import {
  BadRequestException,
  ForbiddenException,
  Injectable,
  NotFoundException,
} from '@nestjs/common';
import {
  ContentStatus,
  MediaEntityType,
  Prisma,
  VideoProvider,
} from '@prisma/client';
import { AuthUser } from '../auth/auth.types';
import { PermissionsService } from '../auth/permissions.service';
import { BusinessSettingsService } from '../business-settings/business-settings.service';
import {
  applySeoMetaToMetadata,
  normalizeSeoMetaInput,
  readSeoMetaFromMetadata,
} from '../common/seo-meta.util';
import { PrismaService } from '../prisma/prisma.service';
import { TenantService } from '../tenant/tenant.service';
import {
  CreateInstructionCommentDto,
  CreateInstructionDto,
  ListPublicInstructionsDto,
  ListInstructionsDto,
  UpdateInstructionDto,
} from './dto/instruction.dto';

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

type InstructionWithRelations = Prisma.instructionsGetPayload<{
  include: {
    media: true;
    author: {
      select: { id: true; firstName: true; lastName: true; email: true };
    };
  };
}>;

const instructionInclude = {
  media: true,
  author: {
    select: {
      id: true,
      firstName: true,
      lastName: true,
      email: true,
    },
  },
} satisfies Prisma.instructionsInclude;

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

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

    const page = query.page ?? 1;
    const pageSize = query.pageSize ?? 12;
    const skip = (page - 1) * pageSize;

    const where = await this.buildWhere(businessId, query);

    const [items, total] = await Promise.all([
      this.prisma.instructions.findMany({
        where,
        orderBy: [{ published_at: 'desc' }, { created_at: 'desc' }],
        skip,
        take: pageSize,
        include: instructionInclude,
      }),
      this.prisma.instructions.count({ where }),
    ]);

    const serialized = await Promise.all(
      items.map((item) => this.serializeInstruction(item, { includeComments: true })),
    );

    return { items: serialized, total, page, pageSize };
  }

  async getOne(businessIdRaw: string, instructionIdRaw: string, actor: AuthUser) {
    const businessId = BigInt(businessIdRaw);
    const instructionId = BigInt(instructionIdRaw);
    await this.assertPermission(businessId, actor.id, 'instructions.read');

    const video = await this.findInstructionOrThrow(businessId, instructionId);

    return {
      instruction: await this.serializeInstruction(video, { includeComments: true }),
    };
  }

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

    const titleFa = this.resolveTitleFa(dto.titleFa, dto.title);
    const titleEn = dto.titleEn?.trim() || null;
    if (!titleFa) {
      throw new BadRequestException('titleFa is required');
    }

    const slug = await this.ensureUniqueInstructionSlug(
      businessId,
      dto.slug ?? slugify(titleEn || titleFa),
    );

    const status = dto.status ?? ContentStatus.published;
    const featuredMediaId = dto.featuredMediaId
      ? BigInt(dto.featuredMediaId)
      : null;

    if (featuredMediaId) {
      await this.assertMediaBelongsToBusiness(businessId, featuredMediaId);
    }

    const authorId = dto.authorId ? BigInt(dto.authorId) : actor.id;
    await this.assertAuthorBelongsToBusiness(businessId, authorId, actor);

    if (dto.categoryId) {
      await this.assertCategoryBelongsToBusiness(
        businessId,
        BigInt(dto.categoryId),
      );
    }

    const embedCode = dto.embedCode?.trim() || null;
    const videoProvider = embedCode ? dto.videoProvider : null;
    if (embedCode && !videoProvider) {
      throw new BadRequestException(
        'videoProvider is required when embedCode is set',
      );
    }
    if (!embedCode && !(dto.descriptionHtml ?? '').trim()) {
      throw new BadRequestException(
        'Provide descriptionHtml or embedCode',
      );
    }

    const created = await this.prisma.$transaction(async (tx) => {
      const item = await tx.instructions.create({
        data: {
          business_id: businessId,
          author_id: authorId,
          title: titleFa,
          title_fa: titleFa,
          title_en: titleEn,
          slug,
          excerpt: dto.abstract?.trim() || null,
          content: this.buildContent(dto.descriptionHtml) as Prisma.InputJsonValue,
          video_provider: videoProvider,
          embed_code: embedCode,
          status,
          featured_media_id: featuredMediaId,
          published_at: status === ContentStatus.published ? new Date() : null,
          metadata: applySeoMetaToMetadata(
            this.buildMetadata(dto.tags),
            normalizeSeoMetaInput(dto.seoMetaTitle, dto.seoMetaDescription),
          ) as Prisma.InputJsonValue,
        },
        include: instructionInclude,
      });

