import { Injectable } from '@nestjs/common';
import { generateShortId } from '../../common/utils/id.util';

export interface LearningSession {
  id: string;
  userId: string;
  knowledgeItemId: string;
  mode: string;
  status: 'active' | 'completed';
  startedAt: Date;
  endedAt: Date | null;
  durationSeconds: number;
}

@Injectable()
export class LearningSessionRepository {
  private sessions: Map<string, LearningSession> = new Map();

  async create(userId: string, dto: any): Promise<LearningSession> {
    const session: LearningSession = {
      id: generateShortId(),
      userId,
      knowledgeItemId: dto.knowledgeItemId || '',
      mode: dto.mode || 'reading',
      status: 'active',
      startedAt: new Date(),
      endedAt: null,
      durationSeconds: 0,
    };
    this.sessions.set(session.id, session);
    return session;
  }

  async end(id: string): Promise<LearningSession | undefined> {
    const session = this.sessions.get(id);
    if (!session) return undefined;
    session.status = 'completed';
    session.endedAt = new Date();
    session.durationSeconds = Math.floor(
      (session.endedAt.getTime() - session.startedAt.getTime()) / 1000,
    );
    return session;
  }

  async findByUserId(userId: string): Promise<LearningSession[]> {
    return Array.from(this.sessions.values()).filter((s) => s.userId === userId);
  }
}