Exercises

type ExerciseType =
  | "multiple-choice" | "select-image" | "match-pairs"
  | "fill-blank" | "word-order" | "listening" | "speaking";

interface ChoiceOption {
  readonly id: string;
  readonly body: readonly RenderFragment[]; // may render text, audio, an image, or several
}

interface ExerciseBase {
  readonly id: string;
  readonly type: ExerciseType;
  readonly instruction?: string;
  readonly prompt: readonly RenderFragment[];
  readonly evaluation: Evaluation;
  readonly feedback?: ExerciseFeedback;   // correct / incorrect / per-option
  readonly settings?: ExerciseSettings;   // per-type toggles
  readonly presentation?: { readonly layout?: "list" | "image-grid" };
}

type Evaluation =
  | { kind: "selected-options"; select?: "one" | "many"; correctOptionIds: readonly string[] }
  | { kind: "ordered-tokens"; correctOrder: readonly string[] }
  | { kind: "matched-pairs"; pairs: readonly { leftId: string; rightId: string }[] }
  | { kind: "filled-blanks"; blanks: readonly BlankAnswer[] }
  | { kind: "typed-answer"; accepted: readonly AcceptedValue[]; normalize?: NormalizationRules }
  | { kind: "spoken-response"; strictness: "lenient" | "standard" | "strict" };

interface MultipleChoiceExercise extends ExerciseBase {
  readonly type: "multiple-choice" | "select-image";
  readonly options: readonly ChoiceOption[];
}

interface MatchPairsExercise extends ExerciseBase {
  readonly type: "match-pairs";
  readonly left: readonly ChoiceOption[];
  readonly right: readonly ChoiceOption[]; // extra right items are distractors
}

interface FillBlankExercise extends ExerciseBase {
  readonly type: "fill-blank";
  readonly stem: readonly BlankSegment[]; // sentence with one or more blanks
  readonly bank?: readonly ChoiceOption[]; // present in tap-to-fill mode
  readonly translation?: RenderFragment;
}

interface WordOrderExercise extends ExerciseBase {
  readonly type: "word-order";
  readonly tokens: readonly ChoiceOption[];
  readonly distractors?: readonly ChoiceOption[]; // extra tokens that stay unused
}

interface ListeningExercise extends ExerciseBase {
  readonly type: "listening";
  readonly stimulus: RenderFragment;      // the audio is the whole question
  readonly answerMode: "select" | "type";
  readonly options?: readonly ChoiceOption[];
}

interface SpeakingExercise extends ExerciseBase {
  readonly type: "speaking";
  readonly target: RenderFragment;        // the phrase to say
}