      if (dto.categoryId) {
        await tx.categoryAssignment.create({
          data: {
            businessId,
            categoryId: BigInt(dto.categoryId),
            entityType: MediaEntityType.instruction,
            entityId: item.id,
          },
        });
      }

      return item;
    });

    return {
      message: 'Instruction created successfully',
      instruction: await this.serializeInstruction(created),
    };
  }

  async update(
    businessIdRaw: string,
    instructionIdRaw: string,
    dto: UpdateInstructionDto,
    actor: AuthUser,
  ) {
    const businessId = BigInt(businessIdRaw);
    const instructionId = BigInt(instructionIdRaw);
    await this.assertPermission(businessId, actor.id, 'instructions.update');

    const existing = await this.prisma.instructions.findFirst({
      where: { id: instructionId, business_id: businessId },
    });

    if (!existing) {
      throw new NotFoundException('Instruction not found');
    }

    const nextTitleFa =
      dto.titleFa !== undefined || dto.title !== undefined
        ? this.resolveTitleFa(dto.titleFa, dto.title)
        : undefined;

    if (
      (dto.titleFa !== undefined || dto.title !== undefined) &&
      !nextTitleFa
    ) {
      throw new BadRequestException('titleFa is required');
    }

    let slug = existing.slug;
    if (dto.slug) {
      slug = await this.ensureUniqueInstructionSlug(businessId, dto.slug, instructionId);
    } else if (nextTitleFa && nextTitleFa !== (existing.title_fa ?? existing.title)) {
      const slugBase =
        (dto.titleEn !== undefined
          ? dto.titleEn?.trim() || null
          : existing.title_en) || nextTitleFa;
      slug = await this.ensureUniqueInstructionSlug(businessId, slugify(slugBase), instructionId);
    }

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

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

    const existingContent = this.asRecord(existing.content);
    const existingMetadata = this.asRecord(existing.metadata);

    const nextContent = { ...existingContent };
    if (dto.descriptionHtml !== undefined) {
      nextContent.html = dto.descriptionHtml ?? '';
    }

    const nextMetadata = applySeoMetaToMetadata(
      {
        ...existingMetadata,
        ...(dto.tags !== undefined ? { tags: dto.tags } : {}),
      },
      normalizeSeoMetaInput(dto.seoMetaTitle, dto.seoMetaDescription),
    );

    let publishedAt: Date | null | undefined = undefined;
    if (dto.status !== undefined) {
      if (
        dto.status === ContentStatus.published &&
        existing.status !== ContentStatus.published
      ) {
        publishedAt = new Date();
      }
      if (dto.status !== ContentStatus.published) {
        publishedAt = null;
      }
    }

    const updated = await this.prisma.$transaction(async (tx) => {
      const nextEmbed =
        dto.embedCode !== undefined ? dto.embedCode?.trim() || null : undefined;
      let nextProvider: VideoProvider | null | undefined = undefined;
      if (dto.videoProvider !== undefined) {
        nextProvider = dto.videoProvider ?? null;
      } else if (nextEmbed !== undefined && !nextEmbed) {
        nextProvider = null;
      }

      const video = await tx.instructions.update({
        where: { id: instructionId },
        data: {
          ...(nextTitleFa !== undefined
            ? { title: nextTitleFa, title_fa: nextTitleFa }
            : {}),
          ...(dto.titleEn !== undefined
            ? { title_en: dto.titleEn?.trim() || null }
            : {}),
          ...(dto.abstract !== undefined
            ? { excerpt: dto.abstract?.trim() || null }
            : {}),
          ...(nextProvider !== undefined ? { video_provider: nextProvider } : {}),
          ...(nextEmbed !== undefined ? { embed_code: nextEmbed } : {}),
          ...(dto.status !== undefined ? { status: dto.status } : {}),
          ...(featuredMediaId !== undefined
            ? { featured_media_id: featuredMediaId }
            : {}),
          ...(authorId !== undefined ? { author_id: authorId } : {}),
          ...(publishedAt !== undefined ? { published_at: publishedAt } : {}),
          slug,
          content: nextContent as Prisma.InputJsonValue,
          metadata: nextMetadata as Prisma.InputJsonValue,
        },
        include: instructionInclude,
      });

