import {
  Injectable,
  NotFoundException,
  BadRequestException,
  Inject,
  Logger,
} from '@nestjs/common';
import type { MultipartFile } from '@fastify/multipart';
import { MongoPrismaService } from '@box/db/prisma/mongo-prisma.service';
import { CacheSyncService } from '../../../cache-sync/cache-sync.service';
import { CacheEntityType } from '../../../cache-sync/cache-sync.types';
import { MediaManagerService } from '@box/core/media-manager/media-manager.service';
import type { StorageStrategy } from '@box/core/media-manager/types';
import { randomUUID } from 'crypto';
import {
  VideoMediaListQueryDto,
  UpdateVideoMediaManageDto,
  UpdateVideoMediaStatusDto,
  BatchUpdateVideoMediaStatusDto,
} from './video-media.dto';
import { MEDIA_STORAGE_STRATEGY } from '../../../shared/tokens';

type MongoAggregateResult = {
  cursor?: {
    firstBatch?: any[];
  };
};

@Injectable()
export class VideoMediaService {
  private readonly logger = new Logger(VideoMediaService.name);
  private isBackfillingVid = false;

  constructor(
    private readonly prisma: MongoPrismaService,
    private readonly cacheSyncService: CacheSyncService,
    private readonly mediaManagerService: MediaManagerService,
    @Inject(MEDIA_STORAGE_STRATEGY)
    private readonly mediaStorageStrategy: StorageStrategy,
  ) {}

  // helper to generate next vid
  private async generateNextVid(): Promise<number> {
    const last = await this.prisma.videoMedia.findFirst({
      where: { vid: { isSet: true } },
      orderBy: { vid: 'desc' },
      select: { vid: true },
    });

    return (last?.vid ?? 0) + 1;
  }

  // backfill vid for videoMedia documents without one
  private async backfillVids(): Promise<void> {
    if (this.isBackfillingVid) {
      this.logger.warn('backfillVids is already running, skipping.');
      return;
    }

    this.isBackfillingVid = true;
    this.logger.log('Starting backfill of vid...');
    try {
      const videosWithoutVid = await this.prisma.videoMedia.findMany({
        where: {
          OR: [{ vid: { isSet: false } }, { vid: null }],
        },
        orderBy: { createdAt: 'asc' },
        select: { id: true },
      });

      if (videosWithoutVid.length === 0) {
        this.logger.log('No videos need backfilling vid.');
        return;
      }

      this.logger.log(
        `Found ${videosWithoutVid.length} videos without vid. Starting backfill...`,
      );

      let nextVid = await this.generateNextVid();

      for (const video of videosWithoutVid) {
        let assigned = false;

        while (!assigned) {
          try {
            await this.prisma.videoMedia.update({
              where: { id: video.id },
              data: { vid: nextVid },
            });

            this.logger.log(
              `Backfilled vid ${nextVid} for videoMedia id ${video.id}`,
            );

            nextVid += 1;
            assigned = true;
          } catch (e: any) {
            // Unique constraint violation → retry with a fresh number
            if (e?.code === 'P2002') {
              this.logger.warn(`Duplicate vid ${nextVid}, retrying...`);
              nextVid = await this.generateNextVid();
            } else {
              throw e;
            }
          }
        }
      }

      this.logger.log(
        `Backfilled ${videosWithoutVid.length} vids successfully.`,
      );
    } finally {
      this.isBackfillingVid = false;
      this.logger.log('Finished backfillVids process.');
    }
  }

  async findAll(query: VideoMediaListQueryDto): Promise<any> {
    // ensure vids are backfilled
    await this.backfillVids().catch((err) =>
      this.logger.error('Backfill vid failed', err?.stack ?? String(err)),
    );

    const page = query.page ?? 1;
    const pageSize = query.size ?? 20;
    const skip = (page - 1) * pageSize;
    const take = pageSize;

    const baseWhere = this.buildVideoListBaseFilter(query);
    const keyword = query.keyword?.trim();

    let total: number;
    let rows: any[];

    if (!keyword) {
      [total, rows] = await Promise.all([
        this.prisma.videoMedia.count({ where: baseWhere }),
        this.prisma.videoMedia.findMany({
          where: baseWhere,
          skip,
          take,
          orderBy: { addedTime: 'desc' },
        }),
      ]);
    } else {
      const regexSource = this.escapeRegex(keyword);
      const matchFilter = this.buildKeywordMatchFilter(baseWhere, regexSource);

