import {
  BadRequestException,
  ForbiddenException,
  Injectable,
  NotFoundException,
} from '@nestjs/common';
import { ConfigService } from '@nestjs/config';
import { MediaType } from '@prisma/client';
import { randomUUID } from 'crypto';
import * as path from 'path';
import sharp from 'sharp';
import { AuthUser } from '../auth/auth.types';
import { PermissionsService } from '../auth/permissions.service';
import { PrismaService } from '../prisma/prisma.service';
import { StorageService } from '../storage/storage.service';
import { ListMediaDto } from './dto/list-media.dto';
import { UpdateMediaDto } from './dto/update-media.dto';

const IMAGE_MIME_TYPES = new Set([
  'image/jpeg',
  'image/png',
  'image/webp',
  'image/gif',
]);

const VIDEO_MIME_TYPES = new Set(['video/mp4', 'video/webm']);

@Injectable()
export class MediaService {
  private readonly maxFileSizeBytes: number;

  constructor(
    private readonly prisma: PrismaService,
    private readonly storage: StorageService,
    private readonly permissions: PermissionsService,
    private readonly config: ConfigService,
  ) {
    const maxMb = Number(this.config.get<string>('MEDIA_MAX_FILE_SIZE_MB', '10'));
    this.maxFileSizeBytes = maxMb * 1024 * 1024;
  }

  async list(businessIdRaw: string, query: ListMediaDto, actor: AuthUser) {
    const businessId = BigInt(businessIdRaw);
    await this.assertCanRead(businessId, actor.id);

    const page = query.page ?? 1;
    const pageSize = query.pageSize ?? 24;
    const skip = (page - 1) * pageSize;

    const where = {
      businessId,
      ...(query.mediaType ? { mediaType: query.mediaType } : {}),
    };

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

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

  async uploadMany(
    businessIdRaw: string,
    files: Express.Multer.File[],
    actor: AuthUser,
  ) {
    const businessId = BigInt(businessIdRaw);
    await this.assertCanCreate(businessId, actor.id);

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

    const business = await this.prisma.business.findUnique({
      where: { id: businessId },
    });

    if (!business?.isActive) {
      throw new NotFoundException('Business not found');
    }

    const items = [];
    for (const file of files) {
      items.push(await this.uploadOne(businessId, business.slug, file, actor.id));
    }

    return { items };
  }

  async update(
    businessIdRaw: string,
    mediaIdRaw: string,
    dto: UpdateMediaDto,
    actor: AuthUser,
  ) {
    const businessId = BigInt(businessIdRaw);
    const mediaId = BigInt(mediaIdRaw);
    await this.assertCanUpdate(businessId, actor.id);

    const media = await this.prisma.media.findFirst({
      where: { id: mediaId, businessId },
    });

    if (!media) {
      throw new NotFoundException('Media not found');
    }

    const updated = await this.prisma.media.update({
      where: { id: mediaId },
      data: {
        altText: dto.altText?.trim() ?? undefined,
        caption: dto.caption?.trim() ?? undefined,
      },
    });

    return this.serialize(updated);
  }

  async remove(businessIdRaw: string, mediaIdRaw: string, actor: AuthUser) {
    const businessId = BigInt(businessIdRaw);
    const mediaId = BigInt(mediaIdRaw);
    await this.assertCanDelete(businessId, actor.id);

    const media = await this.prisma.media.findFirst({
      where: { id: mediaId, businessId },
    });

    if (!media) {
      throw new NotFoundException('Media not found');
    }

    await this.prisma.media.delete({ where: { id: mediaId } });

    try {
      await this.storage.delete(media.storagePath, media.storageDisk);
    } catch {
      // DB row removed; orphaned object can be cleaned later
    }

    return { message: 'Media deleted' };
  }

  private async uploadOne(
    businessId: bigint,
    businessSlug: string,
    file: Express.Multer.File,
    uploadedBy: bigint,
  ) {
    if (!file.buffer?.length) {
      throw new BadRequestException('Uploaded file is empty');
    }

    if (file.size > this.maxFileSizeBytes) {
      throw new BadRequestException(
        `File ${file.originalname} exceeds the maximum allowed size`,
      );
    }

    if (VIDEO_MIME_TYPES.has(file.mimetype)) {
      throw new BadRequestException('Video upload is not enabled for product images yet');
    }

    let width: number | null = null;
    let height: number | null = null;
    let contentType = file.mimetype;

    try {
      const metadata = await sharp(file.buffer).metadata();
      width = metadata.width ?? null;
      height = metadata.height ?? null;

      if (!width || !height) {
        throw new BadRequestException(
          `Could not read image dimensions for ${file.originalname}`,
        );
      }

