import {
  BadRequestException,
  ForbiddenException,
  Injectable,
  NotFoundException,
} from '@nestjs/common';
import { Prisma } from '@prisma/client';
import { AuthUser } from '../auth/auth.types';
import { PermissionsService } from '../auth/permissions.service';
import { PrismaService } from '../prisma/prisma.service';
import { CreateBrandDto, ListBrandsDto, UpdateBrandDto } from './dto/brand.dto';

function slugify(value: string): string {
  return (
    value
      .toLowerCase()
      .trim()
      .replace(/[^a-z0-9]+/g, '-')
      .replace(/^-+|-+$/g, '') || 'brand'
  );
}

type BrandWithImage = Prisma.BrandGetPayload<{
  include: { imageMedia: true };
}>;

@Injectable()
export class BrandsService {
  constructor(
    private readonly prisma: PrismaService,
    private readonly permissions: PermissionsService,
  ) {}

  async list(businessIdRaw: string, query: ListBrandsDto, actor: AuthUser) {
    const businessId = BigInt(businessIdRaw);
    await this.assertPermission(businessId, actor.id, 'brands.read');

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

    const where: Prisma.BrandWhereInput = {
      businessId,
      ...(query.name?.trim()
        ? {
            OR: [
              { nameEn: { contains: query.name.trim(), mode: 'insensitive' } },
              { nameFa: { contains: query.name.trim(), mode: 'insensitive' } },
            ],
          }
        : {}),
    };

    const [items, total] = await Promise.all([
      this.prisma.brand.findMany({
        where,
        orderBy: [{ sort_order: 'asc' }, { nameEn: 'asc' }, { createdAt: 'desc' }],
        skip,
        take: pageSize,
        include: { imageMedia: true },
      }),
      this.prisma.brand.count({ where }),
    ]);

    return {
      items: items.map((item) => this.serialize(item)),
      total,
      page,
      pageSize,
    };
  }

  async getOne(businessIdRaw: string, brandIdRaw: string, actor: AuthUser) {
    const businessId = BigInt(businessIdRaw);
    const brandId = BigInt(brandIdRaw);
    await this.assertPermission(businessId, actor.id, 'brands.read');

    const brand = await this.findBrandOrThrow(businessId, brandId);
    return { brand: this.serialize(brand) };
  }

  async create(businessIdRaw: string, dto: CreateBrandDto, actor: AuthUser) {
    const businessId = BigInt(businessIdRaw);
    await this.assertPermission(businessId, actor.id, 'brands.create');

    const slug = await this.ensureUniqueSlug(
      businessId,
      dto.slug ?? slugify(dto.nameEn),
    );

    let imageMediaId: bigint | null = null;
    if (dto.imageMediaId) {
      imageMediaId = BigInt(dto.imageMediaId);
      await this.assertBrandImageMedia(businessId, imageMediaId);
    }

    const created = await this.prisma.brand.create({
      data: {
        businessId,
        nameEn: dto.nameEn.trim(),
        nameFa: dto.nameFa?.trim() || null,
        imageMediaId,
        about: dto.about?.trim() || null,
        slug,
        sort_order: dto.sortOrder ?? 0,
      },
      include: { imageMedia: true },
    });

    return {
      message: 'Brand created successfully',
      brand: this.serialize(created),
    };
  }

  async update(
    businessIdRaw: string,
    brandIdRaw: string,
    dto: UpdateBrandDto,
    actor: AuthUser,
  ) {
    const businessId = BigInt(businessIdRaw);
    const brandId = BigInt(brandIdRaw);
    await this.assertPermission(businessId, actor.id, 'brands.update');

    const existing = await this.findBrandOrThrow(businessId, brandId);

    let slug = existing.slug;
    if (dto.slug) {
      slug = await this.ensureUniqueSlug(businessId, dto.slug, brandId);
    } else if (dto.nameEn && dto.nameEn !== existing.nameEn) {
      slug = await this.ensureUniqueSlug(
        businessId,
        slugify(dto.nameEn),
        brandId,
      );
    }