      if (dto.categoryId !== undefined) {
        await tx.categoryAssignment.deleteMany({
          where: {
            businessId,
            entityType: MediaEntityType.instruction,
            entityId: instructionId,
          },
        });

        if (dto.categoryId) {
          const categoryId = BigInt(dto.categoryId);
          await this.assertCategoryBelongsToBusiness(businessId, categoryId);
          await tx.categoryAssignment.create({
            data: {
              businessId,
              categoryId,
              entityType: MediaEntityType.instruction,
              entityId: instructionId,
            },
          });
        }
      }

      return video;
    });

    return {
      message: 'Instruction updated successfully',
      instruction: await this.serializeInstruction(updated),
    };
  }

  async remove(businessIdRaw: string, instructionIdRaw: string, actor: AuthUser) {
    const businessId = BigInt(businessIdRaw);
    const instructionId = BigInt(instructionIdRaw);
    await this.assertPermission(businessId, actor.id, 'instructions.delete');

    const existing = await this.prisma.instructions.findFirst({
      where: { id: instructionId, business_id: businessId },
    });

    if (!existing) {
      throw new NotFoundException('Instruction not found');
    }

    await this.prisma.$transaction([
      this.prisma.comment.deleteMany({
        where: {
          businessId,
          entityType: MediaEntityType.instruction,
          entityId: instructionId,
        },
      }),
      this.prisma.categoryAssignment.deleteMany({
        where: {
          businessId,
          entityType: MediaEntityType.instruction,
          entityId: instructionId,
        },
      }),
      this.prisma.instructions.delete({ where: { id: instructionId } }),
    ]);

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

  async listPublic(host: string, query: ListPublicInstructionsDto) {
    const business = await this.tenant.resolveBusinessByDomain(host);
    const businessId = business.id;

    const page = query.page ?? 1;
    const pageSize = query.pageSize ?? 12;
    const skip = (page - 1) * pageSize;

    const where = await this.buildWhere(businessId, {
      ...query,
      status: ContentStatus.published,
    });

    const [items, total] = await Promise.all([
      this.prisma.instructions.findMany({
        where,
        orderBy: [{ published_at: 'desc' }, { created_at: 'desc' }],
        skip,
        take: pageSize,
        include: instructionInclude,
      }),
      this.prisma.instructions.count({ where }),
    ]);

    const serialized = await Promise.all(
      items.map((item) =>
        this.serializeInstruction(item, {
          includeComments: true,
          approvedCommentsOnly: true,
        }),
      ),
    );

    return { items: serialized, total, page, pageSize };
  }

  async getPublicBySlug(host: string, slug: string) {
    const business = await this.tenant.resolveBusinessByDomain(host);
    const businessId = business.id;

    const video = await this.prisma.instructions.findFirst({
      where: {
        business_id: businessId,
        slug,
        status: ContentStatus.published,
      },
      include: instructionInclude,
    });

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

    return {
      instruction: await this.serializeInstruction(video, {
        includeComments: true,
        approvedCommentsOnly: true,
      }),
    };
  }

  async listCommentsPublic(host: string, instructionIdRaw: string) {
    const business = await this.tenant.resolveBusinessByDomain(host);
    const businessId = business.id;
    const instructionId = BigInt(instructionIdRaw);

    await this.assertPublishedInstructionExists(businessId, instructionId);

    const items = await this.prisma.comment.findMany({
      where: {
        businessId,
        entityType: MediaEntityType.instruction,
        entityId: instructionId,
        isApproved: true,
      },
      orderBy: { createdAt: 'desc' },
      include: { approver: true },
    });

    return { items: items.map((item) => this.serializeComment(item)) };
  }

  async createCommentPublic(
    host: string,
    instructionIdRaw: string,
    dto: CreateInstructionCommentDto,
  ) {
    const business = await this.tenant.resolveBusinessByDomain(host);
    const businessId = business.id;
    const instructionId = BigInt(instructionIdRaw);

    await this.assertPublishedInstructionExists(businessId, instructionId);

