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 { TenantService } from '../tenant/tenant.service';
import {
  CreateWebsiteSliderDto,
  ListWebsiteSlidersDto,
  UpdateWebsiteSliderDto,
  WebsiteSliderSlideInputDto,
} from './dto/website-sliders.dto';

const sliderInclude = {
  website_slider_slides: {
    orderBy: [{ sort_order: 'asc' as const }, { id: 'asc' as const }],
    include: {
      media: true,
    },
  },
} satisfies Prisma.website_slidersInclude;

type SliderWithSlides = Prisma.website_slidersGetPayload<{
  include: typeof sliderInclude;
}>;

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

  async listPublic(host: string) {
    const business = await this.tenant.resolveBusinessByDomain(host);
    const sliders = await this.prisma.website_sliders.findMany({
      where: { business_id: business.id, is_active: true },
      orderBy: [{ sort_order: 'asc' }, { created_at: 'asc' }],
      include: sliderInclude,
    });

    return {
      items: sliders.map((slider) => this.serializeSlider(slider, true)),
    };
  }

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

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

    const where: Prisma.website_slidersWhereInput = {
      business_id: businessId,
      ...(query.isActive !== undefined ? { is_active: query.isActive } : {}),
    };

    const [items, total] = await Promise.all([
      this.prisma.website_sliders.findMany({
        where,
        orderBy: [{ sort_order: 'asc' }, { created_at: 'asc' }],
        skip,
        take: pageSize,
        include: sliderInclude,
      }),
      this.prisma.website_sliders.count({ where }),
    ]);

    return {
      items: items.map((slider) => this.serializeSlider(slider, false)),
      total,
      page,
      pageSize,
    };
  }

  async getOne(
    businessIdRaw: string,
    sliderIdRaw: string,
    actor: AuthUser,
  ) {
    const businessId = BigInt(businessIdRaw);
    const sliderId = BigInt(sliderIdRaw);
    await this.assertPermission(businessId, actor.id, 'website.read');

    const slider = await this.findSliderOrThrow(businessId, sliderId);
    return { slider: this.serializeSlider(slider, false) };
  }

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

    const slides = dto.slides ?? [];
    await this.assertSlideMedia(businessId, slides);

    const created = await this.prisma.$transaction(async (tx) => {
      const slider = await tx.website_sliders.create({
        data: {
          business_id: businessId,
          title: dto.title.trim(),
          sort_order: dto.sortOrder ?? 0,
          is_active: dto.isActive ?? true,
        },
      });

      await this.replaceSlides(tx, slider.id, slides);
      return tx.website_sliders.findUniqueOrThrow({
        where: { id: slider.id },
        include: sliderInclude,
      });
    });

    return {
      message: 'Website slider created successfully',
      slider: this.serializeSlider(created, false),
    };
  }

  async update(
    businessIdRaw: string,
    sliderIdRaw: string,
    dto: UpdateWebsiteSliderDto,
    actor: AuthUser,
  ) {
    const businessId = BigInt(businessIdRaw);
    const sliderId = BigInt(sliderIdRaw);
    await this.assertPermission(businessId, actor.id, 'website.update');

    await this.findSliderOrThrow(businessId, sliderId);

    let slides: WebsiteSliderSlideInputDto[] | undefined;
    if (dto.slides !== undefined) {
      slides = dto.slides;
      await this.assertSlideMedia(businessId, slides);
    }

    const updated = await this.prisma.$transaction(async (tx) => {
      await tx.website_sliders.update({
        where: { id: sliderId },
        data: {
          ...(dto.title !== undefined ? { title: dto.title.trim() } : {}),
          ...(dto.sortOrder !== undefined ? { sort_order: dto.sortOrder } : {}),
          ...(dto.isActive !== undefined ? { is_active: dto.isActive } : {}),
        },
      });

      if (slides !== undefined) {
        await this.replaceSlides(tx, sliderId, slides);
      }

      return tx.website_sliders.findUniqueOrThrow({
        where: { id: sliderId },
        include: sliderInclude,
      });
    });

    return {
      message: 'Website slider updated successfully',
      slider: this.serializeSlider(updated, false),
    };
  }

  async remove(
    businessIdRaw: string,
    sliderIdRaw: string,
    actor: AuthUser,
  ) {
    const businessId = BigInt(businessIdRaw);
    const sliderId = BigInt(sliderIdRaw);
    await this.assertPermission(businessId, actor.id, 'website.update');

    await this.findSliderOrThrow(businessId, sliderId);
    await this.prisma.website_sliders.delete({ where: { id: sliderId } });

    return { message: 'Website slider deleted successfully' };
  }

  private async findSliderOrThrow(businessId: bigint, sliderId: bigint) {
    const slider = await this.prisma.website_sliders.findFirst({
      where: { id: sliderId, business_id: businessId },
      include: sliderInclude,
    });

    if (!slider) {
      throw new NotFoundException('Website slider not found');
    }

    return slider;
  }

  private async assertSlideMedia(
    businessId: bigint,
    slides: WebsiteSliderSlideInputDto[],
  ) {
    if (slides.length === 0) {
      return;
    }

    const mediaIds = slides.map((slide) => BigInt(slide.imageMediaId));
    const uniqueMediaIds = [...new Set(mediaIds.map((id) => id.toString()))].map(
      (id) => BigInt(id),
    );

    const found = await this.prisma.media.findMany({
      where: {
        businessId,
        id: { in: uniqueMediaIds },
        mimeType: { startsWith: 'image/' },
      },
      select: { id: true },
    });

    if (found.length !== uniqueMediaIds.length) {
      throw new BadRequestException(
        'One or more slide images were not found for this business',
      );
    }
  }

  private async replaceSlides(
    tx: Prisma.TransactionClient,
    sliderId: bigint,
    slides: WebsiteSliderSlideInputDto[],
  ) {
    await tx.website_slider_slides.deleteMany({ where: { slider_id: sliderId } });

    if (slides.length === 0) {
      return;
    }

    await tx.website_slider_slides.createMany({
      data: slides.map((slide, index) => ({
        slider_id: sliderId,
        image_media_id: BigInt(slide.imageMediaId),
        title: slide.title?.trim() || null,
        link_url: slide.linkUrl?.trim() || null,
        sort_order: index,
        is_active: slide.isActive ?? true,
      })),
    });
  }

  private serializeSlider(slider: SliderWithSlides, publicView: boolean) {
    const slides = slider.website_slider_slides
      .filter((slide) => !publicView || slide.is_active)
      .map((slide) => ({
        id: slide.id.toString(),
        imageMediaId: slide.image_media_id.toString(),
        imageUrl: slide.media.publicUrl,
        title: slide.title,
        linkUrl: slide.link_url,
        sortOrder: slide.sort_order,
        isActive: slide.is_active,
        createdAt: slide.created_at,
        updatedAt: slide.updated_at,
      }));

    return {
      id: slider.id.toString(),
      title: slider.title,
      sortOrder: slider.sort_order,
      isActive: slider.is_active,
      createdAt: slider.created_at,
      updatedAt: slider.updated_at,
      slides,
    };
  }

  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`,
      );
    }
  }
}