import { Injectable, Logger } from '@nestjs/common';
import { ConfigService } from '@nestjs/config';
import * as path from 'path';
import * as fs from 'fs/promises';
import sharp from 'sharp';

const THUMBNAIL_WIDTH = 180;

@Injectable()
export class EmailPageCacheService {
  private readonly logger = new Logger(EmailPageCacheService.name);
  private readonly mailsRoot: string;

  constructor(configService: ConfigService) {
    this.mailsRoot = configService.get<string>(
      'MAILS_DATA_DIR',
      '/mnt/data/mails',
    );
  }

  attachmentDir(attachmentId: number | string): string {
    return path.join(this.mailsRoot, attachmentId.toString());
  }

  previewPath(attachmentId: number | string, page: number): string {
    return path.join(
      this.attachmentDir(attachmentId),
      `page-${page}.preview.png`,
    );
  }

  thumbnailPath(attachmentId: number | string, page: number): string {
    return path.join(
      this.attachmentDir(attachmentId),
      `page-${page}.thumb.png`,
    );
  }

  async generate(
    attachmentId: number | string,
    renderedImages: string[],
  ): Promise<void> {
    const dir = this.attachmentDir(attachmentId);
    await fs.mkdir(dir, { recursive: true });

    for (let i = 0; i < renderedImages.length; i++) {
      const page = i + 1;
      const src = renderedImages[i];
      const previewDest = this.previewPath(attachmentId, page);
      const thumbDest = this.thumbnailPath(attachmentId, page);

      try {
        await fs.copyFile(src, previewDest);
        await sharp(src)
          .resize({ width: THUMBNAIL_WIDTH })
          .png()
          .toFile(thumbDest);
      } catch (err: any) {
        this.logger.warn(
          `E-Mail Page Cache fehlgeschlagen (Attachment ${attachmentId} Seite ${page}): ${err.message}`,
        );
      }
    }
  }

  async hasPreview(
    attachmentId: number | string,
    page: number,
  ): Promise<boolean> {
    try {
      await fs.access(this.previewPath(attachmentId, page));
      return true;
    } catch {
      return false;
    }
  }
}