import {
  Injectable,
  NotFoundException,
  BadRequestException,
} from '@nestjs/common';
import { nanoid } from 'nanoid';
import { ShareConfigRepository } from './repositories/share-config.repository';
import { ShareParticipantRepository } from './repositories/share-participant.repository';
import { ShareLevelProgressRepository } from './repositories/share-level-progress.repository';
import { LevelRepository } from '../wechat-game/repositories/level.repository';
import { pickLevelImageFields } from '../wechat-game/level-fields.helper';
import { CreateShareDto } from './dto/create-share.dto';
import { ReportLevelProgressDto } from './dto/report-level-progress.dto';
import {
  CreateShareResponseDto,
  CreatedShareListResponseDto,
  JoinShareResponseDto,
  ShareLevelDto,
} from './dto/share-response.dto';
import { ReportLevelProgressResponseDto } from './dto/share-level-progress-response.dto';

@Injectable()
export class ShareService {
  constructor(
    private readonly shareConfigRepository: ShareConfigRepository,
    private readonly shareParticipantRepository: ShareParticipantRepository,
    private readonly levelRepository: LevelRepository,
    private readonly shareLevelProgressRepository: ShareLevelProgressRepository,
  ) {}

  async createShare(
    userId: string,
    dto: CreateShareDto,
  ): Promise<CreateShareResponseDto> {
    const uniqueIds = [...new Set(dto.levelIds)];
    if (uniqueIds.length !== 6) {
      throw new BadRequestException('关卡ID不能重复，需要恰好6个不同的关卡');
    }

    // 单次查询验证所有关卡存在
    const levels = await this.levelRepository.findByIds(uniqueIds);
    if (levels.length !== uniqueIds.length) {
      const foundIds = new Set(levels.map((l) => l.id));
      const missing = uniqueIds.filter((id) => !foundIds.has(id));
      throw new NotFoundException(`以下关卡不存在: ${missing.join(', ')}`);
    }

    // 生成 8 位分享码（碰撞重试）
    let shareCode: string;
    let attempts = 0;
    do {
      shareCode = nanoid(8);
      const existing =
        await this.shareConfigRepository.findByShareCode(shareCode);
      if (!existing) break;
      attempts++;
    } while (attempts < 3);

    if (attempts >= 3) {
      throw new BadRequestException('生成分享码失败，请重试');
    }

    const config = await this.shareConfigRepository.create({
      shareCode,
      title: dto.title,
      sharerId: userId,
      levelIds: dto.levelIds,
    });

    return {
      shareCode: config.shareCode,
      title: config.title,
      levelCount: config.levelIds.length,
    };
  }

  async joinShare(userId: string, code: string): Promise<JoinShareResponseDto> {
    const config = await this.shareConfigRepository.findByShareCode(code);
    if (!config) {
      throw new NotFoundException('分享不存在或已过期');
    }

    if (userId !== config.sharerId) {
      await this.shareParticipantRepository.addParticipant(config.id, userId);
    }

    // Single query, then reorder to match levelIds sequence
    const allLevels = await this.levelRepository.findByIds(config.levelIds);
    const levelMap = new Map(allLevels.map((l) => [l.id, l]));

    const levels: ShareLevelDto[] = config.levelIds.map((id, index) => {
      const level = levelMap.get(id);
      if (!level) {
        throw new NotFoundException(`关卡 ${id} 不存在`);
      }
      return {
        id: level.id,
        level: index + 1,
        ...pickLevelImageFields(level),
        answer: level.answer,
        sortOrder: level.sortOrder,
      };
    });

    return {
      shareCode: config.shareCode,
      title: config.title,
      levels,
    };
  }

  async getCreatedShares(userId: string): Promise<CreatedShareListResponseDto> {
    const configs = await this.shareConfigRepository.findBySharerId(userId);
    if (configs.length === 0) {
      return { items: [] };
    }

