feat: Implement `AssociationQuestionViewModel`

[apomalyn]

Requirements

Implement the AssociationQuestion model extending Question. It should be implemented using freezed

• the AssociationQuestion schema is available in #172

Implement a AssociationQuestionViewModel that:

• extends QuestionViewModel
• handle pair selection
• implement a method to validate the selected pair and display the correct flow depending on the answer:
  • classic error flow if wrong but don't go to the next question
  • disable the selected pair
  • if all pairs are answered go to the next question

What needs to be done

• Implement the AssociationQuestion model extending Question
  • format: QuestionFormats.association
  • instruction: InstructionTypes.custom
• Implement AssociationQuestionViewModel view-model under src/practice/questions:
  • extends QuestionViewModel
  • has a
  • int leftSelectedIndex = -1 indicates the current left item selected
  • int rightSelectedIndex = -1 indicates the current right item selected
  • bool error = false
  • List<{String text, String? tts, bool isDisabled = false}> leftColumn
  • List<{String text, String? tts, bool isDisabled = false}> rightColumn
  • int _remainingPairs
  • constructor:
  • takes:
    • AssociationQuestion question
    • everything from QuestionViewModel constructor
  • initialise leftColumn and rightColumn based on the question.pairs. Shuffle the columns after initialization
  • set _remainingPairs = question.pairs.lenght
  • implement a _reset(), it should:
  • leftSelectedIndex = -1
  • rightSelectedIndex = -1
  • error = false
  • implement a _validateSelectedPair(), it should:
  • leftSelectedIndex == -1 || rightSelectedIndex == -1 stop there
  • find the AssociationQuestionPair associated with leftColumn[leftSelectedIndex], check if the rightColumn[rightSelectedIndex] correspond to the pair.
    • if incorrect pair:
    • error should be true
    • reduce the KnowledgeUpdate associated with the pair by 1.
    • call _onError(false, isFinished: false, onContinuePressed: _reset)
    • if correct pair and _remainingPairs = 1:
    • call _onSuccess(skipResultDialog: true)
    • if correct pair and _remainingPairs > 1:
    • update both selected item to be disabled
    • call _reset()
    • reduce _remainingPairs by 1.
  • implement a onOptionPressed(int index, bool isLeft) that
  • update the leftSelectedIndex or rightSelectedIndex based on isLeft
  • calls _validateSelectedPair()

Dependencies

Child of #172

Depends on:

• 171

• 176

Dev notes

• Freezed (documentation) for union types