Merge branch 'develop' into feature/94-add-an-about-menu-item

# Conflicts:
#	yarn.lock

packages/concordia-app/src/assets/css/index.css

@@ -1,6 +1,6 @@
 body.app {
     overflow: auto;
-    margin: 1em !important;
+    margin: 0;
 }
 
 #root {
@@ -18,4 +18,5 @@ body.app {
 
 .ui.inverted.menu {
     background: #0B2540;
+    border-radius: 0;
 }

packages/concordia-app/src/assets/css/loading-component.css

@@ -3,7 +3,7 @@ body {
 }
 
 .loading-screen {
-    margin-top: 10em;
+    margin-top: 12em;
     text-align: center;
     font-size: large;
 }

packages/concordia-app/src/components/PostList/PostListRow/index.jsx

@@ -1,8 +1,8 @@
 import React, {
-  memo, useEffect, useMemo, useState,
+  memo, useEffect, useMemo, useState, useCallback,
 } from 'react';
 import {
-  Dimmer, Icon, Image, Feed, Placeholder,
+  Dimmer, Icon, Image, Feed, Placeholder, Ref,
 } from 'semantic-ui-react';
 import PropTypes from 'prop-types';
 import { useTranslation } from 'react-i18next';
@@ -22,12 +22,13 @@ const { orbit } = breeze;
 
 const PostListRow = (props) => {
   const {
-    id: postId, postIndexInTopic, postCallHash, loading,
+    id: postId, postIndex, postCallHash, loading, focus,
   } = props;
   const getPostResults = useSelector((state) => state.contracts[FORUM_CONTRACT].getPost);
   const [postAuthorAddress, setPostAuthorAddress] = useState(null);
   const [postAuthor, setPostAuthor] = useState(null);
   const [timeAgo, setTimeAgo] = useState(null);
+  const [topicId, setTopicId] = useState(null);
   const [postContent, setPostContent] = useState(null);
   const [postAuthorMeta, setPostAuthorMeta] = useState(null);
   const userAddress = useSelector((state) => state.user.address);
@@ -41,6 +42,7 @@ const PostListRow = (props) => {
       setPostAuthorAddress(getPostResults[postCallHash].value[0]);
       setPostAuthor(getPostResults[postCallHash].value[1]);
       setTimeAgo(getPostResults[postCallHash].value[2] * 1000);
+      setTopicId(getPostResults[postCallHash].value[3]);
     }
   }, [getPostResults, loading, postCallHash]);
 
@@ -116,18 +118,31 @@ const PostListRow = (props) => {
     return authorAvatar;
   }, [authorAvatar, postAuthorAddress]);
 
+  const focusRef = useCallback((node) => {
+    if (focus && node !== null) {
+      node.scrollIntoView({ behavior: 'smooth' });
+    }
+  }, [focus]);
+
   return useMemo(() => (
-      <Dimmer.Dimmable as={Feed.Event} blurring dimmed={loading}>
+      <Dimmer.Dimmable
+        as={Feed.Event}
+        blurring
+        dimmed={loading}
+        id={`post-${postId}`}
+      >
+          <Ref innerRef={focusRef}>
               <Feed.Label className="post-profile-picture">
                   {authorAvatarLink}
               </Feed.Label>
+          </Ref>
           <Feed.Content>
               <Feed.Summary>
-                  <div>
+                  <Link to={`/topics/${topicId}/#post-${postId}`}>
                       <span className="post-summary-meta-index">
-                          {t('post.list.row.post.id', { id: postIndexInTopic })}
+                          {t('post.list.row.post.id', { id: postIndex })}
                       </span>
-                  </div>
+                  </Link>
                   {postAuthor !== null && setPostAuthorAddress !== null && timeAgo !== null
                     ? (
                         <>
@@ -147,19 +162,22 @@ const PostListRow = (props) => {
           </Feed.Content>
       </Dimmer.Dimmable>
   ), [
-    authorAvatarLink, loading, postAuthor, postAuthorAddress, postContent, postIndexInTopic, t, timeAgo,
+    authorAvatarLink, focusRef, loading, postAuthor, postAuthorAddress, postContent, postId, postIndex, t, timeAgo,
+    topicId,
   ]);
 };
 
 PostListRow.defaultProps = {
   loading: false,
+  focus: false,
 };
 
