault(deployer);
+        mintDefault(deployer);
+        uint256 lastMint = mintDefault(deployer);
+
+        assertEq(lastMint, CuT.getLastTokenId());
+    }
+}

contracts/test/hardhat/contracts/FleekERC721/get-last-token-id.t.ts

@@ -0,0 +1,56 @@
+import { loadFixture } from '@nomicfoundation/hardhat-network-helpers';
+import { expect } from 'chai';
+import { TestConstants, Fixtures, Errors } from './helpers';
+import { ethers } from 'hardhat';
+
+const { MintParams, Roles } = TestConstants;
+
+describe('FleekERC721.GetLastTokenId', () => {
+  let fixture: Awaited<ReturnType<typeof Fixtures.default>>;
+
+  const mint = async () => {
+    const response = await fixture.contract.mint(
+      fixture.owner.address,
+      TestConstants.MintParams.name,
+      TestConstants.MintParams.description,
+      TestConstants.MintParams.externalUrl,
+      TestConstants.MintParams.ens,
+      TestConstants.MintParams.commitHash,
+      TestConstants.MintParams.gitRepository,
+      TestConstants.MintParams.logo,
+      TestConstants.MintParams.color
+    );
+
+    return response;
+  };
+
+  beforeEach(async () => {
+    fixture = await loadFixture(Fixtures.default);
+  });
+
+  it('should revert if there is no token minted', async () => {
+    const { contract } = fixture;
+    await expect(contract.getLastTokenId()).to.be.revertedWithCustomError(
+      contract,
+      Errors.ThereIsNoTokenMinted
+    );
+  });
+
+  it('should return the last token id', async () => {
+    const { contract } = fixture;
+
+    await mint();
+
+    expect(await contract.getLastTokenId()).to.be.equal(0);
+  });
+
+  it('should return the last token id after minting multiple tokens', async () => {
+    const { contract } = fixture;
+
+    await mint();
+    await mint();
+    await mint();
+
+    expect(await contract.getLastTokenId()).to.be.equal(2);
+  });
+});

contracts/test/hardhat/contracts/FleekERC721/helpers/errors.ts

@@ -0,0 +1,3 @@
+export const Errors = Object.freeze({
+  ThereIsNoTokenMinted: 'ThereIsNoTokenMinted',
+});

contracts/test/hardhat/contracts/FleekERC721/helpers/index.ts

@@ -1,4 +1,5 @@
 export * from './constants';
 export * from './fixture';
 export * from './utils';
+export * from './errors';
 export * from './events';