    let imageMediaId: bigint | null | undefined = undefined;
    if (dto.imageMediaId !== undefined) {
      if (dto.imageMediaId === null || dto.imageMediaId === '') {
        imageMediaId = null;
      } else {
        imageMediaId = BigInt(dto.imageMediaId);
        await this.assertBrandImageMedia(businessId, imageMediaId);
      }
    }

    const updated = await this.prisma.brand.update({
      where: { id: brandId },
      data: {
        ...(dto.nameEn !== undefined ? { nameEn: dto.nameEn.trim() } : {}),
        ...(dto.nameFa !== undefined ? { nameFa: dto.nameFa?.trim() || null } : {}),
        ...(dto.about !== undefined ? { about: dto.about?.trim() || null } : {}),
        ...(imageMediaId !== undefined ? { imageMediaId } : {}),
        ...(dto.sortOrder !== undefined ? { sort_order: dto.sortOrder } : {}),
        slug,
      },
      include: { imageMedia: true },
    });

    return {
      message: 'Brand updated successfully',
      brand: this.serialize(updated),
    };
  }

  async remove(businessIdRaw: string, brandIdRaw: string, actor: AuthUser) {
    const businessId = BigInt(businessIdRaw);
    const brandId = BigInt(brandIdRaw);
    await this.assertPermission(businessId, actor.id, 'brands.delete');

    await this.findBrandOrThrow(businessId, brandId);
    await this.prisma.brand.delete({ where: { id: brandId } });

    return { message: 'Brand deleted successfully' };
  }

  async assertBrandBelongsToBusiness(businessId: bigint, brandId: bigint) {
    const brand = await this.prisma.brand.findFirst({
      where: { id: brandId, businessId },
    });

    if (!brand) {
      throw new BadRequestException('Brand not found for this business');
    }
  }

  serializeBrandSummary(brand: BrandWithImage | null) {
    if (!brand) {
      return null;
    }

    return this.serialize(brand);
  }

  private async findBrandOrThrow(businessId: bigint, brandId: bigint) {
    const brand = await this.prisma.brand.findFirst({
      where: { id: brandId, businessId },
      include: { imageMedia: true },
    });

    if (!brand) {
      throw new NotFoundException('Brand not found');
    }

    return brand;
  }

  private serialize(brand: BrandWithImage) {
    return {
      id: brand.id.toString(),
      businessId: brand.businessId.toString(),
      nameEn: brand.nameEn,
      nameFa: brand.nameFa,
      about: brand.about,
      slug: brand.slug,
      imageMediaId: brand.imageMediaId?.toString() ?? null,
      imageUrl: brand.imageMedia?.publicUrl ?? null,
      sortOrder: brand.sort_order,
      createdAt: brand.createdAt,
      updatedAt: brand.updatedAt,
    };
  }

  private async assertBrandImageMedia(businessId: bigint, mediaId: bigint) {
    const media = await this.prisma.media.findFirst({
      where: { id: mediaId, businessId },
      select: { id: true, mimeType: true },
    });

    if (!media) {
      throw new BadRequestException('Brand image media not found for this business');
    }

    if (media.mimeType !== 'image/png') {
      throw new BadRequestException('Brand image must be a PNG file');
    }
  }

  private async ensureUniqueSlug(
    businessId: bigint,
    baseSlug: string,
    excludeId?: bigint,
  ) {
    let slug = baseSlug;
    let suffix = 1;

    while (true) {
      const existing = await this.prisma.brand.findFirst({
        where: {
          businessId,
          slug,
          ...(excludeId ? { NOT: { id: excludeId } } : {}),
        },
      });

      if (!existing) {
        return slug;
      }

      suffix += 1;
      slug = `${baseSlug}-${suffix}`;
    }
  }

  private async assertPermission(
    businessId: bigint,
    userId: bigint,
    permission: string,
  ) {
    const allowed = await this.permissions.hasBusinessPermission(
      userId,
      businessId,
      permission,
    );

    if (!allowed) {
      throw new ForbiddenException(
        `Missing permission: ${permission} for this business`,
      );
    }
  }
}