      // Prisma Mongo cannot express regex searches inside array elements, so we fall back to a raw aggregate that uses sanitizedSecondTags.
      const countRes = (await this.prisma.$runCommandRaw({
        aggregate: 'videoMedia',
        pipeline: [{ $match: matchFilter }, { $count: 'total' }],
        cursor: {},
      })) as unknown as MongoAggregateResult;

      total = Number(countRes.cursor.firstBatch?.[0]?.total ?? 0);

      const dataRes = (await this.prisma.$runCommandRaw({
        aggregate: 'videoMedia',
        pipeline: [
          { $match: matchFilter },
          { $sort: { addedTime: -1 } },
          { $skip: skip },
          { $limit: take },
        ],
        cursor: {},
      })) as unknown as MongoAggregateResult;

      rows = (dataRes.cursor.firstBatch ?? []).map((doc: any) => ({
        ...doc,
        id: doc.id ?? doc._id,
      }));
    }

    return {
      total,
      page,
      pageSize,
      items: rows.map((row) => ({
        id: row.id,
        vid: row.vid ?? null,
        title: row.title,
        filename: row.filename,
        preFileName: row.preFileName,
        fieldNameFs: row.fieldNameFs,
        videoTime: row.videoTime,
        size: row.size?.toString?.() ?? '0',
        coverImg: row.coverImg ?? '',
        categoryIds: row.categoryIds ?? [],
        tagIds: row.tagIds ?? [],
        listStatus: row.listStatus ?? 0,
        editedAt: Number(row.editedAt ?? 0),
        updatedAt: row.updatedAt ?? null,
        tags: row.tags ?? [],
        tagsFlat: row.tagsFlat ?? '',
        secondTags: row.secondTags ?? [],
        sanitizedSecondTags: row.sanitizedSecondTags ?? [],
      })),
    };
  }

  private buildVideoListBaseFilter(
    query: VideoMediaListQueryDto,
  ): Record<string, any> {
    const where: Record<string, any> = {};

    if (typeof query.listStatus === 'number') {
      where.listStatus = query.listStatus;
    }

    // filter by tag, by videoMedia.secondTags[]
    if (typeof query.tag === 'string' && query.tag.trim() !== '') {
      where.secondTags = {
        has: query.tag.trim(),
      };
    }

    if (
      typeof query.updatedFrom === 'number' ||
      typeof query.updatedTo === 'number'
    ) {
      const updatedAt: Record<string, Date> = {};

      if (typeof query.updatedFrom === 'number') {
        // epoch seconds → milliseconds → Date
        updatedAt.gte = new Date(query.updatedFrom * 1000);
      }

      if (typeof query.updatedTo === 'number') {
        updatedAt.lte = new Date(query.updatedTo * 1000);
      }

      where.updatedAt = updatedAt;
    }

    return where;
  }

  private buildKeywordMatchFilter(
    baseFilter: Record<string, any>,
    regexSource: string,
  ): Record<string, any> {
    const matchFilter = { ...baseFilter };

    if (Array.isArray(matchFilter.$and)) {
      matchFilter.$and = [...matchFilter.$and];
    }

    const keywordClause = {
      $or: [
        {
          title: {
            $regex: regexSource,
            $options: 'i',
          },
        },
        {
          sanitizedSecondTags: {
            $elemMatch: {
              $regex: regexSource,
              $options: 'i',
            },
          },
        },
      ],
    };

    matchFilter.$and = matchFilter.$and ?? [];
    matchFilter.$and.push(keywordClause);

    return matchFilter;
  }

  private escapeRegex(input: string): string {
    return input.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
  }

  async findOne(id: string): Promise<any> {
    const video = await this.prisma.videoMedia.findUnique({
      where: { id },
    });

