nearoverflow

NEAR dApp (Smart Contract) that is somehow replicates StackOverflow functionality.

Demo of the Contract usage: https://khorolets.github.io/nearoverflow-demo
Frontend repository: https://github.com/khorolets/nearoverflow-demo

What does it do?

Someone asks a question and pays 10 Ⓝ for that (can be custom amount >= 10 Ⓝ)
Question appears in the list
Anyone can answer a question (it costs 1 Ⓝ)
Original question author can choose what answer is correct (on his/her opinion)
Author of the "correct" answer gets question reward (>= 10 Ⓝ) NB! Author can't select his own answer to avoid fraud schemes.
Anyone can upvote the answer for 1 Ⓝ that is immediately transfared to answer author
That's all.

Contract methods

View methods

list_questions() -> HashMap<String, Question>

Returns JSON object where keys are question IDs and values are Question object.

Response Example:

{
    "1": {
        "author_account_id": "account_id_string",
        "content": "Content of the question",
        "reward": 10 000000000000000000000000, // Reward amount (10 Ⓝ)
        "answers": [
            {
                "id": 1, // ID of the answer
                "content": "Content of the answer",
                "account_id": "account_id_of_the_answerer",
                "reward": 0, // Amount of reward that answer already gain
                "is_correct": false // true if this answer is chosen as correct
            },
            ...
        ]
    },
    ...
}

Change methods

create_question(content: String, reward: u128) Must attach >= 10 Ⓝ

Creates question. Creates or increses signer's stake with attached amount. Tokens are hold by the Contract for further transfer to the correct answer (BTW for now we have no mechanism to force fraud author to select correct answer, it's not the point of this example)

create_answer(question_id: u32, content) Must attach 1 Ⓝ

Adds answer to the question with question_id. We still can add answers for any questions even if question alredy has "correct" answer.

upvote_answer(question_id: u32, answer_id: u32) Must attach 1 Ⓝ

Transfers 1 Ⓝ to the author of the answer with answer_id for the question with question_id, increases reward property for the answer, so everybody can see upvotes.

set_correct_answer(question_id: u32, answer_id: u32)

May be called only by author of the question with question_id (author is the account in author_account_id of the question).

Set is_correct to true for the answer with answer_id in quesion with question_id. Transfers question reward to answer author, decreases stake for question author.

Structs used

Stakes

Alias of HashMap<String, u128> to keep an eye on how many tokens question authors "deposited" to the Contract

Question

Holds necessary information about the question

content: String - The question text
reward: u128 - Amount of tokens that will be transferred to an author of "correct" answer
author_account_id: String - Account id of the question author
answers: Vec - List of answers added to the question

Answer

Holds necessary information abut the answer

id: u32 - Incremental id of the answer for the question (ids can repeat in different questions)
content: String - The answer text
account_id: String - Account id of the answer author
reward: u128 - Amount of tokens were transferred to the answer author (after upvoting or setting answer as "correct")
is_correct: bool - Becomes true only if question author marked this answer as "correct"

Ledger

This is the main state of the Contract

stakes: Stakes - hold the staked (deposits)
questions: HashMap<u32, Question> - holds all the questions

khorolets/nearoverflow