    const shareConfigIds = configs.map((config) => config.id);
    const [participantCountMap, rankingRows] = await Promise.all([
      this.shareParticipantRepository.countByShareConfigIds(shareConfigIds),
      this.shareLevelProgressRepository.summarizeByShareConfigIds(
        shareConfigIds,
      ),
    ]);

    const rankingsByShareConfigId = new Map<string, string[]>();
    for (const config of configs) {
      const completedRankings = rankingRows
        .filter(
          (row) =>
            row.shareConfigId === config.id &&
            Number(row.passedLevelCount) === config.levelIds.length,
        )
        .sort((a, b) => {
          const totalTimeDiff =
            Number(a.totalTimeSpent) - Number(b.totalTimeSpent);
          if (totalTimeDiff !== 0) {
            return totalTimeDiff;
          }

          return a.participantId.localeCompare(b.participantId);
        })
        .map((row) => row.participantId);

      rankingsByShareConfigId.set(config.id, completedRankings);
    }

    return {
      items: configs.map((config) => {
        const rankings = rankingsByShareConfigId.get(config.id) ?? [];
        const rankingIndex = rankings.findIndex(
          (participantId) => participantId === userId,
        );

        return {
          id: config.id,
          shareCode: config.shareCode,
          title: config.title,
          levelCount: config.levelIds.length,
          participantCount: participantCountMap.get(config.id) ?? 0,
          userRank: rankingIndex >= 0 ? rankingIndex + 1 : null,
          createdAt: config.createdAt.toISOString(),
        };
      }),
    };
  }

  async reportLevelProgress(
    userId: string,
    dto: ReportLevelProgressDto,
  ): Promise<ReportLevelProgressResponseDto> {
    const [config, level] = await Promise.all([
      this.shareConfigRepository.findByShareCode(dto.shareCode),
      this.levelRepository.findById(dto.levelId),
    ]);

    if (!config) {
      throw new NotFoundException('分享不存在或已过期');
    }
    if (!level) {
      throw new NotFoundException('关卡不存在');
    }

    if (!config.levelIds.includes(dto.levelId)) {
      throw new BadRequestException('该关卡不属于此分享挑战');
    }

    let participant =
      await this.shareParticipantRepository.findByShareConfigAndParticipant(
        config.id,
        userId,
      );
    if (!participant) {
      participant = this.shareParticipantRepository.create({
        shareConfigId: config.id,
        participantId: userId,
      });
      participant = await this.shareParticipantRepository.save(participant);
    }

    const progress =
      await this.shareLevelProgressRepository.findByParticipantAndLevel(
        participant.id,
        dto.levelId,
      );

    if (dto.passed && progress?.passed) {
      return {
        passed: true,
        timeLimit: level.timeLimit,
        withinTimeLimit: this.isWithinTimeLimit(
          level.timeLimit,
          progress.timeSpent,
        ),
      };
    }

    const withinTimeLimit = dto.passed
      ? this.isWithinTimeLimit(level.timeLimit, dto.timeSpent)
      : false;

    const updatedProgress = progress
      ? Object.assign(this.shareLevelProgressRepository.create(progress), {
          passed: dto.passed,
          timeSpent: dto.timeSpent,
          completedAt: dto.passed ? new Date() : progress.completedAt,
        })
      : this.shareLevelProgressRepository.create({
          participantId: participant.id,
          levelId: dto.levelId,
          passed: dto.passed,
          timeSpent: dto.timeSpent,
          completedAt: dto.passed ? new Date() : null,
        });

    await this.shareLevelProgressRepository.save(updatedProgress);

    return {
      passed: dto.passed,
      timeLimit: level.timeLimit,
      withinTimeLimit,
    };
  }

  private isWithinTimeLimit(
    timeLimit: number | null,
    timeSpent: number,
  ): boolean {
    return timeLimit === null || timeSpent <= timeLimit;
  }
}