    const autoApprove =
      await this.businessSettings.isCommentsAutoApprove(businessId);
    const approvedAt = autoApprove ? new Date() : null;

    const created = await this.prisma.comment.create({
      data: {
        businessId,
        entityType: MediaEntityType.instruction,
        entityId: instructionId,
        authorName: dto.authorName.trim(),
        authorEmail: dto.authorEmail?.trim() || null,
        text: dto.text.trim(),
        isApproved: autoApprove,
        approvedAt,
      },
      include: { approver: true },
    });

    return {
      comment: this.serializeComment(created),
      message: autoApprove
        ? 'Comment submitted and is approved'
        : 'Comment submitted and is pending approval',
    };
  }

  async listCommentsAdmin(
    businessIdRaw: string,
    instructionIdRaw: string,
    actor: AuthUser,
  ) {
    const businessId = BigInt(businessIdRaw);
    const instructionId = BigInt(instructionIdRaw);
    await this.assertPermission(businessId, actor.id, 'comments.read');

    const video = await this.prisma.instructions.findFirst({
      where: { id: instructionId, business_id: businessId },
      select: { id: true },
    });

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

    const items = await this.prisma.comment.findMany({
      where: {
        businessId,
        entityType: MediaEntityType.instruction,
        entityId: instructionId,
      },
      orderBy: { createdAt: 'desc' },
      include: { approver: true },
    });

    return { items: items.map((item) => this.serializeComment(item)) };
  }

  private resolveTitleFa(titleFa?: string, title?: string): string {
    return (titleFa ?? title ?? '').trim();
  }

  private async buildWhere(
    businessId: bigint,
    query: (ListInstructionsDto | ListPublicInstructionsDto) & { status?: ContentStatus },
  ): Promise<Prisma.instructionsWhereInput> {
    let entityIds: bigint[] | undefined;

    if (query.categoryId) {
      const assignments = await this.prisma.categoryAssignment.findMany({
        where: {
          businessId,
          categoryId: BigInt(query.categoryId),
          entityType: MediaEntityType.instruction,
        },
        select: { entityId: true },
      });

      entityIds = assignments.map((item) => item.entityId);

      if (entityIds.length === 0) {
        return { id: { in: [] } };
      }
    }

    return {
      business_id: businessId,
      ...(query.status ? { status: query.status } : {}),
      ...(query.provider ? { video_provider: query.provider } : {}),
      ...(entityIds ? { id: { in: entityIds } } : {}),
      ...(query.title?.trim()
        ? {
            OR: [
              {
                title_fa: {
                  contains: query.title.trim(),
                  mode: 'insensitive',
                },
              },
              {
                title_en: {
                  contains: query.title.trim(),
                  mode: 'insensitive',
                },
              },
              {
                title: { contains: query.title.trim(), mode: 'insensitive' },
              },
            ],
          }
        : {}),
    };
  }

  private async findInstructionOrThrow(businessId: bigint, instructionId: bigint) {
    const video = await this.prisma.instructions.findFirst({
      where: { id: instructionId, business_id: businessId },
      include: instructionInclude,
    });

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

    return video;
  }

  private async assertPublishedInstructionExists(
    businessId: bigint,
    instructionId: bigint,
  ) {
    const video = await this.prisma.instructions.findFirst({
      where: {
        id: instructionId,
        business_id: businessId,
        status: ContentStatus.published,
      },
      select: { id: true },
    });

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

  private async serializeInstruction(
    video: InstructionWithRelations,
    options: {
      includeComments?: boolean;
      approvedCommentsOnly?: boolean;
    } = {},
  ) {
    const content = this.asRecord(video.content);
    const metadata = this.asRecord(video.metadata);

    const [categoryAssignment, commentData] = await Promise.all([
      this.prisma.categoryAssignment.findFirst({
        where: {
          businessId: video.business_id,
          entityType: MediaEntityType.instruction,
          entityId: video.id,
        },
        include: { category: true },
      }),
      options.includeComments
        ? this.loadComments(
            video.business_id,
            video.id,
            options.approvedCommentsOnly,
          )
        : Promise.resolve({ commentCount: 0, comments: [] }),
    ]);

