Quiz API by Mateusz Okulus

Running

Copy .env.example to .env

cp .env.example .env

Start the database

docker compose up --build --detach

Database will be initialized with the schema contained in database folder.

If you want to reset the database

docker compose down
docker volume rm quiz-api_postgres-data
docker compose up --build --detach

Install packages and start server.

# install packages
npm install
# generate types based on GraphQL schema
npm run generate-typings
# run tests
npm run test
# start dev server
npm run start:dev

You can now go to http://localhost:3000/graphql to visit GraphQL playground.

GraphQL queries and mutations

Create a quiz

mutation {
  createQuiz(
    createQuizInput: {
      name: "My awesome quiz"
      questions: [
        {
          singleChoiceQuestionInput: {
            prompt: "What is the capital of France?"
            answers: ["London", "Paris", "Berlin", "Madrid"]
            correctAnswer: "Paris"
          }
        }
        {
          multipleChoiceQuestionInput: {
            prompt: "Which countries are in Europe?"
            answers: ["Monaco", "Morocco", "Poland", "Algeria"]
            correctAnswers: ["Poland", "Monaco"]
          }
        }
        {
          sortingQuestionInput: {
            prompt: "Sort the letters"
            answers: ["B", "C", "A"]
            correctOrder: ["A", "B", "C"]
          }
        }
        {
          textQuestionInput: {
            prompt: "What is the famous phrase from Star Wars? "
            correctAnswer: "May the force be with you!"
          }
        }
      ]
    }
  ) {
    id
    name
    questions {
      id
      prompt
      ... on SingleChoiceQuestion {
        answers
        correctAnswer
      }
      ... on MultipleChoiceQuestion {
        answers
        correctAnswers
      }
      ... on SortingQuestion {
        answers
        correctOrder
      }
      ... on TextQuestion {
        correctAnswer
      }
    }
  }
}

Fetch all quizzes

query {
  quizzes {
    id
    name
    questions {
      id
      prompt
      ... on SingleChoiceQuestion {
        answers
        correctAnswer
      }
      ... on MultipleChoiceQuestion {
        answers
        correctAnswers
      }
      ... on SortingQuestion {
        answers
        correctOrder
      }
      ... on TextQuestion {
        correctAnswer
      }
    }
  }
}

Fetch a single quiz

query {
  quiz(id: 1) {
    id
    name
    questions {
      prompt
      ... on SingleChoiceQuestion {
        answers
        correctAnswer
      }
      ... on MultipleChoiceQuestion {
        answers
        correctAnswers
      }
      ... on SortingQuestion {
        answers
        correctOrder
      }
      ... on TextQuestion {
        correctAnswer
      }
    }
  }
}

Score a quiz

query {
  scoreQuizSubmission(
    quizSubmissionInput: {
      quizID: "1"
      submissions: [
        {
          questionID: 1
          singleChoiceQuestionSubmissionInput: { answer: "Paris" }
        }
        {
          questionID: 2
          multipleChoiceQuestionSubmissionInput: {
            answers: ["Monaco", "Poland"]
          }
        }
        {
          questionID: 3
          sortingQuestionSubmissionInput: { answers: ["A", "B", "C"] }
        }
        {
          questionID: 4
          textQuestionSubmissionInput: { answer: "may the force be with you" }
        }
      ]
    }
  ) {
    totalObtained
    totalMaximum
    scores {
      questionID
      obtained
      maximum
    }
  }
}

Update a quiz

Updating just name

mutation {
  updateQuiz(updateQuizInput: { id: 1, name: "New name for the quiz" }) {
    id
    name
    questions {
      id
      prompt
      ... on SingleChoiceQuestion {
        answers
        correctAnswer
      }
      ... on MultipleChoiceQuestion {
        answers
        correctAnswers
      }
      ... on SortingQuestion {
        answers
        correctOrder
      }
      ... on TextQuestion {
        correctAnswer
      }
    }
  }
}

Updating just questions

mutation {
  updateQuiz(
    updateQuizInput: {
      id: 1
      questions: [
        {
          singleChoiceQuestionInput: {
            prompt: "Is this the only question?"
            answers: ["Yes", "No"]
            correctAnswer: "Yes"
          }
        }
      ]
    }
  ) {
    id
    name
    questions {
      id
      prompt

      ... on SingleChoiceQuestion {
        answers
        correctAnswer
      }
      ... on MultipleChoiceQuestion {
        answers
        correctAnswers
      }
      ... on SortingQuestion {
        answers
        correctOrder
      }
      ... on TextQuestion {
        correctAnswer
      }
    }
  }
}

Remove a quiz

mutation {
  removeQuiz(id: 1) {
    id
    name
    questions {
      id
      prompt
      ... on SingleChoiceQuestion {
        answers
        correctAnswer
      }
      ... on MultipleChoiceQuestion {
        answers
        correctAnswers
      }
      ... on SortingQuestion {
        answers
        correctOrder
      }
      ... on TextQuestion {
        correctAnswer
      }
    }
  }
}

Further work

• More efficient SQL queries.

  Ideally SQL queries should only request what the GraphQL query requested. Field for SELECT should be dynamically generated, same for JOINs. For example, when the question prompt is not specified in GraphQL query, it shouldn't be requested in SQL query as well. Right now there is only basic handling of this in findAll and findById, which avoids the JOINs when questions are not requested. At the same time there should only be one round trip to the database, so things like @ResolveField don't seem appropriate.

  I couldn't find a good, established way of doing it with Nest.js. It seems most people parse the GraphQL query and roll their own solution.