 PostListRow.propTypes = {
   id: PropTypes.number.isRequired,
-  postIndexInTopic: PropTypes.number.isRequired,
+  postIndex: PropTypes.number.isRequired,
   postCallHash: PropTypes.string,
   loading: PropTypes.bool,
+  focus: PropTypes.bool,
 };
 
 export default memo(PostListRow);

packages/concordia-app/src/components/PostList/index.jsx

@@ -11,7 +11,7 @@ import { FORUM_CONTRACT } from '../../constants/contracts/ContractNames';
 const { contracts: { [FORUM_CONTRACT]: { methods: { getPost: { cacheCall: getPostChainData } } } } } = drizzle;
 
 const PostList = (props) => {
-  const { postIds, loading } = props;
+  const { postIds, loading, focusOnPost } = props;
   const [getPostCallHashes, setGetPostCallHashes] = useState([]);
   const drizzleInitialized = useSelector((state) => state.drizzleStatus.initialized);
   const drizzleInitializationFailed = useSelector((state) => state.drizzleStatus.failed);
@@ -47,14 +47,15 @@ const PostList = (props) => {
         return (
             <PostListRow
               id={postId}
-              postIndexInTopic={index + 1}
+              postIndex={index + 1}
               key={postId}
               postCallHash={postHash && postHash.hash}
               loading={postHash === undefined}
+              focus={postId === focusOnPost}
             />
         );
       });
-  }, [getPostCallHashes, loading, postIds]);
+  }, [focusOnPost, getPostCallHashes, loading, postIds]);
 
   return (
       <Dimmer.Dimmable as={Feed} blurring dimmed={loading} id="post-list" size="large">
@@ -67,6 +68,7 @@ const PostList = (props) => {
 PostList.propTypes = {
   postIds: PropTypes.arrayOf(PropTypes.number).isRequired,
   loading: PropTypes.bool,
+  focusOnPost: PropTypes.number,
 };
 
 export default PostList;

packages/concordia-app/src/views/Home/index.jsx

@@ -8,20 +8,20 @@ import './styles.css';
 import { drizzle } from '../../redux/store';
 import { FORUM_CONTRACT } from '../../constants/contracts/ContractNames';
 
-const { contracts: { [FORUM_CONTRACT]: { methods: { getNumberOfTopics } } } } = drizzle;
+const { contracts: { [FORUM_CONTRACT]: { methods: { numTopics } } } } = drizzle;
 
 const Home = () => {
   const [numberOfTopicsCallHash, setNumberOfTopicsCallHash] = useState('');
-  const getNumberOfTopicsResults = useSelector((state) => state.contracts[FORUM_CONTRACT].getNumberOfTopics);
+  const numTopicsResults = useSelector((state) => state.contracts[FORUM_CONTRACT].numTopics);
 
   useEffect(() => {
-    setNumberOfTopicsCallHash(getNumberOfTopics.cacheCall());
+    setNumberOfTopicsCallHash(numTopics.cacheCall());
   }, []);
 
-  const numberOfTopics = useMemo(() => (getNumberOfTopicsResults[numberOfTopicsCallHash] !== undefined
+  const numberOfTopics = useMemo(() => (numTopicsResults[numberOfTopicsCallHash] !== undefined
-    ? parseInt(getNumberOfTopicsResults[numberOfTopicsCallHash].value, 10)
+    ? parseInt(numTopicsResults[numberOfTopicsCallHash].value, 10)
     : null),
-  [getNumberOfTopicsResults, numberOfTopicsCallHash]);
+  [numTopicsResults, numberOfTopicsCallHash]);
 
   return useMemo(() => (
       <Container id="home-container" textAlign="center">

packages/concordia-app/src/views/Topic/TopicView/index.jsx

@@ -24,7 +24,7 @@ const { orbit } = breeze;
 const TopicView = (props) => {
   const {
     topicId, topicAuthorAddress: initialTopicAuthorAddress, topicAuthor: initialTopicAuthor,
-    timestamp: initialTimestamp, postIds: initialPostIds,
+    timestamp: initialTimestamp, postIds: initialPostIds, focusOnPost,
   } = props;
   const drizzleInitialized = useSelector((state) => state.drizzleStatus.initialized);
   const drizzleInitializationFailed = useSelector((state) => state.drizzleStatus.failed);
@@ -174,7 +174,7 @@ const TopicView = (props) => {
                   </Step>
               </Step.Group>
           </Dimmer.Dimmable>
-          <PostList postIds={postIds || []} loading={postIds === null} />
+          <PostList postIds={postIds || []} loading={postIds === null} focusOnPost={focusOnPost} />
           {topicSubject !== null && postIds !== null && hasSignedUp && (
               <PostCreate
                 topicId={topicId}
@@ -192,6 +192,7 @@ TopicView.propTypes = {
   topicAuthor: PropTypes.string,
   timestamp: PropTypes.number,
   postIds: PropTypes.arrayOf(PropTypes.number),
+  focusOnPost: PropTypes.number,
 };
 