      contentType =
        this.contentTypeFromFormat(metadata.format) ??
        (IMAGE_MIME_TYPES.has(file.mimetype) ? file.mimetype : 'image/jpeg');
    } catch (error) {
      if (error instanceof BadRequestException) {
        throw error;
      }

      throw new BadRequestException(
        `Unsupported file type: ${file.mimetype || 'unknown'}. Use JPEG, PNG, WebP, or GIF.`,
      );
    }

    const ext = this.extensionFromContentType(contentType);
    const fileName = `${randomUUID()}${ext}`;
    const storageKey = `businesses/${businessSlug}/${businessId}/media/${fileName}`;

    const stored = await this.storage.upload({
      key: storageKey,
      body: file.buffer,
      contentType,
    });

    const created = await this.prisma.media.create({
      data: {
        businessId,
        uploadedBy,
        mediaType: MediaType.image,
        storageDisk: stored.storageDisk,
        storagePath: stored.storagePath,
        publicUrl: stored.publicUrl,
        fileName,
        originalFileName: file.originalname,
        mimeType: contentType,
        fileSizeBytes: BigInt(file.size),
        width,
        height,
      },
    });

    return this.serialize(created);
  }

  private contentTypeFromFormat(format?: string) {
    switch (format) {
      case 'jpeg':
      case 'jpg':
        return 'image/jpeg';
      case 'png':
        return 'image/png';
      case 'webp':
        return 'image/webp';
      case 'gif':
        return 'image/gif';
      default:
        return undefined;
    }
  }

  private extensionFromContentType(contentType: string) {
    switch (contentType) {
      case 'image/jpeg':
        return '.jpg';
      case 'image/png':
        return '.png';
      case 'image/webp':
        return '.webp';
      case 'image/gif':
        return '.gif';
      default:
        return '.jpg';
    }
  }

  private resolveExtension(originalName: string, mimeType: string) {
    const ext = path.extname(originalName).toLowerCase();
    if (ext) {
      return ext;
    }

    switch (mimeType) {
      case 'image/jpeg':
        return '.jpg';
      case 'image/png':
        return '.png';
      case 'image/webp':
        return '.webp';
      case 'image/gif':
        return '.gif';
      case 'video/mp4':
        return '.mp4';
      case 'video/webm':
        return '.webm';
      default:
        return '';
    }
  }

  private serialize(media: {
    id: bigint;
    businessId: bigint;
    uploadedBy: bigint | null;
    mediaType: MediaType;
    storageDisk: string;
    storagePath: string;
    publicUrl: string;
    fileName: string;
    originalFileName: string;
    mimeType: string;
    fileSizeBytes: bigint;
    width: number | null;
    height: number | null;
    durationSeconds: { toNumber?: () => number } | null;
    altText: string | null;
    caption: string | null;
    createdAt: Date;
    updatedAt: Date;
  }) {
    return {
      id: media.id.toString(),
      businessId: media.businessId.toString(),
      uploadedBy: media.uploadedBy?.toString() ?? null,
      mediaType: media.mediaType,
      storageDisk: media.storageDisk,
      storagePath: media.storagePath,
      publicUrl: media.publicUrl,
      fileName: media.fileName,
      originalFileName: media.originalFileName,
      mimeType: media.mimeType,
      fileSizeBytes: media.fileSizeBytes.toString(),
      width: media.width,
      height: media.height,
      durationSeconds: media.durationSeconds
        ? Number(media.durationSeconds)
        : null,
      altText: media.altText,
      caption: media.caption,
      createdAt: media.createdAt,
      updatedAt: media.updatedAt,
    };
  }

  private async assertCanRead(businessId: bigint, userId: bigint) {
    const allowed = await this.permissions.hasBusinessPermission(
      userId,
      businessId,
      'media.read',
    );
    if (!allowed) {
      throw new ForbiddenException('You cannot view media for this business');
    }
  }

  private async assertCanCreate(businessId: bigint, userId: bigint) {
    const allowed = await this.permissions.hasBusinessPermission(
      userId,
      businessId,
      'media.create',
    );
    if (!allowed) {
      throw new ForbiddenException('You cannot upload media for this business');
    }
  }

  private async assertCanUpdate(businessId: bigint, userId: bigint) {
    const allowed = await this.permissions.hasBusinessPermission(
      userId,
      businessId,
      'media.update',
    );
    if (!allowed) {
      throw new ForbiddenException('You cannot update media for this business');
    }
  }

  private async assertCanDelete(businessId: bigint, userId: bigint) {
    const allowed = await this.permissions.hasBusinessPermission(
      userId,
      businessId,
      'media.delete',
    );
    if (!allowed) {
      throw new ForbiddenException('You cannot delete media for this business');
    }
  }
}