import {
  BadRequestException,
  Injectable,
  NotFoundException,
} from '@nestjs/common';
import { InjectRepository } from '@nestjs/typeorm';
import { randomUUID } from 'crypto';
import { existsSync, mkdirSync, unlinkSync } from 'fs';
import { extname, join } from 'path';
import { Repository } from 'typeorm';
import { BusinessImageEntity } from '../../entities/business-image.entity';
import { BusinessEntity } from '../../entities/business.entity';

const ALLOWED_MIME = new Set([
  'image/jpeg',
  'image/png',
  'image/webp',
  'image/gif',
]);
const MAX_FILE_BYTES = 5 * 1024 * 1024;
const MAX_IMAGES_PER_BUSINESS = 10;

@Injectable()
export class BusinessImagesService {
  private readonly uploadRoot: string;

  constructor(
    @InjectRepository(BusinessImageEntity)
    private readonly imageRepo: Repository<BusinessImageEntity>,
    @InjectRepository(BusinessEntity)
    private readonly businessRepo: Repository<BusinessEntity>,
  ) {
    this.uploadRoot = join(process.cwd(), process.env.UPLOAD_DIR ?? 'uploads');
  }

  async listForBusiness(businessId: string): Promise<BusinessImageEntity[]> {
    await this.ensureBusiness(businessId);
    return this.imageRepo.find({
      where: { businessId },
      order: { isCover: 'DESC', sortOrder: 'ASC', createdAt: 'ASC' },
    });
  }

  async upload(
    businessId: string,
    files: Express.Multer.File[],
  ): Promise<BusinessImageEntity[]> {
    await this.ensureBusiness(businessId);

    if (!files?.length) {
      throw new BadRequestException('At least one image file is required');
    }

    const existing = await this.imageRepo.count({ where: { businessId } });
    if (existing + files.length > MAX_IMAGES_PER_BUSINESS) {
      throw new BadRequestException(
        `Maximum ${MAX_IMAGES_PER_BUSINESS} images per business`,
      );
    }

    const dir = join(this.uploadRoot, 'businesses', businessId);
    mkdirSync(dir, { recursive: true });

    const hasCover = await this.imageRepo.exists({
      where: { businessId, isCover: true },
    });

    const saved: BusinessImageEntity[] = [];
    let sortOrder = existing;

    for (const file of files) {
      this.validateFile(file);
      const ext = extname(file.originalname).toLowerCase() || '.jpg';
      const filename = `${randomUUID()}${ext}`;
      const relativeUrl = `businesses/${businessId}/${filename}`;
      const absolutePath = join(this.uploadRoot, relativeUrl);

      const { writeFileSync } = await import('fs');
      writeFileSync(absolutePath, file.buffer);

      const entity = this.imageRepo.create({
        businessId,
        url: relativeUrl,
        originalName: file.originalname,
        sortOrder,
        isCover: !hasCover && saved.length === 0,
      });
      saved.push(await this.imageRepo.save(entity));
      sortOrder += 1;
    }

    return saved;
  }

  async setCover(businessId: string, imageId: string): Promise<BusinessImageEntity> {
    const image = await this.imageRepo.findOne({
      where: { id: imageId, businessId },
    });
    if (!image) {
      throw new NotFoundException('Image not found');
    }

    await this.imageRepo.update({ businessId }, { isCover: false });
    image.isCover = true;
    return this.imageRepo.save(image);
  }

  async remove(businessId: string, imageId: string): Promise<void> {
    const image = await this.imageRepo.findOne({
      where: { id: imageId, businessId },
    });
    if (!image) {
      throw new NotFoundException('Image not found');
    }

    this.deleteFile(image.url);
    const wasCover = image.isCover;
    await this.imageRepo.remove(image);

    if (wasCover) {
      const next = await this.imageRepo.findOne({
        where: { businessId },
        order: { sortOrder: 'ASC', createdAt: 'ASC' },
      });
      if (next) {
        next.isCover = true;
        await this.imageRepo.save(next);
      }
    }
  }

  async listUrlsForBusiness(businessId: string): Promise<string[]> {
    const images = await this.imageRepo.find({
      where: { businessId },
      select: ['url'],
    });
    return images.map((image) => image.url);
  }

  deleteFiles(urls: string[]): void {
    for (const url of urls) {
      this.deleteFile(url);
    }
  }

  async removeAllForBusiness(businessId: string): Promise<void> {
    const urls = await this.listUrlsForBusiness(businessId);
    this.deleteFiles(urls);
    await this.imageRepo.delete({ businessId });
  }

  private validateFile(file: Express.Multer.File): void {
    if (!ALLOWED_MIME.has(file.mimetype)) {
      throw new BadRequestException(
        'Only JPEG, PNG, WebP and GIF images are allowed',
      );
    }
    if (file.size > MAX_FILE_BYTES) {
      throw new BadRequestException('Image must be at most 5 MB');
    }
  }

  private deleteFile(relativeUrl: string): void {
    const absolutePath = join(this.uploadRoot, relativeUrl);
    if (existsSync(absolutePath)) {
      unlinkSync(absolutePath);
    }
  }

  private async ensureBusiness(businessId: string): Promise<void> {
    const exists = await this.businessRepo.exists({ where: { id: businessId } });
    if (!exists) {
      throw new NotFoundException('Business not found');
    }
  }
}