 export default TopicView;

packages/concordia-app/src/views/Topic/index.jsx

@@ -1,18 +1,22 @@
 import React from 'react';
-import { useRouteMatch } from 'react-router';
+import { useLocation, useRouteMatch } from 'react-router';
 import TopicCreate from './TopicCreate';
 import TopicView from './TopicView';
 
 const Topic = () => {
   const match = useRouteMatch();
   const { id: topicId } = match.params;
+  const location = useLocation();
+  const postHash = location.hash;
+  const postId = postHash ? postHash.substring('#post-'.length) : null;
+  const focusPostId = postId ? parseInt(postId, 10) : null;
 
   return topicId === 'new'
     ? (
         <TopicCreate />
     )
     : (
-        <TopicView topicId={parseInt(topicId, 10)} />
+        <TopicView topicId={parseInt(topicId, 10)} focusOnPost={focusPostId} />
     );
 };
 

packages/concordia-contracts/.eslintrc.js

@@ -31,7 +31,9 @@ module.exports = {
         'no-unused-vars': 'warn',
         'no-console': 'warn',
         'no-shadow': 'warn',
-        "no-multi-str": "warn"
+        'no-multi-str': 'warn',
+        'one-var': ["error", { "uninitialized": "always" }],
+        'one-var-declaration-per-line': ['error', 'initializations']
     },
     'settings': {
         'import/resolver': {

packages/concordia-contracts/.solhint.json

@@ -1,3 +1,9 @@
 {
-  "extends": "solhint:default"
+  "extends": "solhint:recommended",
+  "rules": {
+    "compiler-version": ["error","~0.8.0"],
+    "func-visibility": ["warn",{"ignoreConstructors" : true}],
+    "not-rely-on-time": "off",
+    "state-visibility": "off"
+  }
 }

packages/concordia-contracts/contracts/Forum.sol

@@ -1,8 +1,12 @@
 //SPDX-License-Identifier: MIT
-pragma solidity 0.7.1;
+pragma solidity 0.8.0;
-pragma experimental ABIEncoderV2;
 
 contract Forum {
+    // Error messages for require()
+    string public constant USER_HAS_NOT_SIGNED_UP = "User hasn't signed up yet.";
+    string public constant USERNAME_TAKEN = "Username is already taken.";
+    string public constant TOPIC_DOES_NOT_EXIST = "Topic doesn't exist.";
+    string public constant POST_DOES_NOT_EXIST = "Post doesn't exist.";
 
     //----------------------------------------USER----------------------------------------
     struct User {
@@ -20,18 +24,17 @@ contract Forum {
     event UsernameUpdated(string newName, string oldName, address userAddress);
 
     function signUp(string memory username) public returns (bool) {
-        require (!hasUserSignedUp(msg.sender), "User has already signed up.");
+        require(!hasUserSignedUp(msg.sender), USER_HAS_NOT_SIGNED_UP);
-        require(!isUserNameTaken(username), "Username is already taken.");
+        require(!isUserNameTaken(username), USERNAME_TAKEN);
-        users[msg.sender] = User(username,
+        users[msg.sender] = User(username, new uint[](0), new uint[](0), block.timestamp, true);
-            new uint[](0), new uint[](0), block.timestamp, true);
         userAddresses[username] = msg.sender;
         emit UserSignedUp(username, msg.sender);
         return true;
     }
 
     function updateUsername(string memory newUsername) public returns (bool) {
-        require (hasUserSignedUp(msg.sender), "User hasn't signed up yet.");
+        require(hasUserSignedUp(msg.sender), USER_HAS_NOT_SIGNED_UP);
-        require(!isUserNameTaken(newUsername), "Username is already taken.");
+        require(!isUserNameTaken(newUsername), USERNAME_TAKEN);
         string memory oldUsername = getUsername(msg.sender);
         delete userAddresses[users[msg.sender].username];
         users[msg.sender].username = newUsername;
@@ -41,7 +44,7 @@ contract Forum {
     }
 
     function getUsername(address userAddress) public view returns (string memory) {
-        require (hasUserSignedUp(userAddress), "User hasn't signed up yet.");
+        require(hasUserSignedUp(userAddress), USER_HAS_NOT_SIGNED_UP);
         return users[userAddress].username;
     }
 
