import { ConflictException, Injectable, Logger } from '@nestjs/common';
import { InjectRepository } from '@nestjs/typeorm';
import { randomUUID } from 'node:crypto';
import { Repository } from 'typeorm';
import { SyncLog, SyncState } from '../entities';
import type { SyncPlatform, SyncStatus, SyncType } from '../entities/sync-log.entity';

const LEASE_MS = 30 * 60 * 1000;

@Injectable()
export class SyncRunner {
  private readonly logger = new Logger('SyncRunner');

  constructor(
    @InjectRepository(SyncState)
    private readonly syncStateRepo: Repository<SyncState>,
    @InjectRepository(SyncLog)
    private readonly syncLogRepo: Repository<SyncLog>,
  ) {}

  async run(
    platform: SyncPlatform,
    operation: (lastSyncAt: Date | null) => Promise<{
      recordsCount: number;
      status: Extract<SyncStatus, 'success' | 'partial'>;
      message?: string;
    }>,
  ): Promise<SyncLog> {
    const runId = await this.acquireLease(platform);
    let log: SyncLog | undefined;
    try {
      const lastSyncAt = await this.getLastSyncAt(platform);
      log = await this.createSyncLog(platform, lastSyncAt ? 'incremental' : 'full', 'running');
      const result = await operation(lastSyncAt);
      await this.syncStateRepo.update({ platform }, { lastSyncAt: new Date() });
      await this.finishSyncLog(log, result.status, result.recordsCount, result.message);
      return log;
    } catch (error: unknown) {
      const message = error instanceof Error ? error.message : String(error);
      if (log) await this.finishSyncLog(log, 'failed', 0, message);
      this.logger.error(`${platform} sync failed: ${message}`, error instanceof Error ? error.stack : undefined);
      throw error;
    } finally {
      await this.releaseLease(platform, runId);
    }
  }

  private async acquireLease(platform: SyncPlatform): Promise<string> {
    await this.syncStateRepo
      .createQueryBuilder()
      .insert()
      .values({ platform, lastSyncAt: null, runId: null, runningSince: null })
      .orIgnore()
      .execute();

    const runId = randomUUID();
    const result = await this.syncStateRepo
      .createQueryBuilder()
      .update()
      .set({ runId, runningSince: new Date() })
      .where('platform = :platform', { platform })
      .andWhere('(running_since IS NULL OR running_since < :staleBefore)', {
        staleBefore: new Date(Date.now() - LEASE_MS),
      })
      .execute();
    if (result.affected !== 1) throw new ConflictException(`${platform} 同步正在进行中`);
    return runId;
  }

  private async releaseLease(platform: SyncPlatform, runId: string): Promise<void> {
    await this.syncStateRepo
      .createQueryBuilder()
      .update()
      .set({ runId: null, runningSince: null })
      .where('platform = :platform AND run_id = :runId', { platform, runId })
      .execute();
  }

  private async getLastSyncAt(platform: SyncPlatform): Promise<Date | null> {
    const state = await this.syncStateRepo.findOne({ where: { platform } });
    return state?.lastSyncAt ?? null;
  }

  private async createSyncLog(
    platform: SyncPlatform,
    syncType: SyncType,
    status: SyncStatus,
  ): Promise<SyncLog> {
    return this.syncLogRepo.save(
      this.syncLogRepo.create({
        platform,
        syncType,
        status,
        recordsCount: 0,
        startedAt: new Date(),
      }),
    );
  }

  private async finishSyncLog(
    log: SyncLog,
    status: SyncStatus,
    recordsCount: number,
    errorMessage?: string,
  ): Promise<void> {
    log.status = status;
    log.recordsCount = recordsCount;
    log.finishedAt = new Date();
    log.errorMessage = errorMessage ?? null;
    await this.syncLogRepo.save(log);
  }
}
