import { Injectable } from '@nestjs/common';
import { randomUUID } from 'crypto';
import { PrismaService } from '../../shared/prisma/prisma.service';
import { QuotaService } from '../../shared/quota/quota.service';
import { YouTubeApiClient } from './youtube-api.client';
import { hashMetadata } from '../../shared/render-engine/hash';
import { PrivacyStatus, Prisma, Video } from '@prisma/client';

@Injectable()
export class YouTubeSyncService {
  constructor(
    private readonly prisma: PrismaService,
    private readonly quota: QuotaService,
    private readonly ytClient: YouTubeApiClient,
  ) {}

  async fetchRemote(youtubeVideoId: string, channelId: string) {
    if (!(await this.quota.canSpend(1))) throw new Error('Quota exhausted');
    return this.ytClient.getVideoMetadata(youtubeVideoId, channelId);
  }

  async pushUpdate(
    video: { youtubeVideoId: string; channelId: string },
    meta: {
      title: string;
      description: string;
      tags: string[];
      categoryId?: string;
      privacyStatus: PrivacyStatus;
      scheduledAt?: Date | null;
      defaultLanguage?: string;
      defaultAudioLanguage?: string;
      selfDeclaredMadeForKids?: boolean;
      embeddable?: boolean;
      license?: string;
      recordingDate?: Date | null;
    },
    ctx?: { actionId?: string; actionType?: string },
  ) {
    await this.ytClient.updateVideoMetadata(video.youtubeVideoId, meta, video.channelId, ctx);
  }

  async detectConflictsForVideos(
    videoIds: string[],
  ): Promise<{ scanned: number; conflicts: number; quotaExhausted: boolean }> {
    if (videoIds.length === 0) return { scanned: 0, conflicts: 0, quotaExhausted: false };

    const videos = await this.prisma.video.findMany({ where: { id: { in: videoIds } } });

    // Batch API calls are scoped to a channel's OAuth client, so group first.
    const byChannel = new Map<string, Video[]>();
    for (const v of videos) {
      const bucket = byChannel.get(v.channelId);
      if (bucket) bucket.push(v);
      else byChannel.set(v.channelId, [v]);
    }

    let scanned = 0;
    let conflicts = 0;

    for (const [channelId, channelVideos] of byChannel) {
      for (let i = 0; i < channelVideos.length; i += 50) {
        const batch = channelVideos.slice(i, i + 50);
        if (!(await this.quota.canSpend(1))) {
          return { scanned, conflicts, quotaExhausted: true };
        }

        const items = await this.ytClient.getVideosBatch(
          batch.map((v) => v.youtubeVideoId),
          channelId,
          { actionId: randomUUID(), actionType: 'conflict_detection' },
        );
        const remoteByYtId = new Map(items.map((item) => [item.id, item]));

        for (const video of batch) {
          const remote = remoteByYtId.get(video.youtubeVideoId);
          if (!remote) continue; // YouTube didn't return this ID; likely deleted, purge job handles it
          const conflict = await this.applyConflictDetection(video, remote);
          scanned++;
          if (conflict) conflicts++;
        }
      }
    }

    return { scanned, conflicts, quotaExhausted: false };
  }

  private async applyConflictDetection(video: Video, remote: any): Promise<boolean> {
    const remoteDescription = remote.snippet?.description ?? '';
    const remotePrivacyStatus = remote.status?.privacyStatus?.toUpperCase() ?? null;
    const remoteRecordingDate = remote.recordingDetails?.recordingDate
      ? new Date(remote.recordingDetails.recordingDate)
      : null;

    const remoteHash = hashMetadata({
      title: remote.snippet?.title ?? '',
      description: remoteDescription,
      tags: remote.snippet?.tags ?? [],
      categoryId: remote.snippet?.categoryId,
      privacyStatus: remotePrivacyStatus,
      defaultLanguage: remote.snippet?.defaultLanguage,
      defaultAudioLanguage: remote.snippet?.defaultAudioLanguage,
      selfDeclaredMadeForKids: remote.status?.selfDeclaredMadeForKids,
      embeddable: remote.status?.embeddable,
      license: remote.status?.license,
      recordingDate: remoteRecordingDate,
    });

    const conflict = remoteHash !== video.lastSyncedHash;

    if (conflict) {
      const pendingRemoteSnapshot = {
        title: remote.snippet?.title ?? '',
        tags: remote.snippet?.tags ?? [],
        categoryId: remote.snippet?.categoryId ?? null,
        privacyStatus: remotePrivacyStatus,
        defaultLanguage: remote.snippet?.defaultLanguage ?? null,
        defaultAudioLanguage: remote.snippet?.defaultAudioLanguage ?? null,
        selfDeclaredMadeForKids: remote.status?.selfDeclaredMadeForKids ?? false,
        embeddable: remote.status?.embeddable ?? true,
        license: remote.status?.license ?? 'youtube',
        recordingDate: remoteRecordingDate ? remoteRecordingDate.toISOString().slice(0, 10) : null,
      };

      await this.prisma.video.update({
        where: { id: video.id },
        data: {
          remoteConflict: true,
          pendingRemoteSnapshot,
          pendingRemoteDescription: remoteDescription,
        },
      });
    } else if (video.remoteConflict || video.pendingRemoteSnapshot) {
      // Self-heal: remote matches lastSyncedHash again (e.g. the creator reverted their edit).
      await this.prisma.video.update({
        where: { id: video.id },
        data: {
          remoteConflict: false,
          pendingRemoteSnapshot: Prisma.JsonNull,
          pendingRemoteDescription: null,
        },
      });
    }

    return conflict;
  }
}