@@ -60,22 +63,22 @@ contract Forum {
     }
 
     function getUserTopics(address userAddress) public view returns (uint[] memory) {
-        require (hasUserSignedUp(userAddress), "User hasn't signed up yet.");
+        require(hasUserSignedUp(userAddress), USER_HAS_NOT_SIGNED_UP);
         return users[userAddress].topicIDs;
     }
 
     function getUserPosts(address userAddress) public view returns (uint[] memory) {
-        require (hasUserSignedUp(userAddress), "User hasn't signed up yet.");
+        require(hasUserSignedUp(userAddress), USER_HAS_NOT_SIGNED_UP);
         return users[userAddress].postIDs;
     }
 
     function getUserDateOfRegister(address userAddress) public view returns (uint) {
-        require (hasUserSignedUp(userAddress), "User hasn't signed up yet.");
+        require(hasUserSignedUp(userAddress), USER_HAS_NOT_SIGNED_UP);
         return users[userAddress].timestamp;
     }
 
     function getUser(address userAddress) public view returns (User memory) {
-        require(hasUserSignedUp(userAddress), "User hasn't signed up yet.");
+        require(hasUserSignedUp(userAddress), USER_HAS_NOT_SIGNED_UP);
         return users[userAddress];
     }
 
@@ -94,8 +97,8 @@ contract Forum {
         uint topicID;
     }
 
-    uint numTopics;   // Total number of topics
+    uint public numTopics;   // Total number of topics
-    uint numPosts;    // Total number of posts
+    uint public numPosts;    // Total number of posts
 
     mapping(uint => Topic) topics;
     mapping(uint => Post) posts;
@@ -104,7 +107,7 @@ contract Forum {
     event PostCreated(uint postID, uint topicID);
 
     function createTopic() public returns (uint, uint) {
-        require(hasUserSignedUp(msg.sender));  // Only registered users can create topics
+        require(hasUserSignedUp(msg.sender), USER_HAS_NOT_SIGNED_UP);
         //Creates topic
         uint topicID = numTopics++;
         topics[topicID] = Topic(topicID, msg.sender, block.timestamp, new uint[](0));
@@ -121,8 +124,8 @@ contract Forum {
     }
 
     function createPost(uint topicID) public returns (uint) {
-        require(hasUserSignedUp(msg.sender));  // Only registered users can create posts
+        require(hasUserSignedUp(msg.sender), USER_HAS_NOT_SIGNED_UP);
-        require(topicID<numTopics); // Only allow posting to a topic that exists
+        require(topicExists(topicID), TOPIC_DOES_NOT_EXIST);
         uint postID = numPosts++;
         posts[postID] = Post(postID, msg.sender, block.timestamp, topicID);
         topics[topicID].postIDs.push(postID);
@@ -131,12 +134,16 @@ contract Forum {
         return postID;
     }
 
-    function getNumberOfTopics() public view returns (uint) {
+    function topicExists(uint topicID) public view returns (bool) {
-        return numTopics;
+        return topicID < numTopics;
+    }
+
+    function postExists(uint postID) public view returns (bool) {
+        return postID < numPosts;
     }
 
     function getTopic(uint topicID) public view returns (address, string memory, uint, uint[] memory) {
-        require(topicID<numTopics);
+        require(topicExists(topicID), TOPIC_DOES_NOT_EXIST);
         return (
             topics[topicID].author,
             users[topics[topicID].author].username,
@@ -146,12 +153,17 @@ contract Forum {
     }
 
     function getTopicPosts(uint topicID) public view returns (uint[] memory) {
-        require(topicID<numTopics); // Topic should exist
+        require(topicExists(topicID), TOPIC_DOES_NOT_EXIST);
         return topics[topicID].postIDs;
     }
 
+    function getTopicAuthor(uint topicID) public view returns (address) {
+        require(topicExists(topicID), TOPIC_DOES_NOT_EXIST);
+        return topics[topicID].author;
+    }
+
     function getPost(uint postID) public view returns (address, string memory, uint, uint) {
-        require(postID<numPosts);
+        require(postExists(postID), POST_DOES_NOT_EXIST);
         return (
             posts[postID].author,
             users[posts[postID].author].username,

packages/concordia-contracts/contracts/Migrations.sol

@@ -1,9 +1,9 @@
 //SPDX-License-Identifier: MIT
-pragma solidity 0.7.1;
+pragma solidity 0.8.0;
 
 contract Migrations {
     address public owner;
-    uint public last_completed_migration;
+    uint public lastCompletedMigration;
 
     constructor() {
         owner = msg.sender;
@@ -14,11 +14,11 @@ contract Migrations {
     }
 
     function setCompleted(uint completed) public restricted {
-        last_completed_migration = completed;
+        lastCompletedMigration = completed;
     }
 
