studybuddy/packages/backend/convex/quiz.ts

import { getAuthUserId } from '@convex-dev/auth/server';
import { v } from 'convex/values';

import { mutation, query } from './_generated/server';

export const startQuizSession = mutation({
  args: {
    questionIds: v.optional(v.array(v.id('questions'))),
  },
  handler: async (ctx, args) => {
    const userId = await getAuthUserId(ctx);
    if (!userId) throw new Error('Not authenticated');

    // End any active sessions
    const activeSessions = await ctx.db
      .query('quizSessions')
      .withIndex('by_user_and_active', (q) =>
        q.eq('userId', userId).eq('isActive', true),
      )
      .collect();

    for (const session of activeSessions) {
      await ctx.db.patch(session._id, { isActive: false });
    }

    // Get questions
    let questionIds = args.questionIds;
    if (!questionIds || questionIds.length === 0) {
      const allQuestions = await ctx.db.query('questions').collect();
      questionIds = allQuestions.map((q) => q._id);
    }

    // Shuffle questions
    const shuffled = [...questionIds].sort(() => Math.random() - 0.5);

    return await ctx.db.insert('quizSessions', {
      userId,
      activeQuestions: shuffled,
      missedQuestions: [],
      completedQuestions: [],
      currentQuestionIndex: 0,
      isActive: true,
    });
  },
});

export const getActiveSession = query({
  args: {},
  handler: async (ctx) => {
    const userId = await getAuthUserId(ctx);
    if (!userId) throw new Error('Not authenticated');

    const session = await ctx.db
      .query('quizSessions')
      .withIndex('by_user_and_active', (q) =>
        q.eq('userId', userId).eq('isActive', true),
      )
      .first();

    return session;
  },
});

export const getCurrentQuestion = query({
  args: {},
  handler: async (ctx) => {
    const userId = await getAuthUserId(ctx);
    if (!userId) throw new Error('Not authenticated');

    const session = await ctx.db
      .query('quizSessions')
      .withIndex('by_user_and_active', (q) =>
        q.eq('userId', userId).eq('isActive', true),
      )
      .first();

    if (!session) return null;

    const allQuestions = [
      ...session.activeQuestions,
      ...session.missedQuestions,
    ];

    if (allQuestions.length === 0) return null;

    const currentQuestionId = allQuestions[session.currentQuestionIndex];
    const question = await ctx.db.get(currentQuestionId);

    return {
      question,
      sessionId: session._id,
      progress: {
        current: session.currentQuestionIndex + 1,
        total: allQuestions.length,
        completed: session.completedQuestions.length,
      },
    };
  },
});

export const answerQuestion = mutation({
  args: {
    sessionId: v.id('quizSessions'),
    questionId: v.id('questions'),
    selectedAnswer: v.number(),
  },
  handler: async (ctx, args) => {
    const userId = await getAuthUserId(ctx);
    if (!userId) throw new Error('Not authenticated');

    const session = await ctx.db.get(args.sessionId);
    if (!session || session.userId !== userId) {
      throw new Error('Invalid session');
    }

    const question = await ctx.db.get(args.questionId);
    if (!question) throw new Error('Question not found');

    const isCorrect = args.selectedAnswer === question.correctAnswer;

    // Update user progress
    const existingProgress = await ctx.db
      .query('userProgress')
      .withIndex('by_user_and_question', (q) =>
        q.eq('userId', userId).eq('questionId', args.questionId),
      )
      .first();

    if (existingProgress) {
      await ctx.db.patch(existingProgress._id, {
        correctCount: existingProgress.correctCount + (isCorrect ? 1 : 0),
        incorrectCount: existingProgress.incorrectCount + (isCorrect ? 0 : 1),
        lastAttempted: Date.now(),
      });
    } else {
      await ctx.db.insert('userProgress', {
        userId,
        questionId: args.questionId,
        correctCount: isCorrect ? 1 : 0,
        incorrectCount: isCorrect ? 0 : 1,
        lastAttempted: Date.now(),
      });
    }

    // Update session
    const allQuestions = [
      ...session.activeQuestions,
      ...session.missedQuestions,
    ];

    let newActiveQuestions = [...session.activeQuestions];
    let newMissedQuestions = [...session.missedQuestions];
    let newCompletedQuestions = [...session.completedQuestions];

    // Remove current question from active list
    const currentIndex = newActiveQuestions.indexOf(args.questionId);
    if (currentIndex !== -1) {
      newActiveQuestions.splice(currentIndex, 1);
    } else {
      const missedIndex = newMissedQuestions.indexOf(args.questionId);
      if (missedIndex !== -1) {
        newMissedQuestions.splice(missedIndex, 1);
      }
    }

    if (isCorrect) {
      newCompletedQuestions.push(args.questionId);
    } else {
      newMissedQuestions.push(args.questionId);
    }

    const newAllQuestions = [...newActiveQuestions, ...newMissedQuestions];
    const newIndex =
      newAllQuestions.length > 0 ? 0 : session.currentQuestionIndex;

    await ctx.db.patch(args.sessionId, {
      activeQuestions: newActiveQuestions,
      missedQuestions: newMissedQuestions,
      completedQuestions: newCompletedQuestions,
      currentQuestionIndex: newIndex,
    });

    return {
      isCorrect,
      correctAnswer: question.correctAnswer,
      explanation: question.explanation,
    };
  },
});

export const endQuizSession = mutation({
  args: {
    sessionId: v.id('quizSessions'),
  },
  handler: async (ctx, args) => {
    const userId = await getAuthUserId(ctx);
    if (!userId) throw new Error('Not authenticated');

    const session = await ctx.db.get(args.sessionId);
    if (!session || session.userId !== userId) {
      throw new Error('Invalid session');
    }

    await ctx.db.patch(args.sessionId, { isActive: false });
    return null;
  },
});

export const getUserStats = query({
  args: {},
  handler: async (ctx) => {
    const userId = await getAuthUserId(ctx);
    if (!userId) throw new Error('Not authenticated');

    const progress = await ctx.db
      .query('userProgress')
      .withIndex('by_user', (q) => q.eq('userId', userId))
      .collect();

    const totalQuestions = progress.length;
    const totalCorrect = progress.reduce((sum, p) => sum + p.correctCount, 0);
    const totalIncorrect = progress.reduce(
      (sum, p) => sum + p.incorrectCount,
      0,
    );
    const totalAttempts = totalCorrect + totalIncorrect;

    return {
      totalQuestions,
      totalAttempts,
      totalCorrect,
      totalIncorrect,
      accuracy: totalAttempts > 0 ? (totalCorrect / totalAttempts) * 100 : 0,
    };
  },
});