    if (!video) {
      throw new NotFoundException('Video not found');
    }

    const [category, tags] = await Promise.all([
      video.categoryIds && video.categoryIds.length > 0
        ? this.prisma.category.findUnique({
            where: { id: video.categoryIds[0] },
          })
        : null,
      video.tagIds && video.tagIds.length
        ? this.prisma.tag.findMany({
            where: { id: { in: video.tagIds } },
            orderBy: { seq: 'asc' },
          })
        : [],
    ]);

    return {
      id: video.id,
      title: video.title,
      filename: video.filename,
      preFileName: video.preFileName,
      fieldNameFs: video.fieldNameFs,
      videoTime: video.videoTime,
      size: video.size?.toString?.() ?? '0',
      coverImg: video.coverImg ?? '',
      type: video.type,
      formatType: video.formatType,
      contentType: video.contentType,
      country: video.country,
      status: video.status,
      desc: video.desc ?? '',
      categoryIds: video.categoryIds ?? [],
      tagIds: video.tagIds ?? [],
      listStatus: video.listStatus ?? 0,
      editedAt: Number(video.editedAt ?? 0),
      updatedAt: video.updatedAt ?? null,
      categoryName: category?.name ?? null,
      // Existing DTO: tags as {id, name}[]
      tags: video.tags ?? [],
      tagsFlat: video.tagsFlat ?? '',
      secondTags: video.secondTags ?? [],
    };
  }

  async updateManage(id: string, dto: UpdateVideoMediaManageDto) {
    const video = await this.prisma.videoMedia.findUnique({
      where: { id },
    });

    if (!video) {
      throw new NotFoundException('Video not found');
    }

    const updateData: any = {};

    if (typeof dto.title === 'string') {
      updateData.title = dto.title.trim();
    }

    let categoryId: string | null | undefined = dto.categoryId;
    const tagIds: string[] | undefined = dto.tagIds;

    if (dto.categoryId === null) {
      categoryId = null;
    }

    if (typeof categoryId !== 'undefined' || typeof tagIds !== 'undefined') {
      const { finalCategoryIds, finalTagIds, tags, tagsFlat } =
        await this.validateCategoryAndTags(categoryId, tagIds);

      updateData.categoryIds = finalCategoryIds;
      updateData.tagIds = finalTagIds;
      updateData.tags = tags; // NEW: store denormalised tag names (lowercased)
      updateData.tagsFlat = tagsFlat; // existing: text for search
    }

    if (typeof dto.listStatus === 'number') {
      if (dto.listStatus !== 0 && dto.listStatus !== 1) {
        throw new BadRequestException('Invalid listStatus value');
      }
      updateData.listStatus = dto.listStatus;
    }

    updateData.editedAt = BigInt(Date.now());
    updateData.updatedAt = new Date();

    await this.prisma.videoMedia.update({
      where: { id },
      data: updateData,
    });

    // Refresh category video lists cache if category changed or affected
    if (video.categoryIds && video.categoryIds.length > 0) {
      for (const cid of video.categoryIds) {
        await this.cacheSyncService.scheduleAction({
          entityType: CacheEntityType.VIDEO_LIST,
          operation: 'REFRESH',
          payload: { categoryId: cid },
        } as any);
      }
    }
    if (updateData.categoryIds && updateData.categoryIds.length > 0) {
      const oldCategoryIds = new Set(video.categoryIds || []);
      for (const cid of updateData.categoryIds) {
        if (!oldCategoryIds.has(cid)) {
          await this.cacheSyncService.scheduleAction({
            entityType: CacheEntityType.VIDEO_LIST,
            operation: 'REFRESH',
            payload: { categoryId: cid },
          } as any);
        }
      }
    }

    return this.findOne(id);
  }

  async updateStatus(id: string, dto: UpdateVideoMediaStatusDto) {
    const video = await this.prisma.videoMedia.findUnique({
      where: { id },
    });

    if (!video) {
      throw new NotFoundException('Video not found');
    }

    if (dto.listStatus !== 0 && dto.listStatus !== 1) {
      throw new BadRequestException('Invalid listStatus value');
    }

    const editedAt = BigInt(Date.now());
    const updatedAt = new Date();

    await this.prisma.videoMedia.update({
      where: { id },
      data: {
        listStatus: dto.listStatus,
        editedAt,
        updatedAt,
      },
    });