-    function upgrade(address new_address) public restricted {
+    function upgrade(address newAddress) public restricted {
-        Migrations upgraded = Migrations(new_address);
+        Migrations upgraded = Migrations(newAddress);
-        upgraded.setCompleted(last_completed_migration);
+        upgraded.setCompleted(lastCompletedMigration);
     }
 }

packages/concordia-contracts/contracts/PostVoting.sol

@@ -0,0 +1,109 @@
+//SPDX-License-Identifier: MIT
+pragma solidity 0.8.0;
+
+import "./Forum.sol";
+
+contract PostVoting {
+    Forum public forum;
+
+    constructor(Forum addr) {
+        forum = Forum(addr);
+    }
+
+    enum Option { DEFAULT, UP, DOWN }  // DEFAULT -> 0, UP -> 1, DOWN -> 2
+
+    struct PostBallot {
+        mapping(address => Option) votes;
+        mapping(Option => address[]) voters;
+    }
+
+    mapping(uint => PostBallot) postBallots;
+
+    event UserVotedPost(address userAddress, uint postID, Option option);
+
+    function getVote(uint postID, address voter) public view returns (Option) {
+        require(forum.postExists(postID), forum.POST_DOES_NOT_EXIST());
+        return postBallots[postID].votes[voter];
+    }
+
+    // Gets vote count for a specific option (Option.UP/ Option.DOWN only!)
+    function getVoteCount(uint postID, Option option) private view returns (uint) {
+        require(forum.postExists(postID), forum.POST_DOES_NOT_EXIST());
+        return (postBallots[postID].voters[option].length);
+    }
+
+    function getUpvoteCount(uint postID) public view returns (uint) {
+        return (getVoteCount(postID, Option.UP));
+    }
+
+    function getDownvoteCount(uint postID) public view returns (uint) {
+        return (getVoteCount(postID, Option.DOWN));
+    }
+
+    // Gets voters for a specific option (Option.UP/ Option.DOWN)
+    function getVoters(uint postID, Option option) private view returns (address[] memory) {
+        require(forum.postExists(postID), forum.POST_DOES_NOT_EXIST());
+        return (postBallots[postID].voters[option]);
+    }
+
+    function getUpvoters(uint postID) public view returns (address[] memory) {
+        return (getVoters(postID, Option.UP));
+    }
+
+    function getDownvoters(uint postID) public view returns (address[] memory) {
+        return (getVoters(postID, Option.DOWN));
+    }
+
+    function getVoterIndex(uint postID, address voter) private view returns (uint) {
+        require(forum.hasUserSignedUp(voter), forum.USER_HAS_NOT_SIGNED_UP());
+        require(forum.postExists(postID), forum.POST_DOES_NOT_EXIST());
+
+        PostBallot storage postBallot = postBallots[postID];
+        Option votedOption = getVote(postID, voter);
+        address[] storage optionVoters = postBallot.voters[votedOption];
+
+        for (uint voterIndex = 0; voterIndex < optionVoters.length; voterIndex++)
+            if (optionVoters[voterIndex] == voter)
+                return voterIndex;
+
+        revert("Couldn't find voter's index!");
+    }
+
+    function vote(uint postID, Option option) private {
+        require(forum.hasUserSignedUp(msg.sender), forum.USER_HAS_NOT_SIGNED_UP());
+        require(forum.postExists(postID), forum.POST_DOES_NOT_EXIST());
+
+        PostBallot storage postBallot = postBallots[postID];
+        address voter = msg.sender;
+        Option prevOption = postBallot.votes[voter];
+
+        if (prevOption == option)
+            return;
+
+        // Remove previous vote if exists
+        if (prevOption != Option.DEFAULT) {
+            uint voterIndex = getVoterIndex(postID, voter);
+            // Swap with last voter address and delete vote
+            postBallot.voters[prevOption][voterIndex] = postBallot.voters[prevOption][postBallot.voters[prevOption].length - 1];
+            postBallot.voters[prevOption].pop();
+        }
+
+        // Add new vote
+        if (option != Option.DEFAULT)
+            postBallot.voters[option].push(voter);
+        postBallot.votes[voter] = option;
+        emit UserVotedPost(voter, postID, option);
+    }
+
+    function upvote(uint postID) public {
+        vote(postID, Option.UP);
+    }
+
+    function downvote(uint postID) public {
+        vote(postID, Option.DOWN);
+    }
+
+    function unvote(uint postID) public {
+        vote(postID, Option.DEFAULT);
+    }
+}