    return {
      id: video.id.toString(),
      businessId: video.business_id.toString(),
      title: video.title,
      titleFa: video.title_fa ?? video.title,
      titleEn: video.title_en,
      slug: video.slug,
      abstract: video.excerpt ?? '',
      descriptionHtml: (content.html as string | undefined) ?? '',
      videoProvider: video.video_provider ?? null,
      embedCode: video.embed_code ?? '',
      status: video.status,
      categoryId: categoryAssignment?.categoryId.toString() ?? null,
      categoryName: categoryAssignment?.category.name ?? '',
      tags: Array.isArray(metadata.tags) ? (metadata.tags as string[]) : [],
      ...readSeoMetaFromMetadata(metadata),
      authorId: video.author_id?.toString() ?? null,
      author: video.author
        ? {
            id: video.author.id.toString(),
            firstName: video.author.firstName,
            lastName: video.author.lastName,
            email: video.author.email,
          }
        : null,
      coverImageUrl: video.media?.publicUrl ?? null,
      featuredMediaId: video.featured_media_id?.toString() ?? null,
      commentCount: commentData.commentCount,
      comments: commentData.comments,
      publishedAt: video.published_at,
      createdAt: video.created_at,
      updatedAt: video.updated_at,
    };
  }

  private async loadComments(
    businessId: bigint,
    instructionId: bigint,
    approvedOnly?: boolean,
  ) {
    const where: Prisma.CommentWhereInput = {
      businessId,
      entityType: MediaEntityType.instruction,
      entityId: instructionId,
      ...(approvedOnly ? { isApproved: true } : {}),
    };

    const [commentCount, comments] = await Promise.all([
      this.prisma.comment.count({ where }),
      this.prisma.comment.findMany({
        where,
        orderBy: { createdAt: 'desc' },
        take: approvedOnly ? 50 : undefined,
        include: { approver: true },
      }),
    ]);

    return {
      commentCount,
      comments: comments.map((item) => this.serializeComment(item)),
    };
  }

  private serializeComment(
    comment: Prisma.CommentGetPayload<{ include: { approver: true } }>,
  ) {
    return {
      id: comment.id.toString(),
      businessId: comment.businessId.toString(),
      entityType: comment.entityType,
      entityId: comment.entityId.toString(),
      authorName: comment.authorName,
      authorEmail: comment.authorEmail,
      text: comment.text,
      isApproved: comment.isApproved,
      approvedAt: comment.approvedAt,
      approvedBy: comment.approvedBy?.toString() ?? null,
      approver: comment.approver
        ? {
            id: comment.approver.id.toString(),
            firstName: comment.approver.firstName,
            lastName: comment.approver.lastName,
          }
        : null,
      createdAt: comment.createdAt,
      updatedAt: comment.updatedAt,
    };
  }

  private buildContent(descriptionHtml?: string) {
    return {
      html: descriptionHtml ?? '',
    };
  }

  private buildMetadata(tags?: string[]) {
    return {
      tags: tags?.map((tag) => tag.trim()).filter(Boolean) ?? [],
    };
  }

  private asRecord(value: Prisma.JsonValue): Record<string, unknown> {
    if (value && typeof value === 'object' && !Array.isArray(value)) {
      return value as Record<string, unknown>;
    }
    return {};
  }

  private async assertMediaBelongsToBusiness(
    businessId: bigint,
    mediaId: bigint,
  ) {
    const media = await this.prisma.media.findFirst({
      where: { id: mediaId, businessId },
    });
    if (!media) {
      throw new BadRequestException('Media not found for this business');
    }
  }

  private async assertCategoryBelongsToBusiness(
    businessId: bigint,
    categoryId: bigint,
  ) {
    const category = await this.prisma.category.findFirst({
      where: {
        id: categoryId,
        businessId,
        entityType: MediaEntityType.instruction,
        isActive: true,
      },
    });
    if (!category) {
      throw new BadRequestException('Instruction category not found for this business');
    }
  }

  private async assertAuthorBelongsToBusiness(
    businessId: bigint,
    authorId: bigint,
    actor: AuthUser,
  ) {
    if (await this.permissions.isSuperAdmin(actor.id)) {
      return;
    }

    const member = await this.prisma.businessUser.findFirst({
      where: { businessId, userId: authorId },
    });

    if (!member) {
      throw new BadRequestException(
        'Author must be a team member of this business',
      );
    }
  }

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

    while (true) {
      const existing = await this.prisma.instructions.findFirst({
        where: {
          business_id: 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`,
      );
    }
  }
}