    // Refresh category video lists cache if video has a category
    if (video.categoryIds && video.categoryIds.length > 0) {
      for (const categoryId of video.categoryIds) {
        await this.cacheSyncService.scheduleAction({
          entityType: CacheEntityType.VIDEO_LIST,
          operation: 'REFRESH',
          payload: { categoryId },
        } as any);
      }
    }

    return {
      id,
      listStatus: dto.listStatus,
      editedAt: editedAt.toString(),
    };
  }

  async batchUpdateStatus(dto: BatchUpdateVideoMediaStatusDto) {
    if (!dto.ids?.length) {
      throw new BadRequestException('ids cannot be empty');
    }

    if (dto.listStatus !== 0 && dto.listStatus !== 1) {
      throw new BadRequestException('Invalid listStatus value');
    }

    const editedAt = BigInt(Date.now());
    const updatedAt = new Date();

    // Fetch affected videos to get their categories for cache refresh
    const affectedVideos = await this.prisma.videoMedia.findMany({
      where: { id: { in: dto.ids } },
      select: { categoryIds: true },
    });

    const result = await this.prisma.videoMedia.updateMany({
      where: { id: { in: dto.ids } },
      data: {
        listStatus: dto.listStatus,
        editedAt,
        updatedAt,
      },
    });

    // Refresh cache for all affected categories (fire-and-forget)
    const allAffectedCategoryIds = new Set<string>();
    for (const video of affectedVideos) {
      if (Array.isArray(video.categoryIds)) {
        for (const cid of video.categoryIds) {
          allAffectedCategoryIds.add(cid);
        }
      }
    }

    for (const categoryId of allAffectedCategoryIds) {
      await this.cacheSyncService.scheduleAction({
        entityType: CacheEntityType.VIDEO_LIST,
        operation: 'REFRESH',
        payload: { categoryId },
      } as any);
    }

    return {
      affected: result.count,
      listStatus: dto.listStatus,
      editedAt: editedAt.toString(),
    };
  }

  // create an async function to delete a video media by id and return the deleted id also update Redis cache
  async delete(id: string) {
    const video = await this.prisma.videoMedia.findUnique({
      where: { id },
    });

    if (!video) {
      throw new NotFoundException('Video not found');
    }

    await this.prisma.videoMedia.delete({
      where: { id },
    });

    // Refresh category video lists cache if video has a category
    if (video.categoryIds && video.categoryIds.length > 0) {
      for (const categoryId of video.categoryIds) {
        await this.cacheSyncService.scheduleAction({
          entityType: CacheEntityType.VIDEO_LIST,
          operation: 'REFRESH',
          payload: { categoryId },
        } as any);
      }
    }

    return {
      id,
    };
  }

  /**
   * Upload and update VideoMedia cover image.
   */
  async updateCover(id: string, file: MultipartFile) {
    const video = await this.prisma.videoMedia.findUnique({ where: { id } });

    if (!video) {
      throw new NotFoundException('Video not found');
    }

    const previous = {
      path: video.coverImg,
      strategy: video.imgSource as StorageStrategy | undefined,
    };

    const filename = this.sanitizeFilename(file.filename);
    const relativePath = this.buildRelativePath(
      'videos',
      'images',
      id,
      filename,
    );
    const strategy = this.mediaStorageStrategy;

    const uploadResult = await this.mediaManagerService.upload({
      storageStrategy: strategy,
      relativePath: [relativePath],
      localStoragePrefix: 'local',
      fileStreams: [file.file],
    });

    if (uploadResult.status !== 1) {
      throw new BadRequestException('Failed to upload cover image');
    }

    const editedAt = BigInt(Math.floor(Date.now() / 1000));
    const updatedAt = new Date();

    const updated = await this.prisma.videoMedia.update({
      where: { id },
      data: {
        coverImg: relativePath,
        imgSource: uploadResult.storageStrategy,
        editedAt,
        updatedAt,
      },
    });