packages/concordia-contracts/contracts/Voting.sol

@@ -0,0 +1,155 @@
+//SPDX-License-Identifier: MIT
+pragma solidity 0.8.0;
+
+import "./Forum.sol";
+
+contract Voting {
+    // Error messages for require()
+    string constant TOPIC_POLL_DIFFERENT_CREATOR = "Only topic's author can create a poll.";
+    string constant POLL_EXISTS = "Poll already exists.";
+    string constant POLL_DOES_NOT_EXIST = "Poll does not exist.";
+    string constant INVALID_OPTION = "Invalid option.";
+    string constant USER_HAS_NOT_VOTED = "User hasn't voted.";
+
+    Forum public forum;
+
+    constructor(Forum addr) {
+        forum = Forum(addr);
+    }
+
+    struct Poll {
+        uint topicID;
+        uint numOptions;
+        string dataHash;
+        mapping(address => uint) votes;
+        mapping(uint => address[]) voters;
+        bool enableVoteChanges;
+        uint timestamp;
+    }
+
+    mapping(uint => Poll) polls;
+
+    event PollCreated(uint topicID);
+    event UserVotedPoll(address userAddress, uint topicID, uint vote);
+
+    function pollExists(uint topicID) public view returns (bool) {
+        if (polls[topicID].timestamp != 0)
+            return true;
+        return false;
+    }
+
+    function createPoll(uint topicID, uint numOptions, string memory dataHash, bool enableVoteChanges) public returns (uint) {
+        require(forum.hasUserSignedUp(msg.sender), forum.USER_HAS_NOT_SIGNED_UP());
+        require(forum.topicExists(topicID), forum.TOPIC_DOES_NOT_EXIST());
+        require(forum.getTopicAuthor(topicID) == msg.sender, TOPIC_POLL_DIFFERENT_CREATOR);
+        require(!pollExists(topicID), POLL_EXISTS);
+
+        Poll storage poll = polls[topicID];
+        poll.topicID = topicID;
+        poll.numOptions = numOptions;
+        poll.dataHash = dataHash;
+        poll.enableVoteChanges = enableVoteChanges;
+        poll.timestamp = block.timestamp;
+
+        emit PollCreated(topicID);
+        return topicID;
+    }
+
+    function getPollInfo(uint topicID) public view returns (uint, string memory, uint, uint) {
+        require(pollExists(topicID), POLL_DOES_NOT_EXIST);
+
+        uint totalVotes = getTotalVotes(topicID);
+
+        return (
+        polls[topicID].numOptions,
+        polls[topicID].dataHash,
+        polls[topicID].timestamp,
+        totalVotes
+        );
+    }
+
+    function isOptionValid(uint topicID, uint option) public view returns (bool) {
+        require(pollExists(topicID), POLL_DOES_NOT_EXIST);
+        if (option <= polls[topicID].numOptions)    // Option 0 is valid as well (no option chosen)
+            return true;
+        return false;
+    }
+
+    function hasVoted(uint topicID, address voter) public view returns (bool) {
+        require(pollExists(topicID), POLL_DOES_NOT_EXIST);
+        if (polls[topicID].votes[voter] != 0)
+            return true;
+        return false;
+    }
+
+    function getVote(uint topicID, address voter) public view returns (uint) {
+        require(hasVoted(topicID, voter), USER_HAS_NOT_VOTED);
+        return polls[topicID].votes[voter];
+    }
+
+    function getVoteCount(uint topicID, uint option) public view returns (uint) {
+        require(pollExists(topicID), POLL_DOES_NOT_EXIST);
+        require(isOptionValid(topicID, option), INVALID_OPTION);
+        return (polls[topicID].voters[option].length);
+    }
+
+    function getTotalVotes(uint topicID) public view returns (uint) {
+        require(pollExists(topicID), POLL_DOES_NOT_EXIST);
+
+        Poll storage poll = polls[topicID];
+        uint totalVotes = 0;
+
+        for (uint pollOption = 1; pollOption <= poll.numOptions; pollOption++)
+            totalVotes += poll.voters[pollOption].length;
+
+        return totalVotes;
+    }
+
+    // Gets voters for a specific option
+    function getVoters(uint topicID, uint option) public view returns (address[] memory) {
+        require(pollExists(topicID), POLL_DOES_NOT_EXIST);
+        return (polls[topicID].voters[option]);
+    }
+
+    function getVoterIndex(uint topicID, address voter) public view returns (uint) {
+        require(pollExists(topicID), POLL_DOES_NOT_EXIST);
+        require(hasVoted(topicID, voter), USER_HAS_NOT_VOTED);
+        Poll storage poll = polls[topicID];
+        uint votedOption = getVote(topicID, voter);
+        address[] storage optionVoters = poll.voters[votedOption];
+
+        for (uint voterIndex = 0; voterIndex < optionVoters.length; voterIndex++)
+            if (optionVoters[voterIndex] == voter)
+                return voterIndex;
+
+        revert("Couldn't find voter's index!");
+    }
+
+    function vote(uint topicID, uint option) public {
+        require(forum.hasUserSignedUp(msg.sender), forum.USER_HAS_NOT_SIGNED_UP());
+        require(pollExists(topicID), POLL_DOES_NOT_EXIST);
+        require(isOptionValid(topicID, option), INVALID_OPTION);
+        Poll storage poll = polls[topicID];
+        address voter = msg.sender;
+        uint prevOption = poll.votes[voter];
+        if (prevOption == option)
+            return;
+
+        // Voter hasn't voted before
+        if (prevOption == 0) {
+            poll.voters[option].push(voter);
+            poll.votes[voter] = option;
+            emit UserVotedPoll(voter, topicID, option);
+        }
+        else if (poll.enableVoteChanges) {
+            uint voterIndex = getVoterIndex(topicID, voter);
+            // Swap with last voter address and delete vote
+            poll.voters[prevOption][voterIndex] = poll.voters[prevOption][poll.voters[prevOption].length - 1];
+            poll.voters[prevOption].pop();
+            if (option != 0)
+                poll.voters[option].push(voter);
+            poll.votes[voter] = option;
+            emit UserVotedPoll(voter, topicID, option);
+        }
+    }
+}

packages/concordia-contracts/index.js

@@ -1,14 +1,16 @@
-let Forum;
+let Forum, Voting, PostVoting;
 
+/* eslint-disable global-require */
 try {
-  // eslint-disable-next-line global-require
   Forum = require('./build/Forum.json');
+  Voting = require('./build/Voting.json');
+  PostVoting = require('./build/PostVoting.json');
 } catch (e) {
   // eslint-disable-next-line no-console
   console.error("Could not require contract artifacts. Haven't you run compile yet?");
 }
 
 module.exports = {
-  contracts: [Forum],
+  contracts: [Forum, Voting, PostVoting],
   forumContract: Forum,
 };

packages/concordia-contracts/migrations/2_deploy_contracts.js

@@ -1,6 +1,12 @@
 const Forum = artifacts.require('Forum');
+const Voting = artifacts.require('Voting');
+const PostVoting = artifacts.require('PostVoting');
 
 // eslint-disable-next-line func-names
 module.exports = function (deployer) {
-  deployer.deploy(Forum);
+  return deployer.deploy(Forum)
+    .then(async (forum) => Promise.all([
+      deployer.deploy(Voting, forum.address),
+      deployer.deploy(PostVoting, forum.address),
+    ]));
 };

packages/concordia-contracts/package.json

@@ -16,7 +16,7 @@
   },
   "dependencies": {
     "@openzeppelin/contracts": "~3.2.0",
-    "truffle": "~5.1.45"
+    "truffle": "~5.1.55"
   },
   "devDependencies": {
     "eslint": "^6.8.0",