    if (video.categoryIds && video.categoryIds.length > 0) {
      for (const categoryId of video.categoryIds) {
        await this.cacheSyncService.scheduleAction({
          entityType: CacheEntityType.VIDEO_LIST,
          operation: 'REFRESH',
          payload: { categoryId },
        } as any);
      }
    }

    await this.cleanupPreviousCover(previous);

    return {
      id: updated.id,
      coverImg: updated.coverImg,
      imgSource: updated.imgSource,
      editedAt: editedAt.toString(),
    };
  }

  private async cleanupPreviousCover(previous: {
    path?: string | null;
    strategy?: StorageStrategy;
  }) {
    if (!previous.path || !previous.strategy) return;
    await this.mediaManagerService
      .cleanup(previous.strategy, [previous.path], 'local')
      .catch(() => undefined);
  }

  private buildRelativePath(
    domain: string,
    type: 'images' | 'videos' | 'others',
    id: string,
    filename: string,
  ): string {
    return `${domain}/${type}/${id}/${filename}`;
  }

  private sanitizeFilename(name?: string | null): string {
    const raw = (name || 'file').trim();
    const cleaned = raw.replace(/[\\/]+/g, '');
    return cleaned || `${randomUUID()}.jpg`;
  }

  private async validateCategoryAndTags(
    categoryId: string | null | undefined,
    tagIds: string[] | undefined,
  ): Promise<{
    finalCategoryIds: string[];
    finalTagIds: string[];
    tags: string[]; // NEW: denormalised tag names (lowercased)
    tagsFlat: string; // NEW: concatenated names for search
  }> {
    let finalCategoryIds: string[] =
      typeof categoryId === 'undefined' || categoryId === null
        ? []
        : [categoryId];
    let finalTagIds: string[] = [];
    let tags: string[] = []; // NEW
    let tagsFlat = '';

    // Normalize tagIds: remove duplicates
    if (Array.isArray(tagIds)) {
      const unique = [...new Set(tagIds)];
      if (unique.length > 5) {
        throw new BadRequestException('Tag count cannot exceed 5');
      }
      finalTagIds = unique;
    }

    // If tags are provided but categoryId is null/undefined -> error
    if (finalTagIds.length > 0 && finalCategoryIds.length === 0) {
      throw new BadRequestException(
        'Category is required when tags are provided.',
      );
    }

    // Validate category if present
    if (finalCategoryIds.length > 0) {
      const category = await this.prisma.category.findUnique({
        where: { id: finalCategoryIds[0] },
      });

      if (!category) {
        throw new BadRequestException('Category not found');
      }
      if (category.status !== 1) {
        throw new BadRequestException('Category is disabled');
      }
    }

    if (finalTagIds.length > 0) {
      const tagEntities = await this.prisma.tag.findMany({
        where: { id: { in: finalTagIds } },
      });

      if (tagEntities.length !== finalTagIds.length) {
        throw new BadRequestException('Some tags do not exist');
      }

      const distinctCategoryIds = [
        ...new Set(tagEntities.map((t) => t.categoryId.toString())),
      ];

      if (distinctCategoryIds.length > 1) {
        throw new BadRequestException(
          'All tags must belong to the same category',
        );
      }

      const tagCategoryId = distinctCategoryIds[0];

      if (
        finalCategoryIds.length > 0 &&
        tagCategoryId !== finalCategoryIds[0]
      ) {
        throw new BadRequestException(
          'Tags do not belong to the specified category',
        );
      }

      // If categoryId was not provided but tags exist, infer from tags
      if (finalCategoryIds.length === 0) {
        finalCategoryIds = [tagCategoryId];
      }

      // Build tags & tagsFlat: lowercased names
      const tagNames = tagEntities
        .map((t) => t.name?.trim())
        .filter(Boolean) as string[];

      tags = tagNames.map((name) => name.toLowerCase()); // NEW

      tagsFlat = tags.join(' '); // e.g. "funny hot 2025"
    }

    return {
      finalCategoryIds,
      finalTagIds,
      tags,
      tagsFlat,
    };
  }
}