packages/concordia-contracts/test/TestVoting.sol

@@ -0,0 +1,112 @@
+//SPDX-License-Identifier: MIT
+pragma solidity 0.8.0;
+
+import "truffle/Assert.sol";
+import "truffle/DeployedAddresses.sol";
+import "../contracts/Forum.sol";
+import "../contracts/Voting.sol";
+
+contract TestVoting {
+    Forum forum;
+    uint firstTopicId;
+
+    function beforeAll() public {
+        forum = Forum(DeployedAddresses.Forum());
+
+        forum.signUp("testAccount");
+        (firstTopicId,) = forum.createTopic();
+    }
+
+    function testIfPollExists() public {
+        Voting voting = Voting(DeployedAddresses.Voting());
+
+        bool actual = voting.pollExists(firstTopicId);
+
+        Assert.equal(actual, false, "Poll should not exist");
+    }
+
+    function testCreatePoll() public {
+        Voting voting = Voting(DeployedAddresses.Voting());
+
+        uint actual = voting.createPoll(firstTopicId, 3, "asdf", false);
+
+        Assert.equal(actual, firstTopicId, "Topic Id should be 1");
+    }
+
+    function testGetTotalVotes() public {
+        Voting voting = Voting(DeployedAddresses.Voting());
+
+        uint actual = voting.getTotalVotes(firstTopicId);
+
+        Assert.equal(actual, 0, "Topic Id should be 0");
+    }
+
+    function testGetPollInfo() public {
+        Voting voting = Voting(DeployedAddresses.Voting());
+
+        (uint actualNumberOfOptions, string memory actualDataHash, , uint actualNumberOfVotes) = voting.getPollInfo(firstTopicId);
+
+        Assert.equal(actualNumberOfOptions, 3, "Number of votes should be 0");
+        Assert.equal(actualDataHash, "asdf", "Number of votes should be 0");
+        Assert.equal(actualNumberOfVotes, 0, "Number of votes should be 0");
+    }
+
+    function testVote() public {
+        Voting voting = Voting(DeployedAddresses.Voting());
+
+        voting.vote(firstTopicId, 1);
+        uint votesActual = voting.getTotalVotes(firstTopicId);
+
+        Assert.equal(votesActual, 1, "Number of votes should be 1");
+    }
+
+    function testGetVoteCount() public {
+        Voting voting = Voting(DeployedAddresses.Voting());
+
+        uint actualVotesOption0 = voting.getVoteCount(firstTopicId, 1);
+        uint actualVotesOption1 = voting.getVoteCount(firstTopicId, 2);
+        uint actualVotesOption2 = voting.getVoteCount(firstTopicId, 3);
+
+        Assert.equal(actualVotesOption0, 1, "Vote count is not correct");
+        Assert.equal(actualVotesOption1, 0, "Vote count is not correct");
+        Assert.equal(actualVotesOption2, 0, "Vote count is not correct");
+    }
+
+    function testChangeVoteWhenDisabled() public {
+        Voting voting = Voting(DeployedAddresses.Voting());
+
+        (uint topicId,) = forum.createTopic();
+        voting.createPoll(topicId, 3, "asdf", false);
+
+        voting.vote(topicId, 1);
+        uint actualVotesOption0 = voting.getVoteCount(topicId, 1);
+        uint actualVotesOption1 = voting.getVoteCount(topicId, 2);
+        voting.vote(topicId, 2);
+        uint actualVotesOption2 = voting.getVoteCount(topicId, 1);
+        uint actualVotesOption3 = voting.getVoteCount(topicId, 2);
+
+        Assert.equal(actualVotesOption0, 1, "Number of votes should be 1");
+        Assert.equal(actualVotesOption1, 0, "Number of votes should be 0");
+        Assert.equal(actualVotesOption2, 1, "Number of votes should be 1");
+        Assert.equal(actualVotesOption3, 0, "Number of votes should be 0");
+    }
+
+    function testChangeVoteWhenEnabled() public {
+        Voting voting = Voting(DeployedAddresses.Voting());
+
+        (uint topicId,) = forum.createTopic();
+        voting.createPoll(topicId, 3, "asdf", true);
+
+        voting.vote(topicId, 1);
+        uint actualVotesOption0 = voting.getVoteCount(topicId, 1);
+        uint actualVotesOption1 = voting.getVoteCount(topicId, 2);
+        voting.vote(topicId, 2);
+        uint actualVotesOption2 = voting.getVoteCount(topicId, 1);
+        uint actualVotesOption3 = voting.getVoteCount(topicId, 2);
+
+        Assert.equal(actualVotesOption0, 1, "Number of votes should be 1");
+        Assert.equal(actualVotesOption1, 0, "Number of votes should be 0");
+        Assert.equal(actualVotesOption2, 0, "Number of votes should be 0");
+        Assert.equal(actualVotesOption3, 1, "Number of votes should be 1");
+    }
+}

packages/concordia-contracts/truffle-config.js

@@ -10,7 +10,7 @@ module.exports = {
   // to customize your Truffle configuration!
   compilers: {
     solc: {
-      version: '0.7.1',
+      version: '0.8.0',
     },
   },
   contracts_build_directory: path.join(